Development of non-aqueous titrimetric and spectrophotometric methods for the determination of valganciclovir hydrochloride in bulk drug and tablets

Two non-aqueous titrimetric and one visible spectrophotometric methods were developed and validated for the determination of valganciclovir hydrochloride (VLGH) in pure drug and tablets. The titrimetric methods were carried out by titrating the VLGH solution in glacial acetic acid with acetous perchloric acid (HClO₄) in the presence of mercuric acetate and the end point of this titration was being located either visually (method A) or potentiometrically (method B). The spectrophotometric method (method C) was based on the addition of p-dimethylaminobenzaldehyde (DMAB) solution to VLGH solution and the formed yellow condensation product was measured at 420nm. In titrimetric procedures, both the methods A and B were applicable over the range of 4-20mg VLGH, and the calculations were based on a 1:1 reaction stoichiometry (VLGH:HClO₄). In a spectrophotometric method, Beer's law was valid in a concentration range of 5-50 μg/mL VLGH with the corresponding value of molar absorptivity of 4.43×10³L/mol cm for method C. The limits of detection (LOD) and quantification (LOQ) for method C were 0.3 and 0.92μg/mL, respectively. The developed methods were successfully applied to the determination of VLGH in tablets, and the results were statistically compared with those of a reference method by applying Student's t-test and F-test. Further, the validity of the developed methods was confirmed by recovery studies via standard addition technique.