Development of a focused ultrasound-assisted extraction method for the determination of trace concentrations of Cr and Mn in pharmaceutical formulations by ETAAS

This paper reports the development of a new method for the focused ultrasound extraction of Cr and Mn from pharmaceutical formulations and their determination by electrothermal atomic absorption spectrometry (ETAAS). The method was optimized by evaluating the influence of several variables such as the sonication power and time, concentration of HCl in the extractant solution and mass of sample employed in the extraction procedure. The curves of pyrolysis and atomization were constructed for both analytes in order to evaluate the effect of the matrix on the measurement of Cr and Mn. Quantitative extraction of both Cr and Mn was achieved when 25–150 mg of the sample were sonicated for 30 min at 50% power with 5 ml of a 1 mol l−1 HCl solution. The developed method was successfully applied in the determination of Cr and Mn in samples of pharmaceutical formulations containing different active principles such as ciprofloxacin, cephalexin, azithromycin, amlodipine and methionine. There was no statistical (95% confidence level, paired t-test) difference between the results obtained by the proposed method and the results obtained after total digestion of the samples.

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► This work proposes the focused ultrasound assisted extraction of Cr and Mn from tablets for their determination by ETAAS.
► The total extraction of the analytes was achieved by sonicating 25–150 mg of the sample with 5 ml of a 1  mol l−1 HCl solution.
► The sonication time had important influence on the extraction efficiency of both analytes.
► The proposed method was useful for the determination of trace concentrations of Cr and Mn in tablets of different pharmaceutical formulations.