Strategies for chromatographic analysis of pesticide residues in water

Analytical Confirmation of Various Herbicides in Drinking Water Resources in Sugarcane Production Regions of Guangxi, China

This work investigated drinking water contamination by 11 commonly used herbicides in sugarcane production areas in Guangxi, China. The work developed an analytical method for determination of these herbicides in environmental waters. This work studied herbicide residues in drinking water in Guangxi, China. The maximum residues and percent of detects were: (0.091 µg/L, 29.2%, atrazine), (0.018 µg/L, 8.3%, ametryne), (0.188 µg/L, 8.3%, aetolaehlor), (0.139 µg/L, 4%, simazine), (0.585 µg/L, 62.5%, atrazine), (0.311 µg/L, 33.3%, acetochlor), (0.341 µg/L, 58.3%, ametryne), (1.312 µg/L, 29.2%, metolachlor), (0.088 µg/L, 4.2%, alachlor), (0.127 µg/L, 14.3%, atrazine), and (0.453 µg/L, 7.1%, metolachlor), respectively. The results demonstrated that agricultural herbicides were detected in all water samples, including tap, surface and groundwater samples. Since the residues are generally below the safe limits established by the government authorities, the monitored 11 herbicides do not significantly affect the quality of the human environment. This work will provide scientific understanding of pesticide residues in drinking water standards in terms of its consistency with precautionary human health and environmental safety.

Selection of sorbent for removing pesticides during water treatment

This paper presents research on phenoxyacid pesticides removal using sorption methods on activated carbons. It was noted, that physico-chemical properties of adsorbent and adsorbate as well as parameters of the process have influence on adsorption of pesticides, derivatives of phenoxyacetic acid on carbon. The experimental data were analyzed by the Freundlich isotherm. The best for remove from water on carbon NP-5 was 2,4-D. Equilibrium data fitted well with the Freundlich model with maximum adsorption capacity of NP-5 carbon. The exemplary sorption capacity at equilibrium concentration 10 mg L(-1) were: 2,4-D 70 mg g(-1), MCPA 2 mg g(-1), MCPP 0.5 mg g(-1). The results indicated that coconut shell-based NP-5 carbon is most effective for the adsorption of phenoxyacetic acid from aqueous solutions.

Enhanced visual detection of pesticides using gold nanoparticles

The presence of parts per billion (ppb) levels of chlorpyrifos (O,O-Diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) and malathion (S-1,2-bis(ethoxycarbonyl) ethyl O,O-dimethyl phosphorodithioate), two common pesticides found in the surface waters of developing countries, have been visually detected using gold nanoparticles. Visual detection of the presence of pesticide is possible when the color change occurring by the adsorption of pesticides on gold nanoparticles is enhanced by sodium sulfate. The method presented here is simple and there is no need of sample preparation or preconcentration. The response occurs within seconds and the color change is very clear. The detection is possible if chlorpyrifos and malathion are present up to a concentration of 20 and 100 ppb, respectively. The method shows great potential for on-site pesticide monitoring. The method is also applicable as a qualitative technique for the performance evaluation of various household water filters, which claim pesticide removal.

Liquid-phase micro-extraction techniques in pesticide residue analysis

Modern trends in analytical chemistry are towards the simplification and miniaturization of sample preparation, as well as the minimization of organic solvent used. In view of this aspect, several novel micro-extraction techniques are being developed in order to reduce the analysis step, increase the sample throughput and to improve the quality and the sensitivity of analytical methods. One of the emerging techniques in this area is liquid-phase micro-extraction (LPME). It is a miniaturized implementation of conventional liquid/liquid extraction (LLE) in which only microliters of solvents are used instead of several hundred milliliters in LLE. It is quick, inexpensive and can be automated. In the last few years, LPME has been combined with liquid chromatography (LC) and capillary electrophoresis (CE), besides the generally used coupling to gas chromatography (GC), and has been applied to various matrices, including biological, environmental, and food samples. This work is aimed at providing an overview of the major developments of LPME, coupled with chromatography and CE, as reported in the literature. The paper will focus on the application of the technique to different matrices and the aim is to reveal the panorama of opportunities and to try to indicate the potential of LPME in pesticide analysis. A critical review of the first applications to pesticide analyses is presented in the main part of the manuscript. The optimization of LPME as well as advantages and disadvantages are discussed. It is concluded that, because of its high pre-concentration factor, LPME can be introduced with benefit into water analysis for several pesticide groups. In particular, the application of LPME to non-polar pesticides in environmental analysis appears to be promising. However, similar to other micro-extraction techniques, such as solid phase micro-extraction (SPME), serious limitations still remain when analyzing semi-solid and solid environmental, food or biological matrices and/or highly polar compounds. Thus, other pre-concentration techniques may be a good alternative if an analytical problem cannot be sufficiently dealt with LPME.

Investigating the in situ degradation of atrazine in groundwater

This study focused on whether or not atrazine could be degraded by indigenous groundwater bacteria as part of an in situ remediation approach. Groundwater was taken from an unconfined middle upper chalk site where concentrations of atrazine and nitrate were typically in the ranges 0.02-0.2 microg litre-1 and 11.6-25.1 mg NO3-N litre-1 respectively. Sacrificial batch studies were performed using this groundwater spiked with atrazine at a concentration of 10 microg litre-1 in conjunction with a minimal mineral salts liquid (Glu-MMSL) medium which contained glucose as the sole carbon source. Treatments comprised either the Glu-MMSL groundwater cultured bacteria or Pseudomonas sp. strain ADP. Results from sacrificial batches indicated the occurrence of bacterial growth and denitrification as monitored by optical density (absorbance at 600 nm) and NO3-N content. Analysis of atrazine content by solid phase extraction coupled with high-performance liquid chromatography showed no degradation of atrazine over a period of 103 days in either treatment. These results indicated that no acclimatised bacterial community featuring positive degraders to the herbicide atrazine had become established within this chalk aquifer in response to the trace levels encountered.

A simple method for the determination of carbaryl and 1-naphthol in fruit juices by high-performance liquid chromatography-diode-array detection

Carbaryl (Sevin) is a widely used N-methylcarbamate insecticide. In this study, a simple and sensitive reversed-phase, high-performance liquid chromatography method with diode-array detection has been developed for the determination of low levels of carbaryl and its degradation products 1-naphthol in several kinds of canned pure fruit juice. The compounds were captured on a C18 cartridge. The analytes were separated on a C18 column using a linear gradient of 40 to 60% acetonitrile in water in a period of 20 min. The extraction recoveries of carbaryl and 1-naphthol were in the range 93.5 to 98.0% and 90.7 to 96.0% for fruit juice, respectively. The detection limit was below 0.8 ng/ml and the calibration curves showed good linearity between 0.9998 and 0.9999.

Experimental study of the remediation of atrazine contaminated soils through soil extraction and subsequent peroxidation

This paper presents a feasibility study in the field of the remediation of soils contaminated with atrazine. Experimental tests were performed on an artificially contaminated synthetic soil. Atrazine was removed from the soil by flushing with an aqueous solution at 5 vol.% of ethanol. Experimental tests of evaporation and Fenton's oxidation on the extracted solution were then performed in order to transform atrazine into its oxidation products. Tests were performed in the presence of a peroxide excess the ratio between Fe(2+) and H(2)O(2) was 1:10. Peroxide was first added in order to reduce the consumption of hydroxyl radicals by their reaction with the excess of Fe(2+). The degradation mechanism of atrazine during oxidation with Fenton's reagent in the presence of ethanol was investigated. Results showed that due to the non selective nature of Fenton's reagent a high consumption of reagent was needed to achieve a significant atrazine oxidation from solutions at 4.5 vol.% of ethanol. While at a Fe(2+) concentration of 3mM atrazine practically disappeared from pure aqueous solutions within 2h, a degradation yield of only 28.1% was observed in the presence of ethanol even when Fe(2+) concentration was 15 mM.

Headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry for the rapid screening of organophosphorus insecticide residues in strawberries and cherries

A headspace solid-phase microextraction (HS-SPME) method in combination with GC-MS was used for the extraction and quantification of diazinon, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl and ethion. The method was developed using a 100-microm poly(dimethylsiloxane) fiber. The obtained results showed higher responses of the insecticides after addition of aliquots of water and solvent to the fruit samples. Calibration curves that were constructed for the analytes spiked into strawberry and cherry samples followed linear relationships with good correlation coefficients (R2 > 0.986). Linearity range was between 50 and 500 microg/kg and the precision was found to be lower than 15% when applying the optimized HS-SPME procedure to fruit samples. Limits of detection in both strawberry and cherry samples using GC-MS (selected ion monitoring mode) were below 13 microg/kg. Moreover, the HS-SPME method was applied to the analysis of fruit samples and compared with liquid-liquid extraction. Results obtained in this study were in good agreement with those obtained using liquid-liquid extraction demonstrating that the recommended procedure was a fast, accurate and stable sample pretreatment method obtaining good efficiency for the extraction of organophosporus insecticides from strawberries and cherries.

Pesticide residues in thermal mineral water in Greece

Eight different hot springs (SPA) in Greece were monitored over a one-year survey for priority pesticide residues. A specific and effective procedure including solid phase extraction in combination with HPLC and GC analytical methods were applied. Samples that were sensitive to nitrogen-phosphorus (NPD) and/or electron capture (ECD) detectors were analysed by capillary gas chromatography. From the twenty-six water samples, pesticide residues were detected in fourteen of them (54%) but no one exceeding the European Union Maximum Acceptable Concentration (MAC). Lindane (gamma-BHC) was the most frequently detected pesticide. It was found in nine samples (35%) in concentrations from < 0.005 to 0.01 microg/L. Other pesticides detected were phorate (in five samples), propachlor (in two samples) and chlorpyriphos ethyl (in three samples) but in concentrations far below the permissible levels.

Monitoring of the pesticide diazinon in soil, stem and surface water of rice fields

Diazinon is an organophosphorus insecticide (OPP) that is used as a pesticide for Chilo suppressalis (WLK) (Lep., Pyralidae) in rice fields. The extraction of diazinon from soil and the stems of rice plants has been carried out by microwave-assisted extraction (MAE) and the results compared with ultrasonic extraction (USE). The best parameters for MAE are hexane-acetone (8:2 v/v) as a solvent, a 2.5 min extraction time, and 20 ml of the solvent volume. Also, surface-water samples of the rice fields were extracted by solid phase extraction (SPE) using a C18 disc. The optimum conditions of SPE were a sample volume of 750 ml, a pH of 7 and high ionic strength of water. The extracted samples were analyzed by gas chromatography-mass spectrometry (GC-MS). The relative standard deviation (RSD) and regression coefficients related to the linearity were <3.5% (n = 5) and 0.99, respectively. The limit of detection (LOD) is 0.1 ng ml(-1) with selected ion monitoring (SIM) at 137 m/z. The average recoveries of diazinon in soil and stem samples by MAE and surface-water by SPE were 98% (+/-3), 94% (+/-5) and 87% (+/-3), respectively. In June, the concentration of diazinon in soil and stem samples of the rice plants in Guilan province is high (55 ng ml(-1)) and in September is low (2 ng ml(-1)). In surface-water samples, the results are converse. In November, diazinon can not be detected in soil, stem or surface-water samples. Diazinon is degraded to diethylthiophosphoric acid. Also, three microorganism genera (Pseudomonas sp, Flavobacterium sp and Agrobacterium sp) have been found to degrade diazinon in soil and surface water.

Analysis of antifouling biocides Irgarol 1051 and Sea Nine 211 in environmental water samples using solid-phase microextraction and gas chromatography

This study develops a method for the analysis of biocides Irgarol 1051 and Sea Nine 211 in environmental water samples, using solid-phase microextraction (SPME). Their determination was carried out using gas chromatography with flame thermionic (FTD), electron-capture (ECD) and mass spectrometric detection. The main parameters affecting the SPME process such as adsorption-time profile, salt additives and memory effect were studied for five polymeric coatings commercially available for solid-phase microextraction: poly(dimethylsiloxane) (100 and 30 microm), polyacrylate, poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB 65 microm) and Carbowax-divinylbenzene (65 microm). The method was developed using spiked natural waters such as tap, river, sea and lake water in a concentration range of 0.5-50 microg/l. All the tested fiber coatings have been evaluated with regard to sensitivity, linear range, precision and limits of detection. Typical RSD values (triplicate analysis) in the range of 3-10% were obtained depending on the fiber coating and the compound investigated. The recoveries of biocides were in relatively high levels 60-118% and the calibration curves were reproducible and linear (R2>0.990) for both analytes. The SPME partition coefficients (Kf) of both compounds were also calculated experimentally in the proposed conditions for all fibers using direct sampling. Finally the influence of organic matter such as humic acids on extraction efficiency was studied, affecting mostly Sea Nine 211 uptake by the fiber. Optimum analytical SPME performance was achieved using the PDMS-DVB 65 microm fiber coating in ECD and FTD systems for Sea Nine 211 and Irgarol 1051, respectively.

Monitoring of pesticides in drinking and related waters in NE Spain with a multiresidue SPE-GC-MS method including an estimation of the uncertainty of the analytical results

A new method, developed in an EC project (SMT4-CT96-2142) for the determination of 22 pesticides in drinking and related waters, has been used to analyze source and drinking water samples in the area of Barcelona (NE Spain). The procedure includes solid-phase extraction of water and subsequent analysis by GC-MS using few selected ions (SIR) in order to increase their sensitivity. The method was subjected to intra and interlaboratory tests and met the requirements of the EC Directive in terms of accuracy, precision and detection limit (0.025 microg/l range in water samples). A detailed analysis of the uncertainty sources of this method is included, which allows to estimate expanded uncertainties in the 10-20% range. The dominant sources of uncertainty are the solid-phase extraction procedure and the chromatographic quantification. Two triazine compounds, simazine and atrazine, are the main pesticides detected in wells of the Llobregat river and in water of the Ter river, respectively.

Analyses of lindane, vinclozolin, aldrin, p,p'-DDE, o,p'-DDT and p,p'-DDT in human serum using gas chromatography with electron capture detection and tandem mass spectrometry

A sensitive, selective and reliable procedure was developed and validated to determine organochlorinated compounds, which present endocrine-disrupting effects, lindane, vinclozolin, aldrin, p,p'-DDT, o,p'-DDT and p,p'-DDE, in human serum. The analytical methodology combines serum extraction with organic solvents, clean-up of the organic extract using acid treatment with H2SO4, elution of the cleaned-up extract through liquid column chromatography system and analysis of the fraction eluted by gas chromatography (GC) with electron capture detection (ECD) and tandem mass spectrometry (MS-MS) detection mode. Performance characteristics, such as linearity, sensitivity, precision, accuracy or recovery, of both chromatographic methods were studied. The proposed analytical methodology was applied to analyse the target compounds in serum samples from women living in agricultural areas of Almería (Spain). Comparison of the MS-MS and the ECD results was made and the advantage of the MS-MS operation mode to determine endocrine disrupting compounds in complex matrices is also presented.

Development and validation of a high-performance liquid chromatographic method for the determination of clomazone residues in surface water

A method is described for the determination of clomazone residues in surface water by high-performance liquid chromatography with UV detection. The method involves solid-phase extraction with C18 extraction tubes. Clomazone was separated on a C18 column with a mobile phase of methanol-water (65:35, v/v) at pH 4.0 and a flow-rate of 1.0 ml/min. After optimization of the extraction and separation conditions, the method was validated. The method developed can be used for determination of clomazone in surface water, at the limit of 0.1 mcirog/l set by the European Union drinking water directive, with a 400-fold preconcentration.

Preconcentration of contaminants in water analysis

Among the environmental areas, in this review attention will be focused on water matrices and both on organic (e.g., pesticides, herbicides, phenols, polycyclic aromatic hydrocarbons), inorganic species and anion pollutants, since these kinds of substances include a wide number of compounds with different physical and chemical properties and different effects on human health. Analytical methods for control of quality of waters are required to be highly specific and possibly highly sensitive for the determination of even low amounts of pollutants. The main problems encountered during the analysis are the separation of matrix components from the pollutants of interest and the achievement of low detection limits. Therefore an overview on different materials and techniques available for sample concentration and/or matrix removal will be provided and discussed according to the chemical characteristics of the pollutant that has to be enriched.

Quantitative determination of endocrine- disrupting polychlorinated biphenyls and organochlorinated pesticides in human serum using gas chromatography with electron-capture detection and tandem mass spectrometry

A sensitive, selective and reliable procedure was developed and validated to determine organochlorinated compounds, which have endocrine-disrupting effects, in human serum. Target compounds were selected between polychlorinated biphenyls and organochlorinated pesticides. Sample workup consisted of (1) extraction of serum with organic solvents, (2) clean-up of the organic extract using acid treatment with H(2)SO(4), (3) elution of the cleaned-up extract through a liquid column chromatographic system and (4) analysis of the fraction eluted by gas chromatography with electron capture detection (ECD) and tandem mass spectrometry (MS/MS) detection. Performance characteristics, such as linearity, sensitivity, precision, accuracy and recovery, of both chromatographic methods were studied. The proposed analytical methodology was applied to determine the target compounds in serum samples from women living in agricultural areas of Almería (Spain). The results show the advantage of MS/MS over ECD in the analysis of real human serum samples where matrix interferences can be confused with target pesticides.

Identification and quantification of 77 pesticides in groundwater using solid phase coupled to liquid-liquid microextraction and reversed-phase liquid chromatography

This paper describes a method for the extraction, separation, identification, and quantification of 77 pesticides (neutral, acidic, and basic) including some s-triazine metabolites. The method is appropriate for organically (e.g. with humic acids) highly loaded groundwater samples. A comparative study of a pH-controlled mixed solid phase (LiChroprep RP18/LiChrolut EN) extraction with different desorption solvents (acetonitrile or acetonitrile and dichloromethane/methanol) is elaborated. A subsequent liquid-liquid microextraction reduces matrix effects. The pesticides in the sample are separated using RP-HPLC, detected, and identified by diode array. The efficiency is illustrated on a natural groundwater sample from a phreatic aquifer.

Solid-phase microextraction in pesticide residue analysis

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.

Use of solid-phase microextraction for the quantitative determination of herbicides in soil and water samples

An in-depth study of SPME optimization and application has been made, considering not only aqueous (surface water and groundwater samples) but also the more complex soil samples. Seven herbicides widely used in the area of study have been selected including five triazine herbicides (atrazine, simazine, terbumeton, terbuthylazine, terbutryn), molinate, and bromacil. linearity range was between 0.1 and 10 ng/mL and the repeatability below 10% when applying the optimized SPME procedure to water samples. Reproducibility was found to be lower than 20% at the 1 ng/mL level, and the limits of determination in environmental water samples using GC/MS (SIM mode) were well below 0.1 ng/mL (values ranging from 10 to 60 ng/L). Extraction of selected herbicides from soil was carried out by microwave-assisted solvent extraction using methanol in screw-capped vials, leading to recoveries over 80% in spiked soil samples at the 5-200 ng/g level. SPME application over methanolic soil extracts required a 10-fold dilution with distilled water. The recommended procedure was found to be fully applicable for quantitative determination of selected herbicides in soils containing low organic matter content with coefficients of variation below or around 10% and limits of determination ranging from 1 to 10 ng/g. Both procedures were applied to real-world surface water and soil samples where several pesticides were detected including atrazine, simazine, terbuthylazine, and molinate.

Use of solid-phase extraction and high-performance liquid chromatography for the determination of triazine residues in water: validation of the method

A method for determination of some triazine residues in water has been developed. The method involves concentration with C18 solid-phase extraction cartridges followed by high-performance liquid chromatographic analysis using a C18 column with UV detection at 230 nm, a mobile phase of methanol-water (60:40, v/v) at pH 4.6 (phosphoric acid) and a flow-rate of 0.8 ml/min. After optimization of the extraction and separation conditions, the method was validated. The method can be used for determination of atrazine, simazine, cyanazine and ametryn in water, within the international limits of 0.1 microg/l.

Pesticide trace analysis using solid-phase extraction and gas chromatography with electron-capture and tandem mass spectrometric detection in water samples

Gas chromatography (GC) with electron-capture detection (ECD), mass spectrometry (MS) and tandem mass spectrometry (MS-MS) were employed for the identification of 12 pesticides in water samples. For this purpose, a solid-phase extraction procedure with C18 cartridges was used, optimising the breakthrough volume and the saturation concentration. In GC-MS-MS, the lowest detectable concentrations for the pesticides were between 2 and 26 ng l(-1), recoveries ranged from 70 to 133% in water samples spiked at 100 ng l(-1) and the relative standard deviations were in the range 5.3 to 17.4%. The proposed analytical methodology was applied to analyse pesticides in wetland samples from Almería (Spain).

Determination of bentazon residues in water by high-performance liquid chromatography. Validation of the method

A method for determination of bentazon residues in water has been developed. The method involves solid-phase extraction with C18 extraction tubes and high-performance liquid chromatographic analysis. A C18 column and guard column were used with UV detection at 230 nm, a mobile phase of methanol-water (60:40, v/v) at pH 4.6 (phosphoric acid) and a flow-rate of 0.8 ml/min. After optimization of the extraction and separation conditions, the method was validated. The method developed can be used for determination of bentazon in water, within the international limits of 0.1 microgram/l, with a 500-fold pre-concentration.