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A simple, selective and sensitive derivative spectrophotometric method is proposed for the simultaneous determination of gallium(III) and indium(III) in mixtures using 1-(2-pyridylazo)-2-naphthol in cationic micellar medium, without any prior separation. Beer's law is obeyed between 2.80×10 −1 −3.63 and 4.60×10 −1 −9.20 μg ml −1 concentration of Ga(III) and In(III) at 550 and 542 nm, the isodifferential points of indium and gallium complexes in the first-order derivative mode, respectively. The proposed method is successfully applied for the determination of gallium and indium in standard reference materials and synthetic binary mixtures with a relative error of ±2.07 and ±2.55%, respectively.

Derivative photometric methods for trace analysis of Th(IV) and UO(2)(II), and their simultaneous determination in mixtures using 5,8-dihydroxy-1,4-naphthoquinone in a micellar medium are reported. Molar absorptivity and Sandell's sensitivity of 1:2 Th(IV) and 1:1 UO(2)(II) complexes at their lambda(max), 614.5 nm and 637.0 nm are, 1.19 x 10(4) 1/mol/cm and 1.12 x 10(4) 1/mol/cm and 1.95 x 10(-2) mug/cm(2) and 2.13 x 10(-2) mug/cm(2) mug/cm(2), respectively. Calibration graph is linear over the range 9.28 x 10(-2)-18.56 mug/ml of Th(IV) and 9.52 x 10(-2)-19.04 mug/ml of UO(2)(II). Though presence of Th(IV) and UO(2)(II) causes interference in each others determination, 9.28 x 10(-1)-9.28 mug/ml Th(IV) and 9.52 x 10(-1)-9.52 mug/ml UO(2)(II) when present together, can be simultaneously determined using derivative spectra.

A sensitive derivative spectrophotometric method using 1-nitroso-2-naphthol has been developed for determination of trace amounts of cobalt in the presence of a neutral surfactant. Photometric parameters, viz., lambda(max), molar absorption coefficient and analytical sensitivity of the complex formed in micellar media are 420 nm, 3.18x10(4) l mol(-1) cm(-1) and 2.05 ng ml(-1), respectively. Beer's law holds from 0.20 to 3.0 mug ml(-1) of the analyte concentration. The method has a high sensitivity with a detection limit of 1.68 ng ml(-1). A selective determination of cobalt in presence of copper(II) or iron(III) using derivative spectral profiles and without any masking or pre-separation is also reported. Samples of drugs and standard alloys analysed by the proposed method yielded results comparable to those obtained using recommended procedures.

A rapid and sensitive method for the trace level determination of beryllium based on the formation of a 1:2 complex (lambda(max) 560 nm) with 1,4-dihydroxy-9,10-anthracenedione in an aqueous medium containing Triton X-100 is reported. Beer's law is followed in the range 3.60-360 ng ml(-1) of Be(II). The molar absorptivity and Sandell's sensitivity are 1.68x10(4) l mol(-1)cm(-1) and 0.54 ng cm(-2), respectively; detection limit is 0.23 ng ml(-1) of Be(II). Analysis of synthetic mixtures of composition similar to that of alloys and spiked samples of distilled water, gave results that are in agreement with their beryllium content.

A photometric method for trace analysis of Cu(II) with 1-(2-pyridylazo)-2-naphthol (PAN) in presence of a neutral surfactant, Triton X-100, has been reported in normal and derivative modes. The molar absorption coefficient (ϵ) and Sandell's sensitivity ( S ) of PAN-Cu(II) complex at 555 nm is 5.21 × 10 4 l mol −1 cm −1 and 1.22 ng cm −2 respectively. The detection limit of Cu(II) is 4.0 ng ml −1 and Beer's law is obeyed in the range 0.08–4.00 μg ml −1 of the analyte. Copper content of a number of commercially available alcoholic beverages, biological and standard alloy samples is reported. The results obtained are in excellent agreement with those obtained using AAS.

The spectrophotometric determination of beryllium and aluminium with 5,8-dihydroxy-1,4-naphthoquinone in the presence of a non-ionic surfactant is reported. Absorption maxima, molar absorptivity and Sandell's Sensitivity of 1:2 (M:L) beryllium and aluminium complexes are, 585 nm and 598 nm, 1.63 × 10 4 l.mole −1 .cm −1 and 2.04 × 10 4 l.mole −1 .cm −1 , and 0.55 ng/cm 2 and 1.32 ng/cm 2 respectively. Beer's law is obeyed between 7.20-3.96 × 10 2 ng/ml beryllium and 1.08 × 10 1 –1.08 × 10 3 ng/ml aluminium. A method for simultaneous determination of beryllium and aluminium in their mixture using derivative spectra is described. The range 3.6 × 10 1 –3.6 × 10 2 ng/ml beryllium could be determined in the presence of 1.08 × 10 2 –1.08 × 10 3 ng/ml aluminium, and vice versa.