FLOW-INJECTION SPECTROPHOTOMETRIC CATALYTIC DETERMINATION OF MANGANESE IN PLANTS EXPLOITING THE AERIAL OXIDATION OF DIPHENYL CARBAZONE

The catalytic effect of Mn(II) on the aerial oxidation of diphenylcarb azone (DFC) becomes very pronounced in the presence of triethanolamine (TEA), whereas the influence of other potential interferants is stron gly reduced. This feature was exploited to develop an improved flow-in jection procedure for manganese determination in plant digests. In vie w of the high variability of manganese contents in the sample batches, an approach involving two sampling loops was implemented to widen the dynamic range. The proposed system handles about 70 samples per hour, requires only 0.13 mg DFC and 85.7 mg TEA per determination, and yiel ds reproducible signals (r.s.d. of peak heights usually<2%) within two different concentration ranges (0.10-0.80 and 0.50-4.00 mg l(-1) Mn). Detection limit is 0.03 mg l(-1) Mn in the digest (3 mu g g(-1)-dry b asis). Results are in agreement with flame atomic absorption spectrome try. A noteworthy feature of this procedure is the negligible progress of the uncatalyzed reaction. (C) 1998 Elsevier Science B.V. All right s reserved.