Study of sample preparation, by acid digestion assisted by microwave radiation in a closed system, to determine inorganic contaminants in street cocaine samples by ICP OES and ICP MS

Knowledge of the inorganic composition of cocaine makes it possible to correlate the drug with its refinement and dilutions1, it is important to highlight that when aiming to study the adulteration/production of street cocaine it is interesting to carry out the total solubilization of the sample2. Thus, acid digestion using microwave radiation in a closed system is a widely used technique due to the speed and efficiency of digestion3. Thus, acid solubilization procedures and acid digestion assisted by radiation via microwaves of the sample were studied, varying the mass of the sample (0.050g, 0.100g, 0.200g and 0.500g) and concentration of the HNO3 solution (5%, 10% , 30%, 40% and 50% v/v). In order to verify whether the different sample preparation procedures and whether the final acidity interferes with the quantification of the analytes studied. ICP OES analysis was carried out on a high purity sample prepared by direct solubilization and digestion. The result of the intensities test for the elements Co, Cu, Mo, Pb and Zn, with final acidity of HNO3 2% or 4% v/v, demonstrated that samples prepared by direct solubilization or digested by microwaves, with final acidity of HNO3 2% v/v, presented very close intensity values for the elements analyzed, indicating that the types of sample preparation studied (solubilization or digestion) did not present significant interferences in the analysis by ICP OES.