Overview
ISO 17505:2025 - Soil and waste characterization: Temperature dependent differentiation of total carbon (TOC400, ROC, TIC900) specifies a thermal-gradient method to differentiate carbon fractions in dry solid samples (sediment, soils, urban soils, tailings, wastes such as incineration ash, foundry sand and construction waste). The method is based on dry combustion/decomposition to CO2 across a programmed temperature range (approximately 150 °C to 900 °C) to quantify:
- TOC400 - organic carbon released up to 400 °C
- ROC - residual oxidizable carbon (e.g., lignite, hard coal, charcoal, black carbon/soot), measured according to temperature plateaus (600 °C or 900 °C depending on method)
- TIC900 - inorganic carbon released up to 900 °C (including TIC after acid stripping)
The standard applies to samples containing more than 1 g/kg (0.1 % C) per carbon type in the test portion and supports CO2 detection by infrared or other CO2-sensitive sensors.
Key Topics and Requirements
- Principle: Temperature-gradient thermal oxidation/decomposition with switching between oxidizing and non-oxidizing carrier gases for selective carbon release.
- Two procedural variants:
- Method A: oxidative measurement sequence (TOC400 → ROC600 → TIC900A)
- Method B: mixed oxidative/non-oxidative sequence (used for ROC900 and TIC900B distinctions)
- Temperature control: defined plateaus (±20 °C) and minimum holding times for peak integration.
- Interferences addressed: carbides, sulfur and nitrogen compounds, carbonates (which can decompose across ranges), catalytic substances, premature releases/deflagrations, and peak-baseline issues.
- Quality elements: sample pretreatment, calibration, system control standards, reagents, apparatus specifications, measurement, evaluation, expression of results and reporting. Annex A covers performance characteristics; Annex B covers cooling procedures for method B.
Practical Applications and Who Uses It
ISO 17505:2025 is used for environmental assessment and materials characterization where a differentiated understanding of carbon forms is needed:
- Environmental and commercial analytical laboratories conducting soil and waste carbon analysis
- Landfill operators and waste managers assessing disposal/recycling suitability and hazard potential
- Soil scientists and remediation consultants evaluating carbon stability and pyrogenic (black) carbon content
- Regulatory agencies and consultants performing compliance testing or interpreting TOC/TIC-based criteria
Differentiating TOC400, ROC and TIC900 helps distinguish labile organic carbon from persistent pyrogenic carbon and inorganic carbon-useful for risk assessment, carbon accounting and management decisions.
Related Standards
- ISO 10694 / EN 15936 - Methods for TOC/TIC by acid stripping (TIC after acid addition referenced)
- EN 16179, EN 15002, ISO 11464 - Sample pretreatment and preparation standards referenced in ISO 17505:2025
Keywords: ISO 17505:2025, TOC400, ROC, TIC900, soil and waste characterization, temperature dependent differentiation, thermal oxidation, CO2 detection, carbon fractions, environmental laboratory.
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