Development and validation of liquid chromatographic methods for the estimation of the acceptance values of some hazardous preservatives in pharmaceutical formulations. A comparative study

Abstract

Gradient and isocratic liquid chromatography were applied for the simultaneous determination of three preservatives, namely; benzyl alcohol (BA), methyl paraben (MP) and propyl paraben (PP). Separation for both elution modes was carried out using a C18 column kept at 60°C throughout the analysis, accompanied with a flow rate of 2 mL/min and UV detection at 254 nm. Gradient liquid chromatography used a time programme with two solvents (0.1% formic acid and acetonitril), while isocratic elution was performed with 0.1% formic acid: 2-propanol in a ratio of 70:30, v/v. Full validation study was conducted for both separation modes, where both of them were linear over the concentration ranges of 100.0–2000.0, 2.5–100.0, and 2.0–200.0 µg/mL for BA, MP and PP respectively. Using gradient elution, the detection limits for BA, MP, and PP were found to be 50.0, 1.8, and 1.5 µg/mL respectively. The corresponding values in isocratic elution were 60.0, 1.5, and 1.3 µg/mL. On the other hand, the limit of quantification for BA, MP, and PP using gradient mode are 70.0, 2.0, and 1.8 µg/mL respectively. While isocratic elution resulted in corresponding values of: 80.0, 2.3, and 1.7 µg/mL. The accuracy of the proposed method was illustrated from the high percentage recoveries values which were 99.67%, 100.42%, and 99.85% for BA, MP, and PP respectively using gradient mode, with corresponding values of 99.79%, 100.39%, and 99.87% for the isocratic elution mode. In addition, gradient elution was further applied to detect and assay the selected preservatives in different pharmaceutical formulations demonstrating that their quantities are within the stated ranges, and eventually, a comparative overview was introduced.