Selective determination of selenium(IV) from environmental samples by UV-visible spectrophotometry using O-methoxyphenyl thiourea as a chelating ligand

Abstract

A selective extraction–spectrophotometric method has been developed for determination of selenium(IV) using O-methoxyphenyl thiourea (OMePT) as a chelating agent. The basis of the proposed method is the spectrophotometric determination of selenium(IV)–OMePT complex obtained after extraction of selenium(IV) from 3.5 M hydrochloric acid media using OMePT in chloroform solvent. The complex shows maximum absorbance at 350 nm against the reagent blank. The Beer’s law was obeyed over the concentration range 5–60 µg mL⁻¹ of selenium(IV). The optimum concentration range was 20–50 µg mL⁻¹ as evaluated from Ringbom’s plot. The molar absorptivity and Sandell’s sensitivity of the selenium(IV)–OMePT complex in chloroform were 3.312 × 10² L mol⁻¹cm⁻¹ and 0.2384 µg cm⁻², respectively. The composition of selenium(IV)–OMePT complex was 1:2 established from slope ratio method, mole ratio method and Job’s continuous variation method. The complex was stable for more than 72 h. The interfering effect of various foreign ions was studied and suitable masking agents were used wherever necessary to enhance the selectivity of the developed method. The proposed method was successfully applied for the determination of selenium(IV) from real samples, viz. pharmaceutical formulations, shampoo, vegetable sample, synthetic mixtures and environmental samples. Repetition of the method was checked by finding the relative standard deviation (RSD) for 10 determinations which was 0.35%.

Keywords:

• O-methoxyphenyl thiourea
• pharmaceutical samples
• environmental samples
• selenium
• solvent extraction
• spectrophotometry

Acknowledgements

The authors are thankful to the Management, Pravara Rural Education Society, and the Principal, A. C. S. College Satral for providing the necessary facilities in the department. They are also thankful to the Principal, Jijamata College of Science and Arts, Bhende, for constant encouragement.

Additional information

Funding

The authors are thankful to the University Grants Commission, New Delhi, India, for providing the Teacher Fellowship under Faculty Improvement Programme to one of the authors, Ramesh M. Naval, and financial assistance in the form of M. R. P. to Shashikant R. Kuchekar.