Determination of common inorganic anions in tea samples by ion chromatography

Plants exposure to environmental sources of common inorganic anions (chloride, nitrate, phosphate, and sulphate) is discussed. Various commercial tea products were examined for the content of water soluble anions by the use of sample preparation procedure corresponding to the conditions generally applied for the preparation of tea infusions (2 g of tea, 5 min brewing time, 250 ml final volume) widely consumed by humans. Suppressed ion chromatography (IC) (Metrohm Metrosep A Supp 5 (150 mm × 4 mm) column) with conductometric detection was used for the determination. The IC technique allows isolation of the signals of particular anions and their detection (DLs of 0.012 (Cl−), 0.019 (NO3−), 0.047 (PO 43–), and 0.011 (SO 42–) mg l−1) within 15 min.