Overview
ISO 14673-3:2004 (IDF 189-3:2004) specifies a routine method for the determination of nitrate and nitrite in milk and milk products using cadmium reduction and flow injection analysis (FIA) with in-line dialysis. The standard covers sample preparation, reagents, instrumentation and calculation procedures applicable to hard, semi‑hard and soft cheeses, processed cheese, whey powder, milk powder and milk‑based infant food. Detection limits are specified as 0.5 mg NO3‑/kg (nitrate) and 1.0 mg NO2‑/kg (nitrite).
Key topics and technical requirements
- Principle: Extraction of a defatted aqueous sample, protein/fat removal by in‑line dialysis, reduction of nitrate to nitrite on a cadmium column, followed by color development (sulfanilamide + N‑1‑naphthyl ethylenediamine) and spectrophotometric detection at 540 nm with 620 nm reference.
- Reagents: Includes preparation of extraction/carrier buffer (ammonium chloride, pH 8.5), reagent solutions (sulfanilamide and N‑1‑naphthyl ethylenediamine), nitrate/nitrite stock and calibration solutions, and cadmium column regeneration solution.
- Apparatus: Flow injection analyser (FIA) with dialysis module, cadmium reduction column, homogenizer, centrifuge (defatting step), calibrated volumetric glassware and a spectrophotometric flow cell.
- Procedure elements: Sample homogenization, warm buffer extraction, centrifugation and cooling to separate fat, FIA analysis with specified flow rates, calibration using prepared standards, and calculation rules including correction of nitrate values when nitrite exceeds thresholds.
- Quality control: Checking cadmium column reducing capacity, column regeneration, and use of calibration/reference solutions are required. Precision and reporting requirements are defined in the standard.
Applications and users
ISO 14673-3:2004 is intended for:
- Dairy quality control laboratories performing routine monitoring of nitrate/nitrite in cheeses, processed cheese, milk powders, whey powder and infant foods.
- Regulatory and food safety authorities verifying compliance with nitrate/nitrite limits.
- Manufacturers of dairy and infant food products for raw material screening, process control and batch release.
- Food chemists and research labs studying contamination, shelf‑life or processing effects on nitrate/nitrite levels.
Keywords: ISO 14673-3:2004, nitrate and nitrite, milk and milk products, cadmium reduction, flow injection analysis, in-line dialysis, routine method, dairy testing, nitrate detection limit.
Related standards
- ISO 14673-1: Method using cadmium reduction and spectrometry
- ISO 14673-2: Method using segmented flow analysis (Routine method)
These complementary parts cover alternative analytical techniques for nitrate/nitrite determination in dairy matrices.
Open preview (PDF)Milk and milk products — Determination of nitrate and nitrite contents — Part 3: Method using cadmium reduction and flow injection analysis with in-line dialysis (Routine method)
