Microbore liquid chromatographic determination of cadralazine and cephalexin in plasma with large-volume injection

Determination of Cephalexin Monohydrate in Pharmaceutical Dosage Form by Stability-Indicating RP-UFLC and UV Spectroscopic Methods

An ultra-fast liquid chromatographic method and two UV spectroscopic methods were developed for the determination of cephalexin monohydrate in pharmaceutical dosage forms. Isocratic separation was performed on an Enable C₁₈G column (250 mm × 4.6 mm i.d., 5 μm) using methanol:0.01 M TBAHS (50:50, v/v) as the mobile phase at a flow rate of 1.0 ml/min. The PDA detection wavelength was set at 254 nm. The UV spectroscopic method was performed at 261 nm and at 256–266 nm for the AUC method using a phosphate buffer (pH=5.5). The linearity was observed over a concentration range of 1.0–120 μg/ml for UFLC and both of the UV spectroscopic methods (correlation coefficient=0.999). The developed methods were validated according to ICH guidelines. The relative standard deviation values for the intraday and interday precision studies were < 2%, and the accuracy was > 99% for all of the three methods. The developed methods were used successfully for the determination of cephalexin in dry syrup formulation.

Semi-quantitative analysis of cefaclor in human serum by capillary high performance liquid chromatography/fast atom bombardment mass spectrometry

Capillary high performance liquid chromatography (HPLC) was combined with frit fast atom bombardment (FAB) mass spectrometry (MS) and a detailed procedure has been established for on-line analysis of cefaclor in human serum. The capillary column (0.3 mm i.d.) enabled the introduction of entire effluent to the frit interface for FAB-MS; and a special column switching device for injection and concentration enabled the injection of as large as a 500-microliters volume sample. These conditions gave much higher sensitivity than that of previous HPLC/MS system. Thus, low levels of cefaclor could be successfully identified in sera by its mass spectral measurements 2 h after its single oral administration of a 250-mg capsule in two subjects.

Demonstration of the compatibility of narrow-bore packed column high-performance liquid chromatography with conventional detection systems

A number of commercially available high-performance liquid chromatography detectors fitted with conventionally sized flow cells (4.5 to 14 microliters) have been evaluated for use for narrow-bore (1-3 mm i.d.) packed columns. Contrary to the popular misconception, small flow cell volume (and consequently short path length) does not appear to be a prerequisite for successful use of narrow-bore columns. The 1 mm i.d. columns when used with certain detectors gave up to a 17-fold increase in sensitivity, compared with conventional 4.6 mm i.d. columns. This work, which was carried out using conventional injection volumes (50 microliters), shows that narrow-bore HPLC columns can be used in most laboratories to significant advantage without costly conversion of existing equipment.