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 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.

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.

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.

Expression and characterization of carboxylesterase E4 gene from peach-potato aphid (Myzus persicae) for degradation of carbaryl and malathion.

An abridged carboxylesterase E4 (CbE E4) gene was cloned from the peach-potato aphid, Myzus persicae, by reverse transcription-PCR and subcloned into the expression vector pET28b. The abridged CbE E4 gene was successfully expressed in E. coli BL21 (DE3). The recombinant CbE E4 hydrolyzed beta-naphthyl acetate and Carbaryl by 64% within 2.5 h, Malathion by 80% within 1.25 h. However, the hydrolysis of other pesticides (Dichlorovos, Parathion, Pirimicarb and Deltamethrin) was not detected.

[Determination of deoxyribonuceic acids by resonance light scattering technique with benzidine in the presence of the sensitizing sodium dodecyl sulfate].

The resonance light scattering (RLS) spectra of benzidine with deoxyribonucleic acid (ctDNA) in the presence of Sodium Dodecyl Sulfate had been studied. RLS intensity of SDS-benzidine system was enhanced by trace ctDNA and was proportional to the concentrationof ctDNA. Under optima conditions, the linear ranges of the calibration were 0.3-4 mg x L(-1), the linear regression equation was I = 37.17c (ctDNA, mg x L(-1)) + 208.9, r = 0.9992. The limit of detection were 0.17 mg x L(-1) (3delta), RSD% = 3.5%. The method had been applied to the determination of DNA in synthetic samples and gene tobacco sample, and the results were satisfactory.

[Study on the resonance scattering light spectra of atrazine-RNA and its analytical application].

The Resonance Light Scattering (RLS) spectra of atrazine with yeast ribonucleic acid (yRNA) had been studied. At pH 1.50, the enhanced RLS of atrazine-yRNA system is characterized by the maximum scattering peaks at 320 nm and the RLS intensity is proportional to the concentration of yRNA. Under optimal conditions, the linear ranges of the calibration were 0.6-5.0 microg x mL(-1), the linear regression equation was I = 25.88 + 140.0 c(yRNA, microg x mL(-1)), r = 0.9975, with the limit of detection 20.7 ng x mL(-1) (3delta). The method was applied to the determination of yRNA in synthetic samples and RNA in salt cress (Thellungiella halophila) sample satisfactorily. Mechanism studies show that there are two interaction modes between atrazine and RNA: electrostatic mode and intercalative mode.

[Determination of 15 organophosphorus pesticides in cucumber, tomato and pepper samples by capillary gas chromatography with gel permeation chromatographic clean-up].

Fifteen organophosphorus pesticide residues in vegetable samples were extracted and cleaned-up by gel permeation chromatography and detected by capillary GC-FPD. An alternative validation method was established based on GC-NPD detection on an HP-1701 column. The eluting profiles of 15 compounds on a gel permeation column (10 mm i.d. x 200 mm, SX-3) eluted by 1 mL/min cyclohexane-ethyl acetate (volume ratio of 1:1) were established according to GC quantitation. Minimum detection limits of this method were between 5 x 10(-4) mg/kg to 5 x 10(-3) mg/kg. The average fortified recoveries and coefficients of variation of the method were determined. The results show that recoveries are between 77.8%-106%, with an average RSD of 0.10%-16.6%.