Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

Abstract

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60 s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 10³–10⁴ fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0 pg mL⁻¹ and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1 µg L⁻¹ levels.

Keywords:

• preconcentration
• adsorption onto niobium wire
• cadmium
• electrothermal atomic absorption spectrometry
• tungsten tube atomizer

Acknowledgements

The present research was partly supported by Grant–in–Aid for Scientific Research (C) 24510 096 from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. All experiments were conducted at Mie University. Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the authors and do not necessarily reflect the view of the supporting organizations.