Precautions in testing formaldehyde content of textiles
Jul 23, 2019
Precautions in testing formaldehyde content of textiles
Points to note in textile formaldehyde testing:
1, sample storage
In the process of taking a representative sample, the sample should be sealed in time, otherwise the accuracy of the test results will be affected.
Samples should be randomly selected from each batch of products and immediately sealed for specification. Otherwise, the test data will be degraded due to formaldehyde volatilization, which will affect the representativeness of formaldehyde content determination.
2, the choice of sample test number
If the formaldehyde content in the sample is too low, the number of samples should be increased from 1g to 2.5g to ensure the accuracy of the test results. This method is in accordance with the provisions of GB/T2912.1 "Determination of formaldehyde in textiles Part 1: Freely hydrolyzed formaldehyde (water extraction method)".
Using different sample sizes, using the same test method will lead to different conclusions. Because according to GB/T2912.1 "Determination of textile formaldehyde Part 1: freely hydrolyzed formaldehyde (water extraction method)", the measurement range is between 20-3500mg/kg, considering that the formaldehyde content is too low The linear relationship between absorbance and formaldehyde content may deviate from Beer's law, and the test conclusion for selecting a 2.5g sample is reasonable.
3, color development
The extract should first be sucked into the test tube prior to acetylacetone (Nessler's reagent) to prevent oily acetylacetone from adhering to the tube wall to affect the reading of absorbance.
The effective period of acetylacetone and the preparation process have an impact on the formaldehyde test, and strict management must be carried out to ensure the use within the effective period.
It should be noted that after the preparation of the acetylacetone reagent, it must be ensured that it can be used after storage for 12 hours, otherwise it will affect the accuracy of the test. This is because the chemical properties of this Nessler reagent used for color development just after preparation. Not stable enough, it usually takes 12 hours to reach stability. The glass bottle used for storage should be brown to prevent the light from reacting with the reagent and affecting the color development effect.
The formaldehyde content test is a test with high technical and technical requirements, as well as the calibration of the formaldehyde stock solution before the test, the determination of the standard curve, the temperature and time of the extract extraction, the choice of the spectrophotometer and the colorimetric Matching selection of dishes; and so on. These factors have a direct impact on the test results, so the necessary attention must be taken to improve the accuracy of the test results.
