ISO 11905-1-1997 PDF

Full title and description

Water quality — Determination of nitrogen — Part 1: Method using oxidative digestion with peroxodisulfate. This international standard specifies a laboratory method for converting ammonia, ammonium, nitrite and many organic nitrogen compounds to nitrate by oxidative digestion with peroxodisulfate, followed by measurement of the resulting nitrate to report total nitrogen as mg N/L.

Abstract

ISO 11905-1:1997 defines a reference analytical procedure for the determination of nitrogen in water. The method uses alkaline peroxodisulfate oxidation under controlled temperature/pressure to convert oxidisable nitrogen species to nitrate; the digest is then analysed (typically by reduction to nitrite and colorimetric measurement) to determine nitrogen concentration. It is intended for natural waters, seawater, drinking waters, surface waters and many sewage effluents and includes performance criteria, quality controls and safety notes for reagents and apparatus.

General information

• Status: Published; International Standard (confirmed).
• Publication date: May 1997 (edition 1, published 15 May 1997).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 13.060.50 — Examination of water for chemical substances.
• Edition / version: Edition 1 (1997).
• Number of pages: 13 pages (official ISO bibliographic record).

Scope

The standard applies to the determination of nitrogen present as free ammonia, ammonium, nitrite, nitrate and organic nitrogen compounds that are convertible to nitrate under the specified oxidative conditions. Dissolved molecular nitrogen (N2) is not measured. The procedure is applicable to a wide range of aqueous matrices including fresh water, seawater, drinking water, surface water and many sewage effluents, subject to sample pre‑treatment or dilution where required by matrix or organic load.

Key topics and requirements

• Principle: alkaline potassium peroxodisulfate oxidative digestion (heat/pressure) converts oxidisable nitrogen species to nitrate for subsequent quantitative determination.
• Post‑digestion measurement: nitrate in the digest is typically reduced to nitrite (e.g., copperized-cadmium column) and measured colorimetrically (azo dye) or by equivalent validated nitrate determination techniques.
• Range and sensitivity: method performance given for typical test portions (detection limits and upper range depend on test portion volume and nitrate measurement technique); example lower limits often around the low µg N/L region for optimized systems.
• Sample constraints and preparation: guidance on sample aliquot size, required dilutions when COD/TOC are high, and limits for test‑portion oxidant demand to ensure complete oxidation.
• Reagents and apparatus: specifies reagent grades, preparation of oxidant and buffer solutions, digestion vessels (PTFE/autoclave), heating/pressure conditions, and analytical instrumentation.
• Quality assurance: blank tests, calibration, verification of organic‑N recovery, precision data and performance criteria; references to related ISO methods for laboratory quality and precision assessment.
• Safety and waste: notes on handling corrosive reagents and the use and disposal of cadmium-containing reduction columns — appropriate PPE and waste controls are required.

Typical use and users

Environmental and water‑testing laboratories, regulatory and compliance monitoring authorities, wastewater treatment facilities, research laboratories and consultancy organizations use this method as a standardized laboratory procedure for reporting nitrogen concentrations in diverse water matrices. It is used where a validated reference procedure for oxidisable nitrogen species is required.

Related standards

ISO 11905 is a multi‑part subject grouping. Part 1 is the oxidative digestion/peroxodisulfate method (ISO 11905-1:1997). A related technical report, ISO/TR 11905-2:1997, covered bound nitrogen determination by combustion/chemiluminescence but has been withdrawn. EN/European adoption exists as EN ISO 11905-1:1998. The standard also references other ISO documents relevant to laboratory water quality and precision assessment (for example ISO 3696, ISO 5725‑2 and ISO 2854 in its normative/referential material).

Keywords

nitrogen, total nitrogen, water quality, oxidative digestion, peroxodisulfate, nitrate, ammonia, nitrite, analytical method, ISO 11905

FAQ

Q: What is this standard?

A: ISO 11905-1:1997 is an international standard that specifies a laboratory method for the determination of nitrogen in water by oxidative digestion with peroxodisulfate followed by nitrate measurement.

Q: What does it cover?

A: It covers the conversion of oxidisable nitrogen species (ammonia/ammonium, nitrite and many organic nitrogen compounds) to nitrate using peroxodisulfate oxidation, the subsequent measurement of nitrate to report nitrogen as mg N/L, and accompanying performance, QC and safety requirements. Dissolved N2 is excluded.

Q: Who typically uses it?

A: Accredited environmental testing laboratories, regulatory monitoring bodies, wastewater and water utility laboratories, and researchers who require a standardized, validated method for total oxidisable nitrogen in aqueous samples.

Q: Is it current or superseded?

A: ISO 11905-1:1997 remains the published edition and was last reviewed and confirmed by ISO in 2024, so the 1997 edition is currently confirmed as the valid text. (Users should check national adoption records or ISO for any later amendments or replacements before purchase or citation.)

Q: Is it part of a series?

A: Yes — the subject of nitrogen determination by ISO included more than one document: ISO 11905-1:1997 (this method) and ISO/TR 11905-2:1997 (combustion/chemiluminescence for bound nitrogen), the latter of which has been withdrawn. Users should consult ISO and national bodies for related or replacement documents.

Q: What are the key keywords?

A: nitrogen, total nitrogen, peroxodisulfate digestion, oxidative digestion, nitrate measurement, water quality, ISO 11905, environmental analysis.