Troubleshooting in the trace analysis of organochlorine pesticides in water samples

Comparative proteomics unravelled the hexachlorocyclohexane (HCH) isomers specific responses in an archetypical HCH degrading bacterium Sphingobium indicum B90A

Hexachlorocyclohexane (HCH) is a persistent organochlorine pesticide that poses threat to different life forms. Sphingobium indicum B90A that belong to sphingomonad is well-known for its ability to degrade HCH isomers (α-, β-, γ-, δ-), but effects of HCH isomers and adaptive mechanisms of strain B90A under HCH load remain obscure. To investigate the responses of strain B90A to HCH isomers, we followed the proteomics approach as this technique is considered as the powerful tool to study the microbial response to environmental stress. Strain B90A culture was exposed to α-, β-, γ-, δ-HCH (5 mgL^-1) and control (without HCH) taken for comparison and changes in whole cell proteome were analyzed. In β- and δ-HCH-treated cultures growth decreased significantly when compared to control, α-, and γ-HCH-treated cultures. HCH residue analysis corroborated previous observations depicting the complete depletion of α- and γ-HCH, while only 66% β-HCH and 34% δ-HCH were depleted from culture broth. Comparative proteome analyses showed that β- and δ-HCH induced utmost systemic changes in strain B90A proteome, wherein stress-alleviating proteins such as histidine kinases, molecular chaperons, DNA binding proteins, ABC transporters, TonB proteins, antioxidant enzymes, and transcriptional regulators were significantly affected. Besides study confirmed constitutive expression of linA, linB, and linC genes that are crucial for the initiation of HCH isomers degradation, while increased abundance of LinM and LinN in presence of β- and δ-HCH suggested the important role of ABC transporter in depletion of these isomers. These results will help to understand the HCH-induced damages and adaptive strategies of strain B90A under HCH load which remained unravelled to date.

Determination of organochlorine pesticides in vegetable matrices by stir bar sorptive extraction with liquid desorption and large volume injection-gas chromatography-mass spectrometry towards compliance with European Union directives

A novel analytical approach to determine trace levels of 20 organochlorine pesticides (OCPs) in nine vegetable matrices (lettuce, spinach, green bean, green pepper, tomato, broccoli, potato, carrot and onion) is proposed, based on stir bar sorptive extraction followed by liquid desorption and large volume injection-gas chromatography coupled to mass spectrometry using the selected-ion monitoring mode acquisition (SBSE-LD/LVI-GC-MS(SIM)). The experimental procedure consists of a previous ultrasonic extraction of the freeze-dried vegetable samples (100.0mg) with methanol (2mL) followed by centrifugation and dissolution in aqueous media prior to SBSE-LD/LVI-GC-MS(SIM) under optimised conditions. Assays were performed on 30mL aqueous samples using stir bars coated with 47microL of polydimethylsiloxane, an equilibrium time of 180min (1000rpm; 20 degrees C) and acetonitrile as back-extraction solvent, providing convenient analytical performance to monitor OCPs in vegetable matrices at the trace level. Besides the selectivity reached, the data obtained clearly demonstrate that the matrices involved have a strong effect on the recovery yields (10-110%) of the OCPs under study, in particular the green vegetables especially the leafy ones. By using the standard addition methodology, good linearity (r(2)>0.99) and convenient precisions (RSD<20%) were found for almost all cases, depending on the particular OCP and vegetable matrix involved. Furthermore enough sensitivity was also achieved (limit of detection <10microgkg(-1)) for all OCPs under study towards compliance with the European Union regulations for the maximum residue limits of pesticides in agricultural vegetables. The methodology showed to be easy of work-up, fast, almost solventless with low sample amount requirement, when compared with conventional methods of sample preparation to screen pesticides in vegetable matrices.

Optimisation and validation of a solid-phase microextraction method for simultaneous determination of different types of pesticides in water by gas chromatography–mass spectrometry

A solid-phase microextraction (SPME) method for the simultaneous determination of a large number of pesticides (46) with a wide range of polarities and chemical structures (organochlorine, organophosphorous, triazines, pyrethroids and others) in water samples by GC-MS has been developed. Three different fibres and parameters that influence the extraction and desorption efficiency were studied. The selected conditions were: a 60 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 45 min of extraction time, sample agitation and temperature control at 60 degrees C; neither pH adjustment nor ionic strength correction were applied. Good detection limits, linearity and repeatability were obtained with this method for the 46 pesticides studied. The method was validated for 29 pesticides following the recommendations of the international norm ISO/IEC 17025 including the calculation of the uncertainties. The detection limits ranged from 4 to 17 ng l(-1). Furthermore, repeatability (6.9-20.5%) and intermediate precision (4.5-19.7%) were shown to be satisfactory. To validate matrix effects for drinking and surface water analytical recoveries were calculated for these matrices. The accuracy of the method was also evaluated by participating in a proficiency inter-laboratory test.

Evaluation of HCH isomers and metabolites in soils, leachates, river water and sediments of a highly contaminated area

In this work we evaluate the contamination caused by HCH residues in the soil, leachates, river water and sediments of an industrial estate of the NW of Spain. We study the distribution of the isomers in the different matrices, analysing 37 soil samples, collected in eight points at several depths, six natural leachates, four river water samples and three river sediments. Soil and leachate samples present very high levels of HCH isomers, higher than the established by legislation, and some pesticides were also detected in the analysed river water whereas no pesticides were detected in the river sediments. The distribution of isomers was different depending on the matrix analysed. Some natural degradation products and also other organochlorine pesticides were detected in the samples analysed.

Evaluation of zirconocene-based silica phases in organochloride pesticides preconcentration

Silica was chemically modified with zirconocenes, namely Cp(2)ZrCl(2), (MeCp)(2)ZrCl(2), (iBuCp)(2)ZrCl(2) and (nBuCp)(2)ZrCl(2) by grafting. Hybrid silica bearing surface indene groups was synthesized by the sol-gel method, followed by metallation with ZrCl(4)2THF. According to RBS measurements, metal content was 0.2-0.3 wt% Zr/SiO(2) for the grafted systems and 4.5 wt% Zr/SiO(2) for the phase prepared by the sol-gel method. The solid phases were evaluated in the adsorption/preconcentration of organochloride (hexachlorobenzene, lindane, heptachlor, heptachlor epoxide, dieldrin and endrin) pesticides from aqueous solution. For comparative reasons, commercial LC-18 phase was also evaluated. Analyte concentration was monitored by GC-ECD. For the grafted phases, the coordination sphere around the metal center seems not to influence the adsorption/desorption properties of these phases vis-à-vis the studied analytes. Recoveries results for both analytes were comparable to those observed in the case of LC-18 in the case of the phases prepared by the sol-gel method. Experiments using ZrO(2) and ZrO(2)/SiO(2) phases led to lower recovery results.

Extracting Syringe for determination of organochlorine pesticides in leachate water and soil-water slurry: a novel technology for environmental analysis

The Extracting Syringe (ESy), a novel membrane-based sample preparation technique directly coupled as an autosampler to gas chromatography, has been employed for the analysis of organochlorine pesticides (OCPs) in raw leachate water. The ESy has also been applied for extraction of OCPs from contaminated soil samples and its performance has been compared to liquid-solid extraction (LSE) and accelerated solvent extraction (ASE). Extraction of 3-mL leachate sample at the optimised conditions resulted in enrichment factors from 32 (Endrin aldehyde) to 242 (Endrin) and detection limits from 1 to 20 ng/L. The inter-day and intra-day repeatability (% RSD) at 100 and 500 ng/L were <6% and <24%, respectively. The relative recovery at 100 and 500 ng/L ranged from 68% (Aldrin) to 116% (Endrin aldehyde); except Heptachlor that showed 51 and 60%, respectively. The ESy extraction of the slurry-made soil samples revealed occurrence of Endosulfan I (18.2 microg/g soil), 4,4'-DDE (2.6 ng/g soil), Endosulfan II (8.7 microg/g soil) and Endosulfan sulfate (1.1 microg/g soil); showing good agreement with LSE results. The total ESy consumption of organic solvents was 4.2 mL from which only 0.6 mL n-undecane was used during the extraction step (7 microL for the extraction per se), while in the LSE and ASE, it was 420 and 18.1 mL, respectively. The ESy extraction time (0.5 h) was comparable to the ASE time (0.6 h); and the time required for the LSE was 3.75 h. To sum up, the ESy has shown its competency to LSE and ASE technologies, demonstrating its applicability for environmental analysis of organic pollutants, towards green techniques for green environment.

Confirmatory determination of organochlorine pesticides in surface waters using LC/APCI/tandem mass spectrometry⋄

A confirmatory method for the determination of organochlorine pesticides (OCPs) and their metabolites (endrin, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide, 2,4'-DDD, 4,4'-DDD, 2,4'-DDE 4,4'-DDE, 2,4'-DDT, and 4,4'-DDT) in surface waters using liquid chromatography /APCI/tandem mass spectrometry has been developed. Chromatographic separation was carried out on a ChromSpher 5 Pesticide column using a gradient elution with mobile phase 1mM ammonium acetate-acetonitrile. Endrin, alpha-endosulfan, beta-endosulfan , endosulfan sulfate, heptachlor and heptachlor epoxide were determined in the negative ionization mode, while the rest compounds in positive ionization mode. For the identification of the analytes, two multireaction monitoring transitions were selected per compounds except for the heptachlor which selected ion monitoring was used. The linearity of the optimized method ranges after SPE concentration, from 0.009 to 30.60 microgL(-1) with correlation coefficients greater than 0.99. The method recovery values varied from 72 to 119 % for the different fortification levels . The developed method was successfully applied to determine OCPs and their metabolites in surface water samples collected near paddy fields in growing season of rice, at year 2005 in Pathumthani province, Thailand. Endosulfan sulfate was detected in five out of seven samples and three of them could be quantitated in the range of 0.31 to 0.50 microgL(-1).

Synthesis of zirconocene-based silica phases and evaluation in lindane and heptachlor epoxide adsorption/desorption

Silica (350 m(2) g(-1)) was chemically modified with Cp2ZrCl2 and (nBuCp)2ZrCl2 by grafting. Hybrid silica bearing surface indene groups was synthesized by the sol-gel method, followed by metallation with ZrCl(4)2THF. The resulting phases were characterized by Rutherford backscattering spectrometry (RBS), 13C and 29Si magic angle spin nuclear magnetic resonance, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. According to RBS measurements, metal content was 0.2- to 0.3-wt% Zr/SiO2 for the grafted systems and 4.5-wt% Zr/SiO2 for the phase prepared by the sol-gel method. The solid phases were evaluated for the adsorption/preconcentration of lindane and heptachlor epoxide from aqueous solution. For comparative reasons, the commercial LC-18 phase was also evaluated. Analyte concentration was monitored by gas chromatography electron capture detection. For the grafted phases, the coordination sphere around the metal center seems not to influence the adsorption/desorption properties of these phases vis-a-vis the studied analytes. In the case of the phases prepared by the sol-gel method, recovery results were comparable to those observed for LC-18. Experiments using ZrO2 and ZrO2/SiO2 phases led to lower recovery results.