Evaluation and validation of a commercial ELISA for diazinon in surface waters

The performance of a commercially available microtiter plate ELISA kit for the determination of diazinon was evaluated for sensitivity, selectivity, intra-assay repeatability, accuracy, and matrix effects in fortified distilled water and filtered and unfiltered environmental surface water samples. Repeatability and reproducibility studies show that the kit satisfies current EPA criteria for the assessment of analytical methods. Mean recoveries from spiked samples averaged 80.3, 95.5, and 103.5% from distilled, unfiltered surface, and filtered surface waters, respectively. The experimentally determined method detection limit (MDL) for the commercial diazinon microtiter plate format (0.0159 microg L(-)(1)) was comparable to the least detectable dose (LDD) established by the manufacturer (0.022 microg L(-)(1)). Specificity studies indicate that the diazinon polyclonal antibody can readily distinguish the target compound from other structurally similar organophosphorus analogues, with the exception of diazoxon. Cross-reactivity with the oxon was approximately 29%, while reactivity with pirimiphos-methyl, pirimiphos-ethyl, and chlorpyrifos-ethyl was negligible. A slight matrix effect was discovered to be present in both filtered and unfiltered environmental water matrixes, but its effect on the immunoassays is insignificant within experimental error. For validation of the microtiter plate ELISA format, environmental surface and storm runoff water samples were collected, split, and analyzed directly by ELISA and by liquid-liquid extraction followed by GC (California State Department of Food and Agriculture method EM 46.0). Results of the two analytical methods were then compared statistically. A close correlation was found between methods for unspiked and untreated river water samples (r = 0.969) while a much less robust correlation was obtained for runoff waters (r = 0.728). Results from runoff waters exhibit a particularly high positive bias for the ELISA method relative to the GC method. Cross-reactivity of diazoxon and probably other unidentified cross-reacting components may be responsible for the exaggerated account of the target analyte in surface and runoff waters. While excellent for screening purposes, further study is required to elucidate and quantify the factors responsible for the consistent overestimation of ELISA results before the kit can be employed routinely for regulatory compliance monitoring.     

Influence of two insecticides, chlorpyrifos and quinalphos, on arginine ammonification and mineralizable nitrogen in two tropical soil types

Effects of seed treatments with chlorpyrifos [5 g of active ingredient (ai) kg(-1) of seed] and quinalphos (6.25 g of ai kg(-1) of seed) and standing crop treatments with chlorpyrifos (800 g of ai ha(-1)) and quinalphos (1000 g of ai ha(-1)) on arginine deamination and mineralizable nitrogen were monitored, in the sandy loam and loamy sand soils of two tropical semiarid fields, for three consecutive crop seasons. The arginine ammonification activity of rhizospheric microbes was inhibited after seed treatment with chlorpyrifos and quinalphos and their principal metabolites, 3,5,6-trichloro-2-pyridinol (TCP) and 3,5,6-trichloro-2-methoxypyridine (TMP) and 2-hydroxyquinoxaline and quinoxaline-2-thiol, respectively. Quinalphos produced transient inhibitions, whereas chlorpyrifos and its metabolites (TCP and TMP) exerted a greater inhibition in both loamy sand and sandy loam soils. Arginine ammonification by nonrhizospheric microbes was stimulated by standing crop treatments with both pesticides. In the loamy sand soil, the parent compounds stimulated rhizospheric N-mineralization, whereas the metabolites were inhibitory. However, nonrhizospheric N-mineralization was inhibited by both chlorpyrifos and quinalphos and stimulated by their metabolites. A higher magnitude of inhibition of arginine deamination in the loamy sand than in the sandy loam soil could be due to greater bioavailability of the pesticides in the former, resulting from lesser sorption of the pesticides due to alkalinity of the soil and its low content of clay and organic carbon. Although both pesticides affected mineralizable nitrogen, seed treatment with quinalphos and standing crop treatment with quinalphos and chlorpyrifos produced the most significant effects. The recommended doses of the pesticides not only efficiently controlled whitegrubs, which increased pod yields, but also left no residues in harvested kernels. They also caused no long-term inhibition of ammonification, which could have been of significant concern during the short crop period in semiarid areas where nitrogen determines plant productivity.     

The Luke et al. method for determining multipesticide residues in fruits and vegetables: collaborative study

Ten laboratories analyzed unfortified and fortified samples of lettuce, tomatoes, and strawberries for organochlorine and organophosphorus pesticides by applicable portions of the comprehensive multipesticide method of Luke et al. The 3 crops were fortified with 6 pesticides, alpha-BHC, dieldrin, chlorpyrifos, acephate, omethoate, and monocrotophos, each at 3 levels per crop. Included in the 54 fortifications were 16 pairs of blind duplicates: same pesticide, crop, and level. Recoveries were calculated by area comparisons with known reference materials, using the responses obtained from 2 separate element-specific gas chromatographic (GC) systems. The organochlorine pesticides were chromatographed on a methyl silicone column and detected with a Hall 700A electrolytic conductivity detector, and the organophosphorus pesticides were determined with a flame photometric detector after being chromatographed on a specified DEGS column material. Chlorpyrifos was quantitated on both GC systems. Mean recoveries ranged from 82.6% for acephate fortified at 0.5000 ppm in strawberries to 118.1% for 0.0636 ppm fortification of chlorpyrifos in lettuce. Interlaboratory coefficients of variation ranged from 4.0% for 0.6360 ppm fortification of chlorpyrifos in tomatoes to 17.8% for the 0.0636 ppm chlorpyrifos level in lettuce. The procedure features essentially no cleanup before GC and proved comparable to existing multiresidue methods for pesticides of the class types studied, as evidenced by the intra- and interlaboratory measurements of precision and recoveries obtained. The method with the 2 GC systems has been adopted official first action.     

海藻酸钠固定化细菌对毒死蜱的降解特性

毒死蜱的生产和使用日趋广泛,由其造成的环境污染和危害不容忽视。微生物是影响有机磷农药在环境中降解的最主要因素,也被认为是降解有机磷农药最可靠而高效的途径。固定化技术是提高微生物降解农药效率的有效方法之一。本研究以海藻酸钠为载体,采用注射器滴定法将蜡状芽孢杆菌(Bacillus cer-eus)HY-1用海藻酸钠溶胶包埋,研究了反应时间、固定化菌接入量、pH和毒死蜱初始浓度对毒死蜱降解的影响以及固定化菌的重复使用效果。结果表明:海藻酸钠固定化菌能够高效降解基础培养基中的毒死蜱,制备固定化小球海藻酸钠溶胶的最适浓度为2.5%(w/v),小球的平均粒径为3 mm。在培养时间为60 h时,固定化菌对100 mg·L-1毒死蜱的降解率达到最大。固定化小球接入量为160 g·L-1时,对100 mg·L-1毒死蜱的降解率最高。固定化菌对毒死蜱的降解有着较宽泛的pH适应范围,碱性环境更有利于其对毒死蜱的有效降解。当毒死蜱初始浓度为80 mg·L-1和100 mg·L-1时,固定化菌对毒死蜱的降解率较高,达90%左右。固定化菌可重复利用降解毒死蜱,当利用4次后,固定化小球虽已发生崩解,但对100 mg·L-1毒死蜱的降解率仍高达47%。因此,海藻酸钠固定化蜡状芽孢杆菌对水体中毒死蜱的降解率较高,环境适应性较强,固定化菌可在毒死蜱污染的净化去毒方面发挥重要作用。     

New approach to immunochemical determinations for triclopyr and 3,5,6-trichloro-2-pyridinol by using a bifunctional hapten,and evaluation of polyclonal antiserum

The present work describes the design and synthesis of the structurally unique hapten, "bifunctional hapten", to produce a group-specific polyclonal antiserum to triclopyr and 3,5,6-trichloro-2-pyridinol. A bifunctional hapten was designed and synthesized by conjugating commercially available Nepsilon-2,4-dinitrophenyl (DNP)-L-lysine to triclopyr, and then coupling this to carrier proteins such as bovine serum albumin (BSA). The synthesized bifunctional hapten greatly raised the antiserum titer in comparison with that of the conventional hapten, triclopyr. Antiserum with a sufficiently high titer to provide the determinations of targeted compounds was obtained only 63 days after the primary immunization. The obtained antiserum showed the highest affinity to triclopyr (IC(50) = 3.5 nM) and 3,5,6-trichloro-2-pyridinol (IC(50) = 5.1 nM) in homologous ELISA. The cross-reactivities to various agrochemicals and some chlorinated phenolic compounds were determined. Significant cross-reactivity was found to the herbicide 2,4,5-T. The antiserum reacted to both triclopyr and its metabolite. Assay sensitivity was evaluated for effects of various assay conditions, including pH value and concentrations of organic solvents and detergents. Under optimized assay conditions, the quantitative working range of triclopyr ELISA was from 0.1 to 5.2 ng/mL with a limit of detection (LOD) of 0.037 ng/mL, and an IC(50) of 0.72 ng/mL. On the other hand, the quantitative working range of 3,5,6-trichloro-2-pyridinol ELISA was from 0.13 to 6.0 ng/mL with a LOD of 0.052 ng/mL, and an IC(50) of 0.95 ng/mL. Water samples fortified with triclopyr or its metabolite at 1, 5, and 10 ng/mL were directly analyzed without extraction and cleanup by the proposed ELISA. The mean recovery was 101.6%, and the mean coefficient of variation (CV) was 7.1% in the case of the triclopyr ELISA. In the case of the 3,5,6-trichloro-2-pyridinol ELISA, the mean recovery was 99.8%, and the mean CV was 9.5%. The proposed ELISA turned out to be a powerful tool for monitoring of residual triclopyr or 3,5,6-trichloro-2-pyridinol in water samples at trace level.     

Practical immunochemical method for determination of 3,5, 6-trichloro-2-pyridinol in human urine: applications and considerations for exposure assessment

An analytical method is described for the quantitative determination of 3,5,6-trichloro-2-pyridinol (3,5,6-TCP) in human urine. This is the primary analyte found in urine as a result of exposure to chlorpyrifos, chlorpyrifos-methyl, triclopyr, or 3,5,6-TCP. Conjugates of 3,5,6-TCP are released from urine by acid hydrolysis. The free 3,5,6-TCP is purified using C(18) solid-phase extraction, eluting the analyte with 1-chlorobutane. An aliquot of 1-chlorobutane is placed in a vial containing Trichloropyridinol Sample Diluent and evaporated, leaving the 3,5,6-TCP in the aqueous sample diluent. The samples are assayed using the Trichloropyridinol RaPID Assay immunoassay test kit. Final results are calculated using a standard curve constructed by linear regression after a ln/Logit data transformation is performed of the concentration and the absorbance readings, respectively. The calculated lower limit of quantitation for 3,5,6-TCP in fortified control urine samples is 2. 96 ng/mL (2.96 ppb). Residues of 3,5,6-TCP determined using both immunochemical and gas chromatography with mass spectrometric detection correlate well.     

Simplified cleanup and gas chromatographic determination of organophosphorus pesticides in crops

A simple and efficient cleanup method for gas chromatographic determination of 23 organophosphorus pesticides in crops including onion is described. The sample was extracted with acetone. The extract was purified with coagulating solution, which contained ammonium chloride and phosphoric acid, and then filtered by suction. The filtrate was diluted with NaCl solution and reextracted with benzene. The organic layer was evaporated and injected into a gas chromatograph equipped with a flame photometric detector (FPD) and fused silica capillary columns (0.53 mm id) coated with silicone equivalent to OV-1701, OV-1, and SE-52. Onion extract, which contained FPD interferences, was cleaned up on a disposable silica cartridge. Recoveries of most organophosphorus pesticides from spiked crops: mandarin orange, tomato, spinach, sweet pepper, broccoli, lettuce, and onion at levels of 0.02-0.28 ppm, exceeded 80%, but the water-soluble pesticides dichlorvos and dimethoate gave poor recoveries in all crops; the nonpolar pesticides disulfoton, chlorpyrifos, fenthion, prothiophos, and leptophos were not recovered quantitatively in spinach, sweet pepper, broccoli, and lettuce. IBP, edifenphos, phosmet, and pyridaphenthion were not recovered from onion because of adsorption to the silica cartridge. The detection limits ranged from 1.25 to 17.5 ppb on a crop basis.     

Identification of O,O-dialkyl-S-methylphosphorodithioate residues in fish

O,O-Dialkyl-S-methylphosphorodithioates were found in Mississippi River buffalo fish caught near several chemical plants and oil refineries in Hartford and Wood River, IL. These chemicals, which have not been previously recognized as environmental or food contaminants, were identified and quantitated by a procedure similar to the AOAC multiresidue method for organochlorine and organophosphorus pesticides, using gas chromatography (GC) with flame photometric detection (FPD). The key to their identification was a GC/FPD retention time pattern that was virtually the same as that for the diazomethane reaction products of a commercial zinc dialkyl dithiophosphate motor oil additive. GC/mass spectrometry (MS) showed that the compound producing the largest GC/FPD peak contained butoxy groups. The identification of this compound as O,O-di(2-methylpropyl)-S-methyl-phosphorodithioate (Compound C) was confirmed by GC/MS analysis by comparison with the authentic material. The buffalo fish contained 0.15 ppm Compound C and 0.5 ppm total O,O-dialkyl-S-methylphosphorodithioates. Subsequent analyses of fish from other areas showed that these contaminants were not limited to the Hartford-Wood River area. Lower residue levels of Compound C, ranging from 0.01 to 0.05 ppm, were found in fish from the Mississippi River at Sauget, IL, and from the Delaware River and Newark Bay in NJ.     

The persistence and degradation of chlorothalonil and chlorpyrifos in a cranberry bog

The effect of a spray-tank adjuvant on the persistence, distribution, and degradation of two pesticides, chlorothalonil and chlorpyrifos, was studied in a commercial cranberry bog. Pesticides were applied according to label instructions to cranberry plants in paired plot studies. Dislodgeable foliar and whole fruit residues of both pesticides and several degradation products were assessed over a growing season. Residues were also assessed in soil samples collected at fruit harvest. Adjuvant increased both fruit and foliar residues but did not significantly alter the dissipation rate or metabolism of either pesticide. The dissipation of dislodgeable foliar chlorothalonil and chlorpyrifos residues followed first-order kinetics, with estimated half-lives of 12.7 and 3.5 d, respectively. All residue levels on harvested fruit were well below the current U.S. EPA tolerances for fresh cranberries. Chlorothalonil (58%) was the major residue in fruit at harvest (76 d post-chlorothalonil application), with 4-hydroxy-2,5,6-trichloroisophthalonitrile and 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene accounting for 26% and 6% of the total residues, respectively. Degradation products accounted for 88% of the total chlorothalonil residues in soil at fruit harvest. The products 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene, 1-carbamoyl-3-cyano-4-hydroxy-2,5,6-trichlorobenzene, 2,5,6-trichloro-4-methylthioisophthalonitrile, and 2,4,5-trichloroisophthalonitrile have not been previously identified in cranberry bog environments. Chlorpyrifos was detected in fruit at harvest (62 d post-chlorpyrifos application), but no metabolites were found. Chlorpyrifos-oxon and 3,5,6-trichloro-2-pyridinol, however, were detected in earlier fruit samples and in foliage and soil samples.     

蔬菜有机磷农药多残留检测中的样品基质干扰及检测方法的适宜性

为研究NY/T 761-2004(农业行业标准)用于蔬菜有机磷农药多残留检测中的样品基质干扰问题,根据NY/T 761-2004分析众多蔬菜样品,结合气质联用技术,评估蔬菜样品基质对有机磷农药多残留分析的干扰。结果表明,用NY/T 761-2004检测蔬菜有机磷农药多残留时,绿叶菜类、白菜类、瓜类、茄果类、豆类、薯芋类和根菜类蔬菜几乎没有样品杂质峰,有机磷农药测定不受干扰;甘蓝类蔬菜(如紫甘蓝、甘蓝和西兰花等)有显著的样品杂质峰,敌敌畏、甲胺磷、甲拌磷和甲基毒死蜱等测定常受干扰;葱蒜类蔬菜(如蒜、葱和韭菜等)有较强的样品杂质峰,有机磷农药多残留测定无法进行。     

壳聚糖金属配合物对冬枣保鲜作用及降解有机磷农药

为了降低由于冬枣腐烂造成的经济损失及提高冬枣食用安全性,该文研究了室温贮藏条件下壳聚糖锌(Ⅱ)、铈(Ⅳ)配合物对冬枣的保鲜作用,并探讨了其对冬枣表面有机磷农药的降解效果和机理。结果表明,在冬枣贮藏期间,壳聚糖金属配合物涂膜组处理的冬枣的质量损失率、呼吸强度和多酚氧化酶的活性均显著低于对照组,可溶性固形物、维生素C和多酚的质量分数均显著高于对照组,对有机磷农药毒死蜱的降解率显著高于对照组;总有机碳质量分数(TOC)、气相色谱-质谱联用(GC-MS)分析表明,壳聚糖金属配合物降解毒死蜱的中间产物主要为O,O-二乙基(3,5,6-三氯-2-吡啶基)、3,5,6-三氯-2-吡啶醇,最终降解产物为PO43-、NO3- 和Cl-,降解途径主要为氧化和水解作用,不会引起中间产物积累而导致二次污染。研究结果为冬枣的采后保鲜和壳聚糖金属配合物降解有机磷农药的实际应用提供理论依据。     

Development of an enzyme-linked immunosorbent assay for the organophosphorus insecticide bromophos-ethyl

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the organophosphorus insecticide bromophos-ethyl. Four bromophos-ethyl derivatives (haptens) were synthesized and were coupled to carrier proteins through the pesticide thiophosphate group to use as an immunogen or as a coating antigen. Rabbits were immunized with either one of two haptens coupled to bovine serum albumin for production of polyclonal antibodies, and the sera were screened against one of the haptens coupled to ovalbumin. Using the serum with highest titer, an antigen-coated ELISA was developed, which showed an IC(50) of 3.9 ng/mL with a detection limit of 0.3 ng/mL (20% inhibition). An antibody-coated ELISA using an enzyme tracer was also developed, which showed an IC(50) of 6.5 ng/mL with a detection limit of 1.0 ng/mL (20% inhibition). The antibodies showed negligible cross-reactivity with other organophosphorus pesticides except with the insecticides bromophos-methyl and chlorpyrifos in the antibody-coated assay only. Recoveries of bromophos-ethyl from fortified crop and water samples ranged from 82 to 128% and from 95 to 127%, respectively.     

The effect of cooking on chlorpyrifos and 3,5,6-trichloro-2-pyridinol levels in chlorpyrifos-fortified produce for use in refining dietary exposure

Various types of produce were fortified with chlorpyrifos and then boiled, baked, canned, or concentrated as appropriate for the type of produce. Both uncooked and cooked samples were analyzed for chlorpyrifos and 3,5,6-trichloro-2-pyridinol, and then, chlorpyrifos cooking factors were calculated by comparing the postcooked concentration to the uncooked concentration. The cooking factors were dependent upon the commodity and cooking procedure: 0.320-1.19 for boiled samples, 0.022-1.18 for baked pulp, and 0.119-0.661 for canned samples. Concentrating chlorpyrifos-fortified orange juice 4-fold resulted in a concentration factor of only 2.6, indicating a loss of chlorpyrifos. Green bean and green pepper plants treated in the greenhouse yielded higher chlorpyrifos concentrations but similar cooking factors to lab-fortified samples. The cooking factors can be used with food consumption databases and modeling tools to refine the dietary exposure according to current product label uses.     

Isolation and concentration of organophosphorus pesticides from drinking water at the ng/L level, using macroreticular resin.

A screening method has been developed for determining organophosphorus pesticides at ng/L levels in drinking water. Sixteen organophosphorus pesticides, diazinon, diazinon-oxon, dimethoate, ronnel, beta-phosphamidon, methyl parathion, ethyl parathion, malathion, chlorpyrifos, fenitrothion, ruelene, methidathion, ethion, EPN, phosalone, and phosmet, were extracted by Amberlite XAD-2 resin from 100 and 200 L drinking water previously spiked with these pesticides. The pesticides were eluted from the XAD-2 resin with acetone-hexane (15+85). The concentrated extract was analyzed by gas chromatography using a nitrogen-phosphorus selective detector and by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries at the 10 and 100 ng/L spiking levels were greater than 90%, except recoveries for dimethoate and phosphamidon were 37 and 42%, respectively. The analysis of 300 L Ottawa tap water showed no detectable amounts (less than 1 ng/L) of any of the 16 organophosphorus pesticides.     

Use of stable tracer studies to evaluate pesticide photolysis at elevated temperatures

New methods were developed to determine photolysis rates of medium-weight pesticides in the gas phase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glass chamber was constructed that utilized collimated xenon arc irradiation that could heat chamber air to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determined at various air temperatures by comparing the rate of loss of each of the tested pesticides to a photochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents was performed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticides under examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticide chlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24 min corrected for sunlight. These results were comparable to photochemical lifetime estimates from other investigators under sunlight conditions. Elevating temperatures from 60 to 80 degrees C did not affect photolysis rates, and these rates could be extrapolated to environmental temperatures. From 60 to 80 degrees C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 h corrected for sunlight and will thus be important together with hydroxyl radical reactions for removing this substance from the atmosphere. At these elevated temperatures, pesticides and tracer compounds were found to be substantially in the gas phase, and possible effects on reaction rates from wall interactions were minimized.     

Development of green onion and cabbage certified reference materials for quantification of organophosphorus and pyrethroid pesticides

Green onion and cabbage certified reference materials for the analysis of pesticide residues were issued by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Green onion and cabbage samples were grown so as to contain several kinds of organophosphorus and pyrethroid pesticides, and those were collected from a field in the Kochi Prefecture in Japan. The certification was carried out by using multiple analytical methods to ensure the reliability of analytical results; the values of target pesticides (diazinon, fenitrothion, cypermethrin, etofenprox, and permethrin for green onion and chlorpyrifos, fenitrothion, and permethrin for cabbage) were obtained by isotope dilution mass spectrometry. Certified values of target pesticides were 0.96-13.9 and 2.41-6.9 mg/kg for green onion and cabbage, respectively. These are the first green onion and cabbage powder certified reference materials in which organophosphorus and pyrethroid pesticides are determined.     

Reactivity of certain organophosphorus insecticides toward hydroxyl radicals at elevated air temperatures

Methods were developed to determine OH reaction rates for medium-weight organophosphorus pesticides in the gas phase. A 57-L chamber was constructed that utilized xenon arc irradiation (>290 nm) to photolyze the OH precursor, methyl nitrite. Experiments were performed at elevated temperatures ranging from 60 to 80 degrees C to minimize wall sorption. Solid-phase microextraction (SPME) sampling of the gas phase was employed to assess the simultaneous rate of loss of the pesticides in relation to the rate of loss of two reference substances with known OH rate constants. An internal gas-phase standard (hexachlorobenzene), relatively stable to hydroxyl radicals, was used to assess other processes, which included dilution and wall sorption. The relative reaction rates of the organophosphorus insecticides, diazinon and chlorpyrifos, when compared to reference compounds, were unaffected by various air temperatures between 60 and 80 degrees C. Although both insecticides were expected to react at similar rates on the basis of structural activity model predictions, diazinon reacted 3 times more rapidly than chlorpyrifos and gave estimated environmental OH half-lives of 0.5 and 1.4 h, respectively. The degree of sorption onto the chamber walls was minimal and similar for each of the compounds examined. Experimental gas-phase determinations at elevated temperatures may provide important information that can be used when in the assessment of the potential of airborne pesticide risks to nontarget and ecologically sensitive areas.     

毒死蜱有毒代谢物3,5,6-TCP在土壤中的吸附-解吸研究

应用OECD106批平衡方法,研究了毒死蜱的有毒代谢物3,5,6-TCP在6种典型土壤中的吸附-解吸行为。结果表明：Elovich方程、双常数方程和抛物线扩散方程能较好地拟合3,5,6-TCP在第四纪红土、黑土、黄壤和褐土中的吸附动力学过程,而对紫色土和潮沙土的拟合度较低（拟合相关系数小于0.85）;应用Freundlich方程和线性方程拟合第四纪红土、黑土、黄壤和褐土的经验常数nfads均小于1（非线性吸附）,而紫色土和潮沙土的nfads值则接近于1（线性吸附）;3,5,6-TCP在6种土壤中解吸的滞后系数H值均大于1,即解吸速率大于吸附速率。6种土壤对3,5,6-TCP的吸附常数Kfads从1.37-6.74μg1-n·fmLn·fg^-1,吸附系数Kd值从0.50-1.30mL·g^-1,其中第四纪红土和黑土对其吸持力较强（Kd〉1）,因而更应注意环境安全;其他4种土壤的Kd值则均小于1,淋溶风险较大。     

Behavior of Insecticide Chlorpyrifos on Soils and Sediments with Different Organic Matter Content from Provincia de Buenos Aires, República Argentina

Buenos Aires Province (República Argentina) has undergone, in the last years, a great increase in agricultural activities based on the incorporation of new technologies and reduction of diversity to meet the increasing food demand. The increase of intensive agricultural systems in Argentina involves the use of fertilizers and pesticides such as herbicides, insecticides, and fungicides. Chlorpyrifos is one of the insecticides most widely used in these crops and constitutes a risk for human health, birds, and aquatic biota such as macroinvertebrates and fishes. In order to assess the possible contamination that the use of this product may represent for the environment, it is necessary to study its interaction with the different types of soils because fate and transport of environmental pollutants may be influenced by their interactions with soil particles. The behavior of chlorpyrifos was analyzed through the study of the recoveries from spiked solid environmental matrices. A strong dependence with organic matter content was observed along with an important dependence with the initial concentrations employed. Here, we show that chlorpyrifos behavior on solid matrices not only depends on soil chemical composition. A significant dependence of recovery percentages with initial concentrations of the pesticide was evident in all cases. Recovery percentages decreased with an increase of the initial concentration employed, no matter the variations in matrices of chemical compositions.     

HPLC测定水体中毒死蜱及其有毒降解产物TCP

通过比较不同的提取溶剂和使用量,就水体中毒死蜱和TCP残留提取的效果及不同的流动相组成和比例对毒死蜱和TCP测定的影响,建立了水体中毒死蜱及TCP的HPLC残留分析方法。结果表明,水体中毒死蜱和TCP最佳提取溶剂为乙酸乙酯,提取次数为2次,用量分别为50和30mL。色谱条件为：流动相为甲醇：水=90：10或乙腈：水=90：10,流速1mL·min^-1;紫外检测波长300nm。当流动相为甲醇：水=90：10时,毒死蜱和TCP的保留时间分别为6．4和3．6min;当流动相为乙腈：水=90：10时,其保留时间分别为5．6和2．5min。毒死蜱和TCP的检出限分别为0．5和0．15ng。当毒死蜱和TCP在水中的添加浓度为0．01～5mg·L^-1时,标准添加回收率分别为91．4％-105．1％和90．6％～105．4％,变异系数分别为0．99％～4．12％和0．29％～9．33％。水样中毒死蜱和TCP的最小检出浓度分别为2和0．6ng·mL^-1。