Simultaneous spectrophotometric determination of La, Ho, Mn5-Br-PADAP complexes using multivariate calibration with partial least-squares (PLS) data evaluation
Re. Ferreyra et al., Simultaneous spectrophotometric determination of La, Ho, Mn5-Br-PADAP complexes using multivariate calibration with partial least-squares (PLS) data evaluation, FRESEN J AN, 368(6), 2000, pp. 595-600
A simple and fast analytical pocedure is proposed for the simultaneous spec
trophotometric determination of lanthanum, holmium and manganese in synthet
ic ceramics, (La(0.8-x) Ho-x Sr-0.2 MnO3), by using the partial least-squar
es (PLS) method. As chromogenic agent 5-Br-PADAP [2-(5-bromo-2-pyridylazo)-
5-diethylaminophenol was used, which form colored complexes with the three
elements studied. To avoid metal hydrolysis, a mixture of ethanol and Trito
n X-100 at pH 9.5 was used for all experiments. A set of 17 calibration sol
utions measured throughout the 400-700 nm wavelength range was used in the
calibration step. The concentration range for Mn(II) was 1-12 x 10(-6) mol
L-1, while the range for the rare earth elements La(III) and Ho(III) was 2-
8 x 10(-6) mol L-1. In order to demonstrate the applicability of the propos
ed method, a set of artificial samples containing the three analytes in var
iable proportions was prepared and analyzed. The analytical results obtaine
d were quite acceptable with relative errors not greater than 7% in most ca
ses.