Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

Abstract

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 x 10(-4) M; NaCl, 1.0% (w/v). LOD was 1.9 mu g/L with a preconcentration factor of 10-20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.