Capillary electrophoresis (CE), especially in automated systems, offers many advantages over other conventional methods of electrophoresis, such as higher resolution, greater speed, and better accuracy; often with greatly reduced quantities of sample required for testing. Borate buffers provide a reliable ionic vehicle for the voltage mitigated flow of material through glass capillaries, known as electroosmotic flow (EOF). The movement of buffer (and materials to be separated) is presently monitored by measuring the electrical current produced in the outflow of the capillary when voltage is applied to the solution. The interest of this study was the investigation of borate buffers sodium tetraborate decahydrate (Na2B4O7●10H2O), sodium metaborate tetrahydrate (NaBO2●4H2O), and sodium perborate tetrahydrate (NaBO3●4H2O) in terms of their efficacy in sustaining current under the application of high voltage. A CE apparatus was assembled, utilizing a voltage controlled power supply and current monitoring multimeter. Serial dilutions, from 100 mM to 1 mM of the above buffers were created, and tested using glass microcapillaries of ~50 µm inner diameter. Voltages were applied incrementally from 500 V to 5000 V, and resulting current through each borate buffer dilution was measured in the µA range. The sodium tetraborate decahydrate (borax) buffer showed the highest average value for current produced throughout the range of concentration compared to both sodium metaborate and sodium perborate. The tetraborate was then examined with the addition of cationic and ionic surfactants. The results indicate the relationship between ion concentration and EOF velocity in terms of current; the greater number of ions present in solution provide the greater flow through the capillary. The capillaries maintained thermal integrity throughout the range of applied voltages. The determination of sodium tetraborate decahydrate as a comparatively effective borate buffer in CE analysis is useful in terms of optimizing CE applications. In order to study further the behavior of these borate buffers, flow in channels patterned in polydimethylsiloxane (PDMS) was also examined. This effort aims to initiate buffer optimization for PDMS devices, which should aid future EOF-driven separations in lab-on-a-chip applications.

Efficacy of borate buffers in sustaining electroosmotic flow in capillary electrophoresis

254th National Meeting (2017)

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