Overview
ISO 20635:2018 specifies a validated analytical method for the determination of vitamin C (L‑ascorbic acid) in infant formula and adult nutritionals using (ultra) high performance liquid chromatography with ultraviolet detection - (U)HPLC‑UV. The method covers powders, ready‑to‑feed liquids and liquid concentrates, with an application range from 2.5 mg/100 g (limit of quantification) up to 50 mg/100 g expressed in the product as consumed. The procedure can distinguish L‑ascorbic acid from D‑ascorbic acid (isoascorbic/erythorbic acid).
Key topics and technical requirements
- Scope & principle: Extraction of vitamin C using trichloroacetic acid (TCA) in the presence of tris[2‑carboxyethyl]phosphine (TCEP) to reduce and protect ascorbic acid from oxidation, followed by separation on a C‑column with ion‑pairing (decylamine) in a sodium acetate buffer and UV detection at 265 nm.
- Sample types: Powder reconstitutions, ready‑to‑feed liquids and concentrates; starch‑containing samples may require α‑amylase pretreatment.
- Reagents & mobile phase: Key reagents include ascorbic acid standards, TCA, TCEP, sodium acetate buffer (pH 5.4), decylamine and acetonitrile. Mobile phase formulations differ for UHPLC and HPLC (noted in the standard).
- Chromatographic conditions: Separate sets of conditions for UHPLC (shorter run time, smaller column/particles) and HPLC (longer run, larger column). Typical detection: UV at 265 nm.
- Quality control: System suitability tests, calibration with multi‑point standards, filtration and membrane handling, and validated precision (repeatability and reproducibility) data are specified.
- Performance: Defined limit of quantification and validated linear range; instructions for sample preparation, extraction, filtration and calculation.
Applications and users
Who benefits from ISO 20635:2018:
- Food and beverage analytical laboratories performing vitamin C assays in infant formula and adult nutritionals.
- Infant formula and clinical nutrition manufacturers for in‑house quality control and formulation verification.
- Regulatory authorities and third‑party testing bodies assessing compliance with nutrient labeling and infant nutrition standards.
- R&D teams developing fortified formulas and stability studies (to monitor vitamin C degradation).
Practical uses:
- Routine QC testing of production batches.
- Stability and shelf‑life studies for vitamin C retention.
- Regulatory compliance testing and product release.
Related standards
- AOAC Official Method 2012.22 - method equivalent to ISO 20635:2018 (Ultra‑Performance Liquid Chromatography with UV detection for vitamin C in infant formula).
- ISO/TC 34 (Food products) guidance for laboratory and sampling practices may be relevant when implementing ISO 20635.
Keywords: ISO 20635:2018, vitamin C determination, (U)HPLC‑UV, infant formula, adult nutritionals, L‑ascorbic acid, UHPLC, HPLC, chromatography, TCEP, TCA.
Open preview (PDF)Infant formula and adult nutritionals — Determination of vitamin C by (ultra) high performance liquid chromatography with ultraviolet detection ((U)HPLC-UV)
