Revue générale Préparation d'échantillons pour analyses en immunochimie Sample preparation for immunoassay analysis in toxicology

Introduction: Despite the breakthrough of chromatographic techniques coupled to mass spectrometry, immunoanalysis is still a key component of the various techniques used in clinical or forensic toxicology. This article describes different procedures to use immunoassays on unconventional biological matrices such as clotted blood or hair specimens. A focus is made on sample preparation needed to analyse such matrices. Methods: Various immunoassay techniques and their ability to accept unconventional matrices are discussed. An application using protein precipita- tion with acetone is proposed for the analysis of four relevant compounds in toxicology: valproic acid, acetaminophen, digoxin and phenobarbital. Correlations between results obtained on plasma and whole blood after several weeks of storage are presented. A focus is made on sample preparation for hair specimens, vitreous humor and saliva before analysis with immunoassay tests. Results: The procedure presented for the analysis of valproic acid, acetaminophen, digoxin and phenobarbital with CEDIA reagents gives satisfactory results in whole blood. Good correlations are ob- tained between whole blood and plasma for the same samples. Conclusion: Advantages of immunoassay testing are well known, it is a high capacity, rapidity and possibility of automation. The use of immunoassays in forensic toxicol- ogy is complicated by the nature and the quality of the samples available. These immunochemical methods can serve as screening techniques but confirmation of positive results is always recommended.