Many different sample-preparation techniques are available to a drug-discovery scientist performing bioanalytical sample preparation. These techniques vary in several regards, such as simplicity (number of steps), time requirement, materials cost per sample, expertise of the analyst, ease of method development, ability to be automated, concentration factor attained, and cleanliness of the final extract. It is important to note that the sample-preparation needs within drug discovery are different from those in other phases of drug development. In drug discovery, new compounds are introduced as often as weekly, high quantitation limits are acceptable, rapid data generation is demanded, and thus there is little time for method development. The drug-discovery scientist favors a quick and generic sample-preparation method that can be applied to a range of compounds under study. In contrast, once a drug candidate has been selected, studied in animals, and approved for further study with human subjects, clinical assays then require ultrasensitivity and a fully validated, rugged method. At this time, a very selective sample-preparation method is chosen that can also be automated and performed in high throughput.
The distinctions within the drug-discovery environment previously noted naturally favor the use of simpler and faster sample-preparation techniques. However, most all sample-preparation methods are potentially viable choices, as recent applications have demonstrated method-development techniques that are both rapid and selective. Also, there is value for the quick development of a bioanalytical method with selectivity for a series of similarly related structures, as that one method can often meet the needs for PK and toxicokinetic (TK) studies well into the discovery process, rather than just for one initial study. The variety of sample-preparation methodologies for bioanalysis are now detailed.
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