Determination of nineteen pesticides residues (organophosphates, organochlorine, pyrethroids, carbamate, thiocarbamate and strobilurin) in coconut water by SDME/GC-MS

Coconut water is a natural isotonic drink and a rich source of sugars, salts, vitamins, minerals and amino acids, and can be served as a beverage to quench thirst. Palm trees are often attacked by insects and/or pests, therefore reducing their productivity. In order to enhance coconut production, pesticides are often used. Thus, the main objective of this study is to propose a simple and efficient method for the determination of pesticide residues, from different chemical classes, in samples of industrialized and natural coconut water, using single-drop microextraction (SDME), followed by gas chromatography coupled to mass spectrometry (GC-MS). The extraction step using SDME was optimized and it was found that the best experimental conditions for 10 mL of samples were obtained using toluene as an extraction solvent; stirring time of 30 min at 200 rpm; drop volume of 1.0 mu L; and acidification with HCl without salt addition. The chromatographic method was validated and good values were found for the figures of merit, with LOD ranging between 0.1 and 0.88 mu g L-1, and LOQ between 1.21 and 6.69 mu g L-1. The method was successfully applied to real samples of natural and industrialized coconut water, and the pesticides sulfotep, demeton-O, dimethoate, disulfoton, fenitrothion and malathion were determined at concentrations ranging from <LOQ to 12.1 mu g L-1. The proposed methodology presents high sensitivity and the capability for detecting and quantifying low levels of pesticides in coconut water samples. (C) 2013 Elsevier B.V. All rights reserved.