Overview
EN ISO 10390:2022 / ISO 10390:2021 defines a routine instrumental method for the determination of pH in soils, treated biowaste and sludge. The standard covers measurements in the range pH 2 to pH 12 using a glass electrode and a 1:5 (volume/volume) suspension of sample in either water (pH in H2O), 1 mol·L⁻¹ KCl (pH in KCl) or 0.01 mol·L⁻¹ CaCl2 (pH in CaCl2). It is applicable to all types of air-dried soil and treated biowaste samples and includes provisions for sludges and field-moist samples.
Key topics and requirements
- Sample preparation
- Use air-dried (or dried ≤40 °C) samples sieved to 2 mm; treated biowaste may be measured without pretreatment (larger test portions apply).
- Typical test portion: at least 5 mL (use known-capacity spoon); for untreated treated biowaste, larger volumes (e.g., 60 mL into 300 mL liquid) are specified.
- Suspension ratio and conditioning
- Prepare a 1:5 volume suspension (sample:solution).
- Shake/mix for 60 min ± 10 min, then allow to stand 1–3 h; avoid air ingress during equilibration.
- Measurement
- Use a pH-meter with temperature control and slope adjustment, and a suitable glass (or combined) electrode.
- For pH > 10 use an electrode designed for that range or include a pH 12 buffer during calibration.
- Reagents and calibration
- Water with low conductivity, KCl (1 mol·L⁻¹), CaCl2 (0.01 mol·L⁻¹).
- Use appropriate buffer solutions (examples: pH 4.00, 6.88, 9.22 at 20 °C) for calibration at 20 °C ± 2 °C; follow manufacturer instructions for meter/electrode care.
- Validation and reporting
- The standard includes precision information (repeatability/reproducibility data in Annex A) and specifies required test-report elements.
Applications and users
- Environmental and soil testing laboratories performing routine soil pH determination.
- Waste management and composting facilities characterizing treated biowaste and sludge.
- Agricultural advisers, agronomists, researchers and regulatory bodies assessing soil chemistry, land application suitability and compliance.
- Useful for quality control, agronomic recommendations, environmental monitoring and compliance with national/regional regulations.
Related standards
- ISO 11464 (soil sample pretreatment)
- EN 16179, EN 15002 (biowaste/sludge pretreatment and sampling)
- EN 15933:2012 (superseded by EN ISO 10390:2022)
Keywords: EN ISO 10390:2022, ISO 10390:2021, soil pH determination, treated biowaste pH, sludge pH, 1:5 suspension, pH in KCl, pH in CaCl2, glass electrode, pH-meter calibration.
