REVERSED-PHASE SEQUENTIAL INJECTION LIQUID CHROMATOGRAPHIC METHOD FOR SILDENAFIL ASSAY

Abstract

Sequential injection chromatography (SIC) has been recently proposed as an alternative separation technique with potential benefits and some limitations. In the current study, a more pressure resistant selection valve (SV) with additional ports was installed in an SIC assembly. The current SV allowed using a buffer in a Mobile phase (MP) without leakage and analyzing ten solutions with a one-shot run. In addition, a new method for sildenafil assay in tablets, bulk, and synthetic pharmaceutical samples was proposed utilizing the newly developed SIC assembly. Response surface approach was adopted to screen the effect of MP composition on tR, PH, and B and, accordingly, to optimize the method. Sample volume and flow rate were optimized using the univariate approach. The optimum chromatographic conditions were: C18 monolithic column (4.6 × 25 mm), an MP composition of 0.3 M ammonium acetate:acetonitrile (50:50, v/v) at pH 6.8, sample volume 40 µL and flow rate 40 µL/s. UV detection at 240 nm was carried out using miniaturized fiber optic spectrometric devices. A comparative study on some analytical features of the SIC method with those of previous HPLC methods was conducted. The SIC method is more rapid and more reagent-saving and thus safer to the environment. The sample frequency was 40 samples/hr. The total volume of consumed reagents and sample was 2.54 mL.