Dual NPD/ECD detection in comprehensive two-dimensional gas chromatography for multiclass pesticide analysis

A comprehensive 2-D GC (GC x GC) dual detection system, coupled to nitrogen-phosphorus detection (NPD) and electron capture detection (ECD) has been developed for multiclass pesticide analysis in vegetable sample matrices. The second dimension column was connected to the parallel detectors via a microfluidic splitting device. The sample set comprised 17 organochlorine pesticides, 15 organophosphorus insecticides and 9 N-containing fungicides. Selective detection of vegetable sample extracts provides increased information content through simultaneous, correlated GC x GC plots for both ECD and NPD, which demonstrated improved separation of pesticide standards from each other, and from the sample matrix. The efficiency of NPD and ECD modes was investigated and compared; the ECD produced broader peaks, with the ECD generating greater response as measured by S/N ratio. Accuracy and precision of the approach were determined as repeatability and reproducibility for selected pesticides. The RSDs of the intraday (n = 5) and interday (3 days) analyses of the selected pesticides are less than 2.5 and 10%, respectively. The relative ratio of the ECD/NPD response is proposed to offer additional identification of individual pesticides, in addition to the (1)t(R) and (2)t(R) retention coordinates; ratios vary from 19 to over 1000 for selected pesticides that also exhibit ECD and NPD activities.