Dried blood spot (DBS) analysis has emerged as a tool for bioanalysis. Two obstacles that have manifested during DBS analysis are performing dilutions and addition of the internal standard to the DBS card prior to sample spotting. Conventional methods for dilutions and internal standard addition are not optimal as these methods dilute the sample with blank sample extract or add the internal standard in blank solvent during extraction. Experiments were conducted to perform dilutions by reducing the size of the sample punched. A blank punch with a spot the size of the dilution punch removed was extracted with the dilution spot to account for any matrix effects that might have been reduced due to the smaller dilution sample punch. A simple method of adding internal standard to the card prior to spotting the sample was also investigated. Adding internal standard to the card prior to sample addition may compensate for any irregularities encountered during the sample storage, extraction, or analysis.1 HPLC/MS/MS was used for all analyses.

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