Matrix removal and enrichment of cadmium atnd lead in mineral‐rich samples using liquid‐liquid extraction and analysis by flame atomic absorption spectrometry

Abstract

AbstractThe present work aimed to study matrix removal and enrichment of cadmium and lead in samples containing highly mineral‐rich using liquid‐liquid extraction. Cadmium and lead were extracted by sodium diethyldithiocarbamate (DDTC) and ammonium pyrrolidine dithiocarbamate (APDC) in pH 5.0 buffer solution (acetic acid/acetate) to chloroform. Cd and Pb in chloroform were re‐extracted to the aqueous phase by 1.5 M HNO3 and subsequently determined by flame atomic absorption spectrometry (F–AAS). Mineral‐rich samples (soil, sediment, sea salt, etc.) containing various concentrations of interferent elements (Fe (8‐25%), Al (5‐20%), Cu (400‐500 ppm), Zn (300‐400 ppm), NaCl (up to ⁓100%)) were used to determine the effectiveness of matrix removal. Fe was found to form an undissolved complex with APDC and co‐extracted with Cd and Pb, deteriorating the extraction and following analysis manipulation. 8‐hydroxyquinoline was successfully used as a masking reagent to reduce the co‐extraction of Fe, Al, and other elements with Cd and Pb in the form of dithiocarbamate complexes. In this study, enrichment factors of 5 – 10 could be achieved (from 50 to 5 mL). The recoveries of Cd2+ and Pb2+ ions from spiked agricultural soil, tea–planted soil, basalt soil, forestry soil, livestock feed, and sea salt were 97‐101 % and 87‐92% for DDTC and APDC reagents, respectively. The detection limits of cadmium and lead in soil are 0.0069 and 0.072 μgg−1; in livestock feed, 0.0085 and 0.082 μgg−1; in sea salt, 0.0075 and 0.076 μgg−1, respectively The quantification limit of cadmium and lead in a soil sample is 0.023 and 0.24 μgg−1; in livestock feed of 0.028 and 0.27 μgg−1; and in sea salt of 0.025 and 0.25 mgKg−1, respectively. The proposed approach for matrix removal and pre‐concentration of cadmium and lead can also be applied for mineral‐rich samples with better analytical performances when higher sensitivity and multi‐element detection techniques such as inductively coupled plasma optical emission spectrometry or inductively coupled plasma mass spectrometry are used.