The Application of a Surfactant to the Spectrophotometric Determination of Nitrate Concentrations

ABSTRACT

The development of a sensitive spectrophotometric method for measuring nickel at trace concentrations is described. Cetyltrimethylammonium bromide is used as a surfactant in this procedure, while Xylenol orange is used as a colourant. The method was created by testing various combinations of metal ions, xylenol orange (XO), and cetyltrimethylammonium bromide (CTAB). A nickel complex called Ni-XO-CTAB was employed for this purpose. U.V. absorbance measurements of the nickel complex led to the discovery of circumstances optimal for improved absorbance. The data shows that at pH 10.5, stable systems may be generated with mole ratios of 1:2 and 1:6 of XO to CTAB, respectively, when XO and CTAB are mixed together. The formulae for these systems should read [x0 CTAB]2n and [X0 CTAB]6n, where n is an integer. For the nickel complex, we found an absorbance maximum at 622 nm and an extinction coefficient of 6.14 x 104 i. mole-1 cm1. The chemical composition of the nickel complex was analysed using the mole ratio method. There was found to be a Ni:XO molar ratio of 1:2 in this mixture. It has been suggested that the correct formula for nickel complexes involving the two well-established XO: CTAB systems is Ni [XO (CTABT)2]4 and Ni [XO (CTAB)6]4. Researchers tested the methods selectivity by measuring the absorbance of a nickel complex in pure nickel solution and in the presence of other metal ions. The results of this investigation demonstrate that the selectivity of the method is diminished due to interactions with sodium, cadmium, and cobalt ions. We made no attempt to shield our experiment from outside ion interference.

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