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Verification of 5-Methyltetrahydrofolic Acid in Nutritional Products

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Abstract

A simple method for the verification of supplemental (6R,S)-5-methyl-5,6,7,8-tetrahydrofolic acid, “5-MTHF,” in nutritional products is described. Nutritional product samples are prepared for the liquid chromatographic/fluorescence detection (LC/FLD) determination of 5-MTHF by buffer dilution, 10-min centrifugation, and syringe filtration. Method performance has been defined by assessments of 5-MTHF linearity (r 2 averaged 0.9999 ± 0.0001, and all relative calibration errors averaged ≤0.6%, for ten consecutive six-point standard curves), intermediate precision (rsd = 1.1%, n = 9, for three products fortified at ∼1.73 μmol/kg = ∼795 μg/kg, tested on each of 3 days), accuracy (spike recovery average = 92.8 ± 1.0%, n = 9, for nutritional products spiked with 5-MTHF at ∼1.73 μmol/kg, or ∼795 μg/kg), and selectivity (absence of interference from reagent blanks, and from four compounds structurally related to 5-MTHF). The 5-MTHF recovery, as % of unheated controls, from a simulated heat treatment (20 min at 120 °C) averaged 99.1 ± 0.6%, n = 4. The limits of 5-MTHF detection (S/N = 3) and quantification (S/N = 10) were experimentally determined to be 10 μg/kg (∼0.020 μmol/kg) and 30 μg/kg (∼0.060 μmol/kg), respectively (<10× the expected fortification rate). The method provides a simple and inexpensive means for verifying proper fortification, and for assessing the stability to processing and storage conditions, of free 5-MTHF in nutritional products. A finding of interest is the indication that liquid nutritional products may comprise a stable matrix for 5-MTHF fortification.

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Authors and Affiliations

  1. Abbott Laboratories, Abbott Nutrition Division, 3300 Stelzer Road, Columbus, OH, 43219, USA

    Paul W. Johns, Jeffrey H. Baxter & Megan C. Terp

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  1. Paul W. Johns
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  2. Jeffrey H. Baxter
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Correspondence to Paul W. Johns.

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Paul W. Johns declares that he has no conflict of interest. Jeffrey H. Baxter declares that he has no conflict of interest. Megan C. Terp declares that she has no conflict of interest.

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Johns, P.W., Baxter, J.H. & Terp, M.C. Verification of 5-Methyltetrahydrofolic Acid in Nutritional Products. Food Anal. Methods 10, 3255–3263 (2017). https://doi.org/10.1007/s12161-017-0898-y

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