AppNote 5: Stir Bar Sorptive Extraction Based on Restricted Access Material for the Direct Extraction of Drugs and Metabolites in Biological Fluids


App Note 5/2006

An experimental biocompatible stir bar sorptive extraction (SBSE) device was prepared using a restricted access material (RAM) as the SBSE coating. The biocompatible SBSE approach was advantageous in terms of simplifying the sample preparation procedure. The RAM-SBSE bar was able to simultaneously fractionate the protein component from a biological sample, while directly extracting caffeine and its metabolites;
overcoming the present disadvantages of direct sampling in biological matrices by SBSE, such as fouling of the extraction coating by proteins. Analytical Figures of Merit for Caffeine Determination in Plasma:
– Limit of detection (s/n = 3) for caffeine = 25 ng/mL
– Linear over the range of 0.5-100 μg/mL (R2 = 0.9981)
– Injection repeatability and intra-assay precision % R.S.D.
< 8%
The RAM-SBSE device was simple to use, robust and reuseable with over 50 direct extractions of caffeine and its metabolites in biological fluids without significant signal loss.