Multiresidue Method for Determination of 67 Pesticides in Water Samples Using Solid-Phase Extraction with Centrifugation and Gas Chromatography-Mass Spectrometry

Abstract

A new multi-residue method based on solid-phase extraction (SPE) with centrifugation was developed for determination and quantitation of 67 pesticides in water samples. Two SPE cartridges were tested: Chromabond C 18 and Oasis HLB. Parameters that influence the extraction efficiency such as the eluent volume, the sample loading volume, the addition of organic solvent to water sample, sorbent drying and elute concentration were optimized. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 2 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under the optimized conditions, this method showed good recoveries higher than 65% -68% for the 67 analyzed pesticides using the C 18 and HLB cartridges with relative standard deviations lower than 9.7% -12.3%. Limits of quantification were between 2 and 20 ng·L -1 . The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

Occurrence and levels of pesticides in South Lebanon water

“…DDD is always recorded at lower levels, which is in agreement with [34,35] and can be justified that DDD degrades faster than DDE does. In Lebanon, studies about examination of DDT and its metabolites in water sources are unavailable except that reported by Kouzayha et al [21] In their study, only DDD and DDE were detected in groundwater samples at trace levels. On the other hand, research conducted by the American University of Beirut (2004) and the International Development Research Center -Canada (2003) revealed that DDT was recorded at low levels in two areas in Saida, and DDT with its metabolite DDE were observed at measurable amounts in sediments of El-Kabir watershed.…”

“…Kouzayha et al [21] reported in their study the existence of aldrin at low concentrations in one or more groundwater samples taken from three different wells in Lebanon during November 2010. However, it was observed at higher concentrations (50-1550 ng L −1 ) in water samples collected from Black Sea Rivers of Turkey [25] and at concentration range of 10-20 ng L −1 in samples collected from Weiga stations in Ghana.…”

“…SPE cartridges were dried under vacuum, and analytes were eluted with 3 mL DCM followed by 3 mL of MeOH/DCM mixture (1:1) and finally 3 mL of MeOH. The SPE procedure was described by Kouzayha et al [21] The extracts were concentrated to about 0.1 mL using nitrogen gas stream (Techne, UK) at 55°C. Then, 200 μL of ACN solvent was used to reconstruct the obtained extracts.…”

“…[21] MS ion source temperature was held on 230°C, whereas MS quadruple temperature was 150°C and solvent delay was 5.5 min.…”

“…[15,16] Recognizing the negative effects of water contamination by pesticides [17,18,19,20] and the lack of effective analytical projects in Lebanon, this work reports for the first time, the detection and quantification of pesticides in surface water and groundwater (GW) samples collected from South Litani region in particular during the four seasons of year 2012. An optimized and validated SPE followed by GC-MS [21] was applied for this purpose.…”