Simple Method for Determination of Lead in Hair Dyes Using Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry

Abstract

A fast, simple and sensitive method for determining of lead in hair dyes using graphite furnace atomic absorption spectrometry with slurry sampling was developed. Multivariate optimization was used to establish optimal analytical parameters through a fractional factorial and a central composite design. The samples were submitted for direct analysis without prior digestion and were diluted in 2.5% v/v HNO₃ and 1.5% v/v H₂O₂. Palladium (chemical modifier) and rhodium (permanent modifier) were selected from several potential modifiers. The optimal conditions were a pyrolysis time of 10 s (liquid and dust dyes) 20 s (cream dyes), a pyrolysis temperature of 789°C (liquid dyes) or 750°C (cream and dust dyes) and an atomization temperature of 1800°C for all dyes. Under optimum conditions, the calibration graph is linear in the 1.50–50.0 µg L⁻¹ concentration range, with a detection limit of 0.33, 0.44, and 0.39 µg L⁻¹ for liquid, dust, and cream hair dyes, respectively. The relative standard deviation ranged from 1.63 to 4.56%. The recovery rate ranged from 85 to 108%, and no significant differences were found between the results obtained with the proposed method and the microwave decomposition analysis method of real samples. The concentration ranges obtained for lead in the hair dyes samples were 1.00–11.3 µg L⁻¹ for liquid dyes, 14.0–100 µg kg⁻¹ for dust dyes, and 19.9–187 µg kg⁻¹ for cream dyes.

Keywords:

• GFAAS
• Hair dyes
• Lead
• Multivariate optimization
• Slurry sampling

Acknowledgments

The authors are grateful to the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG – PPM-00433-10) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support. A.R.S is thankful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for a fellowship.

Notes

Note: Manufacture's conditions: 600°C (PT) and 1800°C (AT).

^a,b,c Variables optimized.

^a Recommended value 9.0 pg.

^b Mean and standard deviation values (n = 3) for Pb in of hair dyes samples obtained by slurry sampling and microwave-assisted digestion.

^a Clear tones.

^b Dark Tones.