A high-performance liquid chromatographic (HPLC) method for the determinati
on of omeprazole in human plasma is described. Omeprazole and the internal
standard (H168/24) were extracted from plasma samples by solid phase extrac
tion (SPE) using a polymeric sorbent-based cartridge. The separation was ac
complished under reversed phase conditions using an Eclipse XDB-C8 Rapid Re
solution (4.6 x 50 mm) column.
The mobile phase consisted of 23% acetonitrile and 77% of 30.4mM Na2HPO4 an
d 1.76mM KH2PO4 solution, pH 8.4, in which a gradient elution was used to l
inearly change solvent composition to 33% acetonitrile and 67% phosphate bu
ffer during the first minute. Absorbance was monitored at 302 nm for omepra
zole and at 294 nm for the internal standard and the total analysis time wa
s 4 minutes.
The lower limit of quantitation was 10 ng/mL and the calibration function i
s linear to 2000ng/mL. This method has been shown to be appropriate for pha
rmacokinetic studies involving children.