Full validation of an electrothermal atomic absorption assay for zinc in hepatic tissue using a fast sample preparation procedure

The objective of this work was to develop and fully validate an analytical assay to quantify zinc in hepatic tissue. The procedure should be as simple and fast as possible in order to avoid sample contamination. The amount of sample used should also reflect the sample size usually obtained in clinical biopsies, which are about 3-4 mg at most. The validation protocol is in accordance to international guidelines, such as ICH and FDA. The parameters evaluated were precision, accuracy, range, limit of detection and limit of quantification. The method was evaluated in the 2.0-32.0 parts per billion (µg/l) range. Under the described conditions intra and inter day precision of the three levels of quality controls were lower than 9.06 and 5.27, respectively, expressed as relative standard deviation (RSD). The accuracy ranged from 86.35 to 114.71%. Limit of detection and limit of quantification were 0.60 and 2.0 µg/l, respectively. Fresh bovine liver samples were used in order to evaluate the clinical procedure used to collect biopsies. According to the results and experimental protocol, the method is fully validated and ready to use in clinical trials involving zinc quantitation using hepatic samples as small as 2.00 mg of dry tissue.