1.Determination of polar organophosphorus pesticides in aqueous samples by direct injection using liquid chromatography–tandem mass spectrometry Benno A. Ingelse, Ruud C. J. van Dam, Rob J. Vreeken, Hans G. J. Mol and Odile M. Steijger Abstract： It was demonstrated that four out of six of the very polar organophosphorus pesticides (OPs), i.e. acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion, could not be extracted from water using commonly available SPE cartridges. In addition, gc analysis on all six compounds was found to be troublesome due to their polar and thermolabile character. This initiated the development of an alternative highly sensitive and selective method for the determination of the above mentioned very polar OPs in water, based on LC–MS. Large volume (1 ml) water samples were directly injected onto an RP18 HPLC column with a polar endcapping. The latter was essential for obtaining retention and maintaining column performance under 100% aqueous conditions during the sampling. The compounds were ionized using atmospheric pressure chemical ionization and detected on a tandem mass spectrometer operated in multiple reaction-monitoring mode. The detection limits were in the range of 0.01–0.03 μg/l. Compared to conventional gc methods, the developed LC–MS procedure is very straightforward, fast and more reliable. This application demonstrates the applicability of LC–MS for analysis of polar OPs in surface, ground and drinking water, as a more favourable alternative to gc.
Journal of Chromatography A Volume 918, Issue 1, 18 May 2001, Pages 67-78
2.Determination of polar organophosphorus pesticides in vegetables and fruits using liquid chromatography with tandem mass spectrometry: selection of extraction solvent Hans G. J. Mol, , Ruud C. J. van Dam and Odile M. Steijger Abstract： A method based on liquid chromatography (LC)–mass spectrometry (MS)/MS was developed for sensitive determination of a number of less gas chromatography (gc)-amenable organophosphorus pesticides (OPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion) in cabbage and grapes. For extraction, several solvents were evaluated with respect to the possibility of direct injection, matrix-induced suppression or enhancement of response, and extraction efficiency. Overall, ethyl acetate was the most favourable solvent for extraction, although a solvent switch was required. For some pesticide/matrix combinations, reconstitution of the residue after evaporation required special attention. Extracts were analysed on a C18 column with polar endcapping. The pesticides were ionised using atmospheric pressure chemical ionisation on a tandem mass spectrometer in multiple reaction monitoring mode. The final method is straightforward and involves extraction with ethyl acetate and a solvent switch to 0.1% acetic acid/water without further cleanup. The method was validated at the 0.01 and 0.5 mg/kg level, for both cabbage and grapes. Recoveries were between 80 and 101% with R.S.D.<11% (n=5). The limit of quantification was 0.01 mg/kg and limits of detection were between 0.001 and 0.004 mg/kg.
Journal of Chromatography A Volume 1015, Issues 1-2, 10 October 2003, Pages 119-127
3.Determination of organophosphorus pesticide residues in Cilento (Campania, Italy) virgin olive oil by capillary gas chromatography Luca Rastrelli, , Katia Totaro and Francesco De Simone Abstract： In this study, the occurrence of 18 organophosphorus pesticide residues in Cilento (Campania, Italy) virgin olive oil was investigated. Sixty-five samples were taken from the major production areas during 1999–2000. In 31 samples, nine organophosphorus pesticides, namely azinphos-ethyl, chlorpyrifos-methyl, diazinon, dimethoate, fenthion, formothion, methidathion, parathion and parathion-methyl were found in concentrations ranging from 0.030 to 0.120 mg/kg. Acefate, carbophenothion, chlorpyrifos, malaoxon, malathion, methamidophos, omethoate, paraoxon-methyl, and pirimiphos-methyl were not detected in any sample. Analysis was carried out using capillary gas chromatography with a Nitrogen/Phosphorus Detector (NPD) detector, after sample extraction with n-hexane and clean-up by a single-step multi-cartridge system. Recoveries of 18 pesticides at three fortification levels (0.5, 1.0 and 2.5 mg/kg) were in the range 82–110%. Only two samples contained dimethoate residue that exceeded the FAO/WHO Codex Alimentarius maximum residue limits (MRLs).
Food Chemistry Volume 79, Issue 3, November 2002, Pages 303-305
4.Simplified multiresidue method for the determination of organophosphorus insecticides in olive oil Paolo Cabrasa, , Alberto Angionia, Marinella Melisa, Elizabeth V. Minellib and Filippo M. Pirisia
Abstract： A simple and rapid method for the determination of 13 organophosphorus insecticides and theie metabolites in olive oil by gc is described. The pesticide was extracted from oil with acetonitrile and no cleanup was needed. gc-nitrogen-phosphorus detection response factors of pesticides were affected by solvents and coextractive substances. Pesticides in hexane showed on average higher response factors. Standards were prepared in the residue-free oil extract solubilized in hexane to handle effects of matrix and solvent. The low amount of coextractive substances does not decrease the column efficiency, even after a few hundred analyses. Recovery at three fortification levels (ca. 0.1, 1.0 and 3.0 mg/kg) ranged from 74 to 118%, with coefficients of variation ranging from 1 to 16.
Journal of Chromatography A Volume 761, Issues 1-2, 14 February 1997, Pages 327-331
5.Impurity analysis of methamidophos with chromatographic methods C. Bor Fuh and M. L. Wu Abstract： An impurity analysis of methamidophos (O,S-dimethyl phosphoramidothioate) which is one of the frequently used pesticides for crop protections was carried out. Four impurity standards by synthesis and purifications to be used for quantitative impurity analysis were prepared. The chromatographic methods like gas chromatography (gc), liquid chromatography (LC), and gas chromatography–mass spectrometry (gc–MS) were used to analyze and compare the active ingredients and impurity contents. The active ingredient of methamidophos amounts to averages of 70.18% for technical materials and had averages of 52.61% for formulated materials, as determined by chromatographic analysis. There were seven impurities which were more than 0.1% of the sample weight. Hazardous impurities such as trimethyl phosphorothioate (TMP) and isotrimethyl phosphorothioate (i-TMP) were found to be 3.13% and 1.10% for technical methamidophos and 2.37% and 0.86% for formulated methamidophos, respectively. The analytical results of the active ingredient and impurity contents in this study were all consistent with impurity specifications from the Food and Agriculture Organization (FAO) of the United Nations. The residual components of technical methamidophos were around 12%, consisting of Al, Si, K, and P elements after ignition at 450°C for 4 h.
6.Automated on-line gel permeation chromatography-gas chromatography for the determination of organophosphorus pesticides in olive oil Jolan J. Vreulsa, , Raoul J. J. Swena, Vincent P. Goudriaana, Mia A. T. Kerkhoffb, Gijsbertus A. Jongenotterb and Udo A. Th. Brinkman Abstract： An on-line combination of gel permeation chromatography and gas chromatography has been designed using either a laboratory-built or a commercially available LC-gc apparatus to determine organophosphorus pesticides in olive oil. Gel permeation chromatography was used for sample pretreatment, viz. to separate the low-molecular-mass pesticides from the higher-molecular-mass fat constituents of the oil. A mixture of n-decane and the azeotropic mixture of ethyl acetate and cyclohexane was found to give an adequate separation between the fat and the organophosphorus pesticides. The pesticide-containing fraction, monitored by a UV detector, was transferred on-line to the gas chromatograph using a loop-type interface. n-Decane (6%, v/v) was added to the eluent in order to widen the application range of the transfer technique towards more volatile pesticides. After solvent evaporation through the solvent vapour exit and subsequent gc separation, the compounds were selectively detected with a thermionic or a flame photometric detector. The set-up allowed the direct analysis of oil samples after dilution in the gel permeation chromatography eluent without further sample clean-up. Detection limits were about 5 and 10 μg/kg with the thermionic and the flame photometric detector, respectively, when using an injection volume of only 30 μl of the 20-fold diluted oil. The total procedure was linear in the 0.01–10 mg/kg range for both detectors. For twenty organophosphorus pesticides, the relative standard deviations were 3–13% at the 20–60 μg/kg level.
Journal of Chromatography A Volume 750, Issues 1-2, 25 October 1996, Pages 275-286
7.Multiresidue method for determination of 90 pesticides in fresh fruits and vegetables using solid-phase extraction and gas chromatography-mass spectrometry Darinka tajnbaher, , a and Lucija Zupan i -Kralj Abstract： A multiresidue method for analysis of 90 pesticides with different physico-chemical properties in fruits and vegetables was developed. The method involves a rapid and small-scale extraction procedure with acetone using vortex mixing. Solid-phase extraction (SPE) on a highly cross-linked polystyrene divinylbenzene column (LiChrolut EN) was used for clean-up and pre-concentration of the pesticides from the water-diluted acetone extracts. For most fruit and vegetable samples this partial clean-up was sufficient, but some of them with more co-extracting substances need further clean-up (cereals, spinach, carrots, etc.). Diethylaminopropyl (DEA) modified silica was used for efficient removal of interferences caused by various organic acids, sugars, etc. The pesticide residues were determined by gas chromatography with a mass selective detector (GC-MS). The majority of pesticide recoveries for various fruits and vegetables were >80% in the concentration range from 0.01 to 0.50 mg/kg, except for the most polar pesticides (methamidophos, acephate, omethoate) which cannot be determined by this method. The limit of quantitation for most of the pesticides was 0.01 mg/kg with majority of relative standard deviations (R.S.D.s) below 10%. Journal of Chromatography A Volume 1015, Issues 1-2, 10 October 2003, Pages 185-198
以上都是SD数据库中的文献。
8.Determination of Organophosphorus Pesticides in Foods Using an Accelerated Solvent Extraction System Hirotaka Obana, Kosuke Kikuchi, Masahiro Okihashi and Shinjiro Hori
Residual organophosphorus pesticides in foods were determined by accelerated solvent extraction (ASE), gel permeation chromatography and GC–FPD. Pesticides were extracted at 100 °C under 1500 psi pressure in less than 20 min. Wet samples were extracted after mixing with Extrelut drying agent. Four foods were spiked with 19 pesticides at 0.1 ppm or less. The average recoveries of these pesticides were 80–90% and the precision was <10%. Both methamidophos and acephate gave 37–50% recoveries and 6–40% precision. These results suggested that ASE can be used to extract residues of organophosphorus pesticides in foods
9.Determination of buprofezin, methamidophos, acephate, and triazophos residues in Chinese tea samples by gas chromatography Zhang S, Yi J, Ye J, Zheng W, Cai X, Gong Z.
Over the past 7 years, acute food poisoning arising from the consumption of methamidophos-tainted vegetables has occurred sporadically in Hong Kong. To enable prompt remedial and regulatory actions to be taken, a simple and rapid gas chromatographic method was developed to determine methamidophos residues in food remnants. Samples were homogenized and extracted with acetone. Acetone in the resultant extract was removed by rotary evaporation, leaving behind an aqueous solution. After washing with petroleum ether and addition of sodium sulphate, the aqueous solution was re-extracted with chloroform. The chloroform extract was concentrated to dryness and the residue was reconstituted in absolute ethanol for determination by gas chromatography with flame photometric detection. The method was found to be applicable also to the determination of acephate, dimethoate, omethoate and trichlorfon. Mean recoveries of the five organo-phosphorus pesticides at two fortification levels, viz. 1 mg/kg and 10 mg/kg, ranged from 74 to 113%. Relative standard deviations lay between 1.3 and 6.1%. Method detection limits ranged from 0.02 to 0.04 mg/kg. In 1994, 75 food poisoning cases in Hong Kong were suspected to be related to the consumption of methamidophos-tainted vegetables; 13 food remnants were received for analysis, four of them were found to contain high concentrations of methamidophos. Food Addit Contam. 1996 Aug-Sep;13(6):687-93.
10.Determination of Organophosphorus Pesticides in Water, Vegetables and Grain by Automated SPE and MEKC T. Pérez-Ruiz, C. Martínez-Lozano, A. Sanz and E. Bravo Abstract： A sensitive method for the multi-residue analysis of organophosphorus pesticides in environmental samples has been developed. It involves an automated solid phase extraction procedure using a Gilson ASPEC XLi and capillary electrophoresis analysis with UV detection. Acephate, methamidophos, dichlorvos, dicrotophos and malathion could be separated by micellar electrokinetic capillary chromatography using an electrophoretic electrolyte containing 20 mM phosphate buffer (pH 7.5) and 75 mM sodium dodecyl sulphate. A linear relationship between concentration and peak area was obtained within the range 0.2–450 g mL–1 with correlation coefficients greater than 0.996 and detection limits between 7 and 150 ng mL–1. Intra- and inter-day precision values of about 0.8–2.3% RSD (n=11) and 0.9–3.0% RSD (n=15), respectively were obtained. When the preconcentration step was used, an enrichment factor of 250 was easily achieved in the analysis of water samples, making it possible to determinate pesticide residues at concentration levels as low as 0.04 ng mL–1. In analyses of vegetables and grains, the sensitivity levels were about 0.03ug–1. Chromatographia：Volume 61, Numbers 9-10; 493-498
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