HPLC : High Performance Liquid chromatography

High performance liquid chromatography is a powerful tool in analysis. This page looks at how it is carried out and shows how it uses the same principles as in thin layer chromatography and column chromatography.

Carrying out HPLC

Introduction

High performance liquid chromatography is basically a highly improved form of column chromatography. Instead of a solvent being allowed to drip through a column under gravity, it is forced through under high pressures of up to 400 atmospheres. That makes it much faster.

It also allows you to use a very much smaller particle size for the column packing material which gives a much greater surface area for interactions between the stationary phase and the molecules flowing past it. This allows a much better separation of the components of the mixture.

The other major improvement over column chromatography concerns the detection methods which can be used. These methods are highly automated and extremely sensitive. The column and the solvent Confusingly, there are two variants in use in HPLC depending on the relative polarity of the solvent and the stationary phase. Normal phase HPLC This is essentially just the same as you will already have read about in thin layer chromatography or column chromatography. Although it is described as "normal", it isn't the most commonly used form of HPLC. The column is filled with tiny silica particles, and the solvent is non-polar - hexane, for example. A typical column has an internal diameter of 4.6 mm (and may be less than that), and a length of 150 to 250 mm. Polar compounds in the mixture being passed through the column will stick longer to the polar silica than non-polar compounds will. The non-polar ones will therefore pass more quickly through the column. Reversed phase HPLC In this case, the column size is the same, but the silica is modified to make it non-polar by attaching long hydrocarbon chains to its surface - typically with either 8 or 18 carbon atoms in them. A polar solvent is used - for example, a mixture of water and an alcohol such as methanol. In this case, there will be a strong attraction between the polar solvent and polar molecules in the mixture being passed through the column. There won't be as much attraction between the hydrocarbon chains attached to the silica (the stationary phase) and the polar molecules in the solution. Polar molecules in the mixture will therefore spend most of their time moving with the solvent. Non-polar compounds in the mixture will tend to form attractions with the hydrocarbon groups because of van der Waals dispersion forces. They will also be less soluble in the solvent because of the need to break hydrogen bonds as they squeeze in between the water or methanol molecules, for example. They therefore spend less time in solution in the solvent and this will slow them down on their way through the column. That means that now it is the polar molecules that will travel through the column more quickly. Reversed phase HPLC is the most commonly used form of HPLC.
	Note: I have been a bit careful about how I have described the attractions of the non-polar molecules to the surface of the stationary phase. In particular, I have avoided the use of the word "adsorpion". Adsorption is when a molecule sticks to the surface of a solid. Especially if you had small molecules in your mixture, some could get in between the long C18 chains to give what is essentially a solution. You could therefore say that non-polar molecules were more soluble in the hydrocarbon on the surface of the silica than they are in the polar solvent - and so spend more time in this alternative "solvent". Where a solute divides itself between two different solvents because it is more soluble in one than the other, we call it partition. So is this adsorption or partition? You could argue it both ways! Be prepared to find it described as either.
Looking at the whole process A flow scheme for HPLC Injection of the sample Injection of the sample is entirely automated, and you wouldn't be expected to know how this is done at this introductory level. Because of the pressures involved, it is not the same as in gas chromatography (if you have already studied that). Retention time The time taken for a particular compound to travel through the column to the detector is known as its retention time. This time is measured from the time at which the sample is injected to the point at which the display shows a maximum peak height for that compound. Different compounds have different retention times. For a particular compound, the retention time will vary depending on: the pressure used (because that affects the flow rate of the solvent) the nature of the stationary phase (not only what material it is made of, but also particle size) the exact composition of the solvent the temperature of the column That means that conditions have to be carefully controlled if you are using retention times as a way of identifying compounds. The detector There are several ways of detecting when a substance has passed through the column. A common method which is easy to explain uses ultra-violet absorption. Many organic compounds absorb UV light of various wavelengths. If you have a beam of UV light shining through the stream of liquid coming out of the column, and a UV detector on the opposite side of the stream, you can get a direct reading of how much of the light is absorbed. The amount of light absorbed will depend on the amount of a particular compound that is passing through the beam at the time. You might wonder why the solvents used don't absorb UV light. They do! But different compounds absorb most strongly in different parts of the UV spectrum. Methanol, for example, absorbs at wavelengths below 205 nm, and water below 190 nm. If you were using a methanol-water mixture as the solvent, you would therefore have to use a wavelength greater than 205 nm to avoid false readings from the solvent.
	Note: If you are interested, there is a whole section aboutUV-visible spectroscopy on the site. This explores the question of the absorption of UV and visible light by organic compounds in some detail.
Interpreting the output from the detector The output will be recorded as a series of peaks - each one representing a compound in the mixture passing through the detector and absorbing UV light. As long as you were careful to control the conditions on the column, you could use the retention times to help to identify the compounds present - provided, of course, that you (or somebody else) had already measured them for pure samples of the various compounds under those identical conditions. But you can also use the peaks as a way of measuring the quantities of the compounds present. Let's suppose that you are interested in a particular compound, X. If you injected a solution containing a known amount of pure X into the machine, not only could you record its retention time, but you could also relate the amount of X to the peak that was formed. The area under the peak is proportional to the amount of X which has passed the detector, and this area can be calculated automatically by the computer linked to the display. The area it would measure is shown in green in the (very simplified) diagram. If the solution of X was less concentrated, the area under the peak would be less - although the retention time will still be the same. For example: This means that it is possible to calibrate the machine so that it can be used to find how much of a substance is present - even in very small quantities. Be careful, though! If you had two different substances in the mixture (X and Y) could you say anything about their relative amounts? Not if you were using UV absorption as your detection method. In the diagram, the area under the peak for Y is less than that for X. That may be because there is less Y than X, but it could equally well be because Y absorbs UV light at the wavelength you are using less than X does. There might be large quantities of Y present, but if it only absorbed weakly, it would only give a small peak.

Coupling HPLC to a mass spectrometer

This is where it gets really clever! When the detector is showing a peak, some of what is passing through the detector at that time can be diverted to a mass spectrometer. There it will give a fragmentation pattern which can be compared against a computer database of known patterns. That means that the identity of a huge range of compounds can be found without having to know their retention times.

Find what is in chemistry : basic vocabulary,definition

In any case, if you're reading a book or your teacher is making you use the big words, it doesn't do much good to go up to him/her/it and say "Mr. Guch says it's wrong to use big words." For one thing, it'll make both of us look like morons. For another thing, it won't make anybody speak nicer. As a result, you're just going to have to get used to it. I have, however, included a list of vocabulary words below that chemistry students commonly have problems with.

absolute temperature: This is a temperature reading made relative to absolute zero. We use the unit of Kelvins for these readings.

absolute zero: This is the lowest temperature possible. If you remember that temperature is a measurement of how much atoms move around in a solid, you can guess that they stop moving entirely at absolute zero. In reality, bonds still vibrate a little bit, but for the most part you don't see much happening.

• acid: This is anything that gives off H+ ions in water. Acids have a pH less than 7 and are good at dissolving metals. They turn litmus paper red and phenolphthalein colorless.
• acid anhydride: This is an oxide that forms an acid when you stick it in water. An example is SO₃ - when you add water it turns into sulfuric acid, H₂SO₄.
• acid dissociation constant (K_a): This is equal to the ratio of the concentrations of an acid's conjugate base and the acid present when a weak acid dissociates in water. That is, if you have a solution of Acid X where the concentration of the conjugate base is 0.5 M and the concentration of the acid is 10 M, the acid dissociation constant is 0.5/10 = 0.05.
• activated complex: In a chemical reaction, the reagents have to join together into a great big blob before they can fall back apart into the products. This great big blob is called the activated complex (a.k.a. transition state)
• activation energy: The minimum amount of energy needed for a chemical reaction to take place. For some reactions this is very small (it only takes a spark to make gasoline burn). For others, it's very high (when you burn magnesium, you need to hold it over a Bunsen burner for a minute or so).
• activity series: This is when you arrange elements in the order of how much they tend to react with water and acids.
• actual yield: When you do a chemical reaction, this is the amount of chemical that you actually make (i.e. The amount of stuff you can weigh).
• addition reaction: A reaction where atoms add to a carbon-carbon multiple bond.
• adsorption: When one substance collects of the surface of another one.
• alcohol: An organic molecule containing an -OH group
• aldehyde: An organic molecule containing a -COH group
• alkali metals: Group I in the periodic table.
• alkaline earth metals: Group II in the periodic table.
• alkane: An organic molecule which contains only single carbon-carbon bonds.
• alkene: An organic molecule containing at least one C=C bond
• alkyne: An organic molecule containing at least one C-C triple bond.
• allotropes: When you have different forms of an element in the same state. The relationship that white phosphorus and red phosphorus have to each other is that they're allotropes.
• alloy: A mixture of two metals. Usually, you add very small amounts of a different element to make the metal stronger and harder.
• alpha particle: A radioactive particle equivalent to a helium nucleus (2 protons, 2 neutrons)
• amine: An organic molecule which consists of an ammonia molecule where one or more of the hydrogen atoms has been replaced by organic groups.
• amino acid: The basic building blocks of proteins. They're called "amino acids" because they're both amines (they contain nitrogen) and acids (carboxylic acids, to be precise)
• amphiprotic: When something is both an acid and a base. Like amino acids, for example.
• amphoteric: When something is both an acid and a base. Sounds familiar, huh?
• anode: The electrode where oxidation occurs. In other words, this is where electrons are lost by a substance.
• aqueous: dissolved in water
• atomic mass unit (a.m.u.): This is the smallest unit of mass we use in chemistry, and is equivalent to 1/12 the mass of carbon-12. To all intents and purposes, protons and neutrons weigh 1 a.m.u.
• atomic radius: This is one half the distance between two bonded nuclei. Why don't we just measure the distance from the nucleus to the outside of the atom - after all, isn't that the same thing as a radius? It is, but atoms are also (theoretically) infinitely large (due to quantum mechanics), making this impossible to measure.
• atomic solid: A solid where there's a bunch of atoms in the lattice. This is different from an ionic solid, where ions are the things that are sticking together.
• Aufbau principle: When you add protons to the nucleus to build up the elements, electrons are added into orbitals.
• Avogadro's Law: If you've got two gases under the same conditions of temperature, pressure, and volume, they've got the same number of particles (atoms or molecules). This law only works for ideal gases, none of which actually exist.
• base anhydride: An oxide that forms a base when water is added. CaO is an example, turning into calcium hydroxide in water.
• base: A compound that gives off OH- ions in water. They are slippery and bitter and have a pH greater than 7.
• battery: This is when a bunch of voltaic cells are stuck together.
• beta particle: A radioactive particle equivalent to an electron.
• bidentate ligand: A ligand that can attach twice to a metal ion.
• binary compound: A compound only having two elements
• binding energy: The amount of energy that holds the neutrons and protons together in the nucleus of an atom. It's a lot of energy, which is why you don't see nuclei falling apart all over the place.
• bond energy: The amount of energy it takes to break one mole of bonds.
• bond length: The average distance between the nuclei of two bonded atoms.
• Boyle's Law: The volume of a gas at constant temperature varies inversely with pressure. In other words, if you put big pressure on something, it gets small.
• Bronsted-Lowry acid: Acids donate protons [H+ ions] and bases grab them
• buffer: A liquid that resists change in pH by the addition of acid or base. It consists of a weak acid and it's conjugate base (acetic acid and sodium acetate, for example).
• calorimetry: The study of heat flow. Usually you'd do calorimetry to find the heat of combustion of a compound or the heat of reaction of two compounds.
• carboxylic acid: An organic molecule with a -COOH group on it. Acetic acid is the most famous one.
• catalyst: A substance that speeds up a chemical reaction without being used up by the reaction. Enzymes are catalysts because they allow the reactions that take place in the body to occur fast enough that we can live.
• cathode: The electrode in which reduction occurs. Reduction is when a compound gains electrons.
• chain reaction: A reaction in which the products from one step provide the reagents for the next one. This is frequently referred to in nuclear fission (when large nuclei break apart to form smaller ones) and in free-radical reactions.
• Charles's Law: The volume of a gas at constant pressure is directly proportional to the temperature. In other words, if you heat something up, it gets big.
• chemical equation: The recipe that describes what you need to do to make a reaction take place.
• chemical properties: Properties that can only be described by making a chemical change (by making or breaking bonds). For example, color isn't a chemical property because you don't need to change something chemically to see what color it is. Flammability, on the other hand, is a chemical property, because you can't tell if something burns unless you actually try to burn it.
• chirality: When a molecule has a nonsuperimposable mirror image. To imagine this, put your hands together. Although they are mirror images, you can't put them right on top of each other so they are interchangable. Well, normal people can't, anyway.
• chromatography: This is when you use a system containing a mobile phase (usually a liquid in general chemistry classes) and a stationary phase (something dissolved in the liquid) to separate different compounds. This is usually done by exploiting the differing polarities of solutes, though you can do it a whole slew o' ways.
• circuit: The closed path in a circuit through which electrons flow.
• coagulation: When you destroy a colloid by letting the particles settle out.
• colligative property: Any property of a solution that changes when the concentration changes. Examples are color, flavor, boiling point, melting point, and osmotic pressure.
• colloid: It's a suspension.
• combustion: When a compound combines with oxygen gas to form water, heat, and carbon dioxide
• common ion effect: When the equilibrium position of a process is altered by adding another compound containing one of the same ions that's in the equilibrium.
• complex ion: An ion in which a central atom (usually a transition metal) is surrounded by a bunch of molecules like water or ammonia (called "ligands")
• concentration: A measurement of the amount of stuff (solute) dissolved in a liquid (solvent). The most common concentration unit is molarity (M), which is equal to the number of moles of solute divided by the number of liters of solution.
• condensation: When a vapor reforms a liquid. This is what happens on your bathroom mirror when you take a shower.
• conductance: A measurement of how well electricity can flow through an object.
• conjugate acid: The compound formed when a base gains a proton (hydrogen atom).
• conjugate base: The compound formed when an acid loses a proton (hydrogen atom).
• continuous spectrum: A spectrum that gives off all the colors of light, like a rainbow. This is caused by blackbody emission.
• covalent bond: A chemical bond formed when two atoms share two electrons.
• critical mass: The minimum amount of radioactive material needed to undergo a nuclear chain reaction.
• critical point: The end point of the liquid-vapor line in a phase diagram. Past the critical point, you get something called a "supercritical liquid", which has weird properties.
• crystal lattice: see "lattice"
• crystal: A large chunk of an ionic solid.
• Dalton's law of partial pressures: The total pressure in a mixture of gases is equal to the sums of the partial pressures of all the gases put together.
• decomposition: When a big molecule falls apart to make two or more little ones.
• degenerate: Things (usually orbitals) are said to be degenerate if they have the same energy. This term is used a whole lot in quantum mechanics. Also when dealing with kids who steal cars.
• delocalization: This is when electrons can move around all over a molecule. This happens when you have double bonds on adjacent atoms in a molecule (conjugated hydrocarbon)
• denature: When the 3-D structure of a protein breaks down due to heat (or pH, etc), it's said to be denatured. This means that it unravels because the intermolecular forces between atoms in the chain aren't strong enough to hold it together anymore.
• diffusion: When particles move from areas of high concentration to areas of low concentration. For example, if you open a bottle of ammonia on one end of the room, the concentration of ammonia molecules in the air is very high on that side of the room. As a result, they tend to migrate across the room, which explains why you can smell it after a little while. Be careful not to mix this up with effusion (see definition)
• dilution: When you add solvent to a solution to make it less concentrated.
• dipole moment: When a molecule has some charge separation (usually because the molecule is polar), it's said to have a dipole moment.
• dipole-dipole force: When the positive end of a polar molecule becomes attracted to the negative end of another polar molecule.
• dissociation: When water dissolves a compound.
• distillation: This is when you separate a mixture of liquids by heating it up. The one with the lowest boiling point evaporates first, followed by the one with the next lowest boiling point, etc.
• double-displacement reaction (a.k.a. double replacement reaction): When the cations of two ionic compounds switch places.
• effusion: When a gas moves through an opening into a chamber that contains no pressure. Effusion is much faster than diffusion because there are no other gas molecules to get in the way.
• electrolysis: When electricity is used to break apart a chemical compound.
• electrolyte: An ionic compound that dissolves in water to conduct electricity. Strong electrolytes break apart completely in water; weak electrolytes only fall apart a little bit.
(Actually, this isn't entirely true, as Raji Heyovska informs me. Apparently strong electrolytes also dissociate partially in water, though much more so than weak ones. For more info, check out his paper at http://www.jh-inst.cas.cz/~rheyrovs. However, it is also true that the usual definition of a strong electrolyte is one that dissociates completely in water, which is why I include that definition above.)
• electron affinity: The energy change that accompanies the addition of an electron to an atom in the gas phase.
• electronegativity: A measurement of how much an atom tends to steal electrons from atoms that it's bonded to. Elements at the top right of the periodic table (excluding the noble gases) are very electronegative while atoms in the bottom left are not very electronegative (a.k.a. "electropositive")
• electropositive: When something is not at all electronegative. In fact, it tends to lose electrons rather than to gain them. Elements that are electropositive are generally to the left and bottom of the periodic table.
• empirical formula: A reduced molecular formula. If you have a molecular formula and you can reduce all of the subscripts by some constant number, the result is the empirical formula.
• emulsion: When very small drops of a liquid are suspended in another. An example of an emulsion is salad dressing after you've shaken it up.
• enantiomers: molecules that are nonsuperimposable mirror images of each other.
• endothermic: When a process absorbs energy (gets cold).
• endpoint: The point where you actually stop a titration, usually because an indicator has changed color. This is different than the "equivalence point" because the indicator might not change colors at the exact instant that the solution is neutral.
• energy level: A possible level of energy that an electron can have in an atom.
• enthalpy: A measurement of the energy content of a system.
• entropy: A measurement of the randomness in a system.
• enzyme: A biological molecule that catalyzes reactions in living creatures.
• equilibrium: When the forward rate of a chemical reaction is the same as the reverse rate. This only takes place in reversible reactions because these are the only type of reaction in which the forward and backward reactions can both take place.
• equivalence point: The point in a titration at which the solution is completely neutral. This is different than the "endpoint" (see above).
• ester: An organic molecule with R-CO-OR' functionality.
• excess reagent: Sometimes when you do a chemical reaction, there's some of one reagent left over. That's called the excess reagent.
• excited state: A higher energy level that electrons can jump to when energy is added.
• exothermic: When a process gives off energy (gets hot).
• family: The same thing as a "group" (see above)
• first law of thermodynamics: The energy of the universe is constant. It's the same thing as the Law of conservation of energy.
• fission: A nuclear reaction where a big atom breaks up into little ones. This is what happens in nuclear power plants.
• free energy: also called "Gibbs free energy", it's the capacity of a system to do work.
• free radical: An atom or molecule with an unpaired electron. They're way reactive.
• functional group: A generic term for a group of atoms that cause a molecule to react in a specific way. It's really common to talk about this in organic chemistry, where you have "aldehydes, carboxylic acids, amines" and so on.
• gamma ray: High energy light given off during a nuclear process. When a nucleus gives off this light, it goes to a lower energy state, making it more stable.
• geometrical isomer: isomerism where atoms or groups of atoms can take up different positions around a double bond or a ring. This is also called cis- trans- isomerism.
• ground state: The lowest energy state possible for an electron.
• group: A column (the things up and down) in the periodic table. Elements in the same group tend to have the same properties. These are also called "families".
• half-life: The time required for half of the radioactive atoms in a sample to decay. When talking about chemical reactions, it's the amount of time required to make half the reagent react.
• half-reaction: The oxidation or reduction part of a redox reaction.
• halogen: The elements in group 17. They're really reactive.
• heat of reaction: The amount of heat absorbed or released in a reaction. Also called the "enthalpy of reaction"
• heat: The kinetic energy of the particles in a system. The faster the particles move, the higher the heat.
• Hess's Law: The enthalpy change for a change is the same whether it takes place in one big step or in many small ones.
• heterogeneous mixture: A mixture where the substances aren't equally distributed.
• homogeneous mixture: A mixture that looks really "smooth" because everything is mixed up really well.
• Hund's rule: The most stable arrangement of electrons occurs when they're all unpaired.
• hybrid orbital: An orbital caused by the mixing of s, p, d, and f-orbitals.
• hydration: When a molecule has water molecules attached to it.
• hydrocarbon: A molecule containing carbon and hydrogen.
• hydrogen bond: The tendency of the hydrogen atom stuck to an electronegative atom to become attracted to the lone pair electrons on another electronegative atom. It's a pretty strong intermolecular force, which explains why water has such a high melting and boiling point.
• hydrogenation: When hydrogen is added to a carbon-carbon multiple bond.
• hydronium ion: The H+ ion, made famous by acids.
• hydroxide ion: The OH- ion, made famous by bases.
• ideal gas law: PV=nRT
• ideal gas: A gas in which the particles are infinitely small, have a kinetic energy directly proportional to the temperature, travel in random straight lines, and don't attract or repel each other. Needless to say, there's no such thing as an ideal gas in the real world. However, we use ideal gases anyway because they make the math work out well for equations that describe how gases behave.
• ideal solution: A solution in which the vapor pressure is directly proportional to the mole fraction of solvent present
• immiscible: When two substances don't dissolve in each other. Think of oil and water. They're immiscible. Organic compounds and water are frequently immiscible.
• indicator: A compound that turns different colors at different pH values. We generally like to have the color change at a pH of around seven because that's where the equivalence point of a titration is.
• inhibitor: A substance that slows down a chemical reaction.
• inorganic compound: Any compound that doesn't contain carbon (except for carbon dioxide, carbon monoxide, and carbonates).
• insoluble: When something doesn't dissolve.
• intermediate: A molecule which exists for a short time in a chemical reaction before turning into the product.
• intermolecular force: A force that exists between two different molecules. Examples are hydrogen bonding (which is strong), dipole-dipole forces (which are kind of weak), and London dispersion forces (a.k.a. Van der Waal forces), which are very weak.
• ionic bond: A bond formed when charge particles stick together.
• ionization energy: The amount of energy required to pull an electron off of a gaseous atom.
• irreversible reaction: A chemical reaction in which the reagents make products but the products can't reform reagents. Most chemical reactions in basic chemistry classes are thought of as being irreversible.
• isotonic solutions: Solutions containing the same osmotic pressure.
• isotope: When an element has more than one possibility for the number of neutrons, these are called isotopes. All known elements posess isotopes. For the record, the word "isotope" doesn't imply that something is radioactive. TV told you that, and TV is stupid.
• Kelvin: A unit used to measure temperature. One Kelvin is equal in size to one degree Celsius. To convert between degrees Celsius and Kelvins, simply add 273.15 to the temperature in degrees Celsius to get Kelvins.
• ketone: A molecule containing a R-CO-R' functional group. Acetone (dimethyl ketone) is a common one.
• kinetic energy: The energy due to the movement of an object. The more something moves, the more kinetic energy it has.
• Lanthanide contraction: The tendency of the lanthanides to get small when you go from left to right in the periodic table.
• lattice energy: The energy released when one mole of a crystal is formed from gaseous ions.
• lattice: The three-dimensional arrangement of atoms or ions in a crystal.
• law of conservation of energy: The amount of energy in the universe never changes, ever. It just changes form.
• law of conservation of mass: The amount of stuff after a chemical reaction takes place is the same as the amount of stuff you started with.
• Le Chatlier's Principle: When you disturb an equilibrium (by adding more chemical, by heating it up, etc.), it will eventually go back into equilibrium under a different set of conditions.
• Lewis acid: An electron-pair acceptor (carbonyl groups are really good ones)
• Lewis base: An electron-pair donor. Things with lone pairs like water and ammonia are really good ones.
• Lewis structure: A structural formula that shows all of the atoms and valence electrons in a molecule.
• ligand: A molecule or ion that sticks to the central atom in a complex. Common examples are ammonia, carbon monoxide, or water.
• limiting reagent: If you do a chemical reaction and one of the chemicals gets used up before the other one, the one that got used up is called the "limiting reagent" because it limited the amount of product that could be formed. The other one is called the excess reagent.
• line spectrum: A spectrum showing only certain wavelengths.
• London dispersion force: The forces between nonpolar atoms or molecules which is caused by momentary induced dipoles. It's real weak.
• lone pair: two electrons that aren't involved in chemical bonding. Also frequently referred to as an "unshared pair".
• main-block elements: Groups 1,2, and 13-18 in the periodic table. They're called main block elements because the outermost electron is in the s- or p- orbitals. What that has to do with the term "main block" is unclear to me, but hey, that's life.
• mass defect: The difference between the mass of an atom and the sum of the masses of its individual components. Atoms usually weigh a little less than if you added up the weights of all the particles. This is because that extra mass was converted into the energy which holds the atom together (see "binding energy")
• mass: The amount of matter in an object. The more mass, the more stuff is present.
• mechanism: A step-by-step sequence that shows how the products of a reaction are made from the reagents. Mechanisms are very frequently shown during organic chemistry.
• molality: The number of moles of solute per kilogram of solvent in a solution. This is a unit of concentration that's not anywhere near as handy or common as molarity.
• molar mass: The mass of one mole of particles.
• molar volume: The volume of one mole of a substance at STP. If you believe that everything is an ideal gas, this is always 22.4 liters. Unfortunately, there's no such thing as an ideal gas.
• molarity: A unit of concentration equal to moles of solute divided by liters of solution.
• mole fraction: The number of moles of stuff in a mixture that are due to one of the compouds.
• mole ratio: The ratio of moles of what you've been given in a reaction to what you want to find. Handy in stoichiometry.
• mole: 6.02 x 10²³ things.
• molecular compound: A compound held together by covalent bonds.
• molecular formula: A formula that shows the correct quantity of all of the atoms in a molecule.
• monatomic ion: An ion that has only one atom, like the chloride ion.
• neutralization reaction: The reaction of an acid with a base to form water and a salt.
• node: A location in an orbital where there's no probability of finding an electron.
• nonpolar covalent bond: A covalent bond where the electrons are shared equally between the two atoms.
• normal boiling point: The boiling point of a substance at 1.00 atm.
• normal melting point: The melting point of a substance at 1.00 atm.
• normality: The number of equivalents of a substance dissolved in a liter of solution.
• nuclar fusion: When many small atoms combine to form a large one. This occurs during a thermonuclear reaction.
• nuclear fission: This is when the nucleus of an atom breaks into many parts.
• nuclear reaction: Any reaction that involves a change in the nucleus of an atom. Nuclear reactions take loads of energy, which is why you don't see them much around the lab.
• nucleon: A particle (such as proton or neutron) that's in the nucleus of an atom.
• octet rule: All atoms want to be like the nearest noble gas. (Well, they all want to have the same number of valence electrons, anyway). To do this, they either gain or lose electrons (to form ionic compounds) or share electrons (to form covalent compounds).
• optical isomerism: Isomerism in which the isomers cause plane polarized light to rotate in different directions.
• orbital: This is where the electrons in an atom live.
• organic compound: A compound that contains carbon (except carbon dioxide, carbon monoxide, and carbonates)
• osmosis: The flow of a pure liquid into an area of high concentration through a semi-permeable membrane.
• oxidation number: The apparent charge on an atom.
• oxidation: When a substance loses electrons.
• partial pressure: The pressure of one gas in a mixture. For example, if you had a 50:50 mix of helium and hydrogen gases and the total pressure was 2 atm, the partial pressure of hydrogen would be 1 atm.
• Pauli exclusion principle: No two electrons in an atom can have the same quantum numbers.
• percent yield: The actual yield divided by the theoretical yield, times 100.
• period: A row (left to right) in the periodic table.
• periodic law: The properties of elements change with increasing atomic number in a periodic way. That's why you can stick the elements into a big chart and have the elements line up in nice families.
• pH: -log[H+]
• phase diagram: A chart which shows how the phase depends on various conditions of temperature and pressure.
• phase: The state of a compound (solid, liquid, or gas)
• physical property: A property which can be determined without changing something chemically. If that doesn't make sense, see the definition of "chemical change".
• pi-bond: A double bond.
• polar covalent bond: A covalent bond where one atom tries to grab the electrons from the other one. This occurs because the electronegativities of the two atoms aren't the same.
• polyatomic: contains more than one atom.
• polymer: A molecule containing many repeating units. Plastics are polymers and are formed by free radical chain reactions.
• polyprotic acid: An acid that can give up more than one hydronium ion. Examples are sulfuric acid and phosphoric acid.
• potential energy: The energy something has because of where it is. Things that are way up high have more potential energy than things that are way down low because they have farther to fall.
• precision: A measurement of how repeatable a measurement is. The more significant figures, the more precise the measurement.
• pressure: Force/area
• product: The thing you make in a chemical reaction.
• quantum theory: The branch of physical chemistry that describes how energy can only exist at certain levels and makes generalizations about how atoms behave from this assumption.
• radioactive: When a substance has an unstable nucleus that can fall apart, it's referred to as radioactive.
• Raoult's Law: The vapor pressure of a solution is directly proportional to the mole fraction of the solvent.
• rate determining step: The slowest step in a chemical reaction.
• rate law: A mathematical expression for the speed of a reaction as a function of concentration. A hint: It's usually true that things go faster if you have more stuff in the first place.
• redox reaction: A reaction that has both an oxidation and reduction.
• resonance structure: When more than one valid Lewis structure can be drawn for a molecule, these structures are said to be resonance structures. Resonance structures arise from the fact that the electrons are delocalized.
• reversible reaction: A reaction in which the products can make reagents, as well as the reagents making products.
• root mean square velocity (RMS velocity): The square root of the average of the squares of the individual velocities of the gas particles in a mixture. To put it in a way that a normal human can understand, it's the average of how fast the particles in a gas are going (assuming you ignore the direction they're traveling in).
• salt: An ionic compound.
• saturated: When the maximum amount of solute is dissolved in a liquid
• Second law of thermodynamics: Whenever you do something, the universe gets more random.
• semiconductor: A substance that conducts electricity poorly at room temperature, but has increasing conductivity at higher temperatures. Metalloids are usually good semiconductors.
• shielding effect: The outer electrons aren't pulled very tightly by the nucleus because the inner electrons repel them. This repulsion is called the shielding effect, and can be used to explain lots of neat-o stuff.
• sigma bond: A real fancy way of saying "single bond"
• significant figure: The number of digits in a number that tell you useful information. For example, when you weigh yourself on a bathroom scale, it says something like 150 pounds rather than 150.32843737 pounds. Why? Because the thing can only weigh accurately to the nearest pound. Any other digits that are on this number don't mean anything, because they're probably wrong anyway.
• single-displacement reaction (a.k.a. single replacement reaction): When one unbonded element replaces an element in a chemical compound. These are frequently redox reactions.
• solubility: A measurement of how much of a solute can dissolve in a liquid.
• solubility product constant: Abbreviated K_sp, this value indicates the degree to which a compound dissociates in water. The higher the solubility product constant, the more soluble the compound.
• solute: The solid that gets dissolved in a solution.
• solvent: The liquid that dissolves the solid in a solution.
• specific heat capacity: The amount of heat required to increase the temperature of one gram of a substance by one degree.
• spectator ions: The ions in a reaction that don't react.
• spontaneous change: A change that occurs by itself. All exothermic reactions are spontaneous. However, this doesn't mean that all exothermic reactions are fast. The combustion of gasoline is spontaneous, but not very fast unless you add a little energy.
• standard temperature and pressure: One atmosphere and 273 K.
• steric hindrance: This is the idea that the functional groups on big molecules get in the way of a chemical reaction, making it go slower. Imagine a fat guy trying to get into a Honda Prelude - that's steric hindrance.
• stoichiometry: The art of figuring how much stuff you'll make in a chemical reaction from the amount of each reagent you start with.
• STP: See standard temperature and pressure.
• strong acid: An acid that fully dissociates in water
• strong nuclear force: The force that holds the nucleus together. As the name suggests, this force is strong.
• structural formula: See Lewis structure.
• sublimation: When a solid can change directly into a gas. Dry ice does this.
• supercooling: When you cool something below its normal freezing point
• supersaturated: When more solute is dissolved in a liquid than is theoretically possible. This doesn't happen much, as you might imagine.
• surface tension: A measurement of how much the molecules on a liquid tend to like to stick to each other. If something has a high surface tension, it likes to bead up.
• suspension: A mixture that looks homogeneous when you stir it, but where the solids settle out when you stop. Mud is a very short-lived suspension, while peanut butter is a very long-lived suspension.
• synthesis: When you make a big molecule from two or more smaller ones.
• system: Everything you're talking about at the moment.
• temperature: A measurement of the average kinetic energy of the particles in a system.
• theoretical yield: The amount of product which should be made in a chemical reaction if everything goes perfectly.
• thermodynamics: The study of energy
• Third law o' thermodynamics: The randomness of a system at 0 K is zero.
• titration: When the concentration of an acid or base is determined by neutralizing it.
• transition state: See "activated complex"
• triple point: The temperature and pressure at which all three states of a substance can exist in equilibrium.
• unit cell: The simplest part of a crystal that can be repeated over and over to make the whole thing.
• unsaturated: When you haven't yet dissolved all of the solute that's possible to dissolve in a liquid.
• unshared electron pair: two electrons that aren't involved in chemical bonding. Also frequently referred to as a "lone pair".
• valence electron: The outermost electrons in an atom.
• vapor pressure: The pressure of a substance that's present above it's liquid. For example, you can tell that ammonia has a high vapor pressure because the smell of it is very strong above liquid ammonia.
• vaporization: When you boil a liquid.
• volatile: A substance with a high vapor pressure.
• VSEPR: A theory for predicting molecular shapes that assumes that electrons like to be as far from each other as possible. For advanced vocabulary click here.

Analytical Chemistry : a brief introduction

Analytical chemistry; a very important part of the chemistry in the modern world is a study of determination of composition either qualitatively or quantitatively of the materials either that is artificial or natural. In modern time,some people considered it as a bone of 'Instrumental Analysis'; a very similar term.Analytical chemistry has its very practical application.Like biomedical applications,quality control of industrial manufacturing ,environmental monitoring,and especially forensic science.
Methods of Detecting analytes
1. physical means
* mass * color * refractive index * thermal conductivity
2. with electromagnetic radiation (Spectroscopy)
* absorption * emission * scattering
3. by an electric charge
* electrochemistry * mass spectrometry

CONTD.

How to be more smart and intelligent :Important tips

Do you ever feel dumb around other people? Are you embarrassed when you don’t know the answer to a teacher’s question? Everybody has times when they just feel like they don’t know anything. Of course, you can’t know everything, but no matter how smart you are, you can start to become more intelligent today.here is some Gautamblog tips:
Steps:
# Improve your memory. Much of what is generally considered intelligence is simply the ability to remember things well. You can improve your ability to retain and recall memories in a variety of ways, including by using mnemonics and by paying more attention to details.


# Study more effectively. If you find yourself at a loss when your teacher puts you on the spot, or if you perform poorly on exams, you may not be studying enough. Even if you study a lot, improving your study skills can make a big difference. A variety of Gautamblog tips to help you.
# Read a lot. Just about everything that humans know can be found in print, whether in books and magazines or on the internet. Become a voracious reader, and you’ll expose yourself to more ideas and information. If you’re a slow reader, consider learning speed reading. Consider jotting down notes, and perhaps looking up a word or two in the dictionary.
# Visit the library frequently and pick up anything which looks interesting to you. The subject matter is not quite as important as is the act of reading. Always have at hand something good to read.
# Be more curious. How do some people get to know so much? Good memory skills are only part of the answer: you also have to be curious. If you’re satisfied going through life with little or no understanding of things you’re unfamiliar with, you won’t learn much. Make a conscious effort to be more curious by reminding yourself that developing your curiosity will broaden your horizons and help to make you more intelligent.
# Research. Curiosity without initiative is like having a car that’s out of gas — it won’t take you anywhere. Fortunately, when it comes to knowledge you’re never far from a gas station. If you read a word that you don’t know, look it up in the dictionary. If you wonder how airplanes fly, read a book. If you want to know more about politics, pick up a newspaper. With internet access now widespread, there’s less excuse for not finding something out that you want to know.
# Learn how to look things up. If you know how to use references, from an internet search engine to an encyclopedia, you’ll be able to find the information you want more quickly and effectively. Effective researching skills will nourish your curiosity because you’ll become more confident in your ability to access knowledge. If your research skills leave something to be desired, take a class or workshop on how to research, ask a librarian or teacher, or simply practice researching. Or just press the "help" tabs on the internet and computer programs and read.
8. Figure things out on your own. There’s a lot more to intelligence than “book smarts.” We can all learn to perform everyday tasks at work, home, and school better and more intelligently. If you don’t know how to do something, resist the urge to ask somebody else to do it for you or show you how. In most cases, you’ll be able to figure it out on your own, either by trial-and-error or by researching. While it usually takes longer to figure something out than it does to ask about it, you’ll learn more about the overall process, and you’ll remember it better. Most importantly, you’ll exercise your problem-solving skills instead of your “do as you’re told” skills.
9. Ask for help. It’s great to figure things out on your own, but sometimes you don’t have enough time to do so, despite your best efforts. Don’t give up; ask somebody to show you how. Make sure to pay close attention and ask any questions that you have, so that you’ll never have to ask the same thing again.
10. Exercise your mind in different ways. Most of us are good at the things we excel in naturally or the activities we do everyday. Challenge yourself to learn a new skill or to think in a different way, however, and you’ll actually become more intelligent. Choose something you’d like to learn to do (play the accordion, for example) or a subject you don’t do well in (maybe math) and focus on that thing. Initially, you may be uncomfortable and feel even less intelligent than you did before, but if you study or practice diligently, you’ll become more confident, and you’ll make new connections in your mind.
11. Teach others. In order to teach something to somebody else, you’ve got to know it pretty well. When you try to explain an idea or skill to somebody else, you’ll not only remember it better yourself, you’ll also find that the other person’s questions will help you find out how well you really know what you’re talking about.
12. Learn a new word each day. Go through the dictionary and find a word that you don't know already, then practice using it throughout the day.
13. Do your homework if you're in school! Don't procrastinate, finish it last minute, or copy someone's paper. The homework is there for practice, and when you do it, you'll become more confident in that subject. But remember, homework time is not the same as study time, so you can't count homework as studying.

Tips
* Don't limit yourself to what your teachers give you. If you already know everything on your grade level, don't stop studying. Try high school work, then college level — always challenge yourself.
* Don't limit yourself to "smart subjects"; learn about whatever interests you, as this will usually lead to an interest in "smart" subjects. You don't have to start with nuclear physics to be smart.
* Besides looking to learn, always look for new ways to learn. If you aren't big on reading, try watching people, or talking to people, and even the TV - there are many many educational channels available.
* Don't learn simply to learn, it will not work. Find a way to be interested in it, make it fun and you will learn faster, and remember more.
* Always remember that you can’t know everything. Why would you want to, anyway? Being good at one or two things can be more valuable than being considered brilliant.
* Some psychologists now say there are multiple types of intelligence, such as interpersonal intelligence (how to interact and get along with people) and bodily intelligence (coordination, athleticism). Don’t neglect to nurture these aspects of yourself. Even if they don’t make you “smarter,” they can help you lead a happier, more well-rounded life.
* Get enough sleep. Some researchers say, while you sleep, your brain makes new connections. For example if you don't understand how to perform a math equation completely and you 'sleep on it', there is a chance that your brain will have figured it out while you slept.
* Learn a new language because that can open doors to other sources of knowledge. If you can speak to a Chinese Scientist, who does not speak English, you may learn something easier.

can i get iphone for free ?

iphone is one of the most powerful technology used device in modern world. I wish i could get one. Because of the long time contract and expensive monthly payment ;every people can not afford that. But latest news that i got in the various website; can give hope to get one.AT&T may be getting ready to offer the iPhone 3G at a very expensive yet no-commitment price.BoyGeniusReport.com has a report out Wednesday that AT&T plans to offer iPhone 3Gs at $599 or $699 without requiring the customer to sign a new two-year agreement, starting next week.
When the iPhone 3G launched last year, AT&T said it would offer such an option, but never pulled the trigger.
An AT&T representative declined to comment on the report.
The move would seem designed to rid AT&T of iPhone inventory ahead of the launch of a new product later this summer, as most of us are expecting.

Apple didn't allude to any new hardware during its iPhone 3.0 event on Tuesday, but there have been a few signs, and the company has noted that iPhone releases seem to be falling into a yearly schedule around June or July.

iPhones sales soared after Apple and AT&T cut the starting price to $199 last year, but there are definitely some people who would like an iPhone free from AT&T and a two-year commitment to paying a monthly wireless bill, even if it costs them more up front.

Would you buy a $599 8GB iPhone if it meant you didn't have to sign a two-year contract?

Laser Gun : can kill the mosquitoes

Scientists in the U.S. are developing a laser gun that could kill millions of mosquitoes in minutes.The laser, which has been dubbed a "weapon of mosquito destruction" fires at mosquitoes once it detects the audio frequency created by the beating of its wings.

The laser beam then destroys the mosquito, burning it on the spot.Click here for more

Developed by some of the astrophysicists involved in what was known as the "Star Wars" anti-missile programs during the Cold War, the project is meant to prevent the spread of malaria.

Lead scientist on the project, Dr. Jordin Kare, told CNN that the laser would be able to sweep an area and "toast millions of mosquitoes in a few minutes."

Malaria is a life-threatening disease caused by parasites that are transmitted to people from the bites of female mosquitoes.t is particularly prevalent in tropical and sub-tropical regions of the world and kills an African child every 30 seconds, according to the World Health Organization.

There are an estimated 300 million acute cases of malaria each year globally, resulting in more than one million deaths, the WHO reports.

Responding to questions about any potential harm the laser could pose to the eco-system, Kare said: "There is no such thing as a good mosquito, there's nothing that feeds exclusively on them. No one would miss mosquitoes," he said.

"In any case," he added. "The laser is able to distinguish between mosquitoes that go after people and those that aren't dangerous."

He added that other insects would not be affected by the laser's beam.

The research was commissioned by Intellectual Ventures, a Washington, U.S.-based company that was founded by Nathan Myhrvold, a former Microsoft Corporation executive.

His previous boss, Bill Gates, who funded the research, asked Myhrvold to look into new ways of combating malaria.source:CNN

laser

A laser is a source of light that emits the light ;a electromagnetic radiation through a process called stimulated emission. Lasers are highly useful sources in analytical instrumentation because of their high intensities, their narrow bandwidths, and the coherent nature of their outputs. The first laser was described in 1960. Since that thime chemists have found numerous useful application for these sources in high resolution spectroscopy .READ MORE
The word laser originated as an acronym for light amplification by stimulated emission of radiation. The word light in this phrase is used in the broader sense, referring to electromagnetic radiation of any frequency, not just that in the visible spectrum. Hence there are infrared lasers, ultraviolet lasers, X-ray lasers, etc. Because the microwave equivalent of the laser, the maser, was developed first, devices that emit microwave and radio frequencies are usually called masers. In early literature, particularly from researchers at Bell Telephone Laboratories, the laser was often called the optical maser. This usage has since become uncommon, and as of 1998 even Bell Labs uses the term laser.
The back-formed verb to lase means "to produce laser light" or "to apply laser light to". The word "laser" is sometimes used to describe other non-light technologies. For example, a source of atoms in a coherent state is called an "atom laser".
Chemical lasers

Chemical lasers are powered by a chemical reaction, and can achieve high powers in continuous operation. For example, in the Hydrogen fluoride laser (2700-2900 nm) and the Deuterium fluoride laser (3800 nm) the reaction is the combination of hydrogen or deuterium gas with combustion products of ethylene in nitrogen trifluoride. They were invented by George C. Pimentel.

Hollow-Cathode Lamp

The one of the most common source for atomic absorption measurements is the hollow cathode lamp. Usually these kind of lamps consists of a tungsten anode and a cylindrical cathode sealed in a glass tube filled with neon or argon at the pressure of 1 to 5 torr. The cathode is constructed of the metal whose spectrum is desired or serves to support a layer of that metal .
Ionization occurs when a potential difference on the order of 300V is applied across the electrodes. The efficiency of the hollow cathode lamp depends on its geometry and the operating voltage. High voltages,and thus high currents, leads to greater intensities . READ MORE

This advantage is offset somewhat by an increase in Doppler broadening of the emission lines from the lamp. Hollow-cathode lamps are often used as source in AFS. In this application the lamps are pulsed with a duty cycle of 1% to 10% and peak current of 0.1 to 1 A, which increase their peak radiance by a factor of 10 to 100 relative to the steady state radiance of DC operation . A variety of hollow cathode lamps is available commercially . The cathodes of some consists of a mixture of several metals ;such lamps permit the determination fo more than a single element.see more in wikipedia

X-ray Spectrometry

What is X-ray?
X-rays are short-wavelength electromagnetic radiation by the deceleration of high-energy electrons or by electronic transitions of electrons in the inner orbitals or atoms.The wavelength range of X-rays is from about 10e-5A to 100A;conventional X-ray spectroscopy is,however ,highly confined to the region of about 0.1A to 25A (1A=0.1nm=10e-10).
Emission of X-rays
For analytical purposes,X-rays are generated in four ways. 1.by bombardment of a metal target with a beam of high energy electrons ,2) by exposure of a substance to a primary beam of X-rays to generate a secondary beam of X-ray fluorescence,3)by use of a radioactive source whose decay process results in X-ray emissions,and 4)from a synchrotron radiation source. Only limited laboratory in US allows to produce X rays from synchrotron radiation.Contd.
Type rest of the post here

How To Send SMS without any Cost?

Have you ever thought that sending the SMS without any cost? Do you really think it is possible ?

Yes ! you can send the SMS to your friend without paying any money to corresponding phone company in United States. Just open your web browser , sign in your any email and you need to type the receiver cell no. followed by the email address of corresponding mobile company service providers.This is only for mobile companies with in the United States. CLICK HERE FOR MORE

T-Mobile: phonenumber@tmomail.net
Virgin Mobile: phonenumber@vmobl.com
Cingular: phonenumber@cingularme.com
Sprint: phonenumber@messaging.sprintpcs.com
Verizon: phonenumber@vtext.com
Nextel: phonenumber@messaging.nextel.com

Where phonenumber corresponds to the receiver cell number.

OK Have fun by sending the SMS to your friends,loved one without paying any money.

Einstein Brain : What is the difference?

“People like you and I, though mortal of course like everyone else, do not grow old no matter how long we live…[We] never cease to stand like curious children before the great mystery into which we were born.”

Albert Einstein

One sign of the lack of faith in the future progress of technology and the poor acceptance of the neurological basis for mind is the way in which our society treats the “post-mortem” human brain.

In some cases, the brains of those whom modern medicine cannot help are removed after cardiopulmonary arrest and donated (by the permission of the patient or the family) CLICK HERE TO READ MORE fo

for research. In such cases, the brains are preserved so they can be studied over a long period of time. They are also sectioned and prepared in other ways for examination. Such donated brains have helped scientists learn about the human brain, with an eye to improving methods for treating conditions such as Alzheimer’s or mental illness. However, other brains have been preserved mainly because they belonged to famous people.

One of the more famous cases is the brain of Albert Einstein, removed in 1955 and preserved apparently without his or his family’s permission, and then made available for study. According to an NPR report, Einstein’s brain was fixed, sectioned into over 200 blocks, embedded in celloidin, and then stored in formalin.

Since that time, Einstein’s brain has been further sectioned and divided among researchers. A 1985 study by Diamond et al. reported that the Einstein brain sections’ neurons were still observable, and the study’s authors even assumed the number of neurons preserved in Einstein’s brain would be the same as those in recent preserved brains.

Presumably, people have wanted to study the brains of famous people in order to learn something about what made those people special. Turning a person into a mere object of study is a questionable notion, though, and the idea that the study could yield any information about the person’s mind underscores how it is widely accepted by scientists that the brain instantiates the mind, and thus the person.

Neuroscience is still too much in its infancy to make much sense of the evidence of the brain, as the scientific reception to the Diamond study showed. We do not yet know how to “read” the brain for the specific memories and personality traits and other phenomena of mind stored in it. However, because we do know enough now to know that the mind arises from the brain, we must realize that to preserve the brain is to preserve the potential of mind, and to preserve the potential of mind is to preserve the possibility of life for the person whose brain it was.

The neural basis of personhood sits ill with older notions such as immaterial souls or spirits. The neural basis of personhood also fits poorly with existing medical and public policies such as commonly accepted definitions of death and laws related to end of life. If death is understood as irreversible damage to certain identity-critical areas of the brain, the irreversibility of such damage is put into question by every advance in the treatment of injury and disease of the brain, as well as by the brain’s mysterious ability to recover from conditions such as minimally conscious state after many years. The cardiopulmonary-arrest definition of death does not involve the condition of the brain, and the usual definitions of brain-death do not distinguish between identity-critical areas or aspects of the brain and other areas or aspects of the brain. A more rigorous definition of personal death has been developed by Ralph Merkle, who states:

“A person is dead according to the information-theoretic criterion if their memories, personality, hopes, dreams, etc. have been destroyed in the information-theoretic sense. That is, if the structures in the brain that encode memory and personality have been so disrupted that it is no longer possible in principle to restore them to an appropriate functional state then the person is dead. If the structures that encode memory and personality are sufficiently intact that inference of the memory and personality are feasible in principle, and therefore restoration to an appropriate functional state is likewise feasible in principle, then the person is not dead.”

Although there is still some lack of clarity about the “etc.” and “appropriate functional state”, this definition of death at least is founded on the neural basis of personhood. Those who believe in the future progress of technology and accept the neural basis of personhood are led inevitably to understand that preserving the brain is preserving the person, potentially for later resuscitation.

It is not impossible to imagine that, in a more advanced future time, the formalin-fixed, celloidin-embedded brain sections could be reassambled, and if the synaptic circuitry of the neurons were well preserved, any significant damage could be repaired. The brain might be able to be returned to a viable state by reversal of the fixation and removal of the celloidin embedding. Resuscitation of an isolated brain would be unacceptable, but eventually it might be possible to restore the rest of the body around the brain by cloning or regeneration of the cells or some other prosthetic embodiment.

As amazing as it may seem, a patient reduced to a preserved brain, whose mind would be in a stopped state, might be able to be healed, that is, totally restored to a healthy body and a mind which could resume the life it left off, with all the memories and personality intact.

The case of Albert Einstein’s brain is unfortunate. All the impudent cutting, handing around, and tampering with Einstein’s brains sections, and the crude preservation method, may have irreversibly damaged the neural basis of his personhood. Yet we do not know enough today about the brain to know how much of it needs to be preserved, and in what state, to be able to revive a person with future technology. The preservation of the brain, though, would provide a theoretical possibility of future resuscitation. It may not be possible to someday restore Albert Einstein from the remains of his brain, but if it were possible, those in possession of the brain sections would first have to be willing to consider whether their “specimens” might be the restorable fragments of a still potentially living person who deserves to live more than to be studied.

Bisphenol A (BPA) : what is it? Q and A

Bisphenol A, commonly abbreviated as BPA, is an organic compound with two phenol functional groups. It is a difunctional building block of several important plastics and plastic additives. With an annual production of 2–3 million metric tonnes, it is an importantmonomer in the production of polycarbonate.

Suspected of being hazardous to humans since the 1930s, concerns about the use of bisphenol A in consumer products grabbed headlines in 2008 when several governments issued reports questioning its safety, and some retailers pulled products made from it off their shelves.Click here for more...

What is BPA?

Bisphenol A (BPA) is an industrial chemical used to make polycarbonate plastic resins, epoxy resins, and other products.

How is BPA used?

Bisphenol A (BPA) is a chemical building block that is used primarily to make polycarbonate plastic and epoxy resins. Polycarbonate plastic is a lightweight, high-performance plastic that possesses a unique balance of toughness, optical clarity, high heat resistance, and excellent electrical resistance. Because of these attributes, polycarbonate is used in a wide variety of common products including digital media (e.g., CDs, DVDs), electrical and electronic equipment, automobiles, sports safety equipment, reusable food anddrink containers , and many other products.

BPA is also used in the production of epoxy resins. Epoxy resins have many uses including engineering applications such as electrical laminates for printed circuit boards, composites, paints and adhesives, as well as in a variety of protective coatings. Cured epoxy resins are inert materials used as protective liners in metal cans to maintain the quality of canned foods and beverages, and have achieved wide acceptance for use as protective coatings because of their exceptional combination of toughness, adhesion, formability, and chemical resistance.

How much BPA is produced?

In 2002, approximately 2.8 million tons of bisphenol A (BPA) was produced globally (Source: Chemical Market Associates, Inc. (CMAI)). Most BPA is used to make polycarbonate plastic and epoxy resins.

Has BPA been tested for safety?

Yes. Bisphenol A (BPA) is one of the most extensively tested materials in use today. BPA has been safely used in consumer products and researched and studied for over 40 years. The weight of scientific evidence clearly supports the safety of BPA and provides strong reassurance that there is no basis for human health concerns from exposure to BPA.

Does BPA pose a risk to human health?

Safety assessments of bisphenol A (BPA) conclude that the potential human exposure to BPA from polycarbonate plastics and epoxy resins is more than 400 times lower than the safe level of BPA set by the U.S. Environmental Protection Agency. This minimal level of exposure to BPA poses no known risk to human health.

The use of polycarbonate plastic and epoxy resins for food contact applications has been and continues to be recognized as safe by the U.S. Food and Drug Administration, the European Commission's Scientific Committee on Food, the United Kingdom Food Standards Agency, and otherregulatory agencies worldwide.

Am I exposed to BPA from polycarbonate plastics?

Researchers from government agencies, academia, and industry worldwide have studied the potential for bisphenol A (BPA) to migrate from polycarbonate products into foods and beverages. These studies consistently show that the potential migration of BPA into food is extremely low, generally less than 5 parts per billion under conditions typical for uses of polycarbonate products. At this level, a consumer would have to ingest more than 1,300 pounds of food and beverages in contact with polycarbonate every day for an entire lifetime to exceed the safe level of BPA set by the U.S. Environmental Protection Agency. Consequently, human exposure to BPA from polycarbonate plastics is minimal and poses no known health risk.

The use of polycarbonate plastic for food contact applications continues to be recognized as safe by the U.S. Food and Drug Administration, the European Commission Scientific Committee on Food, the United Kingdom Food Standards Agency, the Japan Ministry for Health and Welfare and other regulatory authorities worldwide.

Am I exposed to BPA from can linings?

Government and industry researchers have reported that bisphenol A (BPA) is generally not detected in canned beverages and only extremely low levels (generally less than 37 parts per billion) of BPA have been reported to migrate into some canned foods. At these levels, a consumer would have to ingest more than 500 pounds of canned food and beverages every day for an entire lifetime to exceed the safe level of BPA set by the U.S. Environmental Protection Agency. Consequently, human exposure to BPA from can coatings is minimal and poses no known health risk.

Can coatings continue to be recognized as safe by the U.S. Food and Drug Administration, the U.K. Food Standards Agency, the EU Scientific Committee on Food and other government bodies worldwide.

Does BPA leach out of dental sealants?

Several studies have reported that trace levels of bisphenol A (BPA) may be released from certain dental sealants, but only during a short time period immediately after application of the sealant. In addition, the highest level of BPA exposure reported from dental sealants is more than 50,000 times lower than levels shown to cause toxicity in animal studies. Based on these findings, human exposure to BPA fromdental sealants is minimal and poses no known health risk.

What about claims that very low-dose exposure to BPA has resulted in reproductive effects in laboratory animals?

The low-dose hypothesis for bisphenol A (BPA) has been thoroughly tested with a series of comprehensive, carefully conducted studies. This research includes definitive large-scale studies as well as studies aimed at replicating the results of studies reporting low-dose effects. The consistent lack of low-dose effects found in these studies demonstrates that the low-dose hypothesis is not valid.

The weight of scientific evidence clearly supports the safety of BPA and provides strong reassurance that there is no basis for human health concerns from exposure to low doses of BPA.

Is BPA used in pesticides?

No. According to U.S. Environmental Protection Agency records, bisphenol A (BPA) has not been used as an inert ingredient in pesticide products in the U.S. since at least 1994. BPA's status as an (inert) pesticide ingredient was recently rescinded by EPA, according to the June 11, 1999 Federal Register. According to the notice, BPA was removed from a listing of approved inert substances because it was not in use as an additive.

Is BPA found in the environment?

Although the vast majority of bisphenol A (BPA) is converted at manufacturing sites into products, low-level releases of BPA to the environment are possible. Government researchers have reported that, when detected at all, BPA is found in water at levels generally well below 1 part per billion.

Extensive testing and environmental monitoring shows that BPA is rapidly biodegraded in the environment. The weight of scientific evidence shows that the trace amounts of BPA that are sometimes detected in waterways pose no risk to the environment.

Does BPA adversely impact aquatic organisms?

The weight of evidence from numerous validated studies demonstrates the trace levels of BPA that have been detected in the environment are far below the level at which adverse effects on aquatic organisms would be expected. Bisphenol A (BPA) does not accumulate in aquatic organisms to any appreciable extent and is not classified as bioaccumulative by the U.S. Environmental Protection Agency.

Is there an alternative to BPA in consumer products?

Bisphenol A (BPA) is used primarily to make polycarbonate plastic and epoxy resins, and is integral to the manufacture of both materials. Both polycarbonate and epoxy are unique and versatile materials that out-perform other materials in a broad range of end-uses providing consumers with a unique range of properties not available in other materials. Polycarbonate plastic is a lightweight, high-performance plastic that possesses a unique balance of toughness, optical clarity, high heat resistance, and excellent electrical resistance that make it ideal for a wide variety of applications. Epoxy resins are inert materials that have achieved wide acceptance for use as protective coatings and other applications because of their exceptional combination of toughness, adhesion, formability, and chemical resistance. Epoxy can coatings are essential to protecting food and beverages from contamination.

BPA is one of the most extensively tested materials in use today; its safety has been studied for more than 40 years. The extensive safety data that exist for BPA show that consumer products made with BPA are safe for their intended use and pose no known risks to human health. The U.S. FDA and international agencies charged to protect public health fully support the use of these materials.