In recent years, the use of non-conventional biological sam-ples in replacement to the traditional ones – urine and blood –has been growing in forensic toxicology for verifying the intake ofxenobiotics of several classes. Each biological matrix has its ownpeculiarities and presents advantages and disadvantages of usage.Knowledge of the stability of analytes in the biological materialis essential for toxicological analyses, once various situations con-tribute to variable time intervals between the collection of thematerial, its transportation to the laboratory and the moment ofanalysis [1,2].