Studies on Simultaneous Fluorescence-Spectrophotometric Determination of Ultratrace Niobium(V), Tantalum(V), and Zirconium(IV) Using Partial Least-Squares Algorithm

Abstract

In the presence of cetyltrimethylammonium bromide, a cationic surfactant, highly sensitive molecular fluorescence reactions occur between Nb(V), Ta(V), and Zr(IV) ions and morin (3, 5, 7, 2′, 4′-pentahydroxyflavone) in acidic medium to form stable ternary micellar complexes. Their λex(max)/λem(max)values are 421.0/492.2, 416.2/489.6, and 424.2/507.8 nm, respectively, and their λem(max)values are 490.5, 488.6, and 507.2 nm, respectively, at the same fixed λexof 420.5 nm, indicating their seriously overlapping fluorescence excitation spectra and fluorescence emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20, 0 to 0.50, and 0 to 0.20 mg/liter, respectively, with 0.5 ng/ml for all of sensitivities. The simultaneous molecular fluorescence-spectrophotometric determination of ultratrace or trace Nb(V), Ta(V), and Zr(IV) without separation was made using a partial least-squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 25 and corresponding wavelength range from 450 to 550 nm oriented from λem500 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed λexof 420.5 nm with an optimum calibration sample number of 14 and respective optimum abstracted factor numbers of 6, 4, and 3. With respect to both accuracy and precision of the obtained results, the PLS algorithm is superior to the ordinary least-squares algorithm.