Acid predigestion as a slurry pretreatment for the determination of Ca, Cu, K, Mg, Na and Zn in human scalp hair by flame atomic absorption/emission spectrometry with a high-performance nebulizer

A comparison was carried out between the use of wetting agents, Viscalex HV30 or glycerol, and an acid predigestion of the slurry for the determination of major metals (Ca, Cu, K, Mg, Na and Zn) in human scalp hair by FAAS/FAES with a high-performance nebulizer. Human scalp hair was pulverized in a Zr vibrating ball mill over a period of 20 min (mean particle size about 0.8 μm measured by laser diffraction). The use of wetting agents was only found adequate for dilute slurries; thus, Viscalex HV30 can be proposed for the determination of Zn in scalp hair slurries (relative atomization efficiency close to unit). For all cases, the use of acidified slurries with nitric acid at a concentration of 1.0% offers adequate analytical performance: LODs of 5.0, 3.5, 3.1 and 20.0 mg kg^–1 for Ca, Cu, Fe and K, respectively, and 1.7, 0.6 and 3.5 μg kg^–1 for Mg, Na and Zn. The repeatability of the overall method (n = 11), acid predigestion-slurry pretreatment and FAAS/FAES determination expressed as RSD (%), was between 8.7 for Zn and 18.6 for K. The developed methods were applied to 25 human scalp hair samples from healthy adults.