Overview
ISO 22887:2020 specifies a laboratory method for the determination of total sulfur (S) in fertilizers and soil conditioners by high‑temperature combustion. The procedure converts sulfur species to SO2 at temperatures above 1 100 °C and measures SO2 using either thermal conductivity detection (TCD) or single‑range infrared (IR) detection. The standard covers both solid and liquid fertilizers and raw inputs across a wide concentration range (0.1 % to 97 % w/w).
Key topics and requirements
- Principle: Combustion at >1 100 °C with oxygen converts S to SO2; detection is by TCD (multi‑element) or SO2‑specific IR.
- Apparatus types:
- Apparatus A: Combustion + TCD (helium or argon carrier). Supports multi‑element analysis (C, H, N) using adsorption/desorption separation columns.
- Apparatus B: Combustion + SO2 infrared detector (oxygen carrier) for sulfur‑only analysis; gas stream drying required.
- Calibration & daily checks: Use a minimum of five calibration points spanning expected S ranges; recommended standards include sulfanilamide, ammonium/sodium sulfate, or sublimed sulfur (≥99 %). Monitor daily factor/drift; if drift correction exceeds 0.9–1.1, perform maintenance.
- Sample preparation: Typical test‑portion sulfur mass within calibration range (commonly 20–100 mg). Liquids are sealed in tin capsules or absorbed onto WO3 powder; solids are finely ground and pelletized with WO3 combustion aid (~10:1 ratio).
- Reagents & consumables: High‑purity gases (He/Ar ≥99.995 %, O2 ≥99.5 %), tungsten(VI) oxide (WO3) catalyst/additive, copper/copper oxide wires, desiccants, tin foils/capsules.
- Safety & quality control: Cautions about hot instrument components and burn risk; run blanks, verify calibration daily, and follow manufacturer instructions for instrument settings and maintenance.
Applications and users
ISO 22887:2020 is designed for:
- Fertilizer manufacturers and quality control laboratories performing routine total sulfur analysis.
- Independent testing and accreditation labs validating product specifications and regulatory compliance.
- Instrument manufacturers and service engineers configuring and maintaining combustion analyzers.
- Regulatory bodies and standards committees that require consistent, reproducible sulfur measurement methods.
Benefits include faster, modern elemental analysis compared with older wet‑chemistry techniques (which can be time‑consuming and use hazardous reagents), with options for multi‑element measurement where required.
Related standards
- ISO 8157 - Fertilizers and soil conditioners: Vocabulary (normative reference used by ISO 22887).
Keywords: ISO 22887:2020, total sulfur, fertilizers, high temperature combustion, SO2 detection, TCD, infrared detection, combustion analyzer, calibration, quality control.
