Determination of Epigoitrin in Radix Isatidis by Solid PhaseExtraction-Quantitative Nuclear Magnetic Resonance Spectroscopy / 分析化学

ABSTRACT

The method of quantitative nuclear magnetic resonance spectroscopy (qNMR) for determination of epigoitrin in Radix Isatidis was established based on solid phase extraction (SPE).The twice ultrasonic extraction method using pure water was used for fully extracting epigoitrin in sample, and then the extraction was enriched and concentrated by poly-Sery MCX SPE cartridge.The effect of sample pretreatment and qNMR experimental conditions was investigated.The qNMR experiment conditions were selected using DMSO as solvent, calibrated 2,3,5-triiodobenzoate as internal standard, and P1(pulse width)=14.1 μs, d1(pulse delay time)=5 s, NS(number of scan)=256.The .1H-NMR peaks of δ 5.365-5.399 (H-7b, d, 1H) of epigoitrin were chosen as the quantitative peaks.Method validation was performed including precision (intra-day precision RSD was 0.5%, and the inter-day precision was 0.8%), linearity (correlation coefficient r>0.9991), LOD (0.05 mg/g, standard curve method) and LOQ (0.19 mg/g, S/N≥150).The recoveries of the SPE-qNMR were 97.4%-101.7%.The result showed that the method was stable, accurate and reliable.With this method the epigoitrin in a real Radix Isatidis was determined to be <0.19-1.26 mg/g.SPE combining with qNMR could extend the application field of qNMR, especially in the detection of low-content component in complex samples.