Determination of Residue Levels of DDT and Its Metabolites in Khat and Cabbage Samples using QuEChERS Sample Preparation Method Combined with GC-MS Detection

Abstract

A simple and selective quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction technique coupled with gas chromatography mass spectrometric detection (GC-MS) was developed and validated for simultaneous determination of 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (p,p'-DDT) and its main metabolite 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene(p,p'-DDE) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (p,p'-DDD) in cabbage and Khat samples. The linearity of the analytical response was acceptable with correlation coefficients of 0.992 or better. The precision associated with the analytical method, expressed as %RSD were lower than 8.6 and 9.1% for the intraday and interday precision, respectively.The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method for cabbage sample were in the range of 0.023–0.04 mg/kg and 0.09–0.14 mg/kg respectively. The LOD and LOQ of the proposed method for Khat sample were in the range of 0.02–0.06 mg/kg and 0.07–0.19 mg/kg respectively. The LOD and LOQ of the method were below the maximum residue level set by European Commission for the pesticides in both samples. The recoveries of the method were ranging from 97.16 to 107.99 for cabbage and 72.1 to 90.55 for Khat sample. The analytical applications of this method indicates the presence of p,p'-DDE, p,p'-DDD and p,p'-DDT in both cabbage and Khat samples.