A validated flame AAS method for determining magnesium in a multivitamin pharmaceutical preparation

A rapid method for determining magnesium in a multivitamin pharmaceutical p reparation has been validated. This element is analysed by flame atomic abs orption spectrometry after dissolution of the sample in acid medium. Linear ity, precision, accuracy and robustness of the method hal e been determined , and detection and quantification limits have been calculated. Linearity o f response was verified for concentrations ranging from 0.05 to 0.40 mg l(- 1) of magnesium. Correlation coefficient of the calibration straight lines was always greater than or equal to0.9999. Repeatability of the method gave relative standard deviation (R.S.D.) of 0.6%. Reproducibility of the metho d calculated after analysis of samples by the same analyst in different day s (day-to-day fluctuation) and by two different analysts in different days (analyst-to-analyst fluctuation) gave relative standard deviation of 1.1 an d 1.6%, respectively. Mean recoveries of magnesium obtained after spiking s ample placebos with increasing amounts of magnesium chloride ranged from 98 .9 to 100.8%. Robustness of the method evaluated by changing different expe rimental conditions under which analyses were performed, gave relative stan dard deviation from 0.2 to 0.5%. Limits of detection and quantification wer e 3.8 and 7.0 mug of Mg per gram of sample, respectively. Results show the suitability of the method for direct measurement of magnesium in a water-so luble multivitamin pharmaceutical preparation. (C) 2001 Elsevier Science B. V. All rights reserved.