Graphene oxide‐based solid phase extraction of vitamin B12 from pharmaceutical formulations and its determination by X‐ray fluorescence

In the present study, a novel quantitative method, namely solid phase extraction, was applied to extract vitamin B₁₂ from pharmaceutical formulations. The technique involves the use of graphene oxide (GO) as an efficient adsorbent for solid‐phase extraction of vitamin B₁₂. Collection of GO from aqueous solution was simply achieved by applying filtration assembly. The extracted analyte was directly analyzed by using X‐ray fluorescence (XRF) spectroscopy. Factors affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, enhancement factor of 46, linear dynamic range of 25–1000 µg l^?1 with correlation of determination (R² = 0.998) and limit of detection of 20 µg l^?1 were obtained for vitamin B₁₂. The percent relative standard deviation based on three‐replicate determination was less than 8.1%. The method was successfully applied for extraction and determination of vitamin B₁₂ in different types of pharmaceutical samples such as multivitamin tablet, effervescent tablet and injection sample. The results showed that the proposed method based on GO was a simple, accurate, and highly efficient approach for analysis of vitamin B₁₂. Copyright © 2014 John Wiley & Sons, Ltd.