Effects of system peaks in ion-pair reversed-phase liquid chromatography for noscapine and metabolites

Ion-pair high-performance liquid chromatographic determination of morphine and pseudomorphine in injections

A stability-indicating HPLC procedure has been developed for the determination of morphine and its degradation product pseudomorphine in injection solutions. The reversed-phase chromatographic procedure uses an octadecyl-bonded column with a mobile phase of acetonitrile and aqueous buffer containing an ion-pair reagent. Chromatographic conditions are identified that enable the complete separation of morphine and pseudomorphine without peak deformation or splitting. The only sample preparation required is a simple dilution. The method is found to be precise and linear. The devised method has been applied to the determination of the content of morphine and pseudomorphine in injection solutions stored under normal conditions and after exposure to daylight or heating at 60 degrees C.

Optimization of a peak compression system for a remoxipride metabolite (FLA797) and its application to bioanalysis

A peak compression system is optimized for FLA797 (I), a phenolic tertiary amine and a metabolite to the antipsychotic drug remoxipride. An application is described where this effect is used to give a 6-7-fold improvement of the quantification limit in an assay of I in plasma. The liquid chromatographic system is constructed so that the injection of I dissolved in a solution of a competing amine gives a very high and narrow analyte peak with an apparent efficiency of 1.5 x 10(6) plates/m. When the levels of I in plasma are determined, an internal standard, giving a normal isocratic peak, is added to the plasma sample before the extraction. Concentrations of I down to 0.5-1.0 nM can be determined with reasonable precision. FLA908, another phenolic remoxipride metabolite and a regioisomer to I, eluting as a normal isocratic peak, can be determined simultaneously although only at concentrations higher than 10-15 nM.

Determination of noscapine and its metabolites in plasma by coupled-column liquid chromatography

Noscapine, narcotoline and cotarnine were quantified in deproteinized plasma samples by using a coupled-column liquid chromatographic system. The drug and the metabolites were first separated into two groups on a short polar precolumn (-CN) with an acidic mobile phase, containing a low content of acetonitrile. The metabolites were transferred to a hydrophobic analytical column (C18) and separated with a mobile phase containing a counter ion and a co-ion in an acidic buffer with an high acetonitrile content. Noscapine was transferred to another hydrophobic analytical column (C18) with a mobile phase containing a counter ion in an acidic buffer with an high acetonitrile content. Ultraviolet detection at 310 nm was used for all three compounds. The limits of quantitation were 9 ng/ml for noscapine, 13 ng/ml for cotarnine and 20 ng/ml for narcotoline. The within-day precisions were better than 6% (relative standard deviation), and the absolute recoveries were above 82%.