Overview
ISO 2915:1975 is an internationally recognized standard titled "Wool - Determination of cysteic acid content of wool hydrolysates by paper electrophoresis and colorimetry" developed by the International Organization for Standardization (ISO). This method provides a precise analytical technique for quantifying cysteic acid in wool - an important indicator of oxidation and degradation in wool fibers.
Cysteic acid, an oxidation product derived from the amino acids cystine and cysteine, is typically present in low amounts in raw wool. Its concentration increases due to photochemical weathering and chemical finishing treatments such as bleaching or chlorination. Monitoring cysteic acid content enables textile manufacturers and researchers to evaluate the severity of oxidation and degradation in wool textiles at various production stages.
Key Topics
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Scope and Applicability: The method applies to all-wool textiles in any form including loose wool, sliver, slubbing, yarn, or fabric before and after dyeing. It is also valid for wool after carbonizing and when wool content in blends is precisely known.
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Analytical Principle:
- Wool samples undergo hydrolysis to release amino acids.
- Cysteic acid is separated from other amino acids using paper electrophoresis.
- The cysteic acid-containing zone on the paper is stained using ninhydrin-cadmium reagent.
- Colorimetric measurement quantifies the cysteic acid by comparing its optical density against a cysteic acid standard.
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Sample Preparation: Removal of vegetable matter and extraction with dichloromethane ensure accurate conditions for analysis.
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Hydrolysis Methods: Two hydrolysis procedures using hydrochloric acid are described - one via reflux for 4 hours and the other in sealed tubes for 24 hours at 105°C.
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Electrophoresis Setup: Paper strips impregnated with buffer are run under low-voltage electrical current (200–1500 V) to separate cysteic acid, which migrates 4-6 cm towards the anode.
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Colorimetry: Optical density readings are taken at 500 nm wavelength, allowing quantification of cysteic acid concentration.
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Calculation and Reporting: Results are expressed as a percentage of cysteic acid content relative to the dry mass of the wool specimen, with detailed formulas and requirements for test reports.
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Accuracy and Reproducibility: The standard includes statistical data from interlaboratory trials demonstrating method precision and confidence limits, ensuring reliable and repeatable measurement outcomes.
Applications
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Quality Control in Wool Processing: By measuring cysteic acid content, manufacturers can monitor the extent of oxidative damage and the impact of finishing treatments such as bleaching or chlorination on wool fibers.
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Assessment of Wool Weathering: Textile laboratories can evaluate photochemical degradation caused by environmental exposure including sunlight and atmospheric conditions.
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Research and Development: Enables scientific investigation into wool fiber chemistry and the effects of various processing techniques on wool quality.
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Verification of Textile Blends: Provides a method to quantify wool proportion in blended textiles by monitoring cysteic acid levels specific to wool oxidation.
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Compliance and Standardization: Supports adherence to international wool testing protocols, ensuring uniformity and comparability of test results across industries and countries.
Related Standards
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ISO 2915:1975 corresponds closely with IWTO Test Method 23-70 developed by the International Wool Textile Organization, forming a foundation for standardized wool oxidation testing.
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Other ISO standards on wool and textile testing may complement this method, including those related to fiber identification, tensile properties, and chemical treatments.
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Standards governing colorimetry, electrophoresis techniques, and chemical analysis play a supporting role in ensuring accurate measurement procedures.
By implementing ISO 2915:1975, textile professionals gain a reliable and internationally accepted method to determine cysteic acid content in wool, facilitating improved product quality, durability assessment, and process optimization. Keywords: ISO 2915, wool testing, cysteic acid determination, paper electrophoresis, colorimetry, wool oxidation analysis, textile standards, wool hydrolysates, chemical analysis wool.
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