Robert R. Holloway

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.

Noncrosslinked organosilicon matrix for luminescence-quenching-based fiber optic oxygen sensors

We have developed a silica-filled, noncrosslinked, organosilicon matrix for trapping a luminescent dye. The matrix is used for fiber optic oxygen sensing based on the luminescence quenching phenomenon. The rheological properties of the matrix material are such that it simplifies fabrication of the extremely small sensors required for intra-arterial applications. The dye seems to be distributed between sites in the continuous organosilicon phase and the dispersed silica phase. The relative populations in the two phases can be adjusted by certain additives which generate compounds that elute silica, such as acetic acid. The quenching constant of the system depends not only on the presence or absence of such eluants, but on the chemical nature of the additive as well. We were able to tailor the composition of matrix so as to optimize the sensitivity over the physiological range of oxygen concentration. Our observations on the composition dependence of the oxygen sensitivity of the matrix are presented.