Influence of the mobile phase composition on hyphenated ultraviolet and charged aerosol detection for the impurity profiling of vigabatrin

Recently, charged aerosol detection (CAD), a universal detection technique in liquid chromatography, has been introduced into monographs of the European Pharmacopoeia (Ph. Eur.), which now employs HPLCUV-CAD for assessing the impurities of the drug vigabatrin. The separation of vigabatrin and its impurities is facilitated by ion pair chromatography (IPC) in the compendial method using tridecafluoroheptanoic acid (TDFHA) as ion-pairing reagent. However, the subsequent detection of the impurities by UV-CAD is considerably impaired due to the substantial amount of ion-pairing reagent applied in the method generating high levels of background noise. In this study, the influence of the mobile phase composition on the background noise of the CAD was evaluated applying response surface methodology. The model's results indicated that the chain length of the ion-pairing reagent is a predominant factor for noise generation. Thus, an alternative method for the impurity analysis of vigabatrin using mixed-mode chromatography (MMC) instead of IPC was developed. The dual separation mechanism of the MMC column enabled the choice of a mobile phase better suited for the individual requirements of the UV-CAD detectors, while maintaining excellent selectivity. The MMC method does not require the addition of a post-column solution to reduce the TDFHA concentration in the mobile phase, and, therefore, needs less instrumentation. Moreover, the sample concentration could be halved due to the improved LOQs of the impurities (<50 ng on column) and the analysis time could be shortened (30 to 20 min) due to improved separation efficiency. The MMC method was validated with respect to ICH guideline Q2(R1). (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Charged aerosol detection (CAD) has been introduced into European Pharmacopoeia (Ph. Eur.) monographs for assessing impurities of vigabatrin, facilitated by ion pair chromatography (IPC) using tridecafluoroheptanoic acid (TDFHA) as an ion-pairing reagent. However, high levels of background noise from the ion-pairing reagent have impaired UV-CAD detection. By evaluating the mobile phase composition's influence on background noise using response surface methodology, an alternative method using mixed-mode chromatography (MMC) was developed, enabling better selectivity and shorter analysis time. The MMC method shows improved LOQs, reduced instrumentation needs, and halved sample concentration compared to IPC.