Comparison of Frits Used in the Preparation of Packed Capillaries for Capillary Electrochromatography

The performance of several types of frits, including sintered frits, photopolymerized frits, and frits made by sol-gel technologies, is evaluated. The frits are formed in open capillaries, and the electroosmotic mobilities are calculated and compared to those obtained in an open capillary. Run-to-run, day-to-day, and column-to-column reproducibilities are evaluated. In all cases, the run-to-run reproducibility varied by <4%. The greatest mobility was through the capillaries with the sol-gel frits (1.29 × 10^-3 cm^2/V·s) which also exhibited the best day-to-day reproducibility. The capillaries with the photopolymerized frits had the best column-to-column reproducibility, yet the slowest mobility (1.00 × 10^-3 cm^2/V·s). The second central moment of benzene as a solute is calculated and plotted as a function of time to estimate the differences in peak dispersion among the various frits studied. Although the mobilities through the capillaries with the sintered frits were the least reproducible, these frits are associated with the least amount of band-broadening. An estimation of the dispersion caused by each of the different types of frits is reported.