Anionic surfactants in waters were determined using on-line double microporous membrane extraction-flow injection analysis method. This method was based on the extraction of the ion-association complex (λ_(max)=650 nm) which formed from methylene blue cation and anionic surfactants. The on-line double microporous membrane liquid-liquid extraction phase separators were adopted. Optimization of variables of the flow injection manifold, groove mechanical dimension of the phase separator, and pore size of the membrane was performed. The proposed method had a linear range of 25.0-1000.0 μg/L(r≥0.999). The detection limit was 4.28 μg/L. The relative standard deviation(n=7) of different concentration was 0.7%-6.0%. The recovery was between 96%-110% and the sample throughput was 18 h-1. The method was applied to the analysis of standard Reference materials with satisfactory results. For practical application, two water samples were analyzed with the established method.

A combination technique of LC/ESR, LC/MS and spin trapping was used to identify and characterize the carbon-centered free radicals formed from lipoxygenase-catalyzed peroxidation of dihomo-γ-linolenic acid(DGLA). The spin trap, α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone(POBN), could react with short-lived carbon-centered radicals to form relatively stable adducts. Based on the same retention time of POBN radical adduct in LC/UV/ESR and LC/MS, molecular weight of adduct could be confirmed and the structure of adduct could be confirmed by their LC/MS2 fragment pattern. The results showed that free radicals formed in lipoxygenase-catalyzed peroxidation of DGLA, including ~·C_7H_(13)O_2, ~·C_(10)H_(17)O_2 and ~·C_5H_(11), all stemmed from β-scission of DGLA alkoxyl radicals(8-, 11-, 15-LO~·). The results were helpful for further study of biological activities of these radicals in vivo.

The effects of adsorption time, solid-liquid ratio, sample concentration, flow rate on the adsorption properties of supported ionic liquids(the N-methylimidazolium functionalized silica, SilprMin) for flavonoids were investigated. The results indicated that the adsorption equilibrium for tested compounds, genistein, luteolin and quercetin, was achieved within 30 min, the adsorption efficiencies of these three compounds were improved with the increase of solid-liquid ratio, and decreased with the increase of their concentrations. Moreover, the adsorption isotherm data of the three tested compounds were in good concordance with the Langmuir model. The saturated adsorption capacity of SilprMim for genistein, luteolin and quercetin was 47.7, 52.5 and 63.2 mg/g, respectively. Adsorption efficiency of SilprMim could reach more than 90% at a sample flow rate of 0.5～1.5 mL/min. Using methanol as eluent, the saturated desorption efficiencies of genistein, luteolin and quercetin were 86.1%, 83.3% and 84.6%, respectively. The elution order of the three tested flavonoids was genistein, luteolin and quercetin. SilprMim had strong adsorption and separation capacity for three tested flavonoids, which was hopeful to be applied in separation and purification of naturally occurring flavonoids.

A method was developed for the determination of furocoumarin compounds(psoralen, oxypeucedanin, imperatorin, isoimperatorin) in traditional Chinese medicine samples by dispersive liquid-liquid microextraction(DLLME) coupled with high performance liquid chromatography and the relation of sample solution volume, sediment phase volume with enrichment factors was deducted. Some important parameters that influenced the extraction efficiency were optimized: 50 μL carbon tetrachloride and 300 μL acetonitrile were rapidly injected into 1.5 mL sample solution containing 2.5%(w/V) NaCl. After centrifugation at 3500 r/min for 3 min, the sedimented CCl_4 phase was pumped and recorded the volume, then dissolved with methanol and injected into the HPLC for analysis. Under the optimum conditions, a good linear relationship was obtained in the range of 0.006 6.00 mg/L of both psoralen and oxypeucedanin and 0.006-12.0 mg/L of both imperatorin and isoimperatorin. The limits of detection were 1.0-3.0 μg/L(S/N=3). The relative standard deviations were 2.3%-5.4%(n=5). The enrichment factors ranged from 12.6 to 38.5 folds. The average recoveries ranged from 97.5% to 114.8%. The four kinds of furocoumarin compounds in Radix Angelicae dahuricae and Yuanhu Zhitong tablet were determined by the proposed method with satisfactory results.

A poly(amino black 10B)/Nafion modified glassy carbon(GC) electrode for the detection of dopamine(DA) has been developed. The modified electrode showed an excellent electrocatalytic effect on the oxidation of DA. In cyclic votammetric measurements, the redox peak current increased linearly with the concentration of DA in the range of 2.0×10~(-7) 3.0×10~(-5) mol/L in PBS of pH 6.0, with a correlation coefficient of 0.9993 and 0.9991, respectively. The detection limit(S/N=3) was 1.0×10~(-7) mol/L. Moreover, the modified electrode exhibited good repeatability and long-time stability, and avoided the interference of ascorbic acid. The modified electrode has been used for the determination of DA in the injections and calf serum with good recovery and reproducibility.

A method for the determination of seven kinds of thiocarbamate herbicides, molinate, pebulate, vernolate, triallate, thibencarb, eradicane and butylate in black tea and green tea has been developed. After homogenization, 2.0 g tea sample was soaked with 6 mL water for 1 h. 2.5 g NaCl was then added, and the sample was extracted twice by 20 mL acetonitrile. After concentration, the extract was put through HLB column and eluted by 3 mL acetonitrile. The eluate was then concentrated and dissolved with 2.0 mL hexane-acetone (7∶ 3, V/V) mixture. The preparation was cleaned by Envi-Carb column and eluted with 5 mL hexane-acetone. After concentration, the residue was dissolved by acetonitrile-water (5∶ 5, V/V) solution. Detection was achieved by electrospray ionization(ESI) in positive mode using multiple reaction monitoring. D_3-carbaryl was used as the internal standard, the linear range for the herbicides was 0-200 μg/L and the limit of detection were from 0.093 to 1.77 μg/L, with the correlation coefficients(r) varying from 0.9954 to 0.9988. The recoveries of all thiocarbamate herbicides were from 77.3% to 91.5% at the spiked levels of 5-20 μg/kg. The RSD of each compound was less than 15%. Black tea and green tea samples were successfully analyzed by the proposed method with satisfactory results.

A novel system was developed for the rapid determination of vitexin, vitexin-2″-O-rhamnoside, rutin, and hyperoside in the extract of hawthorn(Crataegus pinnatifida Bge.) leaves with microemulsion liquid chromatography(MELC). The effect on the chromatography of varying the operating paramers was studied. The optimized MELC system with microemulsion was consisting of 1.0%(w/w) brij35-1.1%(w/w) n-butanol-0.1%(w/w) n-octanol-0.3%(v/v) triethylamine, the pH was adjusted to 2.5 with phosphoric acid. The type and concentration of surfactant, types of oil phase, the pH and triethylamine as the organic additive in microemulsion played an important role for separation of four flavonoids. MELC analysis was performed on a Venusil ASB C_(18) analytical column (150 mm× 4.6 mm, i.d., 5 μm). The flow rate was set at 0.8 mL/min and the eluent was detected at 340 nm for the four flavonoids. The calibration curves of the four flavonoids are linear(r>0.9995) over the concentration range of 0.95-140.0 mg/L. The mean recoveries are 98.6% to 101.6%. The results indicate that the optimized method was successfully applied to the analysis of four important flavonoids in the extract of hawthorn leaves.

The cyclic voltammetric behaviors of sodium selenite on the gold electrode modified by L-cysteine self-assembled monolayer (L-Syc,Au/SAMs) has been investigated in 0.05 mol/L H_2SO_4 solutions with sodium selenite. Sensitive anodic stripping current of selenium (Se) with the peak potential at 0.99 V (vs. SCE) has been observed. In comparison with the electrochemical properties of sodium selenite on the modified electrode with those on the naked gold electrode, it was found that selenite was reduced to selenium by the redox interaction with sulfur on the monolayer and the monolayer catalytically oxidizes Se as the electrode was positively scanned. According to the electrochemical properties of sodium selenite both on the naked and modified gold electrode, the Se deposition mechanism and catalytic mechanism as well as bionic membrane model were proposed for the bio-utilization of selenite through nano scale selenium.

A method was proposed for the separation and determination of paraffin waxes in food by HPLC-evaporative light scattering detection (ELSD). A normal-phase column was used to separate nonparaffinic and paraffinic materials without resolving the latter into individual components. The t-test method was adopted for the evaluation of mean difference between response factors of n-alkanes in paraffin waxes on ELSD detector. No mean difference was obtained between response factors, which can be used for quantitative determination of paraffin waxes in food. The determination results obtained by HPLC-ELSD were compared with those by GC-MS. The linear range for the determination of paraffin waxes was in the range from 10 to 500 mg/L with a correlation coefficient of 0.9988, and the limit of detection was 1.0 mg/L. With the spiking level of 10, 50 and 100 mg/kg, the recovery ranged from 84.6% to 105.4% and the relative standard deviation ranging from 5.4% to 7.2%. The proposed method is simple, fast and sensitive.

A newly developed topological vector of atom Y_C, equilibrium electro-negativity of atom q_e, molecular structural information parameter[N_H~i(i=α, β)] and γ calibration parameter were used to describe the local chemical microenvironment of 63 acyclic alcoholic compounds. Quantitative structural spectrum relationships (QSSR) was systematically made on relationship between ~(13)C NMR chemical shifts of 353 carbon atoms and their molecular structure descriptors. By partial least square regression(PLS), the statistical results indicated that the model correlation coefficient and standard error were 0.9915 and 2.4827, respectively. And the average absolute error was only 2.01×10~(-6) between the calculated and experimental chemical shifts for 353 carbon atoms. To validate the estimation stability for internal samples and the predictive capability for external samples of resulting models, leave-molecule-out(LMO) cross validation(CV) and external validation were performed. Compared with the reported result, not only the number of descriptors employed in this study was much fewer, but also the calculation was much easier.