title: Electromigration injection from a small loop in capillary electrophoresis.
abstract: Capillary electrophoresis (CE) is now clearly the separation technique of the decade. One aspect that is still in need of improvement is concentration sensitivity, especially when CE is used in conjunction with on-column UV-visible absorptiometry, by far the most common practice. Electromigration injection (EI) is among the most prominent techniques in CE that serves to improve the attainable limits of detection; it is also the most convenient and simplest of all injection modes. Unfortunately, EI is affected both from sample to sample (the amount of an analyte introduced depends on sample conductance) and from analyte to analyte within a sample (the introduction is strongly biased on analyte electrical mobility). Previously we have shown the utility of small loops affixed at the tip of a capillary (Anal. Chem. 1995, 67, 3853-3860; 1996, 68, 1164-1168). The present paper shows that there are remarkable advantages to be gained from forming a film of the sample solution on a wire loop and using the loop itself as the high-voltage electrode to perform electromigration from a very small sample volume. The sample constituents can be essentially exhaustively electromigrated from this volume in less than 1 min, and the mobility induced bias is dramatically lowered. The observed experimental behavior agrees with theoretical models.
authors: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061.
authors: P K
authors: PK
authors: Dasgupta
authors: K
authors: K
authors: Surowiec