Microemulsion liquid chromatographic method for characterisation of fosinopril sodium and fosinoprilat separation with chemometrical support

The properties of the eluent are the essential factors governing the efficiency in the high-performance liquid chromatography (HPLC) method. A novel approach in retention modelling in the liquid chromatographic separation of fosinopril sodium and its degradation product, fosinoprilat, applying a microemulsion as the mobile phase, was used. The modifications of the mobile phase included the changes to the type of the lipophilic phase, the type and concentration of co-surfactant and surfactant, as well as the pH of the mobile phase. In this study, a full factorial 2(3) design, as the optimal method for screening of the experiment, was applied for selecting factors which had an influence on separation. Optimisation was done by a central composite design. An appropriate resolution with reasonable retention times was obtained with a microemulsion containing 0.9% w/w of cyclohexane, 2.2% w/w of sodium dodecyl sulphate (SDS), 8.0% w/w of n-butanol and 88.9% of aqueous 25 mM disodium phosphate, the pH of which was adjusted to 2.8 with 85% orthophosphoric acid. Separations were performed on an X-Terra 50-mmx4.6-mm, 3.5-mum particle size column at 30 degrees C. UV detection was performed at 220 nm and with a flow rate of 0.3 mL min(-1). The established method was validated and applied for analysis of appropriate tablets. The proposed chromatographic procedure for the separation of fosinopril sodium and its degradation product is less expensive compared with the conventional reversed-phase HPLC method, as well as being simple and rapid. The optimised and validated method can be used for separation, identification and simultaneous determination of fosinopril sodium and fosinoprilat in bulk drug and in pharmaceutical dose forms.

Simultaneous LC determination of trimethoprim and sulphamethoxazole in pharmaceutical formulations

In the present study, a simple, sensitive, precise and rapid reversed-phase high performance liquid chromatographic (HPLC) method with ultraviolet detection for the simultaneous analysis of trimethoprim (TMP) and sulphamethoxazole (SPM) is developed and applied to the determination in commercial pharmaceutical preparations. These compounds are well separated on a Bondapak C(18) reverse phase column using a mobile phase consisted of a mixture of methanol:water (60:40; v/v) adjusted to pH 3 with 10% orthophosphoric acid at a flow rate of 1.8 ml min(-1). The proposed method was linear in the range 2.0-10.0 microgram ml(-1) for TMP and 10.0-50.0 microgram ml(-1) for SPM. The limit of detection were 0.45 and 1.21 microgram ml(-1) for TMP and SPM, respectively. The method which is rapid, simple and does not require any separation step, has been successfully applied to the assay of commercial tablet and oral suspension dosage forms containing TMP and SPM.