Optimization of sample preparation using statistical methods: spectrophotometric determination of Fe and Co in pharmaceutical samples

This work presents alternatives for Fe and Co determination in pharmaceutical samples using flow analysis. The first procedure describes Fe extraction in mineral/vitamin complexes. The best conditions were reached when HNO₃ concentration and volume, sample mass and shaking time were 1.0 mol l⁻¹, 5 ml, 25 mg and 10 min. Three mineral/vitamin complexes of known concentrations (ranging from 12 to 32 g kg⁻¹) were analyzed (10 authentic replicates for each) and recoveries of around 100% were obtained when compared with a well-established mineralization procedure employing concentrated HNO₃ and H₂O₂ (30% w/v). The second work part shows the employment of Tiron and H₂O₂ reaction for Co determination in a drug for inappetence. The results (352±18.7 mg kg⁻¹) were compared with those using Electrothermal Atomic Absorption Spectrometry—ETAAS (346±15.7 mg kg⁻¹). The proposed method showed detection and quantification limits of 0.20 and 0.70 μg l⁻¹, respectively. Both procedures for Fe and Co determination presented time, reagent and effort reduction.