Studies on simultaneous fluorescence-spectrophotometric determination of ultratrace niobium(V), tantalum(V), and zirconium(IV) using partial least-squares algorithm

In the presence of cetyltrimethylammonium bromide, a cationic surfactant, h ighly 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 lambda(cx(max))/la mbda(cm(max)) values are 421.0/492.2, 416.2/489.6, and 424.2/507.8 nm, resp ectively, and their lambda(cm(max)) values are 490.5, 488.6, and 507.2 nm, respectively, at the same fixed lambda(cx) of 420.5 nm, indicating their se riously overlapping fluorescence excitation spectra and fluorescence emissi on 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 fo r all of sensitivities. The simultaneous molecular fluorescence-spectrophot ometric determination of ultratrace or trace Nb(V), Ta(V), and Zr(TV) witho ut separation was made using a partial least-squares (PLS) algorithm and ot her algorithms. The optimum PLS computation conditions are wavelength point number of 25 and corresponding wavelength range from 450 to 550 nm oriente d from lambda(cm) 500 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed lambda(cx) of 420.5 nm with an optimum calibration sample num ber 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 PL S algorithm is superior to the ordinary least-squares algorithm. (C) 1998 A cademic Press.