EN ISO 3696:1995 PDF

Overview

EN ISO 3696:1995 (ISO 3696:1987) – "Water for analytical laboratory use – Specification and test methods" is a CEN-adopted international standard that defines quality grades, specification limits and test methods for water used in inorganic analytical chemistry. The standard covers three laboratory water grades (Grade 1, Grade 2, Grade 3), their required physical appearance (clear, colourless) and analytical test procedures. It is explicitly not applicable to organic trace analysis, surface‑active agent determinations, or biological/medical analyses.

Key topics and requirements

• Three grades of laboratory water
  • Grade 1: Highest purity - essentially free from dissolved/colloidal ionic and organic contaminants; suitable for the most stringent inorganic analyses (including HPLC and sensitive spectrometric techniques).
  • Grade 2: Very low inorganic, organic or colloidal contaminants; suitable for atomic absorption spectrometry (AAS) and trace determinations.
  • Grade 3: Suitable for routine wet chemistry and reagent preparation.
• Physical and analytical requirements
  • Water must be a clear, colourless liquid on visual inspection.
  • pH measurement: specified for Grade 3 (range given at 25 °C); pH for high‑purity grades is not specified because measurement is unreliable at extreme purity.
  • Electrical conductivity: measured at 25 °C using temperature‑compensated conductivity cells; limits are set for each grade (freshly prepared for Grades 1 and 2).
  • Oxidizable matter: limit test by potassium permanganate titration (limits specified for Grade 2 and Grade 3).
  • Reactive silica (SiO2): colorimetric/molybdate test with specified limits for Grade 1 and Grade 2.
  • Absorbance at 254 nm: UV absorbance limits (measured with 1 cm optical path) to control organic contamination.
  • Residue after evaporation at 110 °C: gravimetric test to assess non‑volatile residues (limits specified).
• Test methods and sampling
  • Sampling requires airtight, dedicated containers; tests must be performed in dust‑free, controlled conditions.
  • Detailed procedures for pH meters, conductivity cells, spectrometers, oxidizable matter titration, silica colorimetry and residue determination are provided.

Applications and users

• Laboratories performing inorganic analytical chemistry, including trace metal determinations and atomic absorption spectrometry.
• Quality managers specifying water for instrumental analysis, reagent preparation and routine wet chemistry.
• Manufacturers and suppliers of laboratory water purification systems (distillation, deionization, reverse osmosis) who must meet grade definitions.
• Regulatory or accreditation bodies assessing laboratory compliance with water quality requirements.

Related information

• This document is the EN-adopted version of ISO 3696:1987 (EN ISO 3696:1995). Users should consult the latest editions or amendments and consider additional tests where sterility, pyrogen‑free status or specific surface tension requirements are needed.

Keywords: EN ISO 3696, ISO 3696:1987, laboratory water grades, water for analytical laboratory use, laboratory water specifications, inorganic analysis water, water test methods.