Methodology

Selective masking and demasking for the stepwise complexometric determination of aluminium, lead and zinc from the same solution

Nijhuma Kayal¹ and Nahar Singh²

¹  Analytical Chemistry Section, Central Glass and Ceramic Research Institute, 196, Raja S.C. Mullick Road, Kolkata-32, India

²  Analytical Chemistry section, National Physical laboratory, Dr K.S. Krishnan Marg, New Delhi-12, India

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Chemistry Central Journal 2008, 2:4doi:10.1186/1752-153X-2-4

Published:	6 March 2008

Abstract

Background

A complexometric method based on selective masking and de-masking has been developed for the rapid determination of aluminium, lead and zinc from the same solution in glass and glass frit samples. The determination is carried out using potassium cyanide to mask zinc, and excess disodium salt of EDTA to mask lead and aluminium. The excess EDTA was titrated with standard Mn(II)SO₄ solution using Erichrome Black-T as the indicator. Subsequently selective de-masking agents – triethanolamine, 2,3-dimercaptopropanol and a formaldehyde/acetone mixture – were used to determine quantities of aluminium, lead and zinc in a stepwise and selective manner.

Results

The accuracy of the method was established by analysing glass certified reference material NBS 1412. The standard deviation of the measurements, calculated by analysing five replicates of each sample, was found to be less than 1.5% for the method proposed.

Conclusion

The novelty of the method lies in its simplicity and accuracy afforded by there not being a need for a prior separation or instrumentation. The proposed method was found to be highly selective for the precise determination of aluminum, zinc and lead in the routine analysis of glass batch and allied materials.