Determination of prohibited lead and cadmium traces in hair dyes and henna samples using ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry

Abstract

In this study ultrasound assisted-deep eutectic solvent-based liquid phase microextraction followed by microsampling-flame atomic absorption spectrometry was developed to determine prohibited lead and cadmium traces in hair dye and henna samples. For this purpose, deep eutectic solvent, prepared from choline chloride and phenol, was used as an extraction solvent, dithizone was used as a complexing agent, and THF was used as an aprotic solvent. All parameters that affect extraction efficiency, such as pH, the DES volume and composition, the extraction time, the amount of dithizone, were optimized. Under the optimal conditions, for Pb(II) and Cd(II), enhancement factors of 92 and 57, LODs of 2.5 μg L⁻¹ and 0.75 μg L⁻¹, LOQs of 7.8 μg L⁻¹ and 2.5 μg L⁻¹, linear working ranges of 10–250 μg L⁻¹ and 2.5–50 μg L⁻¹, were obtained, respectively. Relative standard deviation (n = 10) was calculated to be 2.7 for 100 μg L⁻¹ of Pb(II) and 2.1 for 25 μg L⁻¹ of Cd(II). The matrix effect was investigated by comparing the solvent-based calibration curve with the matrix-matched calibration curve. The determination of lead and cadmium in hair dye and henna samples without being affected by the sample matrix was successfully performed. The lead content was between 1.3 and 6.5 μg g⁻¹, and the cadmium content was between 0.028 and 0.54 μg g⁻¹ for the selected hair dye and henna samples.