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Experimental ApparatusA Hitachi Model 330 double beam based spectrophotometer capable of taking 1st -4th order derivatives with a pair of 1.0 cm matched quartz cells was used for recording normal and derivative spectra. An Elico pH meter Model LI-120 with combined glass calomel electrode was used for pH measurement. Scandium has been preconcentrated from a large volume of its aqueous solution after solid phase extraction of its 1-(2-thiazolylazo)-2-naphthol chelate onto ammonium tetraphenylborate-naphthalene adsorbent in the pH range 4.0 -5.8. The solid mass consisting of metal complex along with the adsorbent was dissolved in 5 ml of DMF and quantified by second derivative spectrophotometry. The calibration graph is linear in the concentration range 0.08 -2.8 µg ml -1 with a correlation coefficient of 0.9998. The sensitivity of the method as found from the slope of the calibration plot is 0.185 (d 2 A/dλ 2 ) ml µg -1 . Nine replicate determinations of 7.0 µg of scandium in 5 ml of final DMF solution give second derivative amplitudes as 0.255 with a relative standard deviation of 0.92%. The various instrumental and experimental variables are optimized. The conditions developed have been utilized for its determination in various standard and synthetic samples. The proposed method is found to be reproducible, reliable, sensitive, selective and economical.

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A differential pulse polarographic method is proposed for the trace determination of bismuth and copper from large volumes of aqueous samples after adsorption of their 1-(2-thiazolylazo)-2-naphthol complexes onto microcrystalline naphthalene in the pH ranges of 7.2–9.0 and 4.0–7.8, respectively. Bismuth and copper are desorbed from microcrystalline naphthalene with 9 mL 1M HCl. Well-defined peaks are obtained at Ep = −0.09 and −0.20 V versus a saturated calomel electrode, in an HCl–isoquinoline medium as the supporting electrolyte, for bismuth and copper, respectively. Bismuth is reduced reversibly with a 3-electron change, whereas copper is reduced irreversibly under these conditions. The detection limits are 55 ng/mL for bismuth and 91 ng/mL for copper. Linearity is maintained in the concentration ranges of 0.18–13.5 and 0.30-17.3 μg/mL for bismuth and copper, respectively, with corresponding correlation coefficients of 0.9996 and 0.9885. The relative standard deviations are 1.0% for bismuth at 2.0 μg/mL and 1.4% for copper at 5.0 μg/mL. Various parameters were optimized to develop conditions for the determination of these metal ions in various samples.

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