Validation samples , biomarker characterization

Advances in petroleum characterization at the molecular structure level by GC-MS methods renewed interest in OSC. Within the past few years, at least one-thousand new and novel OSC that previously were not known to be present in petroleum and bitumens have been reported. Tentative molecular structures inferred from GC-MS and other techniques have been confirmed in many cases by synthesis of authentic reference-compounds. The difficult and time-consuming synthetic work has been crucial in validating many of the novel structures. Another key finding has been that immature bitumens and crude oils (samples that have not received significant thermal stress) differ markedly from the previously known OSC in that they have carbon-skeletons resembling ubiquitous biomarker hydrocarbons (e.g., n-alkanes, isoprenoid alkanes, steranes, and hopanes). This similarity, of course, suggests that the hydrocarbons and OSC have common biogenic precursors. 

The number of samples that need to be analyzed likely increases as the drug development proceeds to clinic stages. When an immunoassay is well developed and characterized, sample analysis can be sensitive, fast, and cost effective. Similarly, the considerations for selecting an LC—MS/MS assay or an immunoassay could follow the same approach at different stages of biomarker development, validation, and application. 

Primary validation— the second part of discovery where a larger number of samples are used to verify or eliminate potential biomarkers. This type of experiment is normally focused on the best (statistical) biomarkers observed in the discovery or identified in the discovery experiment and may use different methodology to facilitate a larger number of samples to be used to increase the statistical confidence and eliminate weak or poor biomarkers from the discovery experiment. This is also the stage of the experiment where one starts using samples from related conditions, other geographical areas, etc. The goal of the validation experiment is to focus on the potential biomarkers that are most likely to answer the research question, and to reduce the number of possible biomarkers from the discovery phase before further time, effort, and money are invested in purification, identification, and characterization of the molecule (30-50 samples). 

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