Rapid determination of selected drugs of abuse in human plasma using a monolithic silica HPLC column and solid phase extraction

Two new high performance liquid chromatography (HPLC) assays were developed, which utilized a 100 x 4.6 mm I.D. monolithic silica column and binary mobile phase gradients, for the simultaneous determination of selected drugs of abuse in human plasma. Both methods used gradients consisting of 25 mM pentanesulfonic acid and 25 mM sodium phosphate monobasic monohydrate-acetonitrile (pH 2.9), and mixed mode solid phase extraction procedures. In the first method, cocaine (COC) and its metabolites benzoylecgonine (BE), norcocaine (NC), and cocaethylene (CE), were separated with a pump flow rate of 5.0 mL/min in a total run time of 5 min. All analyses were conducted at ambient temperature. The injection volume was 100 muL and the UV detector was operated at 231 nm. The method vas validated over the range of 50-500 ng/mL for BE, COC, and CE, and 25-2500 ng/mL for NC. The method proved to be accurate ( % bias for all calibration samples varied from -4.5 to 8.5%) and precise (within-run precision ranged from 1.5 to 12.8% and between-run precision ranged from 0.4 to 12.7%). The mean absolute recoveries were 93.5, 95.7, 105.4, and 98.8% for BB, COC, NC, and CE, respectively. In the second method, morphine (MO), hydromorhone (HM), tolazoline (ISTD), codeine (CO), oxycodone (OC), and hydrocodone (HC) were separated with a pump flow rate of 8.0 mL/min in a total run tune of 2 min. All analyses were conducted at 30degreesC temperature. The injection volume was 100 muL and the UV detector vas operated at 208 nm. The method was validated over the range of 50-5000 ng/mL for the opiates studied. The method proved to be accurate (% bias for all calibration samples varied from -8.4 to 2.0%) and precise (within-run precision ranged from 1.7 to 16.9% and between-run precision ranged from 0.4 to 14.8%). The mean absolute recoveries were 95.6, 104, 103, 97.9, and 105% for MO, HM, CO, OC, and HC, respectively. The recovery for the internal standard vas 99.6%. The assays should be suitable for use in routine determination of tire selected drugs of abuse in human plasma.