Huanying Zhou

Determination of Listeria Monocytogenes in Milk Samples by Signal Amplification Quartz Crystal Microbalance Sensor

A piezoelectric crystal biosensor method has been established for detection of listeria monocytogenes (LM) by gold nanoparticles (GNPs) signal amplification. Based on specific recognition of single-stranded DNA (ssDNA) hybridization, a sandwich format of ssDNA probes/complimentary ssDNA probes modified by GNPs/ssDNA of LM was fabricated. This novel strategy allows the detection limit of LM as low as 10 cfu/mL. The biosensor showed friendly biocompatibility, good specificity, acceptable stability, which provided a potential alternative tool for detection of LM in real samples. Furthermore, the developed method could be easily extended to other gene analysis schemes.

A Dip‐and‐Read Test Strip for the Determination of Nitrite in Food Samples for the Field Screening

Abstract A new test strip method for field screening of nitrite in aqueous samples based on the diazo‐coupling reaction between the nitrite and the Griess reagents has been developed. The test strip has a circular sensing zone that contains two layers: the Griess reagents act as the sensing reagent and is immobilized in the bottom layer; the top layer is a cellulose acetate membrane that can be used as a dialysis membrane to remove the matrix from the sample, which can enhance the selectivity of this method. When the test strip was directly dipped into the samples, a color change of the test strip was observed, and the intensity of color that appears on the test strip is proportional to the concentration of nitrite in the range from 0.50 to 25 µg mL−1 in food samples. Under the experimental conditions, as low as 0.20 µg mL−1 nitrite can be observed; most of anionic and cationic species as well as other sample matrixes basically do not interfere with the nitrite measurement.

Rapid Detection of Bisphenol A in Water Samples by High-Performance Liquid Chromatography Based on Syringe Filters with Nylon Membrane Extraction

Syringe filters with nylon membrane extraction combined with high-performance liquid chromatography (HPLC)-UV detection was developed for analyzing bisphenol A (BPA) in water samples. The commercial syringe filters with hydrophilic nylon membranes represent a convenient and practical tool for the selective preconcentration of BPA in real water samples. The method required a small amount of sample (20.0 mL) and minimal sample pretreatment. The factors influencing extraction efficiencies, such as sample volume, the kind and volume of eluted solvent, flow rate, and pH were optimized. Chromatographic separation was achieved on a C18 column using acetonitrile–water mobile phase and pumped isocratically at 1 mL/min. The UV detector was set at 227 nm. The chromatographic run time did not exceed 10 min. Under the optimum conditions (sample volume 20 mL; eluted solvent, acetonitrile, 1 mL; pH 7), the linear range was 0.50–20.00 µg/L with correlation coefficients of 0.9993–0.9999. Limit of Detection (LOD) were in the range of 0.16–0.21 µg/L. Tap water and river water (at spiking levels of 5.00, 10.00, and 15.00 µg/L) were successfully analyzed by the proposed method. The recoveries compared to previous methods were in the range of 91.7–99.3%. The results showed that syringe filters is a very simple, rapid, and efficient pretreatment tool for preconcentration of analytes.

Ultrasound-Assisted Extraction Combined with HPLC-UV for Fast Determination of Sulfamethazine and Its N4-Acetyl Metabolite in Plasma and Phosphate Buffer

A simple and cost effective HPLC-UV method for fast determination of sulfamethazine (SMZ) and its N4-acetyl metabolite, N4-acetyl sulfamethazine (AcSMZ), in plasma and phosphate buffer was developed and validated. The sample treatment was performed by ultrasound-assisted extraction with 1 mL ethyl acetate twice, each time 5 min. Moreover, there was no need for centrifugation and further clean-up, which shortened the measurement time. The total analysis time was less than 30 min. The method proved to be a selective and accurate tool for detection of SMZ and AcSMZ in plasma and phosphate buffer with satisfactory recoveries (85.43–99.29%) and little matrix effects (0.86–0.99). The proposed approach was also applied to the evaluation of pharmacokinetic and drug-metabolite protein binding interaction studies. The results show that SMZ and AcSMZ are non-concentration-dependent, and the metabolite does not bind competitively with the drug to the plasma protein.

A highly sensitive method for detection of bisphenol A in water samples based on functionalised Fe3O4@SiO2@nylon66

ABSTRACT A simple and sensitive method was developed for preconcentration and determination of bisphenol A (BPA) in environmental samples by high performance liquid chromatography (HPLC). The hydrophilic silicon-dioxide- and nylon66-functionalised magnetic material (Fe3O4@SiO2@nylon66) was used as a sorbent for magnetic solid-phase extraction (MSPE). With the anhydrous microemulsion reaction, the Fe3O4@SiO2@nylon66 had shown great characteristics such as good magnetic responsivity, water dispersibility and stability. Based on the materials, various extraction parameters including pH, extraction time, elution time, the number of sorbents, sample volume and elution times were optimised. The whole extraction procedure could be accomplished within 20 min and the materials could be used more than 10 times after regeneration. Under the optimised conditions, different types of water samples (Tap water, river water, sea water and underground water) were successfully analysed to verify the applicability of the proposed method. The recoveries of different samples ranged from 88.54% to 104.46%. An enrichment factor of 250 was achieved with 0.05 μg/L detection limit. Thus, the developed MSPE is a potential technique that can be used for water samples preconcentration or combined with other analytical methods for determination of BPA.

A Highly Sensitive Method for Determination of Copper (II) in Water Samples for Field Screening

Abstract A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL−1. The limit of detection was 0.5 ng mL−1. This method has been used for the field screening of copper (II) with satisfactory results.