ISO 16751:2020

Overview

ISO 16751:2020 - "Soil quality - Environmental availability of non‑polar organic compounds" - specifies a laboratory extraction method to estimate the potentially bioavailable and non‑bioavailable fractions of non‑polar organic contaminants in soil and sediments. The standard uses a receiver phase (examples: Tenax® or cyclodextrin) as an “infinite sink” during a controlled water‑soil extraction to quantify the amount of contaminant that can desorb into the aqueous phase (environmental bioavailability). The method is applicable primarily to non‑polar compounds with aqueous solubility < 100 mg/L (theory extends to higher solubilities, but applicability is defined for <100 mg/L). The protocol defines a 20‑hour desorption period for determining the potential bioavailable fraction.

Key technical topics and requirements

• Scope and target analytes: Non‑polar organic compounds in soils, soil‑like materials and dredged sediments; mainly compounds with low aqueous solubility (Kow often > 3).
• Receiver phases: Two options described - cyclodextrin (complexing agent) and Tenax® (strong adsorbent). Tenax® is cited as an example and not endorsed by ISO.
• Principle: Receiver phase acts as a sink during a water‑soil extraction to capture rapidly desorbing (bioavailable) molecules; remaining contaminant is subsequently measured by a harsh/exhaustive extraction to obtain the non‑bioavailable fraction.
• Procedure elements:
  • Sample preparation (particle size