Drug bioanalysis instrumentation

A systematical approach of sample preparation methods and optimisation of the quality aspects of sample preparation may enhance the efficiency of total analytical methods. This approach may also enhance the quality and knowledge of the methods developed, which actually enhances the quality of individual sample analyses. Unfortunately, in bioanalysis, systematical optimisation of sample preparation procedures is not common practice. Attention to systematical optimisation of assay methods has always been mainly on instrumental analyses problems, such as minimising detection limits and maximising resolution in HPLC. Optimisation of sample extraction has often been performed intuitively by trial and error. Only a few publications deal with systematical optimisation of liquid-liquid extraction of drugs from biological fluids [3,4,5]. 

Because of the widespread use of LC/MS/MS for drug discovery bioanalysis, there is currently less of a necessity for finely tuned solid-phase extractions than there once was in this area. Instead, generic solid-phase extraction conditions that can accommodate many different analyte structures using the same extraction conditions have become more interesting. To make a solid-phase sample preparation useful for LC/MS/MS it must remove as much of the sample salts as possible in order to reduce the effects of ion suppression [47,51—52] and it must remove as many nonvolatile matrix components as possible so that the instrument ion source is not quickly fouled. Because the LC/MS/MS instrument is inherently so selective, added assay selectivity, per se, is no longer an objective of solid-phase extraction. 

The future technological advances in drug discovery will likely involve separation sciences, MS, and hyphenated techniques. More detailed discussions on the technology development and future trends in bioanalysis, laboratory automation, and MS instrumentation have been elaborated in other chapters. Therefore, only three technologies are specifically addressed with regard to their potential application in drug discovery pSFC monolithic column technologies and chip-based separations. 

Zhang et al. (2009c) compared the quantitative performance of a current-generation Orbitrap instrument with that of one of the most commonly used instruments in bioanalysis, an Applied Biosystems API-4000 triple quadmpole system. The study was conducted using a test set of 15 compounds under evaluation in drug discovery, with the quantitation... 

Table 15.1). As a multiple-task instrument, the QTRAP may serve as the LC—MS platform of choice in certain DMPK and bioanalysis laboratories. Specific examples of these laboratories would include (1) bioanalytical laboratories where detection of plasma metabolites or in vitro ADME screening are also performed (2) drug metabolism laboratories where metabolite identification and/or in vitro ADME screening are conducted, and (3) small bioanalysis and drug metabolism laboratories where quantitative and qualitative analyses of drugs and/or metabolites are routinely conducted with limited numbers of LC—MS instruments and scientists. 

In addition to these qualitative studies, quantitative bioanalysis, e.g., in preclinical and clinical studies to provide pharmacokinetic and pharmacodynamic data, is an essential part of drug development. Quantitative bioanalysis is the most important application area of LC-MS, in terms of number of instruments applied and the number of analyses performed. Fast, high-throughput, and routine quantitative analysis by LC-MS also demands fast and automated sample pretreatment strategies and advanced data-processing software. 

MS-MS is currently very widely used in combination with chromatographic separation methods, especially LC. The obvious reason for this is the frequent use of soft ionization techniques in LC-MS interfacing, i.e. electrospray and atmospheric-pressure chemical ionization. MS-MS allows additional structural information as well as the molecular mass information to be obtained. On-line LC-MS-MS is currently the method-of-choice in quantitative bioanalysis in (pre-) clinical pharmacological studies during drug development in pharmaceutical industries. In these studies, the instrument is operated in... 

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