Hanwen Sun

Application of accelerated solvent extraction in the analysis of organic contaminants, bioactive and nutritional compounds in food and feed

Accelerated solvent extraction (ASE) has become a popular green extraction technology for different classes of organic contaminants present in numerous kinds of food and feed for food safety. The parameters affecting ASE efficiency and application advancement of ASE in the analysis of organic contaminants, natural toxins compounds as well as bioactive and nutritional compounds in animal origin food, plant origin food and animal feed are reviewed in detail. ASE is a fully automated and reliable extraction technique with many advantages over traditional extraction techniques, so it could be especially useful for routine analyses of pollutants in food and feed.

Recognition mechanism of water-compatible molecularly imprinted solid-phase extraction and determination of nine quinolones in urine by high performance liquid chromatography

Novel water-compatible molecularly imprinted polymers (MIPs) were synthesized in methanol-water systems with ofloxacin as templates and methacryclic acid as functional monomers. The MIPs were used as a special sorbent for the selective solid-phase extraction (SPE) of nine quinolones from urine samples, showing high affinity to the quinolones in aqueous environment. Its molecular recognition mechanisms were investigated by the molecular simulation and the experimental validation with UV and infrared spectrogram as well as (1)H NMR. Binding capability and chromatographic characteristic were also evaluated. By using the water-compatible MIPs as SPE sorbents, the nine quinolones can be selectively extracted and enriched, while all matrices interferences were eliminated simultaneously. Under the optimal conditions of SPE and high performance liquid chromatography (HPLC), the good linearity of the method was obtained in a range of 0.05-30microg/mL with the correlation coefficient of >0.999 and the relative standard division of 2.0-7.4%. The detection limits (s/n=3) were in a range of 0.036-0.10microg/mL. The proposed method was successfully applied for the selective extraction and separation of the studied quinolones in urine samples.

A simple and high-throughput method of ultrasonic extraction-capillary electrophoresis for determination of melamine in milk

A simple, rapid, sensitive, and low cost method of ultrasonic extraction (USE) and capillary electrophoresis (CE) for the determination of melamine in milk is developed. The most widely used extraction methods of melamine (SPE and LLE) were compared with ultrasonic-assisted extraction by evaluating simplicity, cost and sample clean-up effect, and the conditions of CE were optimized. The melamine was extracted by acetonitrile under the action of ultrasonic energy. After centrifuging, diluting and filtering, the extract was analyzed by CE directly. The determination used 20 mM NaH2PO4 as running buffer (pH 2.6), UV detection at 208 nm, and an applied voltage of 18 kV. The proposed method demonstrated good performance concerning linearity (R2 = 0.9989), precision (2.6–4.8%), limit of detection and quantification (LOD, 0.163 mg kg−1; LOQ, 0.542 mg kg−1) and accuracy (85.1–98.3%). The proposed method is rapid, convenient and low-cost for the determination of melamine in milk products.

Sensitive determination of diethylstilbestrol by high performance liquid chromatography with fluorescence detection with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride as a labeling reagent

A sensitive and reliable high performance liquid chromatograph-fluorescence detection (HPLC-FLD) method for the determination of diethylstilbestrol (DES) in human urine is developed. DES was derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) under mild conditions and separated isocratically on a C18 column. The detection limits of DES at a signal-to-noise ratio (S/N) of 3 was 0.5 ng ml−1, and the recoveries for the addition of different concentrations of DES to samples were in the range of 78.5–88.3% with RSD (n = 5) of less than 6.4%. The method was successfully applied to the determination of DES in human urine samples.

Determination of sulfides in synthesis and isomerization systems by reversed-phase ion-pair chromatography with a mobile phase containing tetramethylene oxide as organic modifier

SummaryA reversed-phase ionpair chromatographic method with tetramethylene oxide as organic modifier has been developed for the simultaneous separation and detection of the sulfides NH2CSNH2, (NH4)2CS3, (NH4)2S, and NH4SCN. The optimized separation conditions were determined by means of a U7 (76) uniform design experiment, and tetramethylene oxide played an important role in adjusting the retention behavior of (NH4)2S and NH4SCN. The linearity of the calibration plots for the four components was investigated; correlation coefficients were from 0.9989–0.9999. The proposed method was successfully applied to the determination of NH2CSNH2, (NH4)2CS3, (NH4)2S, and NH4SCN in synthesis and isomerization samples.

Determination and comparison of competitive isotherms by rectangular pulse method and frontal velocity analysis method

Two different approaches, the rectangular pulse method and a new method, the frontal velocity analysis method are applied to the determination of competitive isotherms for two systems on ODS-silica. Both sets of experimental data are found to fit well to the competitive-Langmuir isotherm equation. The data obtained from the rectangular pulse method and the frontal velocity analysis method are in general agreement with each other and the best coefficients of the competitive isotherms obtained with the two methods are close. This shows that the simpler and easier method, the frontal velocity analysis method can be used to determine binary competitive isotherms.

Determination and Comparison of Ternary Competitive Isotherms by Frontal Velocity Analysis and Rectangular Pulse Method

SummaryA new method, frontal velocity analysis, is applied to the determination of ternary competitive isotherms for benzyl alcohol, 2-phenylethanol and 3-phenylpropanol on ODS-silica 1∶1 methanol-water as mobile phase. Data obtained from the new method are in good agreement with results from the classic rectangular pulse method under the same conditions. This shows that the simpler and easier method, frontal velocity analysis can be used to determine ternary competitive isotherms accurately.