Determination of Nickel in Topical Repellents by Graphite Furnace Atomic Absorption Spectrometry Through Direct Emulsion Injection

A method for simple and rapid determination of nickel from topical repellents by graphite furnace atomic absorption spectrometry (GFAAS) through direct introduction of the samples in the form of emulsion is proposed in this work. The method was optimized by evaluating the influence of several variables such as the mass of sample, concentration and nature of the acid, sonication time employed in the procedure and emulsion stability. The curves of pyrolysis and atomization were constructed in order to evaluate the effect of the possible chemical interference. The optimized conditions were achieved when 500 mg of the sample in 5 mL of aqueous solution of 0.1 mol L-1 HNO3 and 0.1 mol L-1 sodium dodecyl sulfate (SDS) and the analytical signals remained stable until 55 min, without statistically significant variation in the signal. The developed method was applied in the determination of nickel in three samples of topical repellents and the results were compared with those obtained by acid digestion. There was no statistical difference between the obtained values at 95% confidence level when a paired Student t-test was applied.