Dissipation and residue of 2,4-D isooctyl ester in wheat and soil.

A simple analytical method was developed to determine the 2,4-D isooctyl ester residue in wheat and soil by gas chromatography coupled with electron capture detector. Using the method, the dissipation and residue of 2,4-D isooctyl ester in wheat field was investigated. The average recoveries of 2,4-D isooctyl ester ranged from 80.1% to 110.0% with relative standard deviations of 2.4% to 16.1%. The pesticide showed a rapid dissipation rate either in wheat seedling or soil, with the half-lives of 1.0 to 3.0 days. The terminal residue results in wheat grain were much lower than the codex MRL (2.0 mg/kg). It could be considered safe to food and environment when using this herbicide for controlling weeds in wheat field.

Analysis of cyprodinil in leek and pepper and its decline under field conditions.

A HPLC-UV method for determination of cyprodinil in leek, pepper, and soil was developed and the decline of cyprodinil under field conditions in China was investigated. The samples were extracted with acetonitrile. For leek and pepper samples, further clean-up with a florisil SPE column was necessary. Average recoveries of cyprodinil were found in the range of 82.92-107.43% with relative standard deviations of 2.48-14.55%. The pesticide cyprodinil showed a relatively fast decline rate. The half lives were from 2 to 4 days in leek and pepper, from 2-5 days in soil except in Beijing (14.7 days). So the decline of cyprodinil in leek and pepper was almost same in different experiment plots. However, the decline in soil was much complicated, and affected by the precipitation and other climate condition. The results could provide guidance to safe and reasonable use of this pesticide in agriculture.

Dissipation and residue of cyprodinil in strawberry and soil.

The dissipation of cyprodinil under field and greenhouse condition in China was investigated. The pesticide cyprodinil dissipation differed under different cultivate conditions, the half lives were 14.5 and 12.5 days in strawberry and soil, respectively, under the field condition, 5.5 and 6.5 days, respectively, under greenhouse. The results showed that the dissipation rate under greenhouse condition was much faster than under field condition either in strawberry or soil. The terminal residues in strawberries were below the EU maximum residue level (5 mg/kg) after 7 days of application. This study will give a suggestion for the reasonable use of cyprodinil under different cultivate conditions and can also provide reference to set MRL value in strawberry in China.

Residue and dissipation dynamics of flusilazole in apple and soil.

A simple, quick and reliable residue analytical method for flusilazole in apple and soil was developed in this study. The samples were extracted with acetonitrile and determined by liquid chromatography with UV detection. The LOQ of the method was 0.02 mg/kg. The dissipation dynamic and final residues of flusilazole in apple and soil were studied using field trial method. The results of residual dynamics experiment showed that after the apple was treated by flusilazole at treble of recommended high dosage (3.75 g/kg H(2)O), the half-life times of flusilazole in apple and soil were 4.23-7.77 days and 3.04-5.14 days, respectively. Residues of flusilazole in apple at harvest time were all below 0.05 mg/kg at both recommended high dosage and 1.5 times of recommended high dosage.

Famoxadone residue and dissipation in watermelon and soil.

The residue levels and dissipation rate of famoxadone in watermelon and soil were determined by HPLC-UVD. The LODs for famoxadone in watermelon, peel, flesh and soil were 0.002mg/kg (0.004mg/kg in leaf). The fortified recoveries ranged from 84.91% to 99.41% with relative standard deviations (RSDs) of 0.06-4.50%. The dissipation of famoxadone residue over the time in watermelon leaf and soil fitted to the equation C(T)=19.695e(-0.078T) and C(T)=1.369e(-0.129T). The half-lives (T(1/2)) of famoxadone in watermelon leaf and soil were 9.7 and 5.5 days, respectively. The final residue in watermelon was lower than 0.1mg/kg at harvest, which suggested the use of this fungicide to be safe to both human and environment. This work would be helpful in establishing the maximum residue limit (MRL) for famoxadone in watermelon in China, and provide guidance to the proper and safe use of this pesticide in agriculture.

Chlormequat residues and dissipation rates in cotton crops and soil.

A simple and reliable analytical method for chlormequat residues in cotton and soil was established in this study. The residual levels and dissipation rates of chlormequat in cotton crops and soil were determined by High Performance Liquid Chromatography-Mass Spectroscopy (HPLC-MS). The limit of quantification (LOQ) was 0.05, 0.1, 0.1mg/kg for soil, cotton seeds and cotton leaves, respectively. The mean half-life of chlormequat was 4.47 days in cotton plants and was 4.34 days in soil. The final residues of chlormequat in cotton seeds were below 0.5mg/kg (the MRL of China), while the chlormequat residues could not be detected in soil. Low residues in cotton seed and soil suggest that this pesticide may be safe to use under the recommended dosage.

Dissipation and residue of famoxadone in grape and soil.

The analytical method of famoxadone residue and its dissipation in grape and soil were investigated. Famoxadone (68.75% water-dispersible granule) was applied at two dosages (1.25 and 2.5 g l(-1)). Soil and grape samples were collected at intervals and analyzed for famoxadone residues. The results showed that the degradation rate of famoxadone in grape and soil were similar, and their dynamics could be described by C = 1.1738e (-0.0562t ) with correlation coefficient r = 0.9044 in grape and C = 5.6565e (-0.0515t ) with r = 0.9620 in soil, respectively. Half-lives were 12.3 and 13.5 days in grape and soil, respectively. The results indicated that at harvest time, the residues of famoxadone in grape were well below the EU's maximum residue level (2 mg kg(-1)) and was safe to apply in grape.

Dissipation and residues of chlormequat in wheat and soil.

A specific, sensitive method was developed for the analysis of chlormequat in wheat and soil by high performance chromatography/mass spectrometry. The fortified recoveries of soil were from 75.08% to 96.55%, with RSD 3.34%-15.18%, the limit of detection of the analytical method was 0.05 ng at a signal-to-noise ratio of 3, and the limit of quantification was 0.05, 0.1, 0.5 mg/kg for soil, wheat plants and wheat grain, respectively. The degradation dynamics and final residues of chlormequat in Beijing and Changchun were investigated. The half-life of chlormequat in wheat plants were 3.15 days in Beijing and 4.56 days in Changchun, while the half-life in soil was 3.88 days in Beijing and 4.51 days in Changchun. The final residues of chlormequat in soil were not detectable, and the final residues of chlormequat in wheat grain were below 0.50 mg/kg except for 3.51 mg/kg from high dosage plot of Changchun. The fact that all the final residues were below 5 mg/kg (GB2763 in National standards of the People's Republic of China, maximum residue limits for pesticide in food, Beijing, 2005) suggested that chlormequat could be safely used in wheat crops with the suitable dosage and application.

Application of graphitized carbon black to the QuEChERS method for pesticide multiresidue analysis in spinach.

A modified QuEChERS method was optimized to determine 66 pesticide residues in spinach using gas chromatography with mass spectrometric detection in selected-ion monitoring mode. Graphitized carbon black (GCB) at different levels (0, 5, 10, 15, 20, and 25 mg) was used to adsorb the pigments in spinach extracts. Best recoveries with less colored extract samples for all pesticides analyzed were obtained in the presence of 10 mg GCB. Under the optimized condition, analyses of spiked samples were performed at 3 different levels. Correlation coefficients, R2, in the linear range tests were better than 0.99. Average recoveries ranged from 66 to 104%, with the relative standard deviation below 16%. The limits of quantitation ranged from 50 to 250 microg/kg.

Use of graphitic carbon black and primary secondary amine for determination of 17 organophosphorus pesticide residues in spinach.

Graphitized carbon black (GCB) and primary secondary amine (PSA) as dispersive-SPE sorbents were applied to optimize the method for the determination of 17 organophosphorus pesticides in spinach which contained so many pigments using GC with flame photometric detector (FPD). The sample was extracted with ACN, and an aliquot of the extract was concentrated to near dryness. Ethyl acetate or acetone was chosen as the dissolving solvent. Subsequently, dispersive-SPE was used for cleanup, and the type and quantity of sorbents (GCB, PSA and activated carbon) were tested in the experiments. The best results were when acetone was used to dissolve and 30 mg each of GCB and PSA for cleanup. In this condition, recoveries of pesticides analyzed were between 52-117% with RSD below 10%, and LOQ ranged from 10 to 20 microg/kg. This method was simple, effective and efficient, and can protect the GC system to some extent.

Quantitative analysis of three chiral pesticide enantiomers by high-performance column liquid chromatography.

Methods for the enantiomeric quantitative determination of 3 chiral pesticides, paclobutrazol, myclobutanil, and uniconazole, and their residues in soil and water are reported. An effective chiral high-performance liquid chromatographic (HPLC)-UV method using an amylose-tris(3,5-dimethylphenylcarbamate; AD) column was developed for resolving the enantiomers and quantitative determination. The enantiomers were identified by a circular dichroism detector. Validation involved complete resolution of each of the 2 enantiomers, plus determination of linearity, precision, and limit of detection (LOD). The pesticide enantiomers were isolated by solvent extraction from soil and C18 solid-phase extraction from water. The 2 enantiomers of the 3 pesticides could be completely separated on the AD column using n-hexane isopropanol mobile phase. The linearity and precision results indicated that the method was reliable for the quantitative analysis of the enantiomers. LODs were 0.025, 0.05, and 0.05 mg/kg for each enantiomer of paclobutrazol, myclobutanil, and uniconazole, respectively. Recovery and precision data showed that the pretreatment procedures were satisfactory for enantiomer extraction and cleanup. This method can be used for optical purity determination of technical material and analysis of environmental residues.

The chiral separation of triazole pesticides enantiomers by amylose-tris (3,5-dimethylphenylcarbamate) chiral stationary phase.

The amylose-tris(3,5-dimethylphenylcarbamate) chiral stationary phase was synthesized and used to separate the enantiomers of triazole pesticides by high-performance liquid chromatography. The mobile phase was n-hexane-isopropanol applying a flow rate of 1.0 mL/min. Six triazole pesticides were enantioselectively separated. Myclobutanil, paclobutrazol, tebuconazole, and uniconazole obtained complete separation with the resolution factors of 5.73, 2.99, 1.72, and 2.07, respectively, and imazalil and diniconazole obtained partial separation with the resolution factors of 0.79 and 0.77 under the optimized conditions. The effect of the content of isopropanol as well as column temperature on the separation was investigated. A circular dichroism detector was used to identify the enantiomers and determine the elution orders. The results showed the low temperature was good for the chiral separation except for diniconazole. The thermodynamic parameters calculated based on linear Van't Hoff plots showed the chiral separations were controlled by enthalpy.

Application of dispersive liquid-liquid microextraction for the analysis of organophosphorus pesticides in watermelon and cucumber.

In this article, a new method for the determination of organophosphorus pesticides (OPPs) in cucumber and watermelon was developed by using dispersive liquid-liquid microextraction (DLLME) and gas chromatography-flame photometric detection (GC-FPD). Acetonitrile (MeCN) was used as extraction solvent for the extraction of OPPs from plant samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the MeCN extract to another small volume of organic solvent, chlorobenzene, using DLLME. Recovery tests were performed for concentrations between 0.5 and 20 microg/kg; recoveries for each target analyte were in the range between 67 and 111%. The repeatability of the proposed method, expressed as relative standard deviation, varied between 2 and 9% (n=3). Limits of detection of the method for watermelon and cucumber were found ranging from 0.010 to 0.190 microg/kg for all the target pesticides. Compared with the conventional sample preparation method, the proposed method has the advantage of being quick and easy to operate, and having high-enrichment factors and low consumption of organic solvent.

Determination of organophosphorus pesticides in Lycium barbarum by gas chromatography with flame photometric detection.

An analytical method was developed to determine 14 organophosphorus pesticide residues in Lycium barbarum, which is both a botanical medicine and a food. A 5 g sample is mixed with 10 mL ethyl acetate and, after shaking and centrifuging, 5 mL of the upper layer is removed, concentrated, and analyzed by gas chromatography (GC) with flame photometric detection. The essential feature of this method is that, for the purpose of reducing the burden of the GC system, 0.01 g activated carbon is used to absorb pigments during the cleanup procedure. Average recoveries of 14 organophosphorus pesticides added at 0.05, 0.1, and 0.5 mg/kg were 66.84-102.42, 71.07-97.93, and 62.50-96.24%, respectively. Limits of detection ranged from 5 to 15 microg/kg. The identities of the 14 pesticides were confirmed by GC/mass spectrometry detection in the selected-ion monitoring mode. This method is sensitive, simple, rapid, inexpensive, and safe.

Spatial variability of organochlorine pesticides (DDTs and HCHs) in surface soils from the alluvial region of Beijing, China.

The spatial variability in the concentrations of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2,2-bis-(p-chlorophenyl) ethane (DDT) in surface soils was studied on the basis of the analysis of 131 soil samples collected from the surface layer (0-20 cm depth) of the alluvial region of Beijing, China. The concentrations of total HCHs (including alpha-, beta-, gamma-, and delta-isomers) and total DDTs (including p,p'-DDT, p,p'-DDD, p,p'-DDE, and o,p'-DDT) in the surface soils tested were in the range from nondetectable to 31.72 microg/kg dry soil, with a mean value of 0.91, and from nondetectable to 5910.83 microg/kg dry soil, with a mean value of 32.13, respectively. It was observed that concentrations of HCHs in all soil samples and concentrations of DDTs in 112 soil samples were much lower than the first grade (50 microg/kg) permitted in "Environment quality standard for soils in China (GB15618-1995)". This suggests that the pollution due to organochlorine pesticides was generally not significant in the farmland soils in the Beijing alluvial region. In this study, the spatial distribution and trend of HCHs and DDTs were analyzed using Geostatistical Analyst and GS+(513). Spatial distribution indicated how these pesticides had been applied in the past. Trend analysis showed that the concentrations of HCHs, DDTs, and their related metabolites followed an obvious distribution trend in the surface soils from the alluvial region of Beijing.

Application of a single-drop microextraction for the analysis of organophosphorus pesticides in juice.

In this study, a new method for the determination of organophosphorus pesticides (OPPs) (ethoprophos, diazinon, parathion methyl, fenitrothion, malathion, isocarbophos and quinaphos) in orange juice was developed. Single-drop microextraction (SDME) parameters, such as organic solvent, drop volume, agitation rate, extraction time, and salt concentration were optimized through analysis of OPPs in fortified water. The orange juice was simply centrifuged and diluted with water, extracted by SDME and analyzed by gas chromatography (GC) equipped with a flame photometric detection (FPD). Fortification tests were conducted for concentrations between 10 and 500 microg/L; mean relative recoveries for each pesticide were all above 76.2% and below 108.0%. Limits of detection of the method for orange juice were below 5 microg/L for all target pesticides. The repeatability of the proposed method, expressed as relative standard deviation varied between 4.6 and 14.1% (n=5). The proposed method is acceptable in the analysis of OPPs pesticides in juice matrices.

Enantiomeric resolution of chiral pesticides by high-performance liquid chromatography.

Successful enantiomeric separation of 10 chiral pesticides by high-performance liquid chromatography (HPLC) using cellulose-tris(3,5-dimethylphenylcarbamate) (CDMPC) chiral stationary phase (CSP) was performed. The mobile phase was n-hexane modified by ethanol, propanol, 2-propanol (IPA), butanol, or isobutanol. The effects of mobile phase composition and column temperature on the separation were investigated. Baseline separation was obtained with ethofumesate, fluroxypyr-meptyl, malathion, benalaxyl, diclofop-methyl, methamidophos, vinclozolin, and lactofen, whereas near baseline separation was obtained with profenofos and acetochlor. Butanol was the best modifier for benalaxyl; isobutanol was the best modifier for lactofen, malathion, diclofop-methyl, and ethofumesate; and IPA was the best modifier for the other five. Better separations were not always at low temperature. The elution orders of the eluting enantiomers were determined by a circular dichroism (CD) detector. The quantitative analysis methods for the enantiomers of ethofumesate, benalaxyl, and diclofop-methyl were established. Validation parameters include linearity, precision, and limit of detection (LOD). The enantiomeric residual analysis procedures in soil and water samples were also developed using acetone extraction and C(18) solid phase extraction. The methods were reliable for residual analysis of the enantiomers.

Health safety of main water pipe materials supplied in China market.

OBJECTIVE: To assess the health safety of copper, steel and plastic water pipes by field water quality investigations. METHODS: Four consumers were randomly selected for each type of water pipes. Two consumers of every type of the water pipes had used the water pipes for more than 1 year and the other 2 consumers had used the water pipes for less than 3 months. The terminal volume of tap water in copper and steel water pipes should be not less than 0.1 liter, whereas that in plastic water pipes should be not less than 1 liter. RESULTS: The mean values of the experimental results in the second field water quality investigation of the copper and steel water pipes met the Sanitary Standards for Drinking Water Quality. The items of water sample of the plastic water pipes met the requirements of the Sanitary Standards for Drinking Water Quality. CONCLUSION: Copper, steel, and plastic pipes can be used as drinking water pipes.

Chiral separations of pesticide enantiomers by high-performance liquid chromatography using cellulose triphenylcarbamate chiral stationary phase.

The direct chiral separations of pesticide enantiomers by high-performance liquid chromatography by applying self-prepared cellulose triphenylcarbamate chiral stationary phase are performed. The mobile phase is n-hexane modified by isopropanol as a polar modifier. Nine chiral pesticides (benalaxyl, vinclozolin, diclofop-methyl, tebuconazole, quizalofop-ethyl, hexaconazole, lactofen, isocarbophos, and paclobutrazol) show enantioselectivity on the chiral stationary phase. An online circular dichrorism detector is used for identifying the pesticide enantiomers. The influences of the volume content of isopropanol and column temperature on the separations are investigated. The thermodynamic parameters related to the chiral distinguish mechanisms are also calculated.

Direct enantiomeric resolutions of chiral triazole pesticides by high-performance liquid chromatography.

Cellulose-tris (3,5-dimethylphenylcarbamate; CDMPC) was synthesized and coated on aminopropylsilica to prepare chiral stationary phase (CSP). Normal-phase high-performance liquid chromatography (HPLC) methods for the resolutions of five chiral triazole pesticides, diniconazole, tebuconazole, hexaconazole, triadimefon and flutriafol, on the CSP were developed. Several operating parameters such as mobile phase composition, modifier and column temperature were studied for the optimization of the resolutions. Better separations were achieved using 2% iso-butanol for diniconazole, 2% ethanol for tebuconazole, 2% iso-propanol for hexaconazole, 1% n-butanol for triadimefon and 2% n-propanol for flutriafol as modifiers in n-hexane at 0 degrees C with the resolution factors (Rs) of 1.62, 1.66, 2.46, 1.68 and 1.98, respectively. Low temperature was better for the resolutions. Validation of the methods included linearity and precision.