Determination of chromium(VI) in black, green and herbal teas

Speciation analysis of black, green and herbal teas was carried out by treating the samples with 0.1 M Na2CO3 to determine total Cr(VI) and acid digestion (of tea samples in a microwave) was applied to determine the total chromium concentrations by graphite furnace atomic absorption spectrometry (GF-AAS). The Cr(VI) content that could be consumed per unit cup of tea was determined by soaking the leaf or tea bag (or infusion) in 200 mL boiled water and the solution was filtered through a PDVF 0.45 μm hydrophilic filter prior analysis by GF-AAS. s of the investigation showed that concentration of total Cr(VI) in black teas varied between 0.03 and 3.15 μg g−1(with an average of 1.07 ± 1.14 μg g−1), in green tea ranged between 0.03 and 0.14 μg g−1 (with an average of 0.09 ± 0.034 μg g−1) and that in herbal tea was below the limit of detection (LOD) thereby indicating that Cr(VI) levels increase in the order of herbal tea, green tea and black tea. It was also found that up to 17.5 μg L−1 of Cr(VI) could be consumed per unit cup of black tea (200 mL) when standard tea bag (2.0 g) or 2.0 g leaf was used for the preparation of tea. Similarly, black teas were found to contain higher total Cr content (0.28–14.0 μg g−1 with an average of 4.38 ± 4.23 μg g−1) than green (0.22–0.95 μg g−1 with an average of 0.70 ± 0.29 μg g−1) and herbal teas (0.68–1.24 μg g−1 with an average of 0.95 ± 0.27 μg g−1).