Use of 1-(2-thiazolylazo) 2-naphthol in rapid determination of iron in geological matrices

The present work describes the use of 1-(2-thiazolylazo)-2-naphthol (TAN) as a spectrophotomeric reagent for iron determination. TAN reacts with iron(II) forming a brown complex with absorption maximum at 575 and 787 nm. The following parameters were studied: complex stability, pH effect, amount of the TAN, buffer selection, amount of acetate buffer, reductor effect, order of addition of reagents and adherence to Beer's Law. The results demonstrated that iron can be determined with TAN in a pH range of 4.0-6.2 with an apparent molar absorptivity of 1.83 x 10(4) 1 . mol(-1) . cm(-1) (at 787 nm) and 1.41 x 10(4) 1 . mol(-1) . cm(-1) (at 575 nm). Beer's Law is obeyed for at least 3.00 microg/ml. The TAN reacts with other cations, but at 787 nm only the iron(II)-TAN complex absorbs. So, iron can be determined selectively in the presence of several cations. A procedure based on the direct mixture of the sample and a chromogenic solution is proposed, where iron can be determined rapidly and easily. Such procedures were used for the determination of iron in several geological matrices. No significant differences were obtained for TAN method and certificate results.