in the spectrum of lasalocid, which is assigned to ( -+ Na)Na+. With monensin spotted on a TLC plate, the sensitivity of detection was established as well below 0.1 µg.A major concern was the possible interference related to the components in the TLC adsorbent and the masking tape. However, no background interference was observed in the mass range of interest based on blank tests of both fluorescent and nonfluorescent TLC plates and direct tests of the masking tape. Also, contamination of the ion source by the TLC adsorbent, i.e., silica gel, was not observed. However, after the depletion of the FAB matrix liquid, the flake of adsorbent from plastic-backed TLC sheets appeared to remain intact while that from glass TLC plates tended to disintegrate. For this reason we favor the Use of plastic-backed TLC sheets.In conclusion, we have demonstrated a simple and rapid method for directly obtaining FAB spectra of TLC fractions which circumvents the problems associated with the previously cited methods. ACKNOWLEDGMENTWe wish to thank D. B. Borders and . T. Lee of Lederle Laboratories, American Cyanamid Company, for providing the coccidiostats and the TLC separation procedure.LITERATURE CITED(1) Deverse, F.

Fundamental characteristics of a new type of chromatography with micellar solutions of ionic surfactants were examined.Electrokinetic phenomena In open-tubular capillaries move two phases, aqueous and micellar, with different velocities and micellar solubilization operates as the distribution process of solutes. Sodium dodecyl sulfate (SOS) solutions and a 0.05 mm l.d. X 650 mm fused silica tube were employed and high dc voltages up to 25 kV were applied. Linear relationships were observed between current and migration velocities of water, micelle, and any solute, but not between applied voltages and the velocities. This discrepancy can be reasonably Interpreted In terms of the temperature rise of the solution In the tube resulting from Joule heating. Optimum resolutions can be obtained when the capacity factor Is about 2, because retention times are limited between those of an insolublllzed solute or water and a totally solubilized solute or micelle. Observed dependence of capacity factors on current can also be explained by the temperature rise. Thermodynamic parameters in micellar solubilization were presented.

When a neutral analyte zone is injected into a charged pseudostationary phase, the length of the zone is predicted to be narrowed by 1/(1 + k), where k is the retention factor. The conditions for zone narrowing to occur assume negligible electroosmotic flow, a relatively constant electric field along the capillary column, and no pseudostationary phase in the injected analyte mixture. The theoretically expected concentration enhancement was demonstrated experimentally. Consequently, the detection sensitivity of analytes in micellar electrokinetic chromatography (MEKC) can be improved significantly. For example, 9 to 18 parts per billion of an environmentally important racemic herbicide spiked in lake water was separated by MEKC and detected by ultraviolet absorption.

A novel method that combines two on-line concentration techniques in capillary electrophoresis (CE), namely, sample stacking with electrokinetic injection (field-enhanced sample injection, FESI) and sweeping, afforded the detection of positively chargeable analytes in parts per trillion (ppt) levels. The main idea is to selectively introduce by FESI as many molecules of cationic analytes as possible from a very dilute sample solution and focus the resulting zone by sweeping. Limit of detection values (signal-to-noise ratio 3) of 4.1 and 8.0 ppt-the lowest concentration reported by direct UV detection in CE-with average plate numbers of 3.6 x 10(5) and 4.4 x 10(5) are obtained for laudanosine and naphthylamine (standard solutions), respectively. This translates to improvements in peak heights compared with usual injection approaching a million-fold. Optimization schemes and application to quantitative and qualitative analyses are also investigated.

The sweeping phenomenon in electrokinetic chromatography under a considerably homogeneous electric field is theoretically examined and experimentally verified. The roles of analyte charge, retention factor, and electroosmotic flow are given consideration. Experimental studies are performed using micellar electrokinetic chromatography with sodium dodecyl sulfate as a micelle-forming agent. Uses and limitations of the new phenomenon are also critically conveyed.

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