Benchmarking of candidate detectors for multiresidue analysis of pesticides by comprehensive two-dimensional gas chromatography

The present study discusses the relevance, performance and complementarities of flame photometric detector in phosphorus (FPD/P) and sulfur (FPD/S) modes, micro electron capture detector (mu ECD), nitrogen phosphorus detector (NPD), flame ionization detector (FID) and time-of-flight mass spectrometer (TOF/MS) for the comprehensive two-dimensional gas chromatography (GC x GC) analysis of pesticides. A mix of 41 pesticides including organophosphorus pesticides, synthetic pyrethroids and fungicides was investigated in order to benchmark GC x GC systems in terms of linearity (R-2), limits of detection (LOD), and peak shape measures (widths and asymmetries). A mixture of pesticides which contained the heteroatoms phosphorus, sulfur, nitrogen and one or several halogens, was used to acquire a comparative data set to monitor relative detector performances. GC x GC datasets were systematically compared to their GC counterpart acquired with an optimized one-dimensional GC configuration. Compared with FID, considered the most appropriate detector in terms of suitability for GC x GC, the element-selective detector FPD/P and mu ECD best met the peak widths (0.13-0.27 s for FPD/P; 0.22-0.26 s for mu ECD) and tailing factors (0.99-1.66 for FPD/P; 1.32-1.52 for mu ECD); NPD exhibited similar peak widths (0.23-0.30s), but exceeded those of the above detectors for tailing factors (1.97-2.13). These three detectors had improved detection limits of 3-7 times and 4-20 times lower LODs in GC x GC mode compared with FID and TOF-MS, respectively. In contrast FPD/S had poor peak shape (tailing factor 3.36-5.12) and much lower sensitivity (10-20 fold lower compared to FPD/P). In general, element-selective detectors with favorable detection metrics can be considered viable alternatives for pesticide determination using GC x GC in complex matrices. The controversial issue of sensitivity enhancement in GC x GC was considered for optimized GC and GC x GC operation. For all detectors, we found no significant LOD enhancement in GC x GC. (C) 2013 Elsevier B.V. All rights reserved.