Douglass McManigill

Effect of electric field on liquid chromatographic separation of peptide digests. Combining capillary separation techniques.

A system is described which allows operation of a range of capillary based liquid phase separations including capillary electrophoresis, isocratic and gradient capillary electrochromatography, isocratic and gradient capillary liquid chromatography and electrically assisted gradient capillary liquid chromatography. The system was coupled to electrospray ionization mass spectrometry in the electrically assisted capillary liquid chromatography mode to investigate the effect of applied voltage on the selectivity in peptide mapping separations. Analyses were performed on tryptic digests of recombinant human growth hormone and tissue plasminogen activator. The results show a small but useful effect on selectivity that can be used to fine tune specific separations.

Preparative capillary electrophoresis with wide-bore capillary

A wide-bore capillary electrophoresis apparatus for the analysis of analyte ions is provided. The apparatus has a wide-bore capillary that has a restriction zone at one or more ends. The capillary has an inlet end and an outlet end and an opening at each of said ends. The restriction zone is capable of providing fluid communication between the wide bore and the opening at said end. The restriction zone includes a narrow bore extending to the opening and a transition zone providing gradual change of bore diameter from the wide bore to the narrow bore. The apparatus further has a buffer source to supply buffer to the inlet end of the capillary and a power supply for supplying power to drive buffer and analyte ions through the capillary. During CE, electrodes provide electrical communication between the power supply and the inlet end and the outlet end and apply a voltage differential between said ends.

Dispersion in capillary electrophoresis with external flow control methods

Abstract Recently, methods for controlling the bulk flow of the buffer which are independent of the electrophoretic migration have been demonstrated in capillary electrophoresis (CE) systems. These methods include controlling the electroosmosis by radially directed electric fields, and controlling the bulk flow by siphoning. This paper investigates basic dispersion mechanisms at work by examining the dispersion of dimethyl sulfoxide under various external control methods. It is found that the electroosmotic flow control methods exhibit the same dispersive behavior as the conventional CE system. In particular, the results for pH 7 buffers obey the theoretical expression for the plate height in all configurations. However, in all configurations, pH 2.7 buffers do not follow the theory, and counter to intuition, additional pressure can improve the plate height at pH 2.7. Taking all these methods together, one can develop a technique to appropriately adjust the electrophoretic and bulk flow to optimize resolution.

Non-radioactive electron-capture detector

Abstract A non-radioactive electron-capture detector is described which uses a thermionic emitter as a source of electrons. The use of this source allows a unique mode of operation which has greatly enhanced sensitivity, yet at the same time allows a large dynamic range. A signal-to-noise ratio of 180 to 1 has been obtained at the 1-pg level, together with a dynamic range of six orders of magnitude. It appears that with this method it is possible to detect femtogram quantities.