| Heavy metals’ properties are stable and difficult to degrade, with the soil, water and atmospheric environment the heavy metals can be taken into Chinese herbal medicine, eventually threaten human’ health and even life through the food chain. Therefore, detecting the content of heavy metals in Chinese herbal medicine has important significance on human’ health. It is difficult and limited to detect the heavy metals of Chinese herbal medicine after microwave digestion at trace levels due to their low concentrations and matrix interferences. Thus, in order to improve the accuracy of detection, some pretreatment techniques such as preconcentration and separation are still necessary. In this paper, several methods have been studied to explored the determination of seven kinds of commom metals, including arsenic(As), selenium(Se), copper(Cu), chromium(Cr), nickel(Ni), lead(Pb) and cadmium(Cd) in Chinese herbal medicine samples. The main contents are as follows:Part 1 Determination of heavy metals in Chinese herbal medicine by ultrasound-assisted extraction and Inductively Coupled Plasma-Mass SpectrometryA new method based on ultrasonic-assisted extraction technique instead of classical microwave digestion technique for release of heavy metals in eight kinds of Chinese herbal medicine samples and analyzed by ICP-MS has been developed. Variable parameters affecting the extraction procedure were evaluated and optimized. The optimized experimental conditions were acid medium at 10 mL,5.0mol L"1 HNO3, immersion time for 12 h and ultrasonication at 45 kHz 160W for 15 min. The equilibrium temperature and time was 50℃ and 30 min. The calibration plots were found to be lineae in the range of 0.5-50μgL-1 for As, Ni, Se, Cu, Cr, Pb and Cd, and the linear correlation coefficients were between 0.99956 and 0.99998, the recoveries ranged from 86.7% to 96.5% and the relative standard deviation (RSD) were between 3.2% and 6.3%(n=6). The limits of detection (LOD) were 0.007μg L-1 for As,0.19μg L"1 for Ni,0.032μg L-1 for Se,0.26μg L-1 for Cu,0.056μg L-1 for Cr,0.24μg L1 for Pb and 0.003 μg L-1 for Cd, respectively. The method was not only practical and greatly saving the cost, but also has a high sensitivity and good accuracy. This method can be applied to deal with samples on the spot, which ensured the accuracy of experimental results, and the proposed approach was applied to determine As, Ni, Se, Cu, Cr, Pb and Cd in Chinese herbal medicine samples with satisfactory results.Part 2 Determination of total chromium in Chinese herbal medicine samples by suspension dispersive solid phase extraction combined with silver nanoparticles using flame atomic absorption spectrometryA method of separation and preconcentration of chromium at trace level using nanoparticles (Ag NPs) technology and suspension dispersive solid phase extraction is proposed. The silver nanoparticles technology involves chromium combining with synthesized Ag NPs forming aggregation. Suspension dispersive solid phase extraction is based on the reaction of zinc sulfate (ZnSO4) and sodium hydroxide (NaOH) and a zinc hydroxide suspension form, which were dissolved with a certain concentration of hydrochloric and then analyzed by flame absorption spectrometer. The optimum conditions were pH 7.0, Zn(OH)2(0.5 mL 2.0molL-1 NaOH,0.6g ZnSO4),3 mL Ag NPs, HCl for dissolving coprecipitation at 2 mL 2 molL-1, vortex time for 45 s. Linearity was investigated from 10 to 1000μg L-1 and correlation coefficient was 0.9988, The recoveries of 93.4% to 105.3% and enrichment factor of 20 were achieved with 40mL of sample. The LODs was 3.2μg L-1 for total chromium and the relative standard deviation (RSD) was 4.2% at 20μg L-1. This method is simple and successfully applied for determination of chromium in Chinese herbal medicine samples with satisfactory results.Part 3 Study on the determination of copper and nickel in Chinese herbal medicine samples with magnetic solid phase extraction by flame atomic absorption spectrometry (FAAS)The method based on Cu and Ni chelating with APDC and adsorbed by magnetic nanoparticls of Fe3O4-SiO2-APDC has been developed. In this procedure, MPs were added into to Chinese herbal medicine sample solution and the target analyte is adsorbed on the surface of Fe3O4-SiO2-APDC which are separated from the aqueous solution by means of an external magnetic force, and then Cu and Ni were desorbed by acetonitrile for further determination by flame atomic absorption spectrometry (FAAS). The optimum conditions were pH 4.0, the concentration of APDC at 0.40 mg mL-1, the volume of Fe3O4-SiO2-APDC solution for 0.5 mL, vortex time for 2.0 min. The limits of detection (LOD) of Cu and Ni were 3.1μg L-1 and 4.2μg L-1 and the relative standard deviation (RSD) of Cu and Ni were 2.3% and 4.8%, the recoveries of Cu and Ni ranged from 89.6% to 96.8%. The calibration curves were linear in the range of 0.1-10.0 mg L-1 for Cu and Ni. The proposed method was applied to determined Cu and Ni in Chinese herbal medicine samples with satisfactory results. |
PDF Full Text Request