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 t_R, 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.

Keywords:

• chemometric optimization
• high performance liquid chromatography
• method validation
• pharmaceutical analysis
• sequential injection chromatography
• sildenafil

Abbreviations:

• acetonitrile (ACN)
• ammonium acetate (ACT)
• baseline (B)
• excipients (EXP)
• flow injection (FI)
• limit of detection (LOD)
• limit of quantification (LOQ)
• mobile phase (MP)
• number of theoretical plates (N)
• peak height (PH)
• peak symmetry (PS)
• retention time (t_R)
• selection valve (SV)
• sequential injection analysis (SIA)
• sequential injection chromatography (SIC)
• syringe pump (SP)

ACKNOWLEDGMENTS

Dr. Idris thanks the Department of Chemistry, College of Science, King Faisal University, where a part of this work was conducted. Mr. Naheid also thanks the Atomic Energy Council, Sudan Academy of Science, Khartoum, Sudan for permitting him to study for a Master's Degree in Chemistry.

Notes

^a sildenafil; ^b excipients.

Fixed conditions: C18 column (4.6 × 25 mm), UV detection at 240 nm, mobile phase included 0.3 M ammonium acetate, analyte concentration 50 µg/L, and flow rate 40 µL/s.

^a concentration (µg/mL).

^b number of repetitions.