Abstract
An extraction spectrophotometric method for iron determination in rocks, minerals, soils, stream sediments and water samples has been developed. At pH 3-4, iron (III) forms a 1:2:1 ternary complex with thiocyanate and cetyltrimethylammonium bromide (Fe/SCN/CTAB) which is extracted into ethyl acetate. The readily formed purple complex is suitable for extraction spectrophotometric determination of iron in rocks and related materials from submicrogram to milligram levels. The method is free from any interference due to commonly associated ions present in the matrices of rock samples. The present method is at least fourfold more sensitive (ε=3.2×104 l mol−1 cm−1) than the conventional thiocyanate method and, in addition to the enhanced sensitivity and selectivity, it has got definite advantages over the corresponding binary thiocyanate system in terms of substantial improvement in the stability of the complex formed and broadening of Beer's law adherence range (0–6.0 mg/l). The method has been applied to a number of geological and hydrogeochemical samples for the determination of iron and the results obtained have been found to be favourably comparable with those obtained from the standard methods.
Keywords: Extraction; Iron determination; Spectrophotometric method
An extraction spectrophotometric method for iron determination in rocks, minerals, soils, stream sediments and water samples has been developed. At pH 3-4, iron (III) forms a 1:2:1 ternary complex with thiocyanate and cetyltrimethylammonium bromide (Fe/SCN/CTAB) which is extracted into ethyl acetate. The readily formed purple complex is suitable for extraction spectrophotometric determination of iron in rocks and related materials from submicrogram to milligram levels. The method is free from any interference due to commonly associated ions present in the matrices of rock samples. The present method is at least fourfold more sensitive (ε=3.2×104 l mol−1 cm−1) than the conventional thiocyanate method and, in addition to the enhanced sensitivity and selectivity, it has got definite advantages over the corresponding binary thiocyanate system in terms of substantial improvement in the stability of the complex formed and broadening of Beer's law adherence range (0–6.0 mg/l). The method has been applied to a number of geological and hydrogeochemical samples for the determination of iron and the results obtained have been found to be favourably comparable with those obtained from the standard methods.
Keywords: Extraction; Iron determination; Spectrophotometric method
Article Outline
1. Introduction
2. Materials and methods
2.1. Apparatus
2.2. Reagents
2.3. Procedures
2.3.1. Dissolution of samples
2.3.1.1. For rocks, soils and stream sediments
2.3.1.2. For minerals
2.3.2. Colour reaction, extraction and absorbance measurements
3. Results and discussion
3.1. Choice of solvents
3.2. Effect of pH
3.3. Effect of reagent concentration
3.3.1. Thiocyanate
3.4. Cetyltrimethylammonium bromide
3.5. Effect of temperature
3.6. Composition of the complex
3.7. Spectral characteristics, Beer's law, sensitivity and precision of the method
3.8. Effect of diverse ions
3.9. Analytical applications
4. Conclusion
Acknowledgements
References
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