Liquid chromatography coupled to mass spectrometric detection (MS) plays an essential role for the qualitative and quantitative analysis in pharmacokinetics, toxicology, therapeutic drug monitoring, proteomics and metabolomics.Due.to the high selectivity and sensitivity of mass spectrometry, a chromatographic step is not always mandatory prior detection.Depending on the type of analysis, various types of mass analyzers are used either with atmospheric pressure ionization (electrospray, atmospheric pressure chemical ionization, atmospheric pressure photoionization) or matrix-assisted laser desorption/ionization (MALDI).Sample preparation remains a key step in the bioanalytical process, because matrix effects during the ionization process are considered as one of the major drawbacks in MS analysis.With biological samples such as, whole organism extracts, tissues, blood, plasma or urine various off-line and on-line sample preparation strategies are applied.