Overview
ISO 14673-2:2004 (IDF 189-2:2004) defines a routine method for the determination of nitrate and nitrite contents in milk and milk products using segmented flow analysis. The standard applies to milk, cheese, liquid and dried milk products and infant foods. It describes the analytical principle, required reagents and apparatus, sample preparation, calibration, calculation of results and reporting - intended for routine laboratory monitoring of nitrate (NO3–) and nitrite (NO2–) residues.
Key topics and requirements
- Analytical principle: test portions are suspended and dialysed into the analyser; nitrate is chemically reduced to nitrite and both analytes are quantified by spectrometric (colorimetric) detection after reaction with a diazotizing/azonaphthyl reagent.
- Segmented flow analysis (SFA): continuous-flow, segmented sampling with in-line dialysis and reduction column for routine throughput and reproducibility.
- Reduction column: a copperized cadmium column (prepared from cadmium granules) is used to convert nitrate to nitrite prior to colour development for nitrate determination.
- Reagents and standards: the standard specifies use of high‑purity water, cadmium granules, copper(II) sulfate, EDTA, phosphoric-acid based colour reagent (sulfanilamide + N‑1‑naphthylethylenediamine), and sodium nitrate/nitrite calibration solutions.
- Procedure elements: sample-specific preparation (cheese, dried products, liquid milk), column preparation and checking, calibration curves, drift checks, calculation and expression of results in mg/kg (NO3– and NO2–), and precision performance notes.
- Safety and quality: warns about hazardous materials (e.g., cadmium) and requires users to follow safety/regulatory practices; limits and precision statements are included in the standard.
Applications and users
- Who uses it: dairy testing laboratories, food safety/quality control teams, regulatory agencies, research labs analyzing milk, cheese, powdered milk, infant formulas and related products.
- Practical uses:
- Routine monitoring of nitrate and nitrite residues in dairy supply chains.
- Compliance testing for food safety standards and regulatory limits.
- Method transfer and validation for laboratories implementing segmented flow analysis for nitrate/nitrite in dairy matrices.
- Benefits: designed for routine throughput, reproducible quantification, and compatibility with common SFA instrumentation.
Related standards
- ISO 14673-1 and ISO 14673-3: other parts of the same series (cadmium reduction spectrometry and flow-injection methods).
- Normative references used in the document include ISO 648, ISO 835-1 and ISO 1042 for laboratory glassware requirements.
Keywords: ISO 14673-2:2004, segmented flow analysis, nitrate nitrite determination, milk and milk products, routine method, dairy testing, cadmium reduction, colorimetric assay.
Open preview (PDF)Milk and milk products — Determination of nitrate and nitrite contents — Part 2: Method using segmented flow analysis (Routine method)