Graphene Oxide Functionalized Based on Dispersive Solid Phase Extraction of Vitamin B12 Spectrophotometric Determination in Pharmaceutical Samples

Sample treatment is crucial for detecting target compounds in complex matrices. Recently, graphene oxide (GO) and its composites have garnered attention as sorbents for sample preparation; however, their application in vitamin B12 (VB12) extraction has not been fully explored. In this study, a dispersive solid-phase extraction (D-SPE) method was developed for the spectrophotometric determination of VB12 in pharmaceutical samples using GO, chitosan (CTS), and a GO/CTS composite as sorbents. The materials were characterized using FTIR, XRD, BET, and FESEM. Extraction conditions were optimized, such as pH, sorbent amount, contact time, eluent type and volume, and desorption temperature. Under these conditions, the developed D-SPE method achieved linear calibration ranges of 0.05–15, 0.1–10, and 0.02–10 µg mL−1, with correlation coefficients of 0.9997, 0.9990, and 0.9998, respectively, after extracting VB12 with GO, CTS, and GO/CTS. The limits of quantification were in the range of 1.00–2.09 µg mL−1, with relative standard deviations of less than 0.11% (n = 3). Recoveries in pharmaceutical samples ranged from 95.1 to 112.8% (GO), 91.8 to 95.5% (CTS), and 87.5 to 103.8% (GO/CTS). These results demonstrate that the GO/CTS composite is an efficient and reliable adsorbent for extracting VB12 in pharmaceutical applications.