Journal of Chromatography, 603 (1992) 175-184 Elsevier Science Publishers B.V.. Amsterdam CHROM. 23 993 Comparison of gas chromatographic-mass spectrometric methods for screening of chlorotriazine pesticides in soil* Gatl Durand Environmental Chemistry Department, CID-CSIC, c/Jordi Girona 18-26, 08034 Barcelona (Spain) Philippe Gille and Daniel Fraisse Service Central dilnalyse, CNRS, B.P. 22, 69290 Vernaison (France) Damik Barcel6 Environmental Chemistry Department, CID-CSIC, c/Jordi Girona 18-26, 08034 Barcelona (Spain) (First received September 18th, 1991; revised manuscript received January 3rd, 1992) ABSTRACT The performance of a coupled technique resulting from the combination of gas chromatography with a selective mass spectrometric technique (tandem mass spectrometry) (GC-MS-MS) with collisionally activated dissociation (CAD) and multi-reaction monitoring (MRM) was compared with that of GC-low resolution MS (GC-LRMS) at a resolving power of 1000 and GChigh-resolution MS (GC-HRMS) at resolving powers of 5000 and 10 000 for the determination of atrazine, simazine, cyanazine, deethylatrazine and deisopropylatrazine in polluted soil samples. GC-MS-MS daughter ion spectra for the parent ions [Ml+’ and [M - CH,]+ were generated using collisionally activated dissociation and studied. Also, by optimizing the collision energy for maximum sensitivity a method for screening chlorotriazines by MRM was developed. Analyses of soil sample extracts showed that GC-MS-MS overcomes interferences from other chlorotriazines and interfering compounds that could not be removed by GC-HRMS or GC-LRMS at resolving powers of 10 000 and 1000, respectively. The limits of detection for GC-MS-MS and GC-HRMS at a signal-to-noise ratio of 10 ranged between 1 and 24 pg, with a mean relative standard deviation of 25-30%. Soil samples known to contain chlorotriazines and their degradation products were analysed by GC-MS-MS and the results obtained were compared with those given by GC-HRMS at resolving powers of 5000 and 10 000, with quantification differences of 25530%. INTRODUCTION Chlorotriazines are broad-spectrum residual her- bicides used widely for pre-and post-emergency weed control in corn, wheat, barley and sorghum, and also on railways and roadside verges [ 11. Micro- Correspondence to: Dr. D. Barcelo, Environmental Chemistry Department, CIDCSIC, c/Jordi Girona 18-26,08034 Barcelo- na, Spain. * Presented at the 12th International Mass Spectrometry Con- ference, Amsterdam, August 26-30, 1991. bial degradation and volatility are two of the main degradation processes affecting their persistence in soil [2] and yielding dealkylated metabolites which have been detected in different types of soil [3,4]. These studies on the fate of chlorotriazine pesticides in the environment have prompted the need for sen- sitive, specific methods for their determination. The gas chromatographic-mass spectrometric (GC-MS) determination of chlorotriazine pesti- cides using a variety of ionization techniques has been approached in a number of ways. Applications reported so far include GC-MS with electron im- 0021-9673/92/$05.00 0 1992 Elsevier Science Publishers B.V. All rights reserved