Extraction of Residual Chlorinated Pesticides from Cotton Matrix

As a part of developing a certified testing method for residual pesticides analysis in cotton materials using gas chromatography (GC), the target pesticides listed in Oeko-tex standards should be isolated from a homogenized cotton matrix. The sample homogeneity and extraction procedures are the most effective steps in this analysis. Any error in this procedure must leads to incorrect results. Two extraction methods were used throughout this work with different solvents e.g. methanol, hexane, hexane/acetone (1:1 v/v) and dichloromethane. Extraction methods were soxhlet (SOX) and accelerated solvent extraction (ASE). The resulted extracts were concentrated then injected in a GC equipped with Electron Capture Detector (ECD). The qualitative results when compared with those of the NIST standard reference materials (SRM-2261) that certified by the National Institute of Standards and Technology USA, proved that the ASE and SOX techniques with dichloromethane as extracting solvent is more selective for all concerned pesticides for homogenized cotton samples. The ASE extraction with dichlormethane is better for hexachlorobenzene, gamma-HCH, heptachlor, Cis-chlordane, trans-nonchlor and SOX extraction technique with dichloromethane is better for Heptachlor epoxide, 4,4'-DDE, Dieldrin, 2,4'-DDD, 4,4'DDT and Mirex.