Overview
ISO 19747:2020 specifies a laboratory method for the determination of monosilicic acid (reported as silicon, Si) in nonliquid fertilizer materials and soil conditioners. The standard defines an extraction and analysis workflow that correlates well with plant uptake and is intended for nonliquid products, blends and beneficial substances. It is not applicable to liquid silicon fertilizers.
Key topics and technical requirements
- Analyte and reporting: Monosilicic acid reported as silicon (Si).
- Applicable range and sensitivity: Method applicable for Si concentrations 2 to 84 g/kg; LOD 0.6 g/kg Si, LOQ 2 g/kg Si (aligns with plant uptake relevance).
- Extraction principle: Ambient-temperature extraction using a sodium carbonate–ammonium nitrate extractant at pH 9.4.
- Detection: Manual spectrophotometric analysis using the heteropoly blue method measured at 660 nm.
- Calibration and QA: Defined blank and multi-point calibration standards, matrix spike procedure (talc-spiked sample) for recovery checks.
- Apparatus and cleaning: Strict glassware cleaning (e.g., 40 ml/L HNO3 soak for 30 min and triple rinse) to avoid silica contamination; recommendations for plastic ware and class-A glassware.
- Safety and reagents: Handling precautions for oxidizing reagents and concentrated acids; reagent storage and protection from sunlight.
- Validation and quality: Precision, statistical analysis and an international ring study (Annex A) are included to support method robustness. The standard references ISO 8157 for terminology and notes a peer-reviewed AOAC single-lab validated version.
Applications and users
ISO 19747:2020 is useful for:
- Fertilizer manufacturers-product development and quality control to quantify plant-available silicon.
- Regulators and certifiers-compliance testing and labeling of nonliquid silicon fertilizers and soil conditioners.
- Independent testing laboratories-routine analysis for commercial products and research samples.
- Agronomists and researchers-studies on silicon nutrition, plant uptake correlation and agronomic benefit assessments.
Practical uses include verifying monosilicic acid supplying capacity, informing application rates, and supporting claims about silicon bioavailability and crop benefits (stress tolerance, disease resistance, yield impacts).
Related standards
- ISO 8157 - Fertilizers and soil conditioners - Vocabulary (normative reference cited in ISO 19747:2020).
- The ISO 19747 method complements peer-reviewed and AOAC-validated extraction/analysis methods that focus on plant-available silicon.
Keywords: ISO 19747:2020, monosilicic acid, silicon (Si), fertilizers, soil conditioners, heteropoly blue, spectrophotometry, extraction method, sodium carbonate–ammonium nitrate, LOQ, LOD, plant uptake.
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