Determination of Lead in Botanicals/Chinese Prepared Medicines by Using Microwave Digestion with Flow Injection–Inductively Coupled Plasma–Mass Spectrometry

Abstract

Abstract A simple, sensitive, and rapid method was developed for the determination of lead in botanicals and Chinese prepared medicines (CPM) by using closed-vessel microwave digestion with flow injection–inductively coupled plasma–mass spectrometry. The limits of detection and quantitation for the method, based on 0.5 g digested sample, were calculated to be 0.10 and 0.61 mg/kg, respectively. A simple approach was proposed for calibration by multiple linear regression (MLR) with 207Pb, 206Pb, and 204Pb for the determination of lead in botanical and CPM samples. The results from calibration by MLR were compared with those obtained by conventional modes using 207Pb and the sum of 207Pb and 206Pb. The results obtained by the different modes of calibration were in good agreement for botanical and CPM samples. The method was found to have good accuracy for the analysis of botanical reference materials. Method precision based on analyses of different types of CPM samples by different analysts on different days for different levels of lead was between 3.0 and 8.0% (relative standard deviation, n = 6). The effect of possible matrix interference caused by nitric acid and the extent of digestion was investigated with the method of standard additions. Significant matrix interference was not observed for the CPM samples analyzed. MLR was used to examine the effect of variation in isotopic abundance, which was found to present no significant problem in the determination of lead in the botanical and CPM samples.