Multicommutation hydride generation atomic fluorescence determination of inorganic tellurium species in milk

A multicommutated flow system has been developed for hydride generation, atomic fluorescence (HG-AFS) determination of tellurate (Te-VI) and tellurite (Te-IV) in milk samples. After a batch leaching of Te by sonication at room temperature for 10 min with aqua regia, sample slurries in acidic medium were merged with sodium borohydride and HCl to obtain data on Te-IV. Another portion of the acidic slurry was mixed with KBr and passed through a reaction coil introduced inside a microwave oven to reduce quantitatively Te-VI to Te-IV which was analyzed by HG-AFS. The detection limit was 0.57 ng g(-1) in the original samples. The linear range obtained was till 4 ng ml(-1) and the average recovery of different amounts of Te-VI and Te-IV added to real milk samples were 98 +/- 4% and 98 +/- 2%, respectively, indicating the absence of analyte losses or contaminations and original species modification. Average relative standard deviation of 6.3% was found for Te determination in a series of commercially available milk samples containing from 1.0 to 10.1 ng ml(-1) total Te. The proposed method provided a high sampling frequency of 24 h(-1) for the determination of both, free Te-IV and total Te, in a same sample with a two times reduced waste generation and a four times reduced reagent consumption as compared with the continuous hydride generation. Additionally, the method developed requires a minimum operator attention and sample manipulation. (C) 2004 Elsevier Ltd. All rights reserved.