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The anticancer agent CAI was quantitated from human plasma using a C-18 column with a mobile phase consisting of acetonitrile and water (each containing 0.01M ammonium acetate) pumped over a gradient at a flow rate of 1.0 mL min. The detection of CAI and the internal standard, harmine, was accomplished using a photodiode-array detector set at 264 and 323 nm, respectively. The chromatographic run time was 17.5 minutes. The plasma samples were prepared for HPLC analysis using a C-18 solid phase extraction procedure. Two calibration curves were prepared. and the assay was shown to be linear in the concentration range of 0.02 to 0.5 μg/mL for the low curve and 0.25 to 10.0 μg/mL for the high curve, with average correlation coefficients of 0.9933 and 0.9938, respectively. Intra-assay and inter-assay imprecisions were less than 10.0% with an error of accuracy of less than 11.0%. The assay was reproducible with the sensitivity needed for the prediction of CAI levels in the plasma of cancer patients.

An assay of atenolol in human serum is described using a 3 μm silica column with a 60:40 v/v 6.25 mM sodium dihydrogen phosphate pH 3.0-acetonitrile mobile phase at 1 mL/min; the ultraviolet detector was set at 254 nm. Minimum detectability of the drug was estimated to be 20 ng/mL (S/N = 2). The method is linear in the 100–1000 ng/mL range (r = 0.9992, n = 9). An ethylsilane solid phase extraction column was used for sample cleanup and recovery of atenolol from serum was 103 ± 4% (n = 3). Retention times for atenolol and metoprolol (internal standard) were 6.6 and 7.5 min, respectively, and typical theoretical plates were 17,583 and 22,680, respectively. Resolution between internal standard and atenolol peaks was calculated to be 4.5. A typical analysis was completed in less than 45 min. The good sensitivity and reproducibility of the method should render it useful for the assay of atenolol levels in serum.

High performance chromatographic separations of selected cardiovascular agents (propranolol, atenolol, metoprolol, verapamil, diltiazem, nifedipine, clonidine and prazosin) on underivatized silica using aqueous phosphate buffer—acetonitrile mobile phases were studied. Mobile phases differing in organic modifier concentration, ionic strength and buffer pH were prepared and tested for chromatographic separation of selected mixtures of the analytes grouped according to pharmacological activity. The best separations of all analytes were obtained using a mobile phase of 60:40 v/v aqueous pH 3 phosphate buffer—acetonitrile at a 1.0 mL/min flow rate. Substitution of methanol for acetonitrile gave increased retention of the analytes with some reduction in column efficiency measured as plate counts. Although ion-pairing appears to be the primary interactive force between the silica column and the analytes, other forces such as hydrogen bonding and hydrophobic interactions are also involved in the separation.

13- Cis retinoic acid (Accutane®) was extracted from a cream, gel, capsule and beadlet dosage form using supercritical carbon dioxide modified with 5% methanol as the mobile phase. The pump pressure and the extraction chamber and restrictor temperature were experimentally optimized at 325 atm and 45°C, respectively. A 2.5-min static and 5-min dynamic extraction time were used. The supercritical fluid extraction (SFE) eluent was trapped in methanol, injected into the high-performance liquid chromatographic (HPLC) system, and quantitated by ultraviolet detection at 360 nm. Application of the SFE method to spiked placebo dosage forms gave 13- cis retinoic acid recoveries of 98.8, 98.9, 98.8 and 100% for the cream, gel, capsule and beadlet, respectively, with R.S.D.s in the range 0.6–0.9% ( n =4). Inter-day percent error and precision of the extraction were 1.1–2.0 and 0.2–2.4% ( n =3), respectively, and intra-day percent error and precision were 1.0–3.0 and 0.3–2.1% ( n =8), respectively. Percent error and precision data for spiked celite samples in the 0.05–1.0 μg ml −1 range were 0.59–4.75 and 1.8–2.1% ( n =3), respectively. The extraction method was applied to commercial 13- cis retinoic acid dosage forms and the results compared to unextracted samples. Linear regression analysis of concentration versus peak height gave a correlation coefficient of 0.9991 with a slope of 7.468 and a y -intercept of 0.1923. The percent error and precision data were 1.3–5.3 and 0.2–1.5% ( n =4), respectively. The photoisomers of 13- cis retinoic acid were also extracted with the method and recoveries of 90.4–92.4% with R.S.D.s of 1.5–3.4% were obtained ( n =4).

Selected drugs from benzodiazepine, anabolic agent and non-steroidal anti-inflammatory drug (NSAID) therapeutic classes were extracted from water and serum using a supercritical CO2 mobile phase. The samples were extracted at a pump pressure of 329 MPa, an extraction chamber temperature of 45 degrees C, and a restrictor temperature of 60 degrees C. The static extraction time for all samples was 2.5 min and the dynamic extraction time ranged from 5 to 20 min. The analytes were collected in appropriate solvent traps and assayed by modified literature HPLC procedures. Analyte recoveries were calculated based on peak height measurements of extracted vs. unextracted analyte. The recovery of the benzodiazepines ranged from 80 to 98% in water and from 75 to 94% in serum. Anabolic drug recoveries from water and serum ranged from 67 to 100% and 70 to 100%, respectively. The NSAIDs were recovered from water in the 76 to 97% range and in the 76 to 100% range from serum. Accuracy, precision and endogenous peak interference, if any, were determined for blank and spiked serum extractions and compared with classical sample preparation techniques of liquid-liquid and solid-phase extraction reported in the literature. For the benzodiazepines, accuracy and precision for supercritical fluid extraction (SFE) ranged from 1.95 to 3.31 and 0.57 to 1.25%, respectively (n = 3). The SFE accuracy and precision data for the anabolic agents ranged from 4.03 to 7.84 and 0.66 to 2.78%, respectively (n = 3). The accuracy and precision data reported for the SFE of the NSAIDs ranged from 2.79 to 3.79 and 0.33 to 1.27%, respectively (n = 3). The precision of the SFE method from serum was shown to be comparable to the precision obtained with other classical preparation techniques.

The separation of phenylbutazone (PB) and its major metabolite oxyphenbutazone (OPB) using supercritical fluid chromatography (SFC) has been investigated. The separations were studied on octadecylsilane, silica and cyano packed columns with 5% methanol in carbon dioxide as mobile phase and detection at 240 nm. The octadecylsilane column showed the most favourable chromatographic parameters for the analysis of the analytes. Recoveries of PB and OPB from spiked human serum were in the 82–83% range using solid phase extraction on an ODS cartridge. Limits of detection of the SFC assay were 0.1 μg ml −1 for PB and 1.0 μg ml −1 for OPB. Accuracy and precision of the method were in the 0.24-4.94% range for PB and OPB. The SFC method was directly comparable to an HPLC assay of the same analytes. The SFC method was also applied to a commercial 100 mg dosage form of PB with good recovery of PB.