Determination of Cr and Mn in moisturizing creams by graphite furnace atomic absorption spectrometry through direct introduction of the samples in the form of emulsions

• A method for Cr and Mn determination by GF AAS in moisturizing creams was developed.
• The proposed method is based on the introduction of samples in the form of emulsions.
• A detailed study on the optimum conditions for emulsion preparation was performed.
• The thermal behavior of the analytes in the presence of the matrix was studied.

This paper reports the development of a novel method for the determination of Cr and Mn in moisturizing creams by graphite furnace atomic absorption spectrometry (GF AAS) through direct introduction of the samples in the form of emulsion. The method was optimized by evaluating the influence of several variables such as the sonication time, concentration of acid and mass of sample employed in the procedure and emulsion stability. The curves of pyrolysis and atomization were constructed for both analytes in order to evaluate their thermal behavior in the presence of the matrix and to investigate the possible use of different chemical modifiers. The optimized conditions of both Cr and Mn were achieved when 1000 mg of the samples was mixed with 0.5 mol L− 1 HCl solution sufficient to complete 5 mL. Then, the mixture was sonicated for 20 min, using an ultrasonic probe. The emulsions prepared in this way remained stable for 60 min, at least. The developed method was successfully applied in the determination of Cr and Mn in five samples of commercially available moisturizing creams. Recovery tests were performed, yielding recovery percentages in the range of 93%–108% and 87%–104% for Mn and Cr, respectively.