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ISO 17226-2 Chemical determination of formaldehyde content in leather (using colorimetric analysis)
Category:
Formaldehyde Emission
ISO 17226-2 Standard Description
ISO 17226-2 Leather -Chemical determination of formaldehyde content-Part 2: Method using colorimetric analysis
ISO 17226-2 Standard Introduction
ISO 17226-2 is an international standard that outlines the method for determining formaldehyde content in leather using colorimetric analysis. Formaldehyde is a chemical substance with irritant and potential carcinogenic properties, which can cause damage to the respiratory system, skin, and eyes with prolonged exposure. Therefore, its control in leather products is crucial. This standard applies to all types of leather and provides a simple method suitable for routine quality control and safety compliance testing.
ISO 17226-2 Scope
ISO 17226-2 applies to various types of leather products, including but not limited to leather used in footwear, clothing, furniture, and other applications.
ISO 17226-2 Testing Principle
The formaldehyde content in leather is determined through colorimetric analysis, based on the following principles:
◎Leather samples are washed under 40°C conditions with a detergent solution. The washing extract reacts with acetylacetone to form a yellow compound (3,5-diacetyl-1,4-dihydroquinoline).
◎This compound exhibits characteristic absorption at a wavelength of 412 nm. The absorbance is measured and compared with a calibration curve to determine the formaldehyde content.
ISO 17226-2 Testing Procedure
(1) Preparation and Determination of Formaldehyde Stock Solution
◎Preparation of Stock Solution: Transfer 5 mL of approximately 37% formaldehyde solution into a 1000 mL volumetric flask and dilute with water.
◎Concentration Determination: Take 10 mL of the stock solution and add 50 mL of iodine solution. Adjust the solution to a yellow color using sodium hydroxide, then react for 15 minutes. ◎After the reaction, add sulfuric acid, use starch as an indicator, and titrate the excess iodine with sodium thiosulfate. The calculation formula is as follows:
(2) Colorimetric Determination of Formaldehyde in Leather
◎Sampling and Sample Preparation: Samples should be taken according to ISO 2418, and the leather should be cut following the guidelines of ISO 4044. If the determination is based on dry weight, moisture content must be measured according to ISO 4684.
◎Extraction: Weigh (2±0.1) g of leather, add 50 mL of 0.1% detergent solution preheated to 40°C, and agitate the mixture in a 40°C water bath for (60±2) minutes. Afterward, vacuum filter and cool the filtrate.
◎Reaction with Acetylacetone: Take 5 mL of the filtrate and add 5 mL of acetylacetone solution (Solution 1). Stir at 40°C for 30 minutes. After cooling, measure the absorbance (Ep) at 412 nm. Simultaneously, measure the initial absorbance (Ee) of the filtrate using Solution 2.
◎Reagent Blank Test for Formaldehyde: Measure the absorbance of the detergent and Solution 1 blank. For a 20 mm cuvette, it should be ≤0.025 (for a 50 mm cuvette ≤0.063, and for a 40 mm cuvette ≤0.050).
◎Interference Testing: Mix the filtrate with dimethyl ketone solution, heat the mixture, and then react with Solution 1. The absorbance should be <0.05 (for a 20 mm cuvette). If higher, use the ISO 17226-1 method.
◎Calibration Curve Construction: Prepare formaldehyde standard solutions in the range of 0.2-3.0 μg/ml. React with Solution 1 and measure the absorbance. Plot the calibration curve with concentration as the x-axis and absorbance as the y-axis.
ISO 17226-2 Determination Criteria
Calculate the formaldehyde content. Finally, add a known amount of formaldehyde standard solution to the filtrate. The recovery rate should be between 80% and 120%. If it falls outside this range, repeat the analysis.
SATISFY provides a one-stop service for formaldehyde emission testing, including initial evaluation, preparation and submission of relevant documents, full follow-up throughout the testing process, as well as report interpretation, data analysis, and corrective action recommendations. For more details, please contact SATISFY customer service.
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