Determination of Cadmium in Water Samples by Automated Flow-Batch Cloud Point Extraction (CPE) Hyphenated to High-Resolution Continuum Source Flame Atomic Spectrometry (HR-CS FAAS)

Abstract

A computer-controlled multicommuted flow-batch system is reported that allows for the online cloud point extraction of metal ions followed by high-resolution continuum source flame atomic absorption spectrometric (HR-CS GFAAS) detection. This approach combines reduced sample and reagent consumption and a short analysis time with the increased precision and sensitivity characteristic of flow-batch analysis and modern extraction techniques. As proof of concept, cadmium in aqueous solutions was determined by the formation of a hydrophobic complex [Cd(PAN)2]. Parameters related to complex formation (pH, pyridyl-azo-naphthol-PAN concentration, complexation time), cloud point extraction (Triton X-114 concentration, electrolyte composition, rich phase trapping), and the multicommuted flow-batch system (flow rates, timing control) were optimized. A small column packed with hydrophobic cotton was used as the interface between the extraction and detection stages to stack the cadmium-containing rich phase in a short plug. Optimized parameters led to a 5.0 to 75.0 µg L−1 linear range, 1.3 µg L−1 limit of detection, 4.3 µg L−1 limit of quantification and 1.8% coefficient of variation (n = 12). Accuracy was evaluated by analyzing a certified reference material EP-H (drinking water) and by recovery tests employing tap water, groundwater, mineral water, and reuse water samples.