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D5712-15 – Standard Test Method Technical Guide
🧪 Test Method Scope
ASTM D5712-15 defines a standardized procedure for the analysis of total aqueous extractable protein in natural rubber, latex, and elastomeric products. Water-soluble proteins are extracted in a buffer solution, precipitated to concentrate them and separate them from interfering substances, redissolved, and quantified using the colorimetric Modified Lowry method against an ovalbumin standard. The measurement range is based on the limit of detection and quantitation, recorded in micrograms per dm² of the test specimen.
💡 Alternative Methods for QC
While the Modified Lowry method is the reference standard, other validated methods for leachable protein analysis may be used for routine quality control, provided they have been thoroughly validated and a strong correlation established against this specific test method (§1.5).
While the Modified Lowry method is the reference standard, other validated methods for leachable protein analysis may be used for routine quality control, provided they have been thoroughly validated and a strong correlation established against this specific test method (§1.5).
⚙️ Analytical Procedure and Specifications
The extraction, calibration, and measurement steps are tightly controlled for accuracy and industrial compatibility. The dilution factor (F) is critical: it represents the ratio of the volume of NaOH used to redissolve the test specimen extract to the volume of NaOH used for the ovalbumin standards. Maintaining a ratio of one is essential for direct comparison against the calibration curve.
| 🟦 Parameter | 📏 Value / Specification |
|---|---|
| Analytical Method | Modified Lowry Colorimetric Assay |
| Protein Standard | Ovalbumin |
| Absorbance Range | 0.01 to 1.5 AU |
| Measurement Wavelength | 600 to 750 nm |
| Reporting Unit | µg per dm² of test specimen |
⚠️ Interferences and Application Limits
The standard includes a precipitation step specifically to minimize the effects of water-soluble interfering substances from the extraction buffer. However, a critical limitation is explicitly stated in §1.6: this test method has not been validated for use with lubricated products such as condoms. The interaction of commonly marketed lubricants with the Modified Lowry assay has not been determined by an ASTM Interlaboratory Study (ILS).
🚨 Not Validated for Lubricated Condoms
ASTM D5712-15 (§1.6) explicitly states that the method has not been validated for lubricated condoms. The degree to which different lubricants interfere with the assay is unknown. Testing of such products must be carefully qualified against this limitation.
ASTM D5712-15 (§1.6) explicitly states that the method has not been validated for lubricated condoms. The degree to which different lubricants interfere with the assay is unknown. Testing of such products must be carefully qualified against this limitation.
The following referenced standards support the product framework for this test method.
| 📌 Designation | 🎯 Application |
|---|---|
| ASTM D3577 | Specification for Rubber Surgical Gloves |
| ASTM D3578 | Specification for Rubber Examination Gloves |
| ASTM D4483 | Practice for Evaluating Precision for Test Method Standards |
📐 Concentration Range
The recommended analyte concentration range produces an absorbance measurement between 0.01 and 1.5 units at 600 to 750 nm (3.1.4).
The recommended analyte concentration range produces an absorbance measurement between 0.01 and 1.5 units at 600 to 750 nm (3.1.4).
❓ Frequently Asked Questions
🔍 What products can be tested with ASTM D5712-15?
The standard is designed for total aqueous extractable protein analysis in natural rubber (NR) latex and elastomeric products. Per §1.6, lubricated condoms have not been validated for this method.
The standard is designed for total aqueous extractable protein analysis in natural rubber (NR) latex and elastomeric products. Per §1.6, lubricated condoms have not been validated for this method.
💡 How does the Modified Lowry method quantify protein?
It is a colorimetric method where extracted proteins are chemically treated to produce a color change. The absorbance is measured at a wavelength between 600-750 nm and compared against an ovalbumin calibration curve.
It is a colorimetric method where extracted proteins are chemically treated to produce a color change. The absorbance is measured at a wavelength between 600-750 nm and compared against an ovalbumin calibration curve.
⚡ How are measurement interferences minimized?
After the initial buffer extraction, the proteins are acid-precipitated. This step physically separates the target proteins from other water-soluble substances that could interfere with the Lowry color development and quantitation.
After the initial buffer extraction, the proteins are acid-precipitated. This step physically separates the target proteins from other water-soluble substances that could interfere with the Lowry color development and quantitation.
📌 What is the dilution factor (F) in Section 3.1.5?
The dilution factor is the ratio of the NaOH volume used to redissolve the test specimen extract to the NaOH volume used for the standard ovalbumin proteins. A ratio of one indicates a direct volume match for accurate curve comparison.
The dilution factor is the ratio of the NaOH volume used to redissolve the test specimen extract to the NaOH volume used for the standard ovalbumin proteins. A ratio of one indicates a direct volume match for accurate curve comparison.