Journal of Chromatography A, 813 (1998) 379–386 Analysis of triazines by reversed electroosmotic flow capillary electrophoresis–electrospray mass spectrometry * Cheng-Yuan Tsai, Yet-Ran Chen, Guor-Rong Her Department of Chemistry, National Taiwan University, Taipei, Taiwan Received 5 January 1998; received in revised form 28 April 1998; accepted 28 April 1998 Abstract Normal and reversed electroosmotic flow (EOF) capillary electrophoresis (CE) has been studied for the analysis of eight triazine herbicides. Reversed EOF CE, dynamically modified with cetyltrimethylammonium bromide (CTAB), provided better separation than normal CE. All eight triazines were baseline resolved with the use of 50 mM ammonium acetate and 0.7 mM CTAB as the running buffer. The method of sheath liquid was used in the on-line coupling of CE with electrospray mass spectrometry. The composition of sheath liquid was found to be critical in the coupling of reversed EOF CE with MS. The resolution obtained in CE–UV can be preserved in CE–MS if the composition of the sheath liquid is similar to the running buffer.  1998 Elsevier Science B.V. All rights reserved. Keywords: Electroosmotic flow; Triazines; Pesticides 1. Introduction liquid chromatography (HPLC) [2,3], gas chroma- tography (GC) [4], ion chromatography (IC) [5], Triazine derivatives are among the most important thin-layer chromatography (TLC) [6], gas chroma- selective herbicides. Triazine herbicides are usually tography–mass spectrometry (GC–MS) [7–9], and applied as pre and post-emergent weed control to liquid chromatography–mass spectrometry (LC– improve the quality of agricultural products. These MS) [10,11] have been used for the analysis of herbicides are 1,3,5-triazine substituted at the 2, 4 triazines. Recently, mainly because of its superior and 6 positions. The substituent at the 2 position separation efficiency, several groups have explored gives each triazine its specific selectivity. The 4 and the potentials of capillary zone electrophoresis 6 positions are substituted with different aminoalkyl (CZE) [1,12] and micellar electrokinetic chromatog- groups. raphy (MEKC) [13–20] for analysis of triazines. Due to their wide use and relatively high resist- MS is compatible with capillary electrophoresis ance, knowledge of triazines in the environment, (CE) with respect to the sample amount and is one of both qualitatively and quantitatively, is of great the most powerful detection methods for identifica- importance to environmental and water control [1]. tion of separated analytes. Among the ionization Analytical techniques including high-performance techniques, electrospray ionization (ESI) is often considered the most suitable technique for on-line * coupling of CE with MS. MEKC often provides Corresponding author. Fax: 1886-2-23638058; e-mail: grher@mail.ch.ntu.edu.tw better resolution than CZE in the analysis of triazine 0021-9673 / 98 / $19.00  1998 Elsevier Science B.V. All rights reserved. PII: S0021-9673(98)00380-X