Pnv. Tata et Sl. Bramer, High performance liquid chromatographic method for the analysis of omeprazole and 5-hydroxyomeprazole in human plasma, ANAL LETTER, 32(11), 1999, pp. 2285-2295
A sensitive, and reliable HPLC method was validated for the simultaneous me
asurement of omeprazole (OMP) and 5-hydroxyomeprazole (5OH-OMP) in human pl
asma. OMP, 5OH-OMP, and OPC-18827 (the internal standard) were extracted fr
om human plasma by liquid-liquid extraction into CH2Cl2- iso-PrOH (9:1). An
alytes were resolved using a C-18 HPLC column and gradient elution mobile p
hase containing 50 mM phosphate buffer in acetonitrile (22 - 50% in 43 minu
tes followed by 15 minutes equilibration). The eluents were monitored by UV
detection at 302 nm. The HPLC retention times were 12.19 min for 5OH-OMP,
30.25 min for OPC-18827 and 34.18 min for OMP with resolution factors of 28
.3 for 5OH-OMP/ISD and 6.2 for ISD/OMP. Using 0.75 mL of plasma, linearity
was established over the range of 20-800 ng/mL for both analytes. Other met
abolites were completely separated (OMP-sulfone, 27.50 min) or did not elut
e under these conditions (OMP- sulfide). In plasma, the analytes were stabl
e at room temperature (bench top, 4 hrs), or refrigerated (57 hrs) and in t
he autosampler (47 hrs). Sample processing through three freeze/thaw cycles
and 2-, 5- and 10-fold dilution with blank plasma before the analysis had
no significant effect on the analysis of OMP and SOH-OMP (>97% recovery). A
t the lower limit of quantitation, the accuracy was 102.3% for SOH-OMP and
97.3% for OMP. The method is selective and specific for the analytes in the
presence of two other OMP metabolites and endogenous substances.