EN 15490:2007

Overview

EN 15490:2007 is a European Standard developed by CEN focused on the determination of pHe - the acid strength in ethanol intended for use as a blending component in petrol (gasoline). This standard outlines a specific procedure for measuring the pHe value, which is critical to maintaining fuel quality and ensuring compliance with European fuel regulations. The standard is applicable for ethanol blending in petrol, emphasizing analytical accuracy and sample handling to assess ethanol’s acid-base properties in a non-aqueous environment.

The method utilizes a pH meter system with a lithium chloride (LiCl) electrode in an ethanol medium to obtain the pHe value. Although primarily designed for ethanol in fuel applications, this method highlights limitations in precision and reproducibility at regulatory boundaries, with further improvements and replacement testing methods anticipated.

Key Topics

• Scope and Purpose

  • Defines a procedure to measure acid strength (pHe) in ethanol for petrol blending.
  • Essential for verifying ethanol quality and preventing the presence of strong acids or alkalis.

• Measurement Principle

  • Measurement involves a combined pH electrode filled with lithium chloride in 99% ethanol.
  • Temperature control at 22 °C ± 2 °C during testing to stabilize readings.
  • Non-aqueous measurement means pHe values are not directly comparable to aqueous pH.

• Reagents and Equipment

  • Use of high-purity reagents: 99% ethanol, buffer solutions at pH 4, 7, and 10.
  • Instruments include a precise pH meter (0.01 pH resolution), combined electrodes suited for ethanol media, magnetic stirrers, and covered beakers to minimize CO2 contamination.

• Sampling and Handling

  • Sampling procedures follow EN ISO 3170 to avoid atmospheric moisture uptake.
  • Use of sealed glass bottles and syringe sampling to maintain sample integrity.

• Calibration and Verification

  • Calibration with standard buffer solutions in ethanol to ensure accuracy.
  • Daily equipment verification using pH 7 buffer ensures measurement reliability.

• Test Methodology

  • Method involves stirring the ethanol sample, waiting for pHe stabilization (may exceed 4 minutes).
  • Minimizing exposure to atmospheric CO2 is important to reduce measurement drift.
  • Result is expressed to the nearest 0.01 pHe unit.

• Precision and Reproducibility

  • Repeatability and reproducibility figures are provided, highlighting variability sources.
  • The method has limited robustness near ethanol specification limits due to water content influences and electrode response variability.

Applications

• Fuel Quality Control

  • Monitoring acid strength in ethanol used as a gasoline blending component.
  • Ensuring ethanol meets fuel standards to prevent damage to engines and fuel systems.

• Regulatory Compliance

  • Assists laboratories and manufacturers in adhering to European ethanol fuel specifications.
  • Measurement of pHe helps detect presence/absence of harmful strong acids or alkalines in ethanol fuel.

• Research and Development

  • Provides baseline methods for ethanol acidity analysis in biofuel development.
  • Supports further innovation to improve ethanol fuel blend quality through enhanced analytical techniques.

Related Standards

• EN ISO 3170: Petroleum liquids - Manual sampling procedures applicable during ethanol sampling.
• EN ISO 3696: Water for analytical laboratory use - Ensures use of high purity water in testing processes.
• EN ISO 4259: Petroleum products - Guidelines on precision and reproducibility analysis relevant to the evaluation of pHe results.

Practical Notes

• Users must handle samples carefully to minimize contamination and moisture uptake.
• Electrode conditioning and proper calibration are critical for precise results.
• Stability of the pHe reading varies, and prolonged stirring may be necessary to attain accuracy.
• The method is recognized as insufficient for detecting some specification limits; emerging tests will address its limitations.

Keywords

EN 15490:2007, ethanol blending component, petrol blending, pHe determination, acid strength ethanol, ethanol fuel quality, fuel ethanol specifications, pHe measurement procedure, CEN standards ethanol, ethanol sampling and analysis, fuel blend acidity testing, European ethanol fuel standard.