Multi-wavelength calibration: Determination of trace toxic elements in medicine plants by ICP OES

Abstract

In the present work a promising method for elemental impurities quantification, such as As, Cd, Cr, Cu, Ni and Pb in medicinal plants, called Multi-Wavelength Calibration - MWC, is shown. Calibration and quantification are performed with only two solutions. The first solution contains sample and a standard solution of known concentration of each analyte (1:1 v−1), and the second solution contains sample and a blank sample solution (1:1 v−1). The method was validated using addition and recovery tests, and content quantification of each analyte in SRM 1570a and SRM 1575a. The recoveries obtained were between 96.90–99.90% and relative standard deviation of 1.40%. The results obtained in the quantification of SRMs demonstrate excellent method accuracy. The levels of elemental impurities present in medicinal plants had concentrations above that allowed for As, Cr, Cu, Ni and Pb, and higher concentrations for arsenic, when compared to the maximum limits allowed by the Brazilian Pharmaceutical, World Health Organization, National Sanitation Foundation International and European Medicines Agency. The results demonstrated that the MWC is a fast, accurate and highly sensitive alternative to the methods used by the main regulatory agencies to determine elemental impurities in medicinal and phytotherapeutic plants.