Shuren Jiang

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.

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.

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.

Synthesis of three new cyclodextrin derivatives and their application as chiral stationary phases in the determination of optical purity by capillary gas chromatography

SummaryThree cyclodextrin (CD) derivatives were synthesized by substituting the 2,6-OH groups of cyclodextrin with benzyl and the 3-OH group with three different acyl groups (valeryl, heptanoyl, octanoyl). The chromatographic properties of the three CD derivatives were investigated. These derivatives can separate not only the chlorotoluene and xylene isomers but also some racemic compounds, such as methyl trans-2,2-dimethyl-3-(2-methylpropenyl)cyclopropane-carboxylate. Using these CD derivatives as chiral stationary phases, the optical purity of 1-(2,4-dichlorophenyl) ethanol obtained by asymmetric catalytic hydrogenation of 2,4-dichloroacetophone and trans-2,3-epoxyhexanol synthesized by Sharpless epoxidation of trans-2-hexen-1-ol was determined and the catalytic reaction was evaluated.

Direct Optical Resolution of Chiral Pesticides by High Performance Liquid Chromatography on Cellulose tris‐3,5‐Dimethylphenyl Carbamate Stationary Phase Under Reversed Phase Conditions

Abstract The direct optical resolution of five chiral pesticides on a cellulose tris‐3,5‐dimethylphenyl carbamate stationary phase (Chiralcel OD, 250 × 4.6 mm) under reversed‐phase conditions is described. The influence of organic modifiers, pH, and temperature was investigated. The two mobile phases used were water/methanol and water/acetonitrile. Of five chiral pesticides investigated, the three pesticides were observed to obtain the base separation under the suitable conditions and the other two were observed to be partially resolved. The values of α (1.04–6.65) and R s (0.63–13.16) have been reported.

Capillary Gas Chromatography Separation of Pyrethroic Acid Methyl Esters Using Four Acylated Cyclodextrin Derivatives as Chiral Stationary Phases

SummaryFour cyclodextrin derivatives (CDs) were synthesized by substituting 3-OH of 2,6-di-O-pentyl-β-cyclodextrin with four different chain lengths of acyl groups (butyryl, valeryl, heptanoyl, octanoyl). The chromatographic properties of the four CD derivatives as stationary phases of capillary gas chromatography (CGC) were investigated. These CDs exhibit a wide range of application. Not only five pairs of enantiomers of pyrethroic acid methyl esters were separated on the four CDs, but also some other racemic compounds. Among the four CDs, 2,6-di-O-pentyl-3-O-butyryl-β-CD possesses better enantiomer separation abilities to the studied enantiomers of pyrethroic acid methyl esters than the other studied CDs. The extension of chain length of the acyl groups in 3-position of CDs cannot improve the enantiomer separation abilities of the CD derivatives.