A simple, rapid, and sensitive method with high sample throughput was developed for determining arsenic in traditional Chinese medicine (TCM) in the form of uncoated tablets, sugar-coated tablets, black pills, capsules, powders, and syrups. The method involves microwave digestion with flow injection-inductively coupled plasma mass spectrometry (FI-ICP-MS). Method precision was 2.7-10.1 % (relative standard deviation, n = 6) for different concentrations of arsenic in different TCM samples analyzed by different analysts on different days. Method accuracy was checked with a certified reference material (sea lettuce, Ulva lactuca, BCR CRM 279) for external calibration and by spiking arsenic standard into different TCMs. Recoveries of 89-92% were obtained for the certified reference material and higher than 95% for spiked TCMs. Matrix interference was insignificant for samples analyzed by the method of standard addition. Hence, no correction equation was used in the analysis of arsenic in the samples studied. Sample preparation using microwave digestion gave results that were very similar to those obtained by conventional wet acid digestion using nitric acid.
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.
Mercury is a well-known toxic metal which was found to be 0.005 to 0.5 mg/kg for normal plant materials and 1 to 3 mg/kg in contaminated plants that were known to be toxic. 1,2 The Sale of Drugs Act in Singapore states that the amount of mercury in herbal medicine must not be greater than 0.5 mg/kg. Chineseprepared medicines (CPM) come in the form of tablets (coated and uncoated), concentrated pills, syrup, capsules, soluble granules and others. 3 In many ways, CPM were very similar to plant materials, except that different herbs are added to a single product.Methods using wet acid digestion with cold-vapor atomic absorption spectrometry (CVAAS) for the determination of mercury in food were well reported in official methods. 4,5 However, the pretreatment of samples using wet acid digestion can be rather tedious.Microwave digestion using a closed-vessel based on the coupling of electromagnetic radiation with mineral acid to produce high pressure and temperature allows the reaction less time to complete than by conventional means. 6,7 Other than for speed, closed-vessel microwave digestion also minimizes the loss of any volatile analytes, such as mercury. Methods used for the determination of mercury in crop and food samples using a closed vessel and open focused microwave digestion with CVAAS have been reported. [8][9][10] The total mercury in sediments and biological samples were determined using offline microwave digestion with flow-injection CVAAS. 11,12 The aim of this work was to develop a simple, rapid, sensitive and high sample throughput method for the determination of mercury in botanical and CPM samples. The developed method uses two different types of closed vessels for microwave digestion with sodium tetrahydroborate and hydroxylammonium chloride as a reductant in the final determination by CVAAS. The effect of undecomposed organics after closed-vessel microwave digestion and other possible matrix interferences of the method were investigated. The method was used to develop an in-house reference material for day-to-day quality-control purposes. A simple approach of using a statistical qualitycontrol (SQC) chart was proposed for monitoring the stability of an analytical procedure. ExperimentalReagents & standard reference materials High-purity concentrated nitric acid (BDH, Aristar Grade) was used for acid digestion. Deionized water from a Millipore Alpha-Q system that had the capability to produce 18 mΩ cm was used. One certified plant reference material (olive leaves, A method that is both simple and rapid for the determination of mercury in Chinese-prepared medicine (CPM) was developed. The method uses closed-vessel microwave digestion with final analysis by CVAAS with a sodium borohydride and hydroxylammonium hydrochloride solution. The accuracy of the method was checked using botanicalcertified reference materials (BCR62, olive leaves), and close agreement with certified values was achieved. The precision of the method, based on different types of CPM samples and different analysts on different da...
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