Integration of hydride generation and photochemical vapor generation for multi-element analysis of traditional Chinese medicine by ICP-OES

Abstract

A dual-mode chemical vapor generation (DM-CVG) sample introduction system that integrates hydride generation (HG) and photochemical vapor generation (PVG) was coupled to a commercial inductively coupled plasma optical emission spectrometer (ICP-OES) for simultaneous multi-element analysis of traditional Chinese medicine samples for trace hydride-forming elements and non–hydride-forming elements. Three hydride-forming elements (Cd, As, and Ge) and two non–hydride-forming but photochemical vapor–generating elements (Co and Ni) were selected as target elements to validate the proposed method. Optimum experimental conditions for DM-CVG-ICP-OES were carefully investigated, and satisfactory limits of detection (LODs), 0.2–1.4μgL−1, and relative standard deviations (RSDs), 1.3%–4.6%, were obtained for these target elements. A certified reference celery sample (GBW10048) was used to investigate the feasibility of the proposed method for real analysis. Strong suppression on the PVG efficiency occurred either when little nitric acid residue or some unknown coexisting materials remained in the sample solutions. Complete acid-evaporation/catching and moderate dilution of the digests could effectively alleviate this negative effect. Four different acid-evaporation/catching methods were performed and compared. Catching acid by adding an appropriate volume of formic acid gave the best signal response and the results agreed well with the certified values. Satisfactory analytical results were also obtained in real sample analysis of TCM Curcuma wenyujin Y.H. Chen et C. Ling.