A simple and rapid fluorescence polarization immunoassay (FPIA) based on polyclonal antibodies is reported for the first time for the determination of nicotinic acid. First, six nicotinic acid analogues were coupled with fluorescein isothiocyanate isomer I (FITC) to obtain tracers. The influences of tracer structure on the performance of FPIA as well as the structure-activity relationships were explored. Subsequently, the tracer concentration and antibody dilution ratio on the performance of FPIA were investigated. For the optimal conditions, the detection range of FPIA was from 1.1 to 145.6 μg mL−1 and its IC20 value as the limit of detection (LOD) was 1.1 μg mL−1. The cross-reactivity of antibodies with common vitamins was evaluated. The intra-assay recovery was from 92.0% to 101.2% in food and tablets, with inter-assay recoveries between 92.0% and 103.8%. The developed FPIA provided good sensitivity and reproducibility and therefore provided efficient and economic screening for nicotinic acid in food and tablets.
Xi Tian,Yaqing Dong,Yufen Wang,Zhaorui Song,Meng Meng,Sergei A. Eremin,Chuan Deng,Yongmei Yin,Rimo Xi
A rapid and homogenous fluorescence polarization immunoassay (FPIA) for diethyl phthalate is reported. Two haptens and three immunogens for diethyl phthalate were synthesized to generate polyclonal antibodies and fluorescein isothiocyanate labeled diethyl phthalate was prepared as the tracer. The antibodies, methanol concentration, and incubation time were optimized. The cross-reactivities of the optimized antibodies to other phthalate esters were characterized. The antibody shows excellent sensitivity with a limit of detection of 6.0 ng mL−1 and a half-inhibition concentration of diethyl phthalate of 40.4 ng mL−1. The immunoassay had a linear dynamic range from 10 to 200 ng mL−1. The mean coefficient of variation was lower than 11.3% for intra-assay and lower than 14.6% for inter-assay measurements. The limit of detection was 1.46 ng mL−1 in bottled drinking water, 0.34 µg mL−1 in juice, and 50.0 µg g−1 in pharmaceutical capsules. The recovery was from 85.9 to 114.9%, and the coefficients of variation were 4.3 to 17.0%. The developed immunoassay provided good sensitivity, specificity, accuracy, and may serve as an alternative for diethyl phthalate determination for field screening of food, pharmaceuticals, and environmental materials.
危险品化学品经营许可证（带存储）