Automated analysis of polar pesticides in water by on-line solid phase extraction and gas chromatography using the co-solvent effect

In order to meet the requirements of analyzing very low concentrations of pesticides in water (typically at 0.1 μg/l or less), samples have to be concentrated prior to GC-analysis. Samplie pre-concentration by off-line methods based on solid phase extraction (SPE) or liquid-liquid extraction are very time consuming and cumbersome. Moreover, the quantitative performance of the analytical method as a whole in terms of accuracy and reliability is seriously hindered by elaborate, manually performed sample pre-treatment steps. This paper describes an automated method based on solid phase extraction and capillary gas chromatography. The technique was applied for the analysis of 31 polar organophosphorus and organonitrogen pesticides. A commercially available HPLC/GC instrument is modified, using the LC-part for solid phase extraction. The sample, of which only a few ml's is required to obtain sufficiently low detection limits, is delivered by a robotic large volume autosampler. After solid phase extraction and elution, the eluate is transferred into the GC via a so called “loop type interface”. In this paper the instrumentation and analytical methodology is described, as well as the main validation results. The quantitative performance (i.e. recovery and repeatability) of the most polar solutes like metamitron and dimethoate appears to be better than obtained with off-line SPE as a result of the more beneficial ratio between the amount of sorbent and the sample volume. As the loop-type interface causes losses of the most volatile compounds, a co-solvent is added. This co-solvent provides sufficient trapping capacity in the capillary pre-columns to allow quantitative analysis of even the most volatile pesticides. Moreover a better separation of early eluting compounds is also established.     

Multiresidue method to quantify pesticides in fish muscle by QuEChERS-based extraction and LC-MS/MS

Pesticide residues in fish muscle are an environmental and a health safety concern which requires analytical methods presenting high sensitivity and low limits of quantification. In this study, adapted QuEChERS method, coupled to liquid chromatography tandem mass spectrometry (Scheduled MRM-5500 QTRAP), was developed to quantify 13 pesticides (azoxystrobin, clomazone, diflufenican, dimethachlor, carbendazim, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl) in muscle of fish. Quantification limits were below 1 ng g⁻¹ except for clomazone (1.8 ng g⁻¹) and quizalofop (7.4 ng g⁻¹). Best recoveries were observed for perch (>80%) and roach (>68%), except for thifensulfuron-methyl. Lower recoveries had been observed for carp (6% to 86%). Relative standard deviation was lower than 28% for intra-day and 29% for inter-day analysis, respectively. This method was successfully tested on three fish species, naturally or orally exposed: roach (Rutilus rutilus), perch (Perca fluviatilis) and carp (Cyprinus carpio). Few levels were observed in fish naturally exposed, but carp and perch orally contaminated showed measurable levels in their muscles.     

Automatic measurement of pesticides in drinking water using on-line solid-phase extraction, HPLC and chemometry

Using an automated on-line phase extraction device, followed by HPLC, various pesticides groups can be separated and quantified chromatographically in a single run. By using a diode-array detector capable of automatically identifying components and determining their homogeneity by utilizing multiple, non subjective spectral comparison techniques, correct results can be obtained. For peaks that co-elute due to inadequate resolution, Multi Component Analysis (MCA) provides quantitative accuracy with a determination limit as low as 0.010 g/L with few exceptions.     

Measurement of trace levels of antibiotics in river water using on-line enrichment and triple-quadrupole LC-MS/MS

This study presents the development of an automated on-line solid phase extraction (SPE)-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of 23 antibiotics in environmental water samples. After optimisation of LC-MS/MS conditions, SPE parameters such as sorbent type, sample pH or sample volume were optimised. Antibiotic recoveries ranged from 64% to 98% and compared favourably with those achieved using off-line SPE. Limits of detection were in the range 0.5-13.7 ng L⁻¹.This on-line SPE-LC-MS/MS procedure was applied to the analysis of water samples taken in three rivers within the Seine River basin, near Paris (France). The obtained results revealed the occurrence of 12 antibiotics, including tylosin, erythromycin, tetracycline, amoxicillin, trimethoprim, sulfamethoxazole, oxolinic acid, flumequine, norfloxacin, ciprofloxacin, ofloxacin, and vancomycin (2-1435 ng L⁻¹).     

Multiresidue analysis of acidic and polar organic contaminants in water samples by stir-bar sorptive extraction-liquid desorption-gas chromatography-mass spectrometry

The feasibility of stir-bar sorptive extraction (SBSE) followed by liquid desorption in combination with large volume injection (LVI)-in port silylation and gas chromatography-mass spectrometry (GC-MS) for the simultaneous determination of a broad range of 46 acidic and polar organic pollutants in water samples has been evaluated. The target analytes included phenols (nitrophenols, chlorophenols, bromophenols and alkylphenols), acidic herbicides (phenoxy acids and dicamba) and several pharmaceuticals. Experimental variables affecting derivatisation yield and peak shape as a function of different experimental PTV parameters [initial injection time, pressure and temperature and the ratio solvent volume/N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) volume] were first optimised by an experimental design approach. Subsequently, SBSE conditions, such as pH, ionic strength, agitation speed and extraction time were investigated. After optimisation, the method failed only for the extraction of most polar phenols and some pharmaceuticals, being suitable for the determination of 37 (out of 46) pollutants, with detection limits for these analytes ranging between 1 and 800 ng/L and being lower than 25 ng/L in most cases. Finally, the developed method was validated and applied to the determination of target analytes in various aqueous environmental matrices, including ground, river and wastewater. Acceptable accuracy (70-130%) and precision values (<20%) were obtained for most analytes independently of the matrix, with the exception of some alkylphenols, where an isotopically labelled internal standard would be required in order to correct for matrix effects. Among the drawbacks of the method, carryover was identified as the main problem even though the Twisters were cleaned repeatedly.     

离子色谱法同时测定饮用水中强极性农药草甘膦、草铵膦、乙烯利和调节膦

建立了一种梯度洗脱-电导抑制-离子色谱同时测定4种强极性农药的方法.通过对淋洗液及浓度、色谱柱、柱温、进样量等条件的优化,得到最佳检测条件:色谱柱为IonPac AS11-HC分析柱及IonPac AG11-HC保护柱,柱温33℃,进样量50μL,RFIC系统的淋洗液自动发生器在线产生的KOH作为淋洗液,梯度洗脱,淋洗...     

Multiresidue analysis of pesticides in vegetables and fruits using a high capacity absorbent polymer for water

A single extraction and a single clean-up procedure was developed for multi-residue analysis of pesticides in non-fatty vegetables and fruits. The method involves the use of a high capacity absorbent polymer for water as a drying agent in extraction from wet food samples and of a graphitized carbon column for clean-up. A homogeneously chopped food sample (20 g) and polymer (3 g) were mixed to absorb water from the sample and then 10 min later the mixture was vigorously extracted with ethyl acetate (100 ml). The extract (50 ml), separated by filtration, was loaded on a graphitized carbon column without concentration. Additional ethyl acetate (50 ml) was also eluted and both eluates were concentrated to 5 ml for analysis. The procedure for sample preparation was completed within 2 h. In a recovery test, 107 pesticides were spiked and average recoveries were more than 80% from asparagus, orange, potato and strawberry. Most pesticides were recovered in the range 70-120% with usually less than a 10% RSD for six experiments. The results indicated that a single extraction with ethyl acetate in the presence of polymer can be applied to the monitoring of pesticide residues in foods.     

Multiresidue analysis of seventeen pesticides in wine by gas chromatography with mass-selective detection

We have developed a multiresidue method permitting the simultaneous quantitation of 17 pesticides in wine: dicloran, dimethoate, diazinon, chlorpyrifos-methyl, vinclozolin, carbaryl, methiocarb, dichlofluanid, parathion-ethyl, triadimefon, procymidone, myclobutanil, iprodione, imidan, dicofol, phosalone and azinphos-methyl. Solid-phase extraction of 0.5 ml of wine sample is followed by direct injection of 1 microl of the eluent onto a DB-5 MS gas chromatographic column followed by mass-selective detection using one target and two qualifier ions for each pesticide. The extraction and injection steps are carried out with automatic instrumentation. Good resolution of all compounds was achieved with a run-time approximating 23 min. Detection and quantitation limits were around 2 microg/l and 10 microg/l, respectively, with linear calibration curves up to 3 mg/l for most constituents. Recovery in half the compounds was >90%, and >80% in most of the remainder. Imprecision (relative standard deviation) was <10% for most pesticides and <18% in all. Further analytes can be added to the repertoire without difficulty. The method merits consideration together with four other multiresidue methods now available that offer similar analytical characteristics, slower run-times, and a different selection of analytes.     

Multiresidue analysis of 18 organochlorine pesticides in traditional chinese medicine

A simple and efficient method for simultaneous gas chromatographic (GC) determination of 18 organochlorine pesticides [tecnazene, hexachlorobenzene, alpha-benzenehexachloride (BHC), pentachloronitrobenzene (PCNB), gamma-BHC, heptachlor, aldrin, methyl pentachlorophenyl sulfide, beta-BHC, delta-BHC, heptachlor epoxide, alpha-endosulfan, trans-chlorodane, cis-chlorodane, p,p'-dichlorodiphenyl dichloroethylene, o,p'-DDT, p,p'-DDD, and p,p'-DDT] in Traditional Chinese Medicine (TCM) is described. The procedure involves ultrasonic extraction and sulphuric acid treatment as the cleanup method. Detection of the sample is performed by GC-electron capture detection. A series of experiments are conducted to optimize the final pretreatment conditions [acetone-petroleum ether (1:1) as the extract solvent, ultrasonication for 15 min, three steps, concentrated sulphuric acid with 10% water for sulphuric acid treatment]. Recovery studies are performed at 10, 50, and 100 parts-per-billion (ppb) fortification levels of each organochlorine pesticide, except for alpha-endosulfan, which are 20, 100, and 200 ppb. The percentage recoveries range from 77.9% +/- 6.4% to 114.0% +/- 8.1% (average +/- standard deviation). The simple and rapid method may be used to routinely determine organochlorine pesticides in TCM.     

Multiresidue analysis of pesticides in vegetables and fruits using two-layered column with graphitized carbon and water absorbent polymer

A high-throughput multiresidue analysis of pesticides in non-fatty vegetables and fruits was developed. The method consisted of a single extraction and a single clean-up procedure. Food samples were extracted with ethyl acetate and the mixture of extract and food dregs were poured directly into the clean-up column. The clean-up column consisted of two layers of water-absorbent polymer (upper) and graphitized carbon (lower), which were packed in a reservoir (75 ml ) of a cartridge column. The polymer removed water in the extract while the carbon performed clean-up. In a recovery test, 110 pesticides were spiked and average recoveries were more than 95% from spinach and orange. Most pesticides were recovered in the range 70-115% with RSD usually < 10% for five experiments. The residue analyses were performed by the extraction of 12 pesticides from 13 samples. The two methods resulted in similar residue levels except chlorothalonil in celery, for which the result was lower with the proposed method. The results confirmed that the proposed method could be applied to monitoring of pesticide residue in foods.     

Determination of pesticides in drinking water by micellar electrokinetic capillary chromatography

A new analytical procedure using a two-step sample preconcentration (solid-phase extraction (SPE) and field-amplified sample stacking) prior to separation by micellar electrokinetic capillary chromatography was developed for the determination of 14 pesticides such as aldicarb, carbofuran, isoproturon, chlorotoluron, metolachlor, mecoprop, dichlorprop, MCPA, 2,4-D, methoxychlor, TDE, DDT, dieldrin, and DDE in drinking water. Good recoveries of pesticides were obtained using SPE with sample pH adjusted to 2-3. Field-amplified sample stacking was found to give enrichment factors up to 30-fold preconcentration of various pesticides under reversed polarity at -2 kV for 50 s. The optimized background electrolyte (BGE) consisted of 50 mM sodium dodecyl sulfate (SDS), 10 mM borate buffer, 15 mM beta-cyclodextrin (beta-CD), and 22% acetonitrile at pH 9.6, running was under 25 kV and detection at 202 nm. Good linearity was obtained for all pesticides with detection limits down to 0.04-0.46 ng/mL and a working range of 0.1-40 ng/mL. The repeatabilities of migration time and peak area were satisfactory with relative standard deviations (RSDs) between 0.66 and 13.6% and 4.1 and 28%, respectively. All pesticides except dieldrin were found to be detected at concentrations at least tenfold lower than the World Health Organization (WHO) guideline values. The analytical procedure developed offers an economic method for fast screening of multiple pesticide residues in drinking water for health protection. It had been applied to determine carbofuran and MCPA in agricultural run-off water samples, giving satisfactory repeatabilities of 10 and 12%, respectively, with n=5 for the determination of pesticides in contaminated water samples.     

Multiresidue determination of pesticides in drinking and related waters by solid-phase extraction and liquid chromatography with ultraviolet detection: interlaboratory study

As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 17 European laboratories evaluated a method using styrene-divinylbenzene copolymer solid-phase extraction followed by liquid chromatography with diode array detection. The main aim of the study was to evaluate whether the method meets the requirements of EC Drinking Water Directive 98/83 in terms of accuracy, precision, and detection limit for 21 pesticides according to the following requirements: limit of detection, < or =0.025 microg/L; accuracy expressed as recovery, between 75 and 125%; and precision expressed as repeatability relative standard deviation of the method, <12.5%, and as reproducibility relative standard deviation of the method, <25%. Analyses for unknown concentrations were performed with commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except pirimicarb (0.02 microg/L). The criteria for repeatability were met for all compounds. Terbutryn in bottled water and carbendazim in tap water did not meet the criteria for reproducibility. In terms of accuracy, the method met the requirements for all pesticides in both matrixes, except for metamitron. However, several compounds (linuron, terbutryn, propazine, metobromuron, and isoproturon) showed recoveries slightly below 75%.     

Multiresidue determination of pesticides in drinking and related waters by gas chromatography/mass spectrometry after solid-phase extraction: interlaboratory study

As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 15 European laboratories evaluated a method using styrene-divinylbenzene co-polymer solid-phase extraction followed by gas chromatography/mass spectrometry. The main aim of the study was to evaluate whether the method meets the requirements of EC Directive 98/83 in terms of accuracy, precision, and detection limit for 22 pesticides according to the following requirements: limit of detection, < or = 0.025 microg/L; accuracy, expressed as recovery between 75 and 125%; and precision, expressed as repeatability relative standard deviation of the method of < 12.5% and as reproducibility relative standard deviation of the method of < 25%. Analyses for unknown concentrations were performed with fortified commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except dimethoate and desisopropylatrazine (0.02 microg/L). The criteria for repeatability were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and chlorpyrifos, dimethoate, and lindane in tap water. The criteria for reproducibility were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and pendimethalin, chlorpyrifos, dimethoate, terbutryn, and lindane in tap water. In terms of accuracy, the method meets the requirements for all pesticides in both matrixes, except for lindane in bottled water and lindane and chlorpyrifos in tap water.     

Multiresidue determination of 77 pesticides in textiles by gas chromatography-mass spectrometry

A simple and efficient method for multiple determination of 77 pesticides, including one organonitrogen, eight carbamate, 12 pyrethroid, 26 organochloride, 30 organophosphorous compounds, in textiles is developed. Six representative textiles are chosen as test samples. Extraction using hexane-ethyl acetate (1:1) assisted by ultrasonic processor is carried out twice, followed by clean-up using solid-phase extraction on a florisil column. The final solution is analyzed using gas chromatography-mass spectrometry, and 77 pesticides are determined. This method is highly sensitive, selective, and reproducible, with a broad linear range and reliable accuracy. Six blank samples are spiked with 0.50 and 2.00 mg/kg of the 77 pesticides, and the corresponding recoveries are between 64.5% and 99.1%; the precisions range from 4.04% to 14.78%; and the minimum detection limits of this method are 0.02-0.20 mg/kg.     

Multiresidue analysis of pesticides with hydrolyzable functionality in cooked vegetables by liquid chromatography tandem mass spectrometry

It would be preferable for pesticide residues substituted by hydrolyzable functionality to be analyzed after cooking because their structures are apt to degrade during boiling and/or heating. A liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the quantitative determination of 44 pesticide residues with hydrolyzable functional group in five typical vegetable widely consumed in Republic of Korea is described. The sample clean‐up was carried out according to the method of Food Code No. 83 established by the Korea Food and Drug Administration (KFDA). Zorbox XDB‐C₁₈ column was selected for the analysis because of the best peak separation. The LC mobile phase consisted of water and 5 mm methanolic ammonium formate, which resulted in a peak shape with good symmetry at each run. Tandem mass spectroscopic (MS/MS) experiments were performed in ESI positive mode and the multiple reaction monitoring modes. A conventional matrix effect was modified to more comprehensive form 100γ_ij (%). A high matrix effect (相似文献   

气相色谱-质谱法分析蜂蜜中多种有机氯农药残留

建立了气相色谱-电子轰击离子化-质谱法（GC-EI-MS）同时分析蜂蜜试样中12种有机氯农药残留的分析方法.蜂蜜试样用V（正己烷）：V（乙酸乙酯）=5：1混合提取剂超声提取和Florisil硅藻土层析柱净化后,以PCB 103为内标物,采用GC-EI-MS的选择离子监测方式（SIM）分析,同时探讨了一些有机氯农药EI-MS特征离子的结构与断裂机理.当空白试样的加标浓度为10、50、200μg/kg时,加标回收率为80%～112%,相对标准偏差为0.4%～9.8%,方法检出限为0.2～4.0μg/kg,其中8种农药的MDL＜1.0μg/kg,线性范围为10～500μg/kg,相关系数皆大于0.996,此方法已用于蜂蜜试样中多种痕量有机氯农药残留的分析.     

Multiresidue analysis of pesticides in animal liver by gas chromatography using triple quadrupole tandem mass spectrometry

Two methods for extracting organochlorine (OCs) and organophosphorus (OPs) pesticides from animal liver have been developed. The determination was carried out by gas chromatography with electron impact ionization tandem mass spectrometry (GC-(EI-)MS/MS) using a triple quadrupole (QqQ) analyzer. First, a liquid-solid extraction performed with a high-speed homogenizer (Polytron) using ethyl acetate as solvent, and a subsequent clean-up by gel permeation chromatography (GPC) was applied, determining 34 pesticides. Secondly, a matrix solid phase dispersion (MSPD) extraction with octadecylsilyl (C(18)) sorbent combined with a Florisil clean-up and ethyl acetate elution was performed, analyzing 25 compounds. These methodologies have been tested and compared in the sample pre-treatment due to the fatty nature of the matrix. The GPC method was finally selected and validated, yielding recoveries in the range 70-115%, with precision values expressed as relative standard deviation (RSD) lower or equal to 20%, at the spiking levels of 25 and 50 microg kg(-1), and limits of quantification (LOQs) lower than the maximum residue levels (MRLs) set by the European Union in animal products, except for isofenphos. Linearity was also studied ranging between 5 and 300 microg kg(-1) for most of pesticides. This method was applied to the analysis of real liver samples of chicken, pork and lamb.     

Multiresidue method for the analysis of multiclass pesticides in agricultural products by gas chromatography-tandem mass spectrometry

A multiresidue method is described for determining 55 organophosphorus and organochlorinated compounds and pyrethroids commonly used in crop protection. Pesticide residues are extracted from samples with a mixture of ethyl acetate and sodium sulfate, obtaining a final preconcentration of I mg sample (ml extract)(-1). No additional clean-up steps are necessary. Analysis is performed by gas chromatography by using a combination of positive chemical ionisation (PCI) and electron impact (EI) ionisation modes and tandem mass spectrometry (GC-PCI/EI-MS-MS). Good sensitivity and selectivity of the method are obtained with limits of detection (LODs) ranging from 0.07 to 4.21 microg kg(-1) in all the cases, except for methamidophos, permethrin, cypermethrin and difenconazol. Average recoveries between 52 and 114% are obtained and good linearity is observed in the studied ranges (r > or = 0.994). The RSD values are < or = 29% in all the cases. The method has been applied to the analysis of 178 vegetable samples, as a part of the monitoring programme of the Association of Producers and Exporters of Fruits and Vegetables of Almería (COEXPHAL) and quality control systems applied during the assays have demonstrated a good performance and stability with time.     

Multiresidue determination of triarylmethane and phenothiazine dyes in fish tissues by LC-MS/MS

The occurrence of residues of malachite green and its leuco-metabolite in tissues of farmed fish for human consumption have long been of concern and there is extensive literature on methods of analysis and surveillance for these compounds. Recently, concern has been expressed that the use of other related compounds in place of malachite green may go undetected. This paper describes a new method for extending the range of triarylmethane and related phenothiazine dyes that can be detected in fish. In this procedure 13 parent compounds are monitored, with any potential leuco-forms being oxidized back to the parent prior to determination. The method utilizes a buffer–acetonitrile extraction followed by liquid–liquid extraction. Oxidant is added and the extracts further purified by cation exchange chromatography. Final determination is carried out using LC–MS/MS. The method has been validated to the standards of Commission Decision 2002/657/EC.