Determination of mitomycin C in serum by high-performance liquid chromatography with dual-electrode coulometric detection

Voltammetric Determination of Mitomycin c Using a Chemically-Modified Glassy Carbon Electrode

An electrochemical method for the direct determination of mitomycin c (MMC), based on a multi wall carbon nanotube (MWNT)-modified electrode, has been developed. A well-shaped and highly sensitive oxidation peak at 0.79 V was observed on the MWNT-modified electrode for MMC. Further studies show strong evidence that MWNT-modified electrode significantly enhances the sensitivity of determination of MMC since the oxidation peak current of MMC increases remarkably, compared with that with a bare glassy carbon electrode. All the experimental parameters such as pH, scan rate, accumulation conditions, have been examined. A sensitive linear voltammetric response for MMC was obtained over the concentration range of 2.5 × 10-7-1.0 × 10-4 mol/l; the detection limit is 8 × 10-8 mol/l. Compared with other methods, this new-proposed method possesses advantages such as high sensitivity, fast response, low cost and simplicity. Eventually, the proposed method has been successfully employed to detect MMC in urine samples.

Enantioselective high-performance liquid chromatographic determination of nicardipine in human plasma

A sensitive method for the enantioselective high-performance liquid chromatography (HPLC) determination of nicardipine in human plasma is described. (+)-Nicardipine, (-)-nicardipine and (+)-barnidipine as an internal standard are detected by an ultraviolet detector at 254 nm. Racemic nicardipine in human plasma was extracted by a rapid and simple procedure based on C18 bonded-phase extraction. The extraction samples were purified and concentrated on a pre-column using a C1 stationary phase and the enantiomers of nicardipine are quantitatively separated by HPLC on a Sumichiral OA-4500 column, containing a chemically modified Pirkle-type stationary phase. Determination of (+)- and (-)-nicardipine was possible in a concentration range of 5-100 ng ml(-1) and the limit of detection in plasma was 2.5 ng ml(-1). The recoveries of (+)- and (-)-nicardipine added to plasma were 91.4-98.4% and 93.3-96.7%, respectively, with coefficients of variation of less than 9.0 and 9.4% respectively. The method was applied to low level monitoring of (+)- and (-)-nicardipine in plasma from healthy volunteers.

Liquid chromatographic determination of manidipine in serum with electrochemical detection

A highly sensitive and selective method for determining a dihydropyridine calcium antagonist, manidipine, by liquid chromatography using column switching with electrochemical detection was developed. Manidipine in serum was extracted by a rapid and simple procedure based on C8 bonded-phase extraction and then silica extraction. Manidipine and nilvadipine as an internal standard were separated on a C8 bonded-phase HPLC column and detected by high conversion efficiency amperometric detection at +0.7 V. Manidipine and nilvadipine (I.S.) were separated from an endogenous interference peak in serum and concentrated on a pre-column (C18) by column switching using an isocratic mobile phase, and then the corresponding fractions were introduced to an analytical column with a C8 stationary phase. Determination of manidipine was possible over the concentration range 0.5-10 ng/ml: the limit of detection was 0.3 ng/ml. The recovery of manidipine added to serum was 93.1-98.4% with coefficients of variation of less than 7.1%. The method is applicable to drug level monitoring in the serum of healthy volunteers treated with manidipine and to the analysis of pharmacokinetics.

Column-switching high-performance liquid chromatography of ofloxacin in human saliva and correlation of ofloxacin level in saliva and serum

A column-switching high-performance liquid chromatography (HPLC) assay was developed for the determination of ofloxacin in saliva. The saliva samples were directly introduced into a C8 HPLC column using a C18 precolumn. Ofloxacin and lomefloxacin as internal standards were detected spectrophotometrically at 300 nm. Determination of ofloxacin was possible in the concentration range 50-3,000 ng/ml, and the limit of detection was 20 ng/ ml. The recovery of ofloxacin added to saliva was 96.9-101.2% with a coefficient of variation of < 2.9%. These pharmacokinetic studies were made of healthy volunteers after treatment with ofloxacin. The maximum concentration of saliva and serum ofloxacin was 513.3-2,053.0 ng/ml and 768.2-3,089.0 ng/ml for dose of 100 mg or 200 mg, respectively. The AUC0-6 was 1,736.8-6,519.9 ng/h/ml in saliva and 2,875.5-10,086.0 ng/h/ml in serum, respectively. The saliva versus serum concentration ratio was 0.4-0.7 for doses of 100 and 200 mg. A good correlation between saliva and serum level of ofloxacin was obtained by this HPLC method (r = 0.949).

Determination of ofloxacin in human serum by high-performance liquid chromatography with column switching

The chromatographic behaviour of ofloxacin on various sorbents, including ODS, C8, C1, nitril, phenyl and tert,-butyl, as stationary phases was investigated and a high-performance liquid chromatography (HPLC) assay was developed for the determination of ofloxacin in serum. The serum samples were directly introduced onto an HPLC column after filtering through a Morcut II membrane filter to remove proteins. The filtrate was concentrated on a pre-column using a phenyl stationary phase and was then introduced to an analytical column with an ODS stationary phase by column switching. Ofloxacin and enoxacin as an internal standard were detected by ultraviolet absorbance at 300 nm. Determination was possible for ofloxacin over the concentration range 50-2000 ng/ml; the limit of detection was 20 ng/ml. The recovery of ofloxacin added to serum was 88.8-101.7% with a coefficient of variation of less than 5.2%. This method is applicable to pharmacokinetic studies of patients after treatment with ofloxacin.