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Journal of Chromatography A, 736 (1996) 105-114

Determination of polar pesticides in ground water using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization
Niels Henrik Spliid*, Benny KOppen
National Environmental Research Institute, Department of Environmental Chemistry, Frederiksborgvej 399, DK-4000 Roskilde,Denmark

Received 4 July 1995; revised 14 December 1995; accepted 18 December 1995


A method is described for determination of pesticides in ground water by liquid chromatography combined with mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The study demonstrates the sensitivity of the technique, with detection limits for water samples of about0.001-0.005 /zg/l, corresponding to 50-300 pg injected. Performance data for the method such as recovery, precision and linearity are also reported. It is illustrated that the technique is applicable for many different types of pesticide structures, such as triazines, phenylurea herbicides, acetanilides, organophosphorus insecticides, etc. Twelve different pesticides and pesticide degradation products areincluded in the study. The optimization of inlet conditions with respect to sheath gas pressure, vaporizer temperature, capillary temperature and corona current is reported. Applicability of the method for analysis of "real-world" ground water samples is demonstrated.
Keywords: Environmental analysis; Water analysis; Pesticides

1. Introduction

For many years the use of pesticides inagriculture has given rise to concern about the unintended effects on the environment. During the last decade numerous reports on pesticides in ground water have received attention because of the implications for the supply of clean drinking water in the future. Especially in countries mainly relying on ground water for drinking water supply, these findings have caused much concern, e.g. in Denmark,where 99% of the drinking water supply is based on ground water and a consequence has been an increasing need for *Corresponding author.

monitoring ground water quality with respect to content of pesticides. Monitoring for pesticides requires analytical methodology capable of performing determinations at very low concentration levels. A limit of 0.1 /xg/l of individual pesticides in drinking wateris set by a European Union directive [1], which means that methods used for the monitoring of ground water preferably should exhibit detection limits about one tenth of the limit or lower, viz. 0.01 /xg/1 or less. Polar pesticides are those most likely to leach to ground water and are therefore the pesticides primarily to be included in a method applicable for ground water monitoring. A varietyof chromatographic methods have been used for determination of

0021-9673/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0021-9673(95)01360-1


N.H. Spliid, B, KOppen / J. Chromatogr. A 736 (1996) 10.5-114

the more polar pesticides. A review covering both GC and HPLC methods used for the determination of pesticides in water has been published recently [2]. However,since HPLC methods are more suited for polar compounds than are GC methods, which often require derivatisation prior to the analysis or can give problems with thermolabile compounds, HPLC has, in recent years, generally been the preferred method for analysing polar pesticides. HPLC methods are usually based on photometric detection (UV, fluorometric), but HPLC methods using mass spectrometric (MS)detection have also been described for the determination of pesticides in environmental waters [2]. L C - M S methods are especially attractive for their inherent high specificity. A review of the use of L C - M S techniques for polar pesticides has been published very recently by Slobodnik et al. [3], covering both the principles of ionization and applications of the most used L C - M S...