Fanghui Liang

Determination of hormones in milk by hollow fiber-based stirring extraction bar liquid-liquid microextraction gas chromatography mass spectrometry.

The hollow fiber-based stirring extraction bar liquid-liquid microextraction was applied to the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, 17-α-hydroxyprogesterone, medroxyprogesterone, progesterone and norethisterone acetate, in milk. The present method has the advantages of both hollow fiber-liquid phase microextraction and stirring bar sorptive extraction. The stirring extraction bar was used as both the stirring bar of microextraction, and extractor of the analytes, which can make extraction, clean-up and concentration be carried out in one step. When the extraction was completed, the stirring extraction bar was easy isolated from the extraction system with the magnet. Several experimental parameters, including the type of extraction solvent, the number of hollow stirring extraction bar, extraction time, stirring speed, ionic strength, and desorption conditions were investigated and optimized. The analytes in the extract were derived and determined by gas chromatography mass spectrometry. Under optimal experimental conditions, good linearity was observed in the range of 0.20-20.00ng mL(-1). The limits of detection and quantification were in the range of 0.02-0.06ng mL(-1) and 0.07-0.19ng mL(-1), respectively. The present method was applied to the analysis of milk samples, and the recoveries of analytes were in the range of 93.6-104.6% with the relative standard deviations ranging from 1.6% to 6.2% (n=5). The results showed that the present method was a rapid and feasible method for the determination of hormones in milk samples.

Determination of malachite green in environmental water using cloud point extraction coupled with surface-enhanced Raman scattering

A novel, simple and ultra-sensitive method, for rapid detection of trace malachite green (MG) in environmental water using cloud point extraction (CPE) coupled with surface-enhanced Raman scattering (SERS) is described. The colloidal gold nanoparticles (AuNPs) were synthesized by reduction of chloroauric acid (HAuCl4) with trisodium citrate and were used as SERS substrates. The SERS substrates were found to produce enhancement factors of 1.52 × 106 for MG by employing the SERS peak at 1175 cm−1. After the optimization of SERS conditions including the volumes of ethanol, colloidal AuNPs and HCl, the present method was linear for MG at 1175 cm−1 and 1618 cm−1 over the concentration range of 0.5–35.0 μg L−1 and 2.5–40.0 μg L−1, with the correlation coefficients (r) of 0.9971 and 0.9960. The limits of detection (LODs) were 0.10 μg L−1 and 0.70 μg L−1, and the intra- and inter-day relative standard deviations (RSDs) of detection were in the range of 2.0–2.5% and 1.9–3.2% at 1175 cm−1 and 1618 cm−1, respectively. Recoveries obtained by analyzing 4 spiked environmental water samples at 2 levels were between 93.1 and 106.0%.

Selective and sensitive SERS sensor for detection of Hg2+ in environmental water base on rhodamine-bonded and amino group functionalized SiO2-coated Au–Ag core–shell nanorods

Here, we designed a new type of SERS sensor with high selectivity and sensitivity for the determination of Hg2+ at picomolar concentrations based on hydrolysis reactions. The Rhodamine 6G-derived Schiff base bonded and amino group functionalized SiO2-coated Au–Ag core–shell nanorods (Au@Ag@SiO2–NH2-R6G, NR-Rs), which show extraordinary enhancement factors (EF) and good stability, were employed as the SERS substrate of the sensor. The tunable ability of the chemical bonding of the substrate generates appropriate probe molecules bound to the surface of the nanorods (NRs) and improves the selectivity and sensitivity of the SERS sensor dramatically. The limit of detection (LOD) of Hg2+ obtained using the present SERS sensor was 0.33 pmol L−1. Furthermore, the proposed substrate has pH-responsive ability. The present sensor is suitable for the on-site determination of pH and Hg2+ by combining with a portable Raman spectrometer.

Simultaneous determination of thiocyanate ion and melamine in milk and milk powder using surface-enhanced Raman spectroscopy

In this study, a simple and efficient method based on surface-enhanced Raman spectroscopy (SERS) was developed to detect thiocyanate ion (SCN−) and melamine in milk and milk powder. Silver nanoparticles (AgNPs), sodium chloride (NaCl) and sodium hydroxide (NaOH) were used as the substrate, the aggregating agent and the alkaline adjusting agent for the SERS process, respectively. The SERS peak intensity at 445 cm−1 was measured under low NaCl concentration for determining SCN−, followed by the measurement of the SERS peak intensity at 704 cm−1 under high NaCl concentration for determining melamine. The determination conditions for SERS, including the amount of AgNPs, NaCl and NaOH, and the mixing time before measurement, were optimized. By the present method, good linear responses were obtained for SCN− and melamine in the concentration ranges of 2.00–191.00 mg L−1 and 0.01–4.80 mg L−1 respectively, with correlation coefficients higher than 0.998. The present method was successfully applied to the simultaneous determination of SCN− and melamine in four spiked milk samples and three certified milk powder samples. The recoveries of SCN− and melamine in spiked milk samples were 95.15–100.47% and 94.43–102.84%, respectively. The relative standard deviations (RSDs) for determining melamine in certified milk powder samples were lower than 1.6%.

Ionic Liquid-based Microwave-assisted Liquid-liquid Microextraction and High Performance Liquid Chromatography Determination of Sulfonamides from Animal Oils

The authors performed ionic liquid-based microwave-assisted liquid-liquid microextraction(IL-based MALLME) coupled with high performance liquid chromatographic separation for the determination of 6 sulfonamides (SAs) from animal oils. The target analytes were extracted from animal oil samples with sodium hydroxide solution containing 1-butyl-3-methylimidazolium tetrafluoroborateand as the extraction solvent under microwave irradiation. The experimental parameters of the IL-based MALLME, including types of ILs, volume of IL, amount of ion-pairing agent(NH4PF6), pH value of sample solution, and extraction temperature and time were evaluated. The limits of detection and quantification obtained were in a range of 0.4–0.5 μg/kg and a range of 1.2–1.8 μg/kg, respectively. The accuracy of the method was evaluated by analyzing five spiked animal oil samples at two fortified levels(5 and 50 μg/kg), and the recoveries of SAs varied from 81.4% to 114.5% with relative standard deviations ranging from 0.8% to 9.0%.

Determination of proteins in lactic acid bacterium drink and milk powder by micellar electrokinetic chromatography

Micellar electrokinetic chromatography for the determination of proteins in lactic acid bacterium drink and milk powder is proposed. The effects of several experimental parameters, such as the concentrations of tween-20 and urea in the background electrolyte, ionic strength of the background electrolyte, column temperature and applied voltage, on the separation efficiency of the proteins were studied. Under the optimal conditions, the five proteins in lactic acid bacterium drink and milk powder were separated completely from each other and the discrimination of the lactic acid bacterium drink or milk powder adulterated with soybean proteins was achieved. The present method was applied to the quantitative determination of the milk proteins in lactic acid bacterium drink and milk powder, and qualitative identification of soybean proteins in adulterated samples. The analytical performances of the present method were studied and real samples were analyzed. The relative standard deviations and the recoveries for determining the five milk proteins were satisfactory.

Rapid Determination of Rhodamine B in Chili Powder by Surface-Enhanced Raman Spectroscopy

A rapid, simple, and sensitive method for the determination of Rhodamine B in chili powder was established based on surface-enhanced Raman spectroscopy using citrate-coated silver nanoparticles as the substrate. This substrate was found to produce enhancement factors of 1.6 × 107 at 625 per centimeter. A portable Raman spectrometer was used allowing on-site measurements. The effects of the volume of silver nanoparticle solution, the volume of hydrochloric acid, the volume of Rhodamine B, and the mixing time were optimized. The linear dynamic range was from 0.2 to 20.0 micrograms per liter and the limit of detection was 0.08 microgram per liter. The method was applied to the determination of Rhodamine B in chili powder, with recoveries between 81.42 and 97.22 percent, and relative standard deviation values lower than 4.84 percent.