Analytica Chimica Acta 445 (2001) 29–34 Determination of triazine herbicides by capillary liquid chromatography with on-column focusing and temperature gradient M.E. León-González a,∗ , L.V. Pérez-Arribas a , L.M. Polo D´ ıez a , C. Panis b , M.P. San Andrés c a Departmento de Qu´ ımica Anal´ ıtica, Facultad de Ciencias Qu´ ımicas, Universidad Complutense, E-28040 Madrid, Spain b Engineer’s School CPE, 69616 Lyon, France c Departmento de Qu´ ımica Anal´ ıtica, Facultad de Ciencias, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain Received 20 March 2001; received in revised form 11 June 2001; accepted 29 June 2001 Abstract The combination of capillary liquid chromatography, temperature gradient and on-column focusing with large injection volumes offers a powerful tool for the determination of very low concentrations of triazines and their degradation products when very polar degradation products are present. A temperature gradient from subambient temperatures up to 70 ◦ C allows separation of eight triazines in 24 min. The focusing step makes it possible to increase 50 times the sample volume that can be injected into a capillary column. Detection limits (3 × noise) are improved by a factor between 50 and 125 to 9 ng l -1 for hydroxyatrazine and 45 ng l -1 for atrazine. The chromatographic method, combined with solid phase extraction, was applied to the determination of eight triazines in ground water. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Capillary liquid chromatography; Temperature programming; Column focusing; Triazine herbicides; Water 1. Introduction The extensive use of chlorotriazines as selective herbicides in agriculture and their relatively high per- sistence imply that these compounds could now be present in water, soil and food. In the European coun- tries, the maximum admissible amount of these in- dividual herbicides should not exceed 0.1 gl -1 in drinking water, and the alert or alarm threshold values should be 1 or 3 gl -1 , respectively, in surface water ∗ Corresponding author. Tel.: +34-913944331; fax: +34-913944329. E-mail address: leongon@eucmax.sim.ucm.es (M.E. Le´ on-Gonz´ alez). [1]. Triazines can also be altered by physical, chemi- cal and biological processes into one or more degra- dation products, some of which can be more toxic or persistent than the parent compound [2]. Hence, there is a need for analytical procedures for monitoring pes- ticides and their transformation products in environ- mental matrices. Triazines have been determined using a variety of techniques, including gas chromatography (GC) with selective detection [3–6], liquid chromatogra- phy (LC) [2,7–11] and a combination of these tech- niques with mass spectrometry (MS) [2,4,12–16]. Although GC allows triazines determination, when thermolabile components of the group, such as metho- protryn, or very polar metabolites are present, LC 0003-2670/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0003-2670(01)01243-0