A Single-Laboratory Validation of a UPLC Method for Determination of Folic Acid in Various Dietary Supplement Dosage Forms.

Background: Folic acid is an essential nutrient necessary for the synthesis of nucleic acids (DNA and RNA) and certain amino acids. There are no scientifically validated analytical methods for folic acid applicable to all dosage forms.

Objective: A single-laboratory method was validated for the determination of folic acid content in various dietary supplement dosage forms. This method used ultra-performance liquid chromatography/diode-array detector (UPLC/PDA) to determine the folic acid content in dietary supplements in the form of tablets, two-piece capsules, powder drinks, softgels, and gummies.

Method: The ultra-performance liquid chromatography/diode-array detector method was evaluated for linearity, limit of detection (LOD), limit of quantification (LOQ), repeatability, recovery, specificity, and system suitability.

Results: Linearity of the folic acid standard was shown to be linear in the range of 0.45 µg/mL to 7.37 µg/mL. LOD and LOQ of folic acid were 0.089 and 0.268 µg/mL, respectively. The repeatability of nine samples from five matrixes resulted in 1.15-4.82% relative standard deviation (RSD). Five samples with five different matrixes spiked with 25, 50, and 100% of working standard concentration and had a recovery range of 95.48-104.72%. The chromatograms and spectra of the blank, standard, and sample solutions showed that the method was free of interference for folic acid. The system suitability results of different matrixes showed that the UPLC/PDA system is suitable for folic acid analysis. All the AOAC INTERNATIONAL SMPR® 2022.002 requirements were fulfilled.

Conclusions: The ultra-performance liquid chromatography/diode-array detector method compares favorably with the requirements of AOAC SMPR 2022.002.

Highlights: The UPLC/PDA method is fast and suitable for all dietary supplement matrixes studied. The method meets the requirements of SMPR 2022.002.