Investigating the applicability of polar fabric phase sorptive extraction for the HPLC quantitation of salivary vitamin B₁₂ following administration of sublingual tablets and oral sprays

In this study, a simple and rapid fabric phase sorptive extraction (FPSE) protocol combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV) was developed for the monitoring of salivary vitamin B₁₂ levels. Different sol-gel coated cellulose and polyester membranes were evaluated and sol-gel Carbowax 20 M coated polyester membranes were chosen for the selective extraction of the target analyte from saliva samples. Face-centered central composite design (FC-CCD) was employed for the investigation and optimization of sample volume, extraction time and stirring rate, while the other experimental factors were investigated using the classical one-factor-at-a- time" (OFAT) method. Validation of the FPSE-HPLC-UV method was conducted according to the FDA guidelines for bioanalytical methodologies. The lower limit of quantification for vitamin B₁₂ was 0.10 μg mL^-1 and the linear range was 0.10-10.0 μg mL^-1. The relative recoveries for intra-day and inter-day studies were 87.5-113.8% and 88.2-119.2%, respectively. The relative standard deviation was better than 8.2% in all cases, demonstrating good method precision. The sol-gel Carbowax 20 M coated FPSE membranes were found to be reusable for up to 25 times. Finally, the proposed scheme was successfully employed for the quantitation of salivary vitamin B₁₂ at different time points following the administration of sublingual tablets and oral sprays.