Semi-micro solid phase extraction with electrospun polystyrene fiber disks

A technique is described for performing solid phase extraction (SPE) at a send-microscale. 10 mg of electrospun polystyrene fibers (average diameter 2.7 mu m) were packed into a SPE barrel to form a disk (5 mm x 1 mm). The device was employed to evaluate the extraction of four steroids: prednisone, hydrocortisone, cortisone acetate and 19-nortestosterone from water and plasma matrices. The analytes were desorbed from the fibers with 100 mu l methanol and monitored by high performance liquid chromatography with a diode array detector (HPLC-DAD). The semi-micro SPE method provided extraction recoveries of 51.14-80.13% in plasma and 66.07-93.43% in water. The breakthrough volumes at 500 ng ml(-1) ranged from 200-400 mu l for all analytes. At optimal conditions, the four analytes followed an excellent linear relationship in the range 12.5-400 ng ml(-1) with coefficients of determination (r(2)) greater than 0.99 and the limits of detection ranged from 0.75 to 1.29 ng ml(-1). Due to its simplicity, it is anticipated that the method will greatly simplify disk solid phase extraction.