Navigating Residue on Evaporation, OM, and E&L

In the highly regulated worlds of pharmaceutical and food packaging, the material "barrier property" is only half the story. While we often focus on what stays out (Oxygen and Moisture), it is equally critical to monitor what moves in—specifically, the migration of chemicals from the packaging material into the product.

To ensure safety, the industry relies on a hierarchy of tests: Residue on Evaporation (ROE), Overall Migration (OM), and Extractables & Leachables (E&L).

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1. Defining the Terms

While these terms can be confusing, they are essentially different "lenses" used to view the same physical phenomenon: the transfer of mass.

  • Gravimetric Testing: This is the fundamental physical method. It involves using a high-precision microbalance to measure the weight of solids left behind after a solvent has been evaporated.
  • Residue on Evaporation / Non-Volatile Residue: These terms refer to the actual "dry matter" captured. In medical standards (like ISO 8536), this is the primary way to quantify total extractables.
  • Overall Migration (The Food Framework): Governed by EN 1186, this is the regulatory requirement for food contact. It measures the total quantity of substances—toxic or not—that transfer to food simulants.
  • E&L (The Pharma Framework): A comprehensive safety study for drugs packaging. Residue on Evaporation is typically the "Tier 1" screening phase of an E&L study, used to determine the total potential load of chemicals leached out of the packaging before identifying them via mass spectrometry.

2. Standard Operating Procedure (SOP) Outline

Whether you are testing for food (EN 1186) or medical devices (ISO 8536, ISO 3826), the core gravimetric procedure remains consistent.

Step 1: Contact & Extraction

The specimen is immersed in a "simulant" (such as water, ethanol, or acetic acid) that mimics the product's chemistry. It is stored at a controlled temperature and time to simulate its shelf-life.

Step 2: Evaporation

The simulant is collected and placed into water bath and oven for evaporation to dryness under precise conditions.

Step 3: Constant Weight Analysis

The remaining "Residue on Evaporation" is dried until it reaches a constant weight. A microbalance measures the residue, often down to 0.1 mg precision.

Step 4: Calculation

The migration is calculated based on the surface area of the packaging (mg/dm^2) or the volume of the product (mg/kg).

Modern integrated testers, such as Labthink C840, automate the testing procedure to offer not only greater precision but also safer operation.



3. Safety and Regulatory Significance

The Safety Net

The primary importance of these tests is risk mitigation. If a material shows a high Residue on Evaporation, it indicates that the polymer or adhesive is unstable. In the pharmaceutical industry, this could lead to "Leachables" reacting with the drug's active ingredients, potentially causing patient toxicity or reducing the drug's efficacy.

Global Compliance

  • Food Safety: In the EU, Regulation 10/2011 sets a strict Overall Migration Limit (OML) of 10 mg/dm^2. Any material exceeding this cannot be used for food contact.
  • Medical Integrity: Under ISO 8536-4 and ISO 3826, ROE tests are mandatory for infusion sets and blood bags to ensure that plasticizers (like DEHP) and other additives do not leach into the bloodstream during transfusion.

4. Conclusion

Integrating Residue on Evaporation testing into your Performance Qualification is not just a regulatory hurdle—it is a cornerstone of quality design. By understanding the relationship between OM and E&L, manufacturers can ensure their packaging provides a safe, inert environment for the products they protect.

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