Wavelet smoothing applied to the determination of trace arsenic, lead, antimony and selenium in environmental water by ICP-OES

An efficient mathematical smoothing approach, based on wavelet transform, is proposed for the processing of weak signals of As, Pb, Sb and Se in inductively coupled plasma optical emission spectrometry (ICP-OES). The effects of mother wavelet, transform approach and decomposition number on the performances of the wavelet transform were investigated. The Haar wavelet was selected as the mother wavelet; wavelet smoothing was used to reduce the noise and the decomposition number selected was 2 or 3, according to the behavior of noise in the raw spectra. To evaluate the feasibility of the developed method, several synthetic water samples obtained by spiking trace As, Pb, Sb and Se in doubly distilled water were examined. The results showed that the intense noises were successfully removed from the raw spectra and the deformed weak signals of the examined elements became symmetrical and distinct. The average recoveries for As, Pb, Sb and Se were 100.4%, 103.1%, 103.5% and 101.1%, respectively. The analytical results of trace As, Pb, Sb and Se in environmental water samples agreed quite well with those by graphite furnace atomic absorption spectrometry (GFAAS). The proposed method can be an alternative to the classical smoothing techniques in determining trace elements with low sensitivity by ICP-OES.