Determination of nickel in hair samples by graphite furnace atomic absorption spectrometry and flow-through stripping chronopotentiometry

Abstract

Nickel in hair samples was determined by GF AAS and stripping chronopotentiometry after a dry ashing mineralisation with a mixture of nitrous oxides, oxygen and ozone. The use of common matrix modifiers brought no significant improvement in the GF AAS measurement. The detection limit, trueness and precision were found to be 0.15 mg kg⁻¹ of the hair sample, 4.3%, and 4.1%, respectively. The linear range was found to be 0.44–3.3 mg kg⁻¹. The stripping chronopotentiometric determination is based on the deposition of nickel ions from an ammonia buffer solution in a porous glassy carbon electrode followed by its stripping into an acidic solution by constant current. Copper interfered and was removed from the acidified sample solution by means of a minicolumn packed with pearl cellulose chemically modified with 8-hydroxychinolinol. Copper was trapped completely whereas nickel passed the column. The detection limit, trueness and precision were found to be 0.032 mg kg⁻¹ in the hair sample, 5.8%, and 6.1%, respectively. The linear range was found to be 0.1–20 mg kg⁻¹. Good agreement between the two methods was found for most hair samples.