RESUMO
A novel immunochromatographic assay was developed, which could provide visual evidence of triazophos in agro products, and also could directly identify the safety status by setting visual cut-off limit of detection in maximal residual limit ( MRL) value. Three test lines ( T1, T2, T3) were applied to the nitrocellulose membrane with different concentrations of Triazophos-OVA, and one control line (C) was settled with goat anti mouse IgG antibody. Thereafter, by combining with conjugate pad which immobilized monoclonal antibody labeled with 20 nm Colloidal gold particles, absorbent pad and PVC plate, a chromatographic test strip was assembled. With optimization of sample extraction and solvents selection, the test strips were employed for the determination of triazophos in rice, cabbage and apple. The results revealed that the cut-off limit of detection could reach 0. 005, 0. 01 and 0. 02 μg / mL represented by test line T3, T2 and T1, respectively. After modification, the cut-off limit of detection was resettled to 0. 05, 0. 1 and 0. 2 μg / mL according to the MRL values which enforced by the national standard of GB2763. Using acetonitrile for the sample extraction, the extracts were diluted 10 times or solvent exchanged with equivalent volume by PBS solution, and then tested by strips descripted above mentioned. The two test strips could precisely identified the safety status of agro product with MRL as threshold within 8-12 min. Furthermore, the residues value of triazophos could be quantified by the multiple quantitative test lines. Parallel GC data indicated that the strip had no false negative. This MRL-based multiple quantitative triazophos detection strip would provide a simple, direct, accurate and the most intuitionistic performance for the evaluation of agro product safety.
RESUMO
A simple,rapid and sensitive upconversion immunochromatographic assay(UICA) was developed to detect imidaclothiz using NaYF4:Yb,Er upconversion nanoparticles(UCNPs) labeled with anti-imidaclothiz monoclonal antibody. The amino-modified UCNPs were conjugated with anti-imidaclothiz monoclonal antibody to prepare the UICA strip,which could realize the quantitative detection of imidaclothiz using a fluorescence photometer with an external 980 nm laser source. The working conditions of the UICA were systematically optimized, and the sensitivity, specificity, precision and accuracy were assessed by the studies of cross-reactivity (CR), spiked recovery and validation with HPLC. Under the optimal conditions (pH 8. 0, 0.3 mol/L NaCl,2.5% methanol and 0.2% PEG2000), the UICA could be completed in 25 min for the detection of imidaclothiz. The half-maximal inhibition concentration (IC50), limit of detection (IC10) and linear range (IC10-IC90) were 97.37 ng/mL,26.30 ng/mL and 26.30-363.08 ng/mL, respectively. The UICA had no CR with the analogues of imidaclothiz except for imidacloprid. The average spiked recoveries were 71.8%-97.2% with the relative standard deviations of 0.7%-10.7% in the matrices of paddy water, soil,pear,peach,wheat,cucumber,tomato and rice. The detection results of UICA for the authentic paddy water and pear samples were consistent with that of high performance liquid chromatography (HPLC).