Evaluation of endosulfan residues in vegetables grown in greenhouses † Francisco J Arrebola, 1 Francisco J Egea-Gonza´lez, 1 Mercedes Moreno, 1 Alberto Ferna´ndez-Gutie´rrez, 2 Maria E Herna´ndez-Torres 1 and Jose´ L Martı ´nez-Vidal 1 * 1 Department of Analytical Chemistry, University of Almerı´a, 04071 Almerı´a, Spain 2 Department of Analytical Chemistry, University of Granada, 18071 Granada, Spain Abstract: The reduction in residue levels of endosulfan with time after treatment of tomatoes, green beans, peppers and cucumbers grown in different types of commercial greenhouses ¯at- and asymmetric-roof greenhouses) in AlmerõÂa Spain) was investigated. A study of the major and minor degradation products of endosulfan in peppers and cucumbers endosulfan-sulfate, -ether and -lactone) was carried out using gas chromatography±tandem mass spectrometry GC±MS/MS). To establish the in¯uence of environmental conditions on the degradation of endosulfan, several ®eld trials have been carried out in which crops were sprayed at different rates full, half- and quarter- of those rates recommended) during two seasons spring and winter). For statistical purposes, the disappearance of endosulfan with time was considered to follow a pseudo-®rst-order reaction. Analysis of variance ANOVA) has been applied to the results obtained. Half-lives of residue disappearance were 4.03±4.68 days in green beans, 4.03±4.20 days in tomatoes, 8.22 days in peppers and 7.97 days in cucumbers. Half-lives in spring were shorter than in the winter season. The application rate and the type of greenhouse did not in¯uence the half-lives. # 2001 Society of Chemical Industry Keywords: endosulfan; diminution; metabolism; degradation; residues; tomatoes; green beans; peppers; cucumbers; greenhouses 1 INTRODUCTION Endosulfan 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a- hexahydro-6,9-methano-2,4,3-benzodioxathiepine 3- oxide) is a chlorinated sulfurous ester insecticide derived from bicyclo[2.2.1]hept-2-ene) used in many countries. It is a broad-spectrum non-systemic contact and stomach insecticide with vapour phase action at temperatures exceeding 20 °C which is effective for control of sucking, chewing and boring insects and mites on a very wide range of crops. 1 Technical grade endosulfan contains two stereo- isomers: a- and b-endosulfan a:b 70:30). Both a- and b-endosulfan are fairly resistant to photodegradation, 2 but the main dominant breakdown products endo- sulfan-sulfate and endosulfan-alcohol) are susceptible to photolysis. 3,4 In warm-blooded animals, endosulfan penetrates the intact skin and is also absorbed by inhalation and from the gastrointestinal tract. 5±8 It is metabolized and excreted in the urine and faeces as oxidation products such as the sulfate and the alcohol, and also endosulfan-lactone and endosulfan-ether resulting from the cleavage of the cyclic sul®te group. 9±11 The use of pesticides on fruits and vegetables is affected by its approved use pattern given in `Good Agricultural Practices' based on a knowledge of the rate of degradation of pesticide residues. The latter process depends, among other things, on climatologi- cal conditions, type of application, plant species, dose, the interval between application and harvest, and the type of greenhouse. In the past, endosulfan residues were commonly found by regulatory agencies in residue monitoring. 12 Almerõ Âa Spain) is an area where signi®cant amounts of pesticides are used. About one million metric tons of vegetables are produced annually in greenhouses. Endosulfan represents 5.3% of the total amount of pesticides applied and 10.7% of the insecticides. 13 It has been detected in most cases beneath the maxi- mum residue limits, MRLs) in 33.3% of 2105 vegetable samples pepper, cucumber, watermelon, baby marrow, green bean, tomato, melon and auber- gine) analyzed in our laboratory. All the analysis were carried out under quality conditions accredited by ENAC Spanish Institution of Accreditation) in the period 1997±1999. By July 2000, the MRL for endosulfan in different crops in the European Union will be reduced 14 from 1 (Received 12 February 2001; accepted 5 March 2001) * Correspondence to: Jose´ L Martı ´nez-Vidal, Department of Analytical Chemistry, University of Almerı ´a, 04071 Almerı ´a, Spain † This article is dedicated to Dr Antonio Arrebola Ramı ´rez of the University of Granada, in memoriam. Contract/grant sponsor: Comisio´n Interministerial de Ciencia y Tecnologı ´a (CICYT); contract/grant number: PB97-0789-C02-01 Contract/grant sponsor: Instituto Nacional de Investigacio´n y Tecnologı ´a Agraria y Alimentaria (INIA); contract/grant number: CALOO-064 # 2001 Society of Chemical Industry. Pest Manag Sci 1526±498X/2001/$30.00 645 Pest Management Science Pest Manag Sci 57:645±652 2001) DOI: 10.1002/ps.332