Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS

Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH , MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract anti mony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (similar to 220 mg) of the freeze-dried samples were analysed by flow injection hyd ride generation atomic absorption spectrometry (m-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and pe rchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves , GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with eve ry batch of samples to ensure the accuracy and precision of the applied ana lytical procedures. The use of hydrofluoric acid in the digestion mixture l eads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generall y low and lower for Sb than for As. Solutions of 0.66 mol L-1 NaOH liberate d highest amounts of Sb with similar to 10% for poplar leaves, and similar to 19% each for pine shoots and spruce shoots. Distinctly higher concentrat ions of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yie lds of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10-35% f or the fresh material and 7-37% for the freeze-dried samples.