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ISO 29943-2:2017 — Guidance on Measurement of Nitrosamines from Condoms — Part 2: MTBE Extraction
Alternative MTBE extraction method for N-nitrosamine measurement in condoms | Organic solvent extraction | Quality control applications
1. Alternative Extraction Using MTBE
ISO 29943-2:2017 specifies an alternative method for measuring N-nitrosamines released from condoms using methyl tert-butyl ether (MTBE) as the extraction solvent. Unlike the aqueous artificial sweat method in Part 1, MTBE extraction targets the total extractable nitrosamine content rather than physiologically-relevant migration. This approach is particularly useful for raw material qualification and process optimization, where the goal is to measure the maximum potential nitrosamine burden.
Note: MTBE extraction typically yields higher nitrosamine values than artificial sweat extraction because the organic solvent penetrates the latex matrix more effectively, extracting nitrosamines that may not migrate under aqueous physiological conditions.
2. Method Comparison and Applications
The choice between artificial sweat extraction (ISO 29943-1) and MTBE extraction (ISO 29943-2) depends on the testing objective. For regulatory compliance and CE marking, artificial sweat extraction is the preferred method as it simulates in-use conditions. For quality control during manufacturing, MTBE extraction provides a more conservative estimate of nitrosamine content and better sensitivity for detecting process changes.
| Parameter | ISO 29943-1 (Artificial Sweat) | ISO 29943-2 (MTBE) |
|---|---|---|
| Extraction solvent | Artificial sweat (aqueous) | Methyl tert-butyl ether |
| Physiological relevance | High — simulates use conditions | Low — measures total content |
| Extraction efficiency | Moderate (surface migration) | High (matrix penetration) |
| Typical application | Regulatory compliance | QC / process development |
| Solvent disposal | Aqueous waste | Organic solvent waste |
Safety Precaution: MTBE is highly flammable (flash point −10 °C) and can form explosive peroxides upon prolonged storage. All extractions must be performed in a fume hood with explosion-proof equipment. Peroxide formation should be tested weekly for MTBE stocks older than 3 months.
3. Practical Implementation Guidance
The MTBE extraction procedure requires careful temperature control because MTBE has a boiling point of 55 °C. Extraction at 40 ± 1 °C must be conducted in sealed vessels to prevent solvent loss. The sample-to-solvent ratio should be optimized to ensure complete coverage while maintaining analytical sensitivity. After extraction, the MTBE phase is separated, concentrated under a gentle nitrogen stream, and reconstituted in an appropriate solvent for GC-TEA or GC-MS/MS analysis.
4. Frequently Asked Questions
Q1: Can results from the two methods be compared directly?
A: No. MTBE extraction typically gives 2-5 times higher values. Always specify the method when reporting results.
A: No. MTBE extraction typically gives 2-5 times higher values. Always specify the method when reporting results.
Q2: What are the alternatives to MTBE?
A: Some laboratories have validated dichloromethane or ethyl acetate as alternative extraction solvents. However, any alternative must be cross-validated against the reference MTBE method.
A: Some laboratories have validated dichloromethane or ethyl acetate as alternative extraction solvents. However, any alternative must be cross-validated against the reference MTBE method.
Q3: Is MTBE extraction suitable for all condom types?
A: Yes, but polyurethane condoms may require longer extraction times (up to 6 hours) due to their different polymer structure and lower solvent swelling ratio.
A: Yes, but polyurethane condoms may require longer extraction times (up to 6 hours) due to their different polymer structure and lower solvent swelling ratio.
