The dissipation rates of trichlorfon and its degradation product dichlorvos in cabbage and soil

The residual levels and dissipation rate of trichlorfon, and its degradation product, dichlorvos, in cabbage crops and the soil in which these were grown, were determined by gas chromatography at two geographically distant experimental sites, one in Kunming and one in Beijing, China. Trichlorfon was applied at two dosages (900 g ai ha⁻¹ and 1350 g ai ha⁻¹). Maximum final residues of trichlorfon in soil and cabbage were 1.23 mg kg⁻¹ and 1.81 mg kg⁻¹ respectively at Kunming, and 0.35 mg kg⁻¹ and 0.70 mg kg⁻¹ respectively at Beijing. However, the final residues of dichlorvos in both cabbage and soil was only 0.04 mg kg⁻¹ at Kunming, and only 0.03 mg kg⁻¹, or “not detectable”, at Beijing. The mean half-life of trichlorfon in cabbage was 1.80 d with a dissipation rate of 90% over 5 d, while that in soil was 3.05 d with a dissipation rate of 90% over 14 d at one experimental site. The dissipation rates of trichlorfon and its degradation product dichlorvos at the two experimental sites were different, suggesting that degradation of these pesticides was affected by local soil characteristics and climate. When applied at both the recommended dosage and at 1.5 times this, no detectable residues of either trichlorfon or dichlorvos were found in soil or cabbage at harvest. Although trichlorfon can easily degrade into dichlorvos, which is highly toxic to humans and other animals, the observed low residual levels of dichlorvos suggest that trichlorfon is safe when applied at the recommended dosage.     

Method development and application for triazine herbicides analysis in water,soil and sediment samples from KwaZulu-Natal

Penoxsulam is a triazolopyrimidine sulfonamide group of rice herbicide. The phototransformation of penoxsulam was studied under UV light (λ_max ≥ 290 nm) and sunlight in aqueous methanol and acetonitrile solvent system using TiO₂ as sensitizer. The rate of photodegradation of penoxsulam in different solvent systems followed first-order kinetics and calculated half-lives was found to be in the range of 51.89–73.41 h and 62.70–97.09 h for UV light and sunlight respectively in the presence or absence of sensitizer. From this study, a total of six photoproducts were identified and characterized on the basis of Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved were hydrolysis, photo oxidation of the sulfonamide group, breaking of sulfonamide bond, loss of amino and sulfonic acid group.     

Molecularly imprinted polymer for analysis of trace atrazine herbicide in water

A molecularly imprinted polymer (MIP) for atrazine was synthesized by non-covalent method. The binding capacity of MIP was 1.00 mg g^{? 1} polymer. The selectivity and recovery were investigated with various pesticides which are mostly, found in the environment, for both similar and different chemical structure of atrazine. The competitive recognition between atrazine and structurally similar compounds was evaluated and it was found that the system provided highest recovery and selectivity for atrazine while low recovery and selectivity were obtained for the other compounds. The highest recovery was obtained from MIP compared with non-imprinted polymer (NIP), a commercial C₁₈ and a granular activated carbon (GAC) sorbent. The method provided high recoveries ranged from 94 to 99% at two spiked levels with relative standard deviations less than 2%. The lower detection limit of the method was 80 ng L^{? 1}. This method was successfully applied for analysis of environmental water samples.     

Behaviour and mobility of preemergent herbicides in turfgrass: A field study

Abstract

The quality of many golf courses and other turfgrass areas often requires high levels of cultural management. The fact that this level of maintenance usually includes the use of preemergent herbicides has caused concern about their potential for ground water contamination. Much of this concern is based on extrapolation from agricultural situations rather than data developed from studies conducted in field turfgrass situations. To address this data gap, a two‐year field project evaluating the behaviour and mobility of the commonly used preemergent herbicides, benfluralin, trifluralin, bensulide, oxadiazon. pendimethalin, and DCPA with its two metabolites was conducted at OARDC/The Ohio State University, Wooster, Ohio, in 1988–89. Plots were located on a site with thatch (WT) and one with no thatch (NT)to further clarify the impact of thatch on herbicide behavior. Treatments were applied in April and samples of thatch and four zones of soil (0–2.5, 2.5–5, 7.5–10 and 22.5–25cm) were collected throughout the year and analyzed for residue dissipation. Residues of pendimethalin, benfluralin, and trifluralin in the 22.5–25 cm zone were below the limit of determination. No detectable oxadiazon residues were found in this zone at the WT site in 1988 but on two occasions, residues of 0.01 and 0.02 kg/ha were found in 1989. At the NT site, residues in this zone on one occasion were 0.02 kg/ha in 1988 and none in 1989. Residues of bensulide in the same zone ranged not detectable (ND)‐0.02 kg/ha in both locations. The DCPA residues in the 22.5–25 cm zone ranged ND‐0.10 kg/ha (WT), ND‐0.27 kg/ha (NT) in 1988. and ND‐0.02 kg/ha (WT), ND‐0.04 kg/ha (NT) in 1989. The residues of SDS 1449, the less stable of two dacthal metabolites, were very low but higher in 1988 than in 1989 in both locations. The SDS 954 residues in 22.5–25 cm zone ranged ND‐0.1 kg/ha (WT), and ND‐0.16 kg/ha (NT) in 1988, and ND‐0.26 kg/ha (WT), and ND‐0.27 kg/ha (NT) in 1989.

Some amount of all herbicides applied carried over into the spring of the year following application but oxadiazon and bensulide were the most persistent.     

Headspace solid phase microextraction method for determination of triazine and organophosphorus pesticides in soil

A headspace solid phase microextraction method (HS-SPME) for simultaneous determination of five pesticides belonging to triazine and organophosphorus pesticide groups in soil samples was developed. Microextraction conditions, such as temperature, extraction time and sodium chloride (NaCl) content were investigated and optimized using 100 μ m polydimethyl-siloxane (PDMS) fiber. Detection and quantification were done by gas chromatography-mass spectrometry (GC-MS). Relative standard deviation (RSD) and recovery values for multiple analysis of soil samples fortified at 30 μ g kg^{? 1} of each pesticide were below 13 % and higher than 70 %, respectively. Limits of detection (LOD) for all the compounds studied were less than 3.2 μ g kg^{? 1}. The proposed method was applied in the analysis of some agricultural soil samples.     

Rapid screening for organochlorine and organophosphorus pesticides in milk using C18 and graphitized carbon black solid phase extraction cleanup

Abstract

A rapid, multiresidue, solid phase extraction (SPE) technique for the isolation and gas chromatographic determination of organochlorine and moderately polar organophosphorus pesticide residues in milk is described. Milk is sonicated with an acetonitrile‐acetone‐methanol mixture and centrifuged. The supernatant is subjected to a cleanup using both C₁₈ and graphitized carbon black SPE columns. The pesticide residues are determined by gas chromatography with electron capture and flame photometric detection. The method required minimal volumes of solvent and resulted in the production of minimal volumes of hazardous waste.     

Application of a novel cold activated carbon fiber-solid phase microextraction for analysis of organochlorine pesticides in soil

A novel and simple analytical procedure using cold activated carbon fiber-solid phase microextraction (CACF-SPME) was applied to determine organochlorine pesticides (OCs) in soil samples. The pesticides in this study consist of α -, β -, γ -, and δ -hexachlorocyclohexane (HCH). By heating the sample while cooling the fiber, the developed method not only provides better performance in terms of sensitivity, linearity and recovery but also offers shorter adsorption procedure than that of traditional headspace-solid phase microextraction (HS-SPME). The experimental conditions such as the amount of water, adsorption time and adsorption temperature were optimized. Matrix effects were investigated with different types of soils. We concluded that using the standard addition method was required for quantification purposes. The limits of detection obtained using the proposed method range from 0.01 to 0.05 ng/g, and the recoveries for CACF-SPME are in the range of 80.01% to 89.68% with relative standard deviation (RSDs) better than 8.60%. The proposed method was further applied to determine OCs in real agricultural soil. The results are in good agreement with those obtained using traditional ultrasonic extraction. The research demonstrates the suitability of the CACF-SPME for the analysis of OCs in soil.     

Microwave/SPME method to quantify pesticide residues in tomato fruits

A new analytical method using focused microwave-assisted extraction (FMAE), coupled with solid phase micro-extraction (SPME), has been elaborated to determine 25 pesticides used in tomato cultivation. Microwave energy was used for a fast and controlled heating of solvent to selectively extract compounds. Calibration curves were plotted from blank tomato samples spiked at different concentrations with standards. A linear response was obtained between 10 and 1000 μ g/Kg for pyrethroids and between 0.1 and 5000 μ g/Kg for other compounds. For all studied substances, the resulting correlation coefficient (r²) was greater than 0.99. Limits of detection (LOD) and quantification (LOQ) were measured lower than 8 and 25 μ g/Kg, respectively. The relative standard deviation (RSD) was determined below 15% for all pesticides. Field incurred tomato samples were used to validate the new FMAE/SPME method. Observed analysis results by using this technique were in good agreement compared to those obtained by two accredited trading laboratories using traditional methods. Four tomato samples, bought in a local market, were also tested with the FMAE/SPME method.     

Determination of the insecticide diflubenzuron in mushrooms by kinetic method and high-performance liquid chromatographic method

In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-diflubenzoil)urea] is proposed. The method is based on the inhibited effect of diflubenzuron on the oxidation of sulphanilic acid (SA) by hydrogen peroxide in phosphate buffer in presence Cu(II) ion. Diflubenzuron was determined with linear calibration graph in the interval from 0.31 to 3.1 μg mL^?1 and from 3.1 to 31.0 μg mL^?1. The optimized conditions yielded a theoretical detection limit of 0.18 μg mL^?1corresponding to 0.036 mg Kg^?1mushroom sample based on the 3S_b criterion. The RSD is 5.03–1.83 % and 2.81–0.71 % for the concentration interval of diflubenzuron 0.31–3.1 μg mL^?1and 3.1–31.0 μg mL^?1, respectively. The reaction was followed spectrophotometrically at 370 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of diflubenzuron in spiked mushroom samples of different mushroom species. The HPLC method was used like a comparative method to verify results.     

Solid phase extraction with silicon dioxide microsphere adsorbents in combination with gas chromatography-electron capture detection for the determination of DDT and its metabolites in water samples

The goal of the present study was to investigate the feasibility of silicon dioxide (SiO₂) microspheres without special modification to enrich dichlorodiphenyltrichloroethane (DDT) and its main metabolites, p,p′-dichlorodiphenyl-2,2-dichloroethylene (p,p′-DDD) and p,p′-dichlorodiphenyldichloroethylene (DDE) in combination with gas chromatography-electron-capture detection. The experimental results indicated that an excellent linear relationship between the recoveries and the concentrations of DDT and its main metabolites was obtained in the range of 0.2–30 ng mL^?1 and the correlation coefficients were in the range of 99.96–99.99%. The detection limits based on the ratio of signal to the baseline noise (S/N = 3) were 2.2, 2.9, 3.8 and 4.1 ng L^?1 for p,p′-DDD, p,p′-DDT, o,p′-DDT, and p,p′-DDE, respectively. The precisions of the proposed method were all below 10% (n = 6). Four real water samples were utilized for validation of the proposed method, and satisfactory spiked recoveries in the range of 72.4–112.9% were achieved. These results demonstrated that the developed method was a simple, sensitive, and robust analytical method for the monitoring of pollutants in the environment.     

Determination of etoxazole residues in fruits and vegetables by SPE clean-up and HPLC-DAD

A method for determination of etoxazole residues in apples, strawberries and green beans was developed and validated. The analyte was extracted with acetonitrile from foodstuff and a charcoal-celite cartridge was used for clean-up of raw extracts. Reversed phase high performance liquid chromatography with photodiode array detector (HPLC-DAD) was used for the determination and quantification of etoxazole residues in the studied samples. The calibration graphs of etoxazole in a solvent or three blank matrixes were linear within the tested intervals 0.01–2 mg L^?1, with correlation coefficient of determination >0.999. The combined solid phase extraction (SPE) clean-up and the chromatographic method steps were sensitive and reliable for simultaneous determination of etoxazole residues in the studied samples. The average recoveries of etoxazole in the tested foodstuffs were between 93.4 to 102% at spiking levels of 0.01, 0.10, and 0.50 mg kg^?1, with relative standard deviations ranging from 2.8 to 4.7%, in agreement with directives for method validation in residue analyses. The limit of detection (LOD) of the HPLC-DAD system was 100 pg. The limit of quantification of the entire method was 0.01 mg kg^?1.     

固相萃取—气相色谱—质谱测定再生水中邻苯二甲酸酯类物质

探讨了一种再生水中邻苯二甲酸酯类物质的测定方法——固相萃取—气相色谱—质谱,检测了相关再生水标准中涉及的邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)两类物质。在质量浓度为20～1 000μg/L时,两类物质的回归方程的相关系数均大于0.999,检出限分别是0.060、0.002μg/L,DBP、DEHP的相对标准偏差分别为4.1%～7.4%、5.1%～6.1%。利用固相萃取技术进行预处理,平均加标回收率为96.6%、89.6%。检测了北京市4座再生水厂出水中DBP和DEHP含量,其中,DBP在1.74～5.59μg/L,低于《城市污水再生利用景观环境用水水质》(GB/T 18921—2002)规定的限值(不超过0.1mg/L),但高于《城市污水再生利用地下水回灌水质》(GB/T 19772—2005)规定的限值(不超过3μg/L);DEHP在0.42～4.93μg/L,满足GB/T 19772—2005要求(不超过8μg/L)。     

SPE和LC-MS／MS联用同时检测水体中的15种抗生素

采用（SPE）固相萃取柱进行分离富集,使用LC—MS／MS联用仪进行检测,建立了一种高效、低成本的可同时检测水体中多种抗生素的方法,并在河北省子牙河流域汪洋沟水体抗生素污染现状调查中得到应用。实验结果表明,（1）最优实验条件的选择为：水样体积为1L,洗脱剂用量为10mL,pH为3．0;（2）回收率达到69．2％～86．3％,相对标准偏差在1．8％～8．4％之间,表明检测结果准确度和灵敏度均较高;（3）在所检测的15种抗生素中,头孢西丁、土霉素、氯唑西林和布洛芬4种抗生素是该河流的主要抗生素污染物,其含量比重（中位数）高达73．5％,检测浓度最高（中位数）的是磺胺类抗生素,浓度为100．4ng／L;（4）各抗生素的含量从上游到下游大体呈逐渐衰减的趋势,这主要归因于下游支流的稀释作用,但水体中抗生素浓度仍远高于已有报道的地区;（5）污染源解析表明,水体中抗生素主要来源于制药企业的废水,部分来源于附近居民的生活污水。     

Adaptation and validation of QuEChERS method for the analysis of trifluralin in wind-eroded soil

This study was carried out to develop and validate a reliable analytical procedure for trifluralin analysis in wind-eroded sediments. Soil sediments trapped in BEST sediment traps were subjected to QuEChERS extraction method, incorporating a simple simultaneous cleanup step, followed by trifluralin analysis with GC-ECD. Results revealed that QuEChERS method offered a potential alternative technique for pesticide extraction from soil samples. The validity of analytical method was performed by the method-performance criteria such as, recovery, LOD, LOQ repeatability, precision, and all found to be within the required limits. It was also observed in this study that herbicide concentrations in the wind-eroded sediment did not vary with the time and trap height. Trifluralin concentrations of surface soil after four erosion events were higher (626.05 μg/kg) than wind-eroded soil (450.08 μg/kg).     

Effects of soil composition on solid phase microextraction determination of triazine and organophosphorus pesticides

The influence of organic matter and clay contents on headspace solid phase microextraction (HS-SPME) determination of triazine and organophosphorus pesticides in different soils was studied. The results of the study showed that content of soil organic matter dominantly participated in sorption of triazines (simazine, atrazine and prometryn) to soil, while sorption of organophosphorus pesticides (phorate and tebupirimfos) could not be explained only by contents of dominant soil sorption components (soil organic matter and clay). Sorption of all pesticides studied to different soil types was similar at their lower concentrations while the influence of soil composition was expressed at higher concentration levels. Except for phorate, the obtained sorption trends were different from those obtained by direct SPME mode (DM-SPME) and exhaustive liquid-solid extraction (LSE) method. These results indicated that most likely co-extractants from the analyzed medium complicated evaporation and diffusion of the pesticides to the PDMS fiber during HS-SPME sampling.     

超声波辅助萃取测定土壤中的多溴联苯醚

对土壤中多溴联苯醚(PBDEs)的测定方法进行了研究.土壤样品经超声波辅助萃取后用硅胶氧化铝复合柱净化,再用带电子捕获检测器的气相色谱仪(GC-ECD)进行测定.该方法测定PBDEs各单体的相关系数(R2)为0.999 54～0.999 97,方法线性关系良好.基质加标空白回收率在74.9%～118.1%,相对标准偏差(RSD)为5.9%～8.9%,方法检测限为5.9～9.2 ng/kg.     

Development of an efficient extraction method for oxytetracycline in animal manure for high performance liquid chromatography analysis

Oxytetracycline (2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a major member of the tetracycline antibiotics family of which are widely administered to animals in concentrated animal feeding operations for purposes of therapeutical treatment and health protection. With the disposal of animal manure as fertilizer into agricultural land, tetracyclines enter the environment. However, tetracyclines chelate with multivalent cations and proteins, resulting in low extraction efficiencies from animal manure for tetracycline residue analysis. In this study an efficient extraction method for oxytetracycline from steer manure using methanol/water solution amended with chelating organic acid was developed for the analysis of high performance liquid chromatography. The effect of species and amount of amendment acids, shaking time, methanol/water ratio, manure weight, and repeated times of extraction was investigated. It was optimized to amend 2.5 g citric acid and 1.1 g oxalic acid with 10.0 g manure sample in a 50-ml centrifuge tube and extract with 15 ml methanol/water (9:1 in volume) by vigorously shaking for 30 min in a reciprocating shaker. After centrifugation at 11,000 rpm, supernatant is collected. Sample was extracted for a total of 3 times. The developed extraction method was further applied to extract oxytetracycline from fresh and aged cow manure, swine and poultry manure, and soil. Satisfactory recoveries ranging from (84.1 ± 2.4) % to (102.0 ± 3.1) % were obtained, demonstrating that the optimized extraction method is robust for oxytetracycline from different manure sample matrixes.     

Evaluation of flow injection analysis method with spectrophotometric detection for the determination of atrazine in soil extracts

A method for determining atrazine in soil extracts was evaluated by flow injection analysis with spectrophotometric detection. The method is based on the reaction of atrazine with pyridine in an acid medium followed by the reaction with NaOH and sulfanilic acid. Several analytical conditions were previously studied and optimized. Under the best conditions of analysis, the limits of detection and quantification were 0.15 and 0.45 mg L^?1, respectively, for a linear response between 0.50 and 2.50 mg L^?1, and a sampling throughput of 21 determinations per hour. Using the standard addition method, the maximum relative standard deviation of 17% and recovery values between 80 and 100% were observed for three extracts from soil samples with different composition. The proposed method is simple, low-cost and easy to use, and can be employed for studies involving atrazine in soil samples or for screening of atrazine in soils.     

Development of an analytical method for analysis of flubendiamide,des-iodo flubendiamide and study of their residue persistence in tomato and soil

Flubendiamide is a new insecticide that has been found to give excellent control of lepidopterous pests of tomato. This study has been undertaken to develop an improved method for analysis of flubendiamide and its metabolite des-iodo flubendiamide and determine residue retention in tomato and soil. The analytical method developed involved extraction of flubendiamide and its metabolite des-iodo flubendiamide with acetonitrile, liquid-liquid partitioning into hexane-ethyl acetate mixture (6:4, v v^?1) and cleanup with activated neutral alumina. Finally the residues were dissolved in gradient high pressure liquid chromatography (HPLC) grade acetonitrile for analysis by HPLC. The mobile phase, acetonitrile-water at 60:40 (v v^?1) proportion and the wavelength of 235 nm gave maximum peak resolution. Using the above method and HPLC parameters described, nearly 100 % recovery of both insecticides were obtained. There was no matrix interference and the limit of quantification (LOQ) of the method was 0.01 mg kg^?1. Initial residue deposits of flubendiamide on field-treated tomato from treatments @ 48 and 96 g active ingredient hectare^?1 were 0.83 and 1.68 mg kg^?1,respectively. The residues of flubendiamide dissipated at the half-life of 3.9 and 4.4 days from treatments @ 48 and 96 g a.i. ha^?1, respectively and persisted for 15 days from both the treatments. Des-iodo flubendiamide was not detected in tomato fruits at any time during the study period. Residues of flubendiamide and des-iodo flubendiamide in soil from treatment @ 48 and 96 g a.i. ha^?1 were below detectable level (BDL, < 0.01 mg kg^?1) after 20 days. Flubendiamide completely dissipated from tomato within 20 days when the 480 SC formulation was applied at doses recommended for protection against lepidopterous pests.     

Development of an analytical method for analysis of flubendiamide, des-iodo flubendiamide and study of their residue persistence in tomato and soil

Flubendiamide is a new insecticide that has been found to give excellent control of lepidopterous pests of tomato. This study has been undertaken to develop an improved method for analysis of flubendiamide and its metabolite des-iodo flubendiamide and determine residue retention in tomato and soil. The analytical method developed involved extraction of flubendiamide and its metabolite des-iodo flubendiamide with acetonitrile, liquid-liquid partitioning into hexane-ethyl acetate mixture (6:4, v v?1) and cleanup with activated neutral alumina. Finally the residues were dissolved in gradient high pressure liquid chromatography (HPLC) grade acetonitrile for analysis by HPLC. The mobile phase, acetonitrile-water at 60:40 (v v?1) proportion and the wavelength of 235 nm gave maximum peak resolution. Using the above method and HPLC parameters described, nearly 100 % recovery of both insecticides were obtained. There was no matrix interference and the limit of quantification (LOQ) of the method was 0.01 mg kg?1. Initial residue deposits of flubendiamide on field-treated tomato from treatments @ 48 and 96 g active ingredient hectare?1 were 0.83 and 1.68 mg kg?1, respectively. The residues of flubendiamide dissipated at the half-life of 3.9 and 4.4 days from treatments @ 48 and 96 g a.i. ha?1, respectively and persisted for 15 days from both the treatments. Des-iodo flubendiamide was not detected in tomato fruits at any time during the study period. Residues of flubendiamide and des-iodo flubendiamide in soil from treatment @ 48 and 96 g a.i. ha?1 were below detectable level (BDL, < 0.01 mg kg?1) after 20 days. Flubendiamide completely dissipated from tomato within 20 days when the 480 SC formulation was applied at doses recommended for protection against lepidopterous pests.