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suppress EOF. However, the conductivity of these buffers is relatively high, resulting in high current, excessive Joule heating, and the electrolysis of water causing bubble formation during the separation. These phenomena may lead to peak broadening, loss Table 1. Separation of Proteins by CE a mode b sample c capillary buffer detection d LOD ref CZE human immunoglobin G uncoated 15-100 mM H3PO4, 20 mM borate, various amounts of ACN, PEG, Triton-X, and SDS 3 CZE model proteins; Lys, Cyt, Chy, Try coated and uncaoted 40 mM acetate, pH 4.5 UV 4 CZE human serum; globulin isoforms, HAS, transferrin uncoated proprietary reagent set UV 5 CZE human serum; transferrin isoforms proprietary dynamic double coating unreported Tris/borate concn, pH 10 UV 6 CZE model proteins; RibA, BSA, ADH, Lys PB dynamic coating 2 mM PB 5mM Tris LIF amol 7

The adsorption of thiophene (C4H4S) on γ-Al2O3 has been investigated in ultrahigh vacuum (UHV) using infrared (IR) spectroscopy and temperature-programmed desorption (TPD). Following thiophene adsorption onto γ-Al2O3 at 130 K, TPD reveals two peaks with maximum rates of desorption at 175 and ∼220 K. The former peak is assigned to desorption of multilayer thiophene while the latter peak is assigned to desorption of weakly chemisorbed thiophene from the alumina surface. IR spectroscopy of adsorbed thiophene at submonolayer coverages provides further evidence that thiophene interacts only weakly with the alumina support; no decomposition of the thiophene overlayer is observed upon heating to 600 K under UHV conditions or a partial pressure of thiophene of 3.0 Torr. Three kinds of adsorbed thiophene species exist on the alumina surface at saturation coverage:  one in which thiophene interacts with hydroxyl groups, presumably via hydrogen bonding, a second in which thiophene is coordinated via its sulfur atom to coordinately unsaturated Al3+ sites on the surface, and a third species which is present only at high thiophene coverages. The heat of adsorption for thiophene on γ-Al2O3 has been determined under equilibrium conditions (P Th = 3.0 Torr) to be ΔH ads = −28.9 kJ/mol. A direct correlation has been established between the IR and TPD data, permitting integrated extinction coefficients to be determined for adsorbed thiophene in both the monolayer and multilayer coverage regimes. Extinction coefficients in the two coverage regimes are markedly different, underscoring the need to use care when interpreting the IR spectral intensities for adsorbed species. While, as expected, this study has shown that thiophene adsorbs only weakly on γ-Al2O3, more importantly it has shown that the combined IR−TPD methods can be used to determine both the thiophene coverage and the mode of bonding with the surface.

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In two-dimensional capillary electrophoresis, a sample undergoes separation in the first dimension capillary by sieving electrophoresis. Fractions are periodically transferred across an interface into a second dimension capillary, where components are further resolved by micellar electrokinetic capillary electrophoresis. Previous instruments employed one pair of capillaries to analyze a single sample. We now report a multiplexed system that allows separation of five samples in parallel. Samples are injected into five first-dimension capillaries, fractions are transferred across an interface to 5 second-dimension capillaries, and analyte is detected by laser-induced fluorescence in a five-capillary sheath-flow cuvette. The instrument produces detection limits of 940 +/- 350 yoctomoles for 3-(2-furoyl)quinoline-2-carboxaldehyde labeled trypsin inhibitor in one-dimensional separation; detection limits degrade by a factor of 3.8 for two-dimensional separations. Two-dimensional capillary electrophoresis expression fingerprints were obtained from homogenates prepared from a lung cancer (A549) cell line, on the basis of capillary sieving electrophoresis (CSE) and micellar electrophoresis capillary chromatography (MECC). An average of 131 spots is resolved with signal-to-noise greater than 10. A Gaussian surface was fit to a set of 20 spots in each electropherogram. The mean spot width, expressed as standard deviation of the Gaussian function, was 2.3 +/- 0.7 transfers in the CSE dimension and 0.46 +/- 0.25 s in the MECC dimension. The standard deviation in spot position was 1.8 +/- 1.2 transfers in the CSE dimension and 0.88 +/- 0.55 s in the MECC dimension. Spot capacity was 300.