EN 13405:2002

Overview

EN 13405:2002 is a CEN European Standard that specifies a validated analytical procedure for the determination of dialkyl‑tetralins (DAT) - chemically 1,4‑dialkyl‑2,3‑dihydro‑naphthalene - in linear alkylbenzene (LAB). The method covers mass fractions from 0.5 % to 10 % and is targeted at laboratories performing quality control and compositional analysis of LAB used in surfactant manufacture. The technique uses high performance liquid chromatography (HPLC) with a normal‑phase silica column and ultraviolet detection.

Key topics and technical requirements

• Analyte and scope: Determination of DAT in LAB between 0.5–10 % (mass fraction).
• Analytical principle: Isocratic HPLC on a micro‑particulate silica stationary phase using 2,2,4‑trimethylpentane (iso‑octane) as mobile phase and UV detection at 254 nm.
• Calibration approach: A “modified” external standard technique - tetrahydronaphthalene (THN) is used as the external standard and DAT is assumed to have the same molar response as THN.
• Chromatography conditions (specified in the standard):
  • Column: normal‑phase silica, 250 mm × 4 mm (micro‑particulate).
  • Flow rate: 0.5 mL/min (one column) or 1.0 mL/min (two columns in series).
  • Injection volume: 20 µL; isocratic run time: 30 min.
  • Sample prep: dissolve LAB in 2,2,4‑trimethylpentane (10 g/L), filter (0.5 µm).
• Calculation: DAT mass fraction computed from peak areas, taking into account THN calibration concentration and the molar mass ratio (DAT/THN). Results reported to one decimal place.
• Precision: Repeatability and reproducibility data from interlaboratory tests are provided (e.g., repeatability ≤ 0.1 % for mass fractions up to 2 %; reproducibility limits up to 0.8 % at higher concentrations).

Applications and users

• Quality control laboratories in petrochemical and surfactant manufacturing - ensure LAB feedstocks meet impurity specifications.
• Analytical chemists performing HPLC-based purity or impurity profiling of LAB.
• Raw material suppliers and formulators of anionic surfactants where DAT impurities can affect product performance or regulatory compliance.
• Regulatory and compliance labs needing a standardized method for reporting DAT content in commercial LAB batches.

Practical benefits include reproducible quantification of DAT impurities using readily available HPLC equipment and a clear precision profile for result interpretation.

Related standards and references

• EN ISO 3696:1995 - Water for analytical laboratory use (referred for reagent water quality).
• Annex A of EN 13405:2002 references the UOP Method 673‑88 for determining LAB carbon number distribution by gas chromatography (useful for average molar mass calculations).
• Published by CEN (European Committee for Standardization); national adoption information is provided in the standard.

Keywords: EN 13405, dialkyl‑tetralins, DAT, linear alkylbenzene, LAB, HPLC, surface active agents, tetrahydronaphthalene, THN, analytical method, surfactant QC.