A polyclonal antibody against ochratoxin A (OTA) was produced from rabbits immunized with the OTA–BSA conjugate. A competitive
direct enzyme-linked immunosorbent assay (cdELISA) and a membrane-base colloidal gold immunoassay in flow-through format were
developed for the rapid detection of OTA in various food matrices. In the cdELISA, the concentration causing 50% inhibition
was 0.07 ng mL−1, and the effects of different chemical conditions (ionic strength, pH value, and organic solvent) were studied. The sensitivity
of the assay was higher than those previously reported. A simple, rapid, and efficient extraction method was developed and
74–110% recoveries of spiked samples were obtained. Fifty percent methanol extracts of some food samples such as barley, wheat,
oat, corn, rice, and raisins could be analyzed directly by immunoassay after dilution in PBS; grape juice and beer samples
could be analyzed directly after dilution with PBS; for coffee samples, a more complex method was used to remove the matrix
effect effectively. Membrane-based colloidal gold immunoassays had a visual detection limit of 1.0 ng mL−1 for OTA with a detection time of less than 10 min. For the validation of the cdELISA and membrane-based colloidal gold immunoassay,
samples were analyzed by high-performance liquid chromatography. The correlation between data obtained using the microwell
assay and HPLC was good (R2 = 0.984). The developed immunoassay methods are suitable for the rapid quantitative or qualitative determination of OTA in
food samples. 相似文献
Nanoporous carbon with a high specific surface area and unique porous structure represents an attractive material as an adsorbent in analytical chemistry. In this study, a magnetic nanoporous carbon (MNC) was fabricated by direct carbonization of Co-based metal-organic framework in nitrogen atmosphere without using any additional carbon precursors. The MNC was used as an effective magnetic adsorbent for the extraction and enrichment of some phenylurea herbicides (monuron, isoproturon, diuron and buturon) in grape and bitter gourd samples prior to their determination by high performance liquid chromatography with ultraviolet detection. Several important experimental parameters that could influence the extraction efficiency were investigated and optimized. Under the optimum conditions, a good linearity was achieved in the concentration range of 1.0–100.0 ng g−1 for monuron, diuron and buturon and 1.5–100.0 ng g−1 for isoproturon with the correlation coefficients (r) larger than 0.9964. The limits of detection (S/N = 3) of the method were in the range from 0.17 to 0.46 ng g−1. The results indicated that the MNC material was stable and efficient adsorbent for the magnetic solid-phase extraction of phenylurea herbicides and would have a great application potential for the extraction and preconcentration of more organic pollutants from real samples. 相似文献
A nanoporous carbon derived from an aluminum-based metal-organic framework was deposited on stainless steel wires in a sol–gel matrix. The resulting fibers were applied to the solid-phase microextraction of the polycyclic aromatic hydrocarbons (PAHs) naphthalene, acenaphthene, fluorene, phenanthrene and anthracene from water and soil samples. The fiber was then directly inserted into the GC injector and the PAHs were quantified by GC-MS. The effects of salt addition, extraction temperature, extraction time, sample volume and desorption conditions on the extraction efficiency were optimized. A linear response to the analytes was observed in the 0.1 to 12 μg∙L−1 range for water samples, and in the 0.6 to 30 μg∙kg−1 for soil samples, with the correlation coefficients ranging from 0.9934 to 0.9985. The limits of detection ranged from 5.0 to 20 ng∙L−1 for water samples, and from 30 to 90 ng∙kg−1 for soil samples. The recoveries of spiked samples were between 72.4 and 108.0 %, and the precision, expressed as the relative standard deviations, is <12.8 %.
A novel method for the determination of five sulfonylurea herbicides in soil was developed by a dispersive solid-phase extraction
(DSPE) clean-up followed by dispersive liquid–liquid microextraction (DLLME), prior to sweeping micellar electrokinetic chromatography
(MEKC). In the DSPE-DLLME, 10 g of soil sample was first extracted with 10 mL of acetonitrile containing 5% formic acid (pH 3.0).
The extract was then cleaned-up by a DSPE with C18 as sorbent. A 1 mL aliquot of the resulting extract was then added into a centrifuge tube containing 5 mL of water adjusted
to pH 2.0 and 60.0 μL chlorobenzene (as extraction solvent) for DLLME procedure. Then, the organic sample extraction solution
was evaporated to dryness, and reconstituted with 20.0 μL of 1.0 mmol L−1 Na2HPO4 (pH 10.0) for sweeping-MEKC analysis after DLLME. Under optimized conditions, the method provided as high as 3,000- to 5,000-fold
enrichments factors. The linearity of the method was in the range of 3.3–200 ng g−1 for chlorimuron ethyl and bensulfuron methyl, and in the range of 1.7–200 ng g−1 for tribenuron methyl, chlorsulfuron and metsulfuron methyl, with the correlation coefficients (r) ranging from 0.9965 to 0.9983, respectively. The limits of detection (LODs) ranged from 0.5 to 1.0 ng g−1. The intraday relative standard deviations (RSDs, n = 5) were below 5.3% and interday RSDs (n = 15) within 6.8%. The recoveries of the method for the five sulfonylureas from soil samples at spiking levels of 5.0, 20.0,
and 100.0 ng g−1 were 76.0–93.5%, respectively. The developed method has been successfully applied to the analysis of the target sulfonylurea
herbicide residues in soil samples with a satisfactory result. 相似文献
Okadaic acid (OA) is a lipophilic marine biotoxin. In this study, OA was coupled with the carrier proteins keyhole limpet hemocyanin and bovine serum albumin as immunity and detection antigens by an active ester method. The polyclonal antibody against OA was prepared successfully, an indirect competitive ELISA (ciELISA) developed for the detection of OA in shellfish, and the reactive conditions of ciELISA optimized. The LOD (15% inhibition concentration) for the microwell plates was 1.28 +/- 0.38 ng/mL, corresponding to 12.8 +/- 3.8 ng/g. Two extraction methods were used to remove shellfish matrix interference with high recovery of spiked samples, and the methanol extraction of shellfish mussel was analyzed after dilution in phosphate-buffered saline. For validation of the optimized ciELISA, spiked and natural samples were analyzed by ciELISA, and HPLC with fluorescence detection. The correlation of linear regression equation was y = 1.0064x - 10.234, and the correlation coefficient was 0.9347. From the results of the comparative study, the established ciELISA assay using polyclonal antibody against OA could be used in preliminary screening of suspicious shellfish samples. 相似文献
The effects of thermal processing (TP) and flat sweep frequency and pulsed ultrasound (FSFPU) treatment with different frequency modes on the activity, conformation and physicochemical properties of mushroom polyphenol oxidase (PPO) were investigated. The results showed that the relative enzymatic activity of PPO gradually decreased with increasing temperature and duration, and thermosonication decreased the PPO activity to a greater extent compared with thermal processing. FSFPU treatment with dual-frequency of 22/40 kHz mode showed the most significant effect. Circular dichroism (CD) showed that the content of α-helix and β-turn dropped, while that of β-sheet and random coil raised after FSFPU treatment. The intensity of endogenous fluorescence decreased, indicating that PPO protein unfolded and the tertiary structure was destroyed. The amount of free sulfhydryl, protein aggregation index, and turbidity all rose. Moreover, FSFPU treatment led to the aggregation of protein from the analysis of atomic force microscope (AFM). Conclusively, FSFPU can be used as an effective method to inhibit the activity of endogenous enzymes in food. 相似文献