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A microfabricated fluidic device that combines micellar electrokinetic chromatography and high-speed open-channel electrophoresis on a single structure for the rapid automated two-dimensional analysis of peptides has been devised and demonstrated. The microchip operates by rapidly sampling and analyzing effluent in the second dimension from the first dimension. Second-dimension analyses are performed and completed every few seconds, with total analysis times of less than 10 min for tryptic peptides. The peak capacity of the two-dimensional separations has been estimated to be in the 500-1000 range. The orthogonality of the separation techniques, an important factor for maximizing peak capacity or resolution elements, was verified by examining each technique independently for peptide separations. The two-dimensional separation strategy was found to greatly increase the resolving power over that obtained for either dimension alone.

A new quadruple-potential waveform is introduced for detection of carbohydrates using pulsed amperometry. The new waveform cleans the electrode by application of a potential more negative than the potential limit. In contrast to a commonly used triple-potential waveform, negative cleaning allows the time during which gold oxide is formed to be minimized, thus minimizing the dissolution and resulting recession of the gold working electrode as a result of gold oxide formation/reduction cycles. Preventing gold electrode recession is shown to improve long-term reproducibility. Waveform parameters were chosen to maximize signal-to-noise ratio and freedom from electrode fouling caused by matrix components in the sample. Compared to the triple-potential waveform, the quadruple-potential waveform shows similar minimum detection limits but greatly improved long-term reproducibility.

This paper describes a new detection method that uses a six-potential waveform to detect all amino acids without derivatization. The detection limits are less than 1 pmol for most of the analytes. The anion-exchange separation uses a ternary gradient with water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. We present results of waveform optimization experiments designed to minimize gradient artifacts and to achieve optimum conditions for the quantitative analysis of common amino acids. Analytical results for protein hydrolysates are discussed and compared with those obtained by cation exchange followed by ninhydrin derivatization and spectrophotometric detection.

Capillary electrophoresis combined with suppressed conductivity detection is a highly sensitive and selective method for the determination of UVtransparent ionic species. Using direct injection techniques (no electrostacking), minimum detection limits for common organic and inorganic ions are in the rangeof 1-10 ppb. Suppressors are made from short ion-exchange membrane capillaries and are placed between the separation capillary and the detector cell. The suppressor is placed in the destination vial, which contains regenerant and the ground electrode. The method is dependent on the presence of electroendoosmotic flow in the capillary to transport analyte and buffer ions through the suppressor.