Usefulness of enzymatic hydrolysis procedures based on the use of pronase E as sample pre-treatment for multi-element determination in biological materials

Several minor (Cu, Fe, Mg and Zn) and trace (Ag, As, Cd and Pb) elements were extracted from biological materials, such as human hair and mussel, using an enzymatic hydrolysis procedure based on pronase E. The reaction conditions, viz., pH and temperature, were fixed at optimum values of 7.4 and 37 degrees C, respectively. Other variables affecting the enzymatic hydrolysis procedure, such as enzymatic hydrolysis time, enzyme concentration, volume of enzyme solution and sample mass, were studied and optimized. The pH value was adjusted with a TRIS-HCl solution as buffer system. The minor elements were measured by FAAS while trace elements were determined by ETAAS under optimum conditions. In order to determine the total element concentration in samples, a microwave-induced acid digestion procedure in laboratory-made low pressure PTFE bombs was optimized. The enzymatic hydrolysis was effective for mussel samples (recoveries of about 100% were obtained for As, Cd, Cu and Mg); however, it was poor for human hair (recoveries were lower than 70%).