Determination of organochlorine pesticides in cocoa beans and powders based on dispersive liquid–liquid microextraction using on organic and ionic solvents followed by gas chormatography- electron capture detector

Abstract

Absrtact Background: Nowadays, after food supply, food safety is one of the most important priorities of different countries. The presence of pesticides in food and agricultural products is a vital issues among scientists. Organochlorine pesticides are synthetic chlorinated pesticides that are widely used around the world. They are a major concern due to their widespread distribution, difficult biodegradation, long-term environmental stability, lethal poisons, and transmission from food to humans. Therefore organochlorine pesticides used has been banned or restricted in many countries.Hawever, there is illegally evidence of the continued use of these compounds in crops, especially cocoa trees. Cocoa is a valuable product and it is mainly exported to foreign markets. So, it must be free of any pesticides or the amount of pesticides in the permitted amount. Accordingly, residual pesticides of OCPs are measured by analytical methods, especially gas chromatography. However, due to the complexity of the matrix of cocoa samples and the low concentration of pesticides, direct analysis is not possible and pesticides must be extracted before measurement. So far, various methods for extracting pesticides have been developed, among which microextraction methods have been further developed. The aim of this study was to develop new preparation methods for the analysis of residual OCPs in cocoa powder and grain samples based on liquid-liquid micro-extraction. Potentially, the efficiency of these methods will be evaluated using a variety of organic and ionic solvents, and the compounds extracted by gas chromatography equipped with an electron abduction detector will be analyzed. Materials and Methods: In this study, new sample preparation methods based on liquid-liquid microextraction were developed and used to extract and pre-concentrate the studied pesticides from cocoa powders and beans samples. In these methods, the efficiency of different solvents including heavier (Chloroform) and lighter than water organic solvents (Decanol) and ionic liquids (N,N -diethanol ammonium chloride: pivalic acid) were assayed in the extraction of the analytes and the results were compared. Results & Conclusion: In order to achieve maximum efficiency, the proposed method was optimized by one parameter at a time. T-test was also used to evaluate the data. In the first part of this research work (liquid-extraction micro-extraction combined with homogeneous liquid-liquid extraction), under optimal extraction conditions, the detection limit values are in the range of 0.024 to 0.041 ng / g and the concentration factor is in the range of 50-89. Percentages were obtained. In the second part (liquid-extraction micro-extraction along with liquid-three-phase liquid extraction based on deep eutectic solvents), the detection limit values were in the range of 0.011-0.031 ng / g and the concentration factor was in the range of 74-92. In the third part (liquid-diffusion micro-extraction based on temperature-enhanced cooling concentration with centrifugation), the detection limit values were in the range of 0.05-0.027 ng / g and the concentration factor was in the range of 69-85. Which shows the high efficiency of the proposed methods. The three methods developed have several advantages including low detection and measurement limits, high concentration factor, good reproducibility, acceptable sensitivity and accuracy, high extraction efficiency, short extraction time, ease of operation and insignificant matrix effect, method simplicity and no need They show complex possibilities. These reports suggest that these methods have been effective in quantitatively analyzing OCPs in cocoa samples. The proposed methods can be used as a routine analytical method for the analysis of selected organochlorine pesticides in cocoa powder and grain samples. Analysis of the studied samples showed that in some samples there were residues of Aldrin and Diclobenyl pesticides in the amounts of ng / g. Keywords: Organochlorine pesticides, Cocoa, Liquid-dispersive microextraction, Gas chromatography, Electron abduction detector