APPLYING THE SCIENCE 5.4 CE and XRF

Electiopherogram of the separaticai of 0.2 mg/mL Co and 14 mg/mL cyanocobalamin in deionized water. Buffer conditions 75 mM Tiizma run buffCT, pH 8.0. Separation conditicais 4-s hydrodynamic injectirai via suction at 1/2 ambient pressure (380 mbar) and 10-kV run potential. Spectral acquisition rate, 0.1 s  

CE can be operated in several modes. The approach described in the previous paragraph is referred to as capillary zone electrophoresis, or CZE. A variant called capillary gel electrophoresis uses a capillary tube filled with gel, essentially a miniaturized version of slab-gel techniques. The third variant, and the one of most forensic significance, is micellar electrokinetic chromatography (MEK or MECK). MEK is a modification designed to improve the separation of neutral spedes, which are easily separated from cations and anions, but not well separated among themselves. 

The detector module of a CE system is usually spectroscopic. Hence, its sensitivity is a function of path length, which introduces one of the fundamental problems of linking a flowing separation system to a detector designed for 

Because of its versatility, CE is making inroads into forensic laboratories. Instrumentation is also fairly inexpensive and easy to mamtain, a prerequisite for the wide adoption. Toxicology in particular has embraced CE for drugs and analytes, which can be acidic, basic, or neutral, and hydrophobic or hydrophilic. 

As sample enters the inlet, it is ionized through a complex series of reactions. The first step is ionization of N2 by Ni, a /3 emitter. Because the instrument runs at ambient pressures, there exists a reservoir of reactant ions of the form H(H20)n that surrenders protons to ions, depending on relative proton affinities. What enters the drift region is a complex mixture of and other clus- 

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