Overview
ISO 21438-1:2022 - "Workplace atmospheres - Determination of inorganic acids by ion chromatography - Part 1: Non-volatile acids (sulfuric acid and phosphoric acid)" specifies a validated method to determine the time-weighted average mass concentration of sulfuric and phosphoric acids in workplace air by ion chromatography with conductivity detection. The standard applies to personal (worker) and static (area) sampling of airborne particles (as defined in ISO 7708). It does not cover sulfur trioxide and does not distinguish acids from their corresponding salts or between phosphoric acid and diphosphorus pentoxide when both are present.
Key topics and technical requirements
- Analytical principle: Ion chromatography (IC) separation of anions with conductivity detection to quantify sulfate and phosphate.
- Scope of sampling: Designed for particulate (non-volatile) acid measurement - supports both personal sampling and area sampling.
- Sampler and filter handling: Guidance on sampler selection, filter types and preparation, loading, flow-rate setting, field blanks, sample transport and storage to maintain sample integrity.
- Laboratory procedure: Reagent preparation, dissolution/extraction of filter samples, calibration solution preparation, and instrumental analysis protocols.
- Quality control (QC): Reagent and laboratory blanks, quality control solutions, use of certified reference materials, and participation in external quality assessment schemes.
- Performance metrics: Estimation of instrumental detection limits, method detection/quantification limits, bias, precision and measurement uncertainty; evaluation of analytical range and upper limits.
- Interferences & limitations: Notes on sampling/analytical interferences and the method’s inability to differentiate acids from salts or phosphoric anhydride where co-presence occurs.
- Reporting: Requirements for test records and laboratory reports, including expression of results and uncertainty reporting.
- Environmental corrections: Temperature and pressure correction guidance (informative annex).
Practical applications and users
ISO 21438-1:2022 is intended for:
- Industrial hygienists and occupational health professionals monitoring worker exposure to sulfuric and phosphoric acids.
- Analytical laboratories performing workplace air monitoring using ion chromatography.
- Employers and safety managers in industries that use or produce sulfuric/phosphoric acid compounds (e.g., metal finishing, battery manufacturing, fertilizer production, chemical processing).
- Regulatory and enforcement agencies setting or evaluating occupational exposure compliance.
This standard helps ensure consistent, reproducible air monitoring, supports exposure assessment, and aids evaluation of control measures in workplaces where particulate inorganic acids are present.
Related standards
- ISO 7708 (particle size fraction definitions for health-related sampling)
- ISO 18158 (workplace air terminology)
- ISO 21832 / EN 13205 (sampler and method performance evaluation)
- Other ISO methods cited for laboratory apparatus and water quality (e.g., ISO 3696)
Keywords: ISO 21438-1:2022, workplace atmospheres, ion chromatography, sulfuric acid, phosphoric acid, air monitoring, personal sampling, occupational exposure, particle sampling, conductivity detection.