Determination of thallium in vegetative plant leaves near industrial areas by high-resolution continuum source electrothermal atomic absorption spectrometry after salt induced cloud point extraction

Abstract

A rapid analytical procedure is described for the separation and pre-concentration of ultra trace level thallium from the microwave assisted nitric acid digests of plant samples and determination using high resolution continuum source electrothermal atomic absorption spectrometry (HR-CS-ETAAS). The method is based on the extraction of ionic thallium spices formed in-situ in the nitric acid digests of plant leaves with Triton X-100 micelles, in presence of HCl and NaCl. The hydrophobic solubilising sites of Triton X-100 micelles are used for the pre-concentration of hydrophobic species of thallium from bulk aqueous phase into a small surfactant rich phase. The main parameters affecting the extraction process are evaluated and optimized. A rapid temperature program completed within 15 s is used for the determination of thallium using a permanent ZrIr modifier. Under the optimized conditions, the pre-concentration factor and limit of detection are 25 and 0.05 ng mL−1, respectively. A characteristic mass of 12 pg is obtained on measuring the integrated absorbance with central pixel ±1. The recoveries are in the range of 95–99% at 1 ng mL−1 with 2–3% relative standard deviation. The accuracy of the method is verified by analyzing certified reference materials such as BCR 060 aquatic plant and NIST 1572 citrus leaves. The obtained values are in good agreement with the certified values. The procedure is also applied to real samples such as spinach, cabbage, aquatic, and tobacco plant leaves collected near thermal power plants and industrial areas.