Overview
ISO 6868:2026, titled Workplace air - Quantitative determination of quartz and cristobalite in bulk materials by X-ray powder diffraction methods, is an international standard developed by ISO. It specifies standardized procedures for the quantitative measurement of crystalline silica (CS) major polymorphs, specifically quartz and cristobalite, in bulk materials using X-ray powder diffraction (XRPD) techniques.
The document defines three primary analytical methods and provides guidance on laboratory practices, specimen preparation, and equipment requirements. It is particularly relevant for laboratories conducting routine workplace air quality testing and for organizations concerned with occupational exposure to crystalline silica, a recognized health hazard in many industries.
Key Topics
- Crystalline Silica Quantification: The standard focuses on measuring the mass percentage of quartz and cristobalite, the two most common and hazardous crystalline silica polymorphs, in various bulk materials.
- X-ray Powder Diffraction (XRPD): Utilizes XRPD, specifically with Bragg-Brentano geometry, to analyze loose powder specimens with a median grain size between 1 μm and 10 μm.
- Sample Types and Preparation: Only loose powders are suitable; block specimens are excluded. Detailed procedures are provided for specimen crushing, grinding, drying, and mounting.
- Analytical Methods:
- External Standard Method: Comparison of sample response with certified reference materials.
- Internal Standard Method: Addition of a known phase not present in the sample to aid quantification.
- Spiking/Standard Addition Method: Addition of known quantities of quartz or cristobalite to samples, useful for low-content matrices.
- Instrumentation: Requirements for diffractometer configuration, specimen holders, microbalances, and preparation equipment such as mills, ovens, and filtration assemblies.
- Calibration and Reference Materials: Use of certified quartz and cristobalite standards, including guidance on choosing internal standards.
- Performance Characteristics: Discussion of detection limits, measurement uncertainty, and method equivalency.
Applications
The practical applications of ISO 6868:2026 span several key areas where crystalline silica exposure must be assessed or monitored:
- Occupational Health and Safety: Enables accurate CS quantification in materials encountered in mining, construction, manufacturing, and other industries where dust exposure poses health risks.
- Regulatory Compliance: Supports compliance with workplace air quality regulations and helps organizations demonstrate adherence to occupational exposure limits for crystalline silica.
- Material Characterization and Risk Assessment: Facilitates risk analysis by determining CS content in raw materials, intermediate products, and waste, especially when materials undergo processes like drilling, crushing, or grinding.
- Chemical Classification and Labelling: Assists in classifying bulk materials and mixtures under regulations such as the Globally Harmonized System (GHS) for chemical labeling.
- Laboratory Quality Assurance: Provides laboratories with standardized analytical protocols and reporting requirements to ensure consistency and reliability in routine CS measurement.
Related Standards
To ensure robust and reliable workplace air and material testing, ISO 6868:2026 should be used in conjunction with related standards, such as:
- ISO 14488 – Particulate materials - Sampling and sample splitting for the determination of particulate properties
- ISO 18158 – Workplace air - Terminology
- ISO 7708 – Air quality - Particle size fraction definitions for health-related sampling
These documents provide complementary definitions, sampling methods, and terminology essential to successful implementation of quartz and cristobalite measurement methods outlined in ISO 6868:2026.
Keywords: ISO 6868:2026, crystalline silica, quartz, cristobalite, X-ray powder diffraction, XRPD, workplace air quality, occupational exposure, Bragg-Brentano geometry, bulk materials, silica monitoring, laboratory standard, sample preparation, air quality standards.
