prEN 15925

Overview

The prEN 15925 standard, developed by CEN Technical Committee CEN/TC 260, specifies a precise method for the extraction of total sulfur present in various chemical forms within inorganic fertilizers. It addresses the analytical extraction of sulfur in elemental form and in compounds such as thiosulfate, sulfite, and sulfate. This standard is essential for controlling and verifying sulfur content in fertilizers, ensuring compliance with labeling requirements and quality regulations.

This document supersedes the previous EN 15925:2011 and incorporates important technical updates, including revised water quality parameters and improved procedural clarifications. prEN 15925 aligns with European regulatory frameworks, helping fertilizer manufacturers and testing laboratories maintain consistency and accuracy in elemental sulfur analysis.

Key Topics

• Scope and Applicability
  The method applies exclusively to inorganic fertilizers with declared sulfur content in multiple chemical forms: elemental sulfur, thiosulfate, sulfite, and sulfate. It defines extraction and determination protocols applicable throughout the fertilizer industry.

• Extraction Principle
  Elemental sulfur is first converted into polysulfides and thiosulfates in alkaline medium. Subsequent oxidation with hydrogen peroxide converts all sulfur forms into sulfate ions, which are then quantified using methods described in EN 15749.

• Reagents and Apparatus
  Required reagents include diluted hydrochloric acid, sodium hydroxide solution, hydrogen peroxide, and barium chloride solution of analytical grade, accompanied by distilled or demineralized water with strict conductivity limits (< 0.5 mS/m at 25 °C).
  Equipment includes electric hot plates, beakers, volumetric flasks, and filtration apparatus necessary for sample oxidation and sulfate determination.

• Procedure Overview
  The procedure involves weighing a representative sample, alkaline digestion with sodium hydroxide, oxidation with hydrogen peroxide, acidification, filtration, and sulfate measurement. Special instructions apply based on total sulfur concentration, ensuring accurate analysis for products ranging from low to high sulfur content.

• Test Reporting
  The standard mandates comprehensive reporting of results, including method reference, sample identification, sampling dates, full procedural details, and any relevant observations affecting results.

Applications

The prEN 15925 standard is vital for:

• Fertilizer Quality Control:
  Ensuring that sulfur content in inorganic fertilizers is accurately determined helps manufacturers comply with product specifications and regulatory requirements.

• Regulatory Compliance:
  Testing aligns with European fertilizer legislation, facilitating market approval and certification processes.

• Agricultural Efficiency:
  Precise sulfur analysis aids farmers and agronomists in choosing fertilizers with appropriate nutrient profiles, optimizing crop nutrition and yield.

• Research and Development:
  Laboratories developing new fertilizer formulations rely on standardized sulfur extraction methods for performance evaluation.

• International Trade:
  Harmonized analysis methods support consistent quality assessment across borders, simplifying certification and customs procedures.

Related Standards

prEN 15925 references and complements several key documents:

• EN 1482-2:
  Provides general provisions for sampling and sample preparation of fertilizers, essential for obtaining representative samples before sulfur extraction.

• EN 12944-1 and EN 12944-2:
  Define terminology related to fertilizers, ensuring uniform vocabulary in sulfur analysis and reporting.

• EN 15749:
  Specifies the determination of sulfate content using multiple analytical techniques-a critical step following sulfur extraction per prEN 15925.

This suite of standards collectively supports rigorous quality assurance and facilitates traceability and consistency in fertilizer sulfur testing.

Keywords: inorganic fertilizers, sulfur extraction, total sulfur determination, sulfur forms, fertilizer quality control, sulfur analytics, fertilizer sulfur content, prEN 15925, CEN standard, sulfur in fertilizers, fertilizer testing methods, sulfate analysis, chemical forms of sulfur