A SERS-based competitive immunoassay for highly sensitive and specific detection of ochratoxin A.

Ochratoxin A (OTA) is a well-known carcinogenic contaminant in food commodities. The highly sensitive and specific detection of the OTA level is an essential way to prevent the health risks to humans/animals. In this work, an SERS-based competitive immunoassay platform has been developed for the detection of OTA. This assay contains two compartments: OTA-BSA-immobilized SERS nanotags and anti-OTA antibody-functionalized magnetic beads. In the presence of target OTA, a competitive reaction towards magnetic beads occurs between the target OTA and SERS nanotags. The characteristic peaks of SERS nanotags adsorbed onto magnetic beads were used for the quantitative analysis of OTA. Under optimized conditions, a good linear relationship was obtained in the range of 1 pg mL-1 to1000 pg mL-1. The limit of detection (LOD) was estimated to be 0.61 pg mL-1 using the IUPAC standard method. In addition, this proposed method was also successfully applied for the detection of OTA in wine samples and satisfactory recovery rates were obtained in the range of 90.60% to 103.3%. It is believed that this SERS-based competitive method holds great potential for highly sensitive and specific detection of mycotoxins.

Speciation analysis of mercury in water samples by dispersive liquid-liquid microextraction coupled to capillary electrophoresis.

In this study, a method of pretreatment and speciation analysis of mercury by dispersive liquid-liquid microextraction along with CE was developed. The method was based on the fact that mercury species including methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and Hg(II) were complexed with 1-(2-pyridylazo)-2-naphthol to form hydrophobic chelates and l-cysteine could displace 1-(2-pyridylazo)-2-naphthol to form hydrophilic chelates with the four mercury species. Factors affecting complex formation and extraction efficiency, such as pH value, type, and volume of extractive solvent and disperser solvent, concentration of the chelating agent, ultrasonic time, and buffer solution were investigated. Under the optimal conditions, the enrichment factors were 102, 118, 547, and 46, and the LODs were 1.79, 1.62, 0.23, and 1.50 µg/L for MeHg, EtHg, PhHg, and Hg(II), respectively. Method precisions (RSD, n = 5) were in the range of 0.29-0.54% for migration time, and 3.08-7.80% for peak area. Satisfactory recoveries ranging from 82.38 to 98.76% were obtained with seawater, lake, and tap water samples spiked at three concentration levels, respectively, with RSD (n = 5) of 1.98-7.18%. This method was demonstrated to be simple, convenient, rapid, cost-effective, and environmentally benign, and could be used as an ideal alternative to existing methods for analyzing trace residues of mercury species in water samples.

[Simultaneous determination of four phthalate esters in water samples using ultrasound-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography].

Ultrasound-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography (UA-DLLME-HPLC) was developed for the determination of four typical phthalate esters (PAEs). The analyzed PAEs included dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and di-n-octyl phthalate (DnOP). The UA-DLLME parameters such as types/volumes of extraction/dispersion solvents, ultrasonic time, ionic strength and extraction time, were investigated. Enrichment factor (EF)was employed to evaluate the extraction efficiency. The conditions were finally chosen: CCl4 (40 microL)/ acetonitrile (1.0 mL) as extraction/dispersion solvents; 30 g/L NaCl; ultrasound/centrifugation of 5 min. Under the optimized extraction conditions, UA-DLLME exhibited strong enrichment ability for the four PAEs. The EFs for DMP, DEP, DBP and DnOP obtained were 71, 144, 169 and 159, respectively. The limits of detection were 3.78, 1.77, 3.07 and 3.30 microg/L for DMP, DEP, DBP and DnOP, respectively. The satisfactory recoveries for three water samples at three spiked levels ranged from 82.99%-114.47%, with the relative standard deviations of 1.93%-8.31%. It is a convenient, speedy, environmentally benign method for the routine analysis of PAEs in water samples.