In recent years there has been much discussion related to the use of fewer animals for pre-clinical safety and efficacy testing. In addition, regulatory agencies have requested testing in pediatric patient populations for all new drug compounds. With the development of more sensitive instrumentation, the need for smaller blood sample size analysis, has been realized. Over the years, techniques such as Dried Blood Spot (DBS) have been utilized to sample less than 50 uL of blood. While DBS seems to work well for many analyses, the historical PK database for most clinical trials has been through the quantitation of drugs from plasma or serum.