Page 135 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry
P. 135

P1: GLM/GJK  P2: GRB Final Pages  Qu: 00, 00, 00, 00
 Encyclopedia of Physical Science and Technology  En005H-218  June 15, 2001  20:33




















                                                                       Electrophoresis






              S. P. Spragg
              Birmingham University, England



               I. Underlying Theory
              II. Free-Solution Electrophoresis
              III. Electrophoresis in a Stationary Matrix
              IV. Electrophoresis in Oscillating Electric Fields








              GLOSSARY                                            F is the product of the particulate coefficient and Avo-
                                                                  gadro’s number (see Mole).
              Chemical potential Ability to do chemical work; analo-  Isoelectric point When organic ampholytes (also see
                gous to mechanical potentials.                    Polyampholyte) have two covalently linked basic and
              Conductance Inverse of electrical resistance of an ionic  acidic ionic groups, the isoelectric point equals the hy-
                solution. A specific conductance is defined as the in-  drogen ion concentration where the net charge is zero.
                                   3
                verse resistance of 1 M of solution under a potential  Isotachophoresis A procedure similar in many respects
                of1V.                                             to isoelectric focusing, since it separates macroions
              Coulomb Unit of electrical charge having dimensions of  through differences in charge rather than size (the
                ampere seconds. Bringing 1 mol of charges of mag-  important property for polyacrylamide gel electro-
                nitude ze (e = charge of an election, z = number of  phoresis).
                charges per particle) up to a potential V requires doing  Mobility Normalized velocity of a particle. In elec-
                work on the charge equal to zeVN (N = Avogadro’s  trophoresis the mobility is the velocity per volt × me-
                                                                       2
                                                                               −1
                number); here, eN is called the faraday (F), having  ter (m sec −1  V ); this is different from the mobility
                units of coulombs per mole.                       coefficients found in diffusion and sedimentation.
              Electrochemical equivalence Number of moles of an ion  Mole Chemical quantity used to describe a unit contain-
                required to carry1Fof charge.                     ing ∼6.03 × 10 23  molecules or ions; this constant is
              Electrodes Conducting units inserted in a solution; neg-  called either Avogadro’s or Lochschmidt’s number.
                ative electrode is called the cathode, and positive elec-  Polyampholyte Polymerized ampholyte in which some
                trode is called the anode. A reversible electrode is pro-  of the ionizable groups of the monomeric ampholyte
                duced by coating the metal with one of its salts, for  remain free after polymerization to form a macroion.
                example, silver/silver chloride.                  A protein is a common example and is formed by con-
              Frictional coefficients Generally, these are introduced in  densation of amino acids (called zwitterions) through
                hydrodynamics in order to ascribe a Newtonian friction  the terminal carboxyl group of one with the terminal
                to particles or molecules. A molar frictional coefficient  amino group of the next to form a peptide.




                                                                                                          363
   130   131   132   133   134   135   136   137   138   139   140