ISO 20635:2018

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.