Continuous ultrasound-assisted extraction of cadmium from vegetable samples with on-line preconcentration coupled to a flow injection-flame atomic spectrometric system

Abstract

A fully on-line flow injection method is described for the quantitative acid extraction of cadmium, preconcentration of this trace metal using a minicolumn containing a chelating resin and its determination by flame atomic absorption spectrometry (FAAS). The on-line acid extraction step was carried out using a continuous ultrasound-assisted extraction system (CUES). The acid extract was preconcentrated on a minicolumn packed with a chelating resin (CHELITE P, with aminomethylphosphoric acid groups), cadmium elution was carried out with hydrochloric acid, and this trace metal was continuously monitored by FAAS. A Plackett–Burman experimental design was used for optimization of the analytical procedure. The method allowed a total sampling frequency of 16 samples per hour, with a relative standard deviation for the complete procedure of 2.1; the detection and quantification limits were 0.014 µg/g and 0.067 µg/g for 60 mg of sample, respectively. The accuracy was verified using a standard reference material (NCS DC 73351 tea leaves). The analytical procedure was applied to the determination of trace amounts of cadmium in real vegetable and fruit samples.

Keywords:

• Ultrasound-assisted acid extraction
• Minicolumn preconcentration
• Cadmium
• Vegetable samples
• Flame atomic absorption spectrometry
• Flow injection analysis

Acknowledgements

The authors are grateful to the financial support provided by the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Ministerio de Ciencia y Tecnología (Project no. CAL01-043).