Comparison between Alkaline Solubilization Methods and Acid Digestion of Animal Tissue for Determination of Metals by Flame Atomic Absorption Spectrometry

Usually, the methodologies found in the literature on biological tissue digestion are usually time consuming and use high amounts of reagents. In this study, two methods of preparation of bovine testis samples were evaluated: acid digestion using nitric acid and alkaline solubilization using tetramethylammonium hydroxide. The analytical validation study evaluated the parameters of linearity, limits of detection (acid digestion 0.10; 1.02; 0.16; 0.67 mg kg(-1) for Cu, Fe, Mn and Zn, respectively; alkaline solubilization 0.12; 0.74; 0.16; 0.23 mg kg(-1) for Cu, Fe, Mn and Zn, respectively) and quantification (acid digestion 0.34; 3.40; 0.53; 2.20 mg kg(-1) for Cu, Fe, Mn and Zn, respectively; alkaline solubilization 0.41; 2.50; 0.54; 0.77 mg kg(-1) for Cu, Fe, Mn and Zn, respectively), precision (RSD < 7.3% for repeatability and RSD < 15.0% for intermediary precision) and accuracy, being that the percentage of recovery obtained in the acid digestion of 105.50% (Cu), 103.30% (Fe), 94.90% (Mn) and 89.60% (Zn) and in the alkaline solubilization 100.80% (Cu), 98.70% (Fe), 103.70% (Mn) and 95.70% (Zn), therefore, the two procedures were efficient for this type of matrix. The times required for acid digestion and an alkaline solubilization were 1h30min and 1h, respectively.