Journal of Chromatography A, 1190 (2008) 350–357 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Optimization of separation and detection conditions for the multiresidue analysis of pesticides in grapes by comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry Kaushik Banerjee ∗ , Sangram H. Patil, Soma Dasgupta, Dasharath P. Oulkar, Shubhangi B. Patil, Rahul Savant, Pandurang G. Adsule National Research Centre for Grapes, P.O. Manjri Farm, Pune 412 307, India article info Article history: Received 21 December 2007 Received in revised form 29 February 2008 Accepted 5 March 2008 Available online 12 March 2008 Keywords: Grape Pesticide residues Multiresidue analysis GC×GC–TOFMS Deconvolution Recovery abstract A comprehensive GC×GC–TOFMS method was optimized for multiresidue analysis of pesticides using a combination of a non-polar (RTX-5MS, 10 m × 0.18 mm × 0.2 m) and a polar capillary column (TR-50MS, 1m × 0.1 mm × 0.1 m), connected in series through a dual stage thermal modulator. The method resolved the co-elution problems as observed in full scan one-dimensional GC–MS analysis and allowed chromato- graphic separation of 51 pesticides within 24min run time with library-searchable mass spectrometric confirmation. Four pesticides, viz. chlorpyrifos-methyl, vinclozoline, parathion-methyl and heptachlor could be baseline separated on GC×GC, which were otherwise closely eluting and interfering each other’s detection in 1 D GC–MS run. Similarly, it could be possible to separate myclobutanil, buprofezin, flusi- lazole and oxyfluorfen on GC×GC. Although in 1 D GC–MS, these closely eluting compounds could be identified through deconvolution algorithm and ‘peak-find’ option of the Chromatof ® software but the spectral purity significantly improved on GC×GC analysis. Thorough optimization was accomplished for the oven temperature programming, ion source temperature and GC×GC parameters like modulation period, duration of hot pulses, modulation-offset temperature, acquisition rate, etc. to achieve best pos- sible separation of the test compounds. The limit of detection significantly improved by 2–12 times on GC×GC–TOFMS against GC–TOFMS because of sharper and narrower peak shapes. The method was tested for grape matrix after preparing the samples using previously described method and recoveries of the entire test pesticides were within 70–110% at 10ng/g level of fortification. GC×GC–TOFMS was found to be an excellent technique for library-based screening of pesticides with high accuracy and sensitivity. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) offers unprecedented separation power in multiresidue analysis. Combi- nation of a long non-polar with a short and polar capillary column connected in series through a thermal modulator provides enor- mous peak capacity, which is utilized in separating mixture of large number of compounds in single chromatographic run. The TOF mass analyzer further enhances the separation process on the basis of relative flight times of ions as decided by their mass/charge (m/z) ratio. Although quite a number of papers described the sep- aration efficiency of this technique [1–4], the literature evaluating ∗ Corresponding author at: National Referral Laboratory, National Research Centre for Grapes, P.O. Manjri Farm, Pune 412307, Maharashtra, India. Tel.: +91 20 26914245; fax: +91 20 26914246. E-mail address: kbgrape@yahoo.com (K. Banerjee). the quantitative performance of this technique in pesticide residue analysis in agricultural products is rather limited [5]. The commercial cultivation of grapes in India receives frequent application of a large number of pesticides throughout cropping season to control a variety of pests and diseases. Pesticide residue is a major concern for the grape industry, since a significant fraction of the total production is consumed as fresh fruit without any pos- sibility of peeling or decontamination treatments. Since pesticide residues may also appear from indirect sources like soil, contam- inated agro-inputs (e.g. manures, fertilizers, growth regulators, irrigation water, etc.), drift from adjoining fields of other agricul- tural crops, etc. it makes residue monitoring a challenging task and establishes the need for monitoring both the recommended as well as non-recommended chemicals [6,7] to ensure consumer safety. The quality regulations and food safety standards are becom- ing more stringent in most countries. Thus, target-oriented residue analysis using quadrupole or ion trap GC–MS with selected ion monitoring (SIM) [8–10] or tandem mass spectrometry (MS/MS) [11,12] is not always sufficient to provide complete information 0021-9673/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2008.03.017