Degradation study of thiamine hydrochloride and analysis of expired ampoules using a novel, validated HPLC-UV method

Thiamine is a vital vitamin and one-sided diet carries a high risk of deficiency. Supplementation is simple with appropriate pharmaceutical products. Unfortunately, the availability of medicines is still not guaranteed everywhere in the world, while at the same time, perfectly good medicines are being disposed of after their expiry date. For this reason, the shelf-time has often been critically questioned in recent years. Analysing finished pharmaceutical products, stored for decades under uncontrolled conditions, offers a rare insight in real-world stability of pharmaceuticals. Hence, this study examined 80-year-old thiamine hydrochloride ampoules. For comparison, test solutions were stored at 60 °C for 40 days in order to induce degradation reactions. A novel HPLC-UV method was developed and validated in accordance with ICH Guideline Q2(R2). Gradient elution, using a hydrophilic end-capped C18 column (150 × 4.6 mm, particle size 5 µm) with eluent A water/formic acid (100/0.1 v/v) and eluent B acetonitrile/formic acid (100/0.1 v/v) from 0% B to 90% B under UV detection (254 nm), enables the separation of thiamine, 6 degradation products, the preservatives methyl- and propylparaben and their degradation product p-hydroxybenzoic acid. The method enables the structural elucidation of degradation products using high-resolution tandem mass spectrometry experiments. A significant degradation of thiamine hydrochloride, with a residual content of 30.1, 37.2, and 44.8%, was observed. In addition to the expected degradation products, resulting from hydrolysis, further degradation products were formed, that were not expected in the given acidic range. Stress samples showed the same degradation profile as the expired ampoules.