What is the National Standard TCVN 11899-4:2017 on the desiccator method for determination of formaldehyde release in Vietnam?
- What is the National Standard TCVN 11899-4:2017 on the desiccator method for determination of formaldehyde release in Vietnam?
- Vietnam: What are the regulations on requirements for reporting the results under the National Standard TCVN 11899-4:2017
- Vietnam: What is the information included in the test report according to the National Standard TCVN 11899-4:2017?
What is the National Standard TCVN 11899-4:2017 on the desiccator method for determination of formaldehyde release in Vietnam?
At Chapter 8 of the National Standard TCVN 11899-4:2017, it specifies the determination of formaldehyde:
- Overview
The determination of formaldehyde in aqueous solutions is done using spectrophotometry with the acetylaceton method.
- Principle
The determination is based on the Hantzsch reaction, in which formaldehyde reacts with ammonium ions and acetylacetone to produce diacetyldihydrolutidine (DDL). DDL has the highest absorption at a wavelength of 412 nm. The reaction is characteristic of formaldehyde (refer to Reference [1]).
- Procedure
Using a pipette (5.10), take 25 ml of the formaldehyde solution and transfer it into a 100 ml volumetric flask (5.12). Add 25 ml of the acetylacetone-ammonium acetate solution (4.1) and close the flask with a cap.
Heat the sealed flask in a water bath (5.7) at a temperature of (65 ± 2)°C for 10 minutes. Then store the solution at a temperature of 20°C for (60 ± 5) minutes, avoiding direct light, before determining the absorption of the solution at a wavelength of 412 nm using water as the reference solution, using a spectrophotometer (5.6). Use a similar procedure for the determination of formaldehyde in a medium (7.4.2).
If the maximum absorption occurs at a wavelength other than 412 nm, all measurements, including calibration, can be performed at that wavelength.
- Calibration curve
+ Overview
The calibration curve is established using a standard formaldehyde solution, and the concentration of the solution is determined by iodometric titration. The calibration curve should be checked at least once a month. The calibration curve can be determined using the method in 8.4.2 or an equivalent appropriate method.
If the monthly calibration has a variation of less than 2% compared to the average value, the interval between calibration checks can be increased. All increased calibration check times must be recorded.
+ Standard formaldehyde solution
Dilute about 1 ml of formaldehyde solution (concentration from 35% to 40%) in a 1000 ml volumetric flask (5.9) with water and fill it up to the mark.
To accurately determine the formaldehyde concentration of this solution, mix 20 ml of this formaldehyde solution with 25 ml of iodine solution (4.2) and 10 ml of sodium hydroxide solution (4.4). Let it stand for 15 minutes, avoiding light, and then add 15 ml of sulfuric acid solution (4.5). Back titrate the excess iodine with sodium thiosulfate solution (4.3). Near the end point of the titration, add a few drops of starch solution (4.6) as an indicator. Perform a parallel blank test using 20 ml of water.
Hàm lượng formaldehyt, tính bằng miligam trên lít (mg/l), p(HCHO), được tính theo công thức (1)
The formaldehyde content, expressed in milligrams per liter (mg/l), p(HCHO), is calculated using formula (1):
p(HCHO) = (Vo - V) x 15 x c(Na2S2O3) x 1000/20 (1)
Where:
c(Na2S2O3) is the concentration of the thiosulfate solution (4.3), expressed in moles per liter (mg/l).
V is the volume of thiosulfate solution (4.3) consumed in the titration, expressed in milliliters (ml).
Vo is the volume of thiosulfate solution (4.3) consumed in the blank test, expressed in milliliters (ml).
Note: 1 ml of 0.1 mol/l thiosulfate solution (4.3) is equivalent to 1 ml of 0.05 mol/l iodine solution (4.2) and 1.5 mg of formaldehyde.
- Calibration formaldehyde solution
Using the determined concentration value in 8.4.2, calculate the volume of the solution containing 3 mg of formaldehyde. Transfer this solution into a 1000 ml volumetric flask (5.9) using a microburette (5.11), and fill it up to the mark with water; 1 ml of this calibration solution contains 3 µg of formaldehyde.
- Determination of the calibration curve
Using a volumetric pipette (5.10), take 0 ml, 5 ml, 10 ml, 20 ml, 50 ml, and 100 ml of the standard formaldehyde solution (8.4.3) into separate 100 ml volumetric flasks (5.8) and fill them up to the mark with water. Analyze 25 ml of each diluted solution using spectrophotometry according to the procedure described in 8.3. The blank value is determined in parallel, using a solution made from 25 ml of water and 25 ml of acetylacetone-ammonium acetate solution (4.1), which is used to determine the absorbance value of the standard solution. Plot a graph of the absorbance values against the formaldehyde concentration, ρ (from 0 mg/l to 3 mg/l). The slope, f, is calculated from the graph, either manually or using software.
- Determination of formaldehyde content in the embroidered glass plate in the humidity absorber
The formaldehyde concentration G in the embroidered glass plate in the humidity absorber of the test samples, expressed in milligrams per liter (mg/l), is calculated using formula (2):
G = f x (αd - αb) x 1800 / A (2)
Where:
αb is the absorption of the formaldehyde solution in the medium (7.4.2).
αd is the absorption of the solution from the humidity absorber containing the test sample (8.3).
A is the total contact area of the test sample, expressed in square centimeters (cm2).
f is the slope of the calibration curve of the formaldehyde solution, expressed in milligrams per milliliter (mg/l) (8.4.4).
What is the National Standard TCVN 11899-4:2017 on the desiccator method for determination of formaldehyde release in Vietnam?
Vietnam: What are the regulations on requirements for reporting the results under the National Standard TCVN 11899-4:2017
In Section 9 of the National Standard TCVN 11899-4:2017, the requirements for reporting the results are as follows:
- The formaldehyde content from the test sample is calculated as the total amount of formaldehyde in the glass plate, expressed in milligrams per liter (mg/l), and accurate to 0.01 mg/l.
- The average value and two (or three) individual values must be recorded in the test report.
Vietnam: What is the information included in the test report according to the National Standard TCVN 11899-4:2017?
In Section 10 of the National Standard TCVN 11899-4:2017, it is specified that the test report must include the following information:
- Reference to this standard
- Name and address of the testing laboratory
- Sampling report according to TCVN 11903 (ISO 16999)
- Date of the testing report
- Type and thickness (δ) and density of the plate
- Date of sample collection
- Date of formaldehyde determination
- Relevant technical product requirements
- Surface treatment, if applicable
- Names of the equipment used, in case multiple different devices are allowed to be used in this standard
- Test results, expressed as published in Section 9
- Formaldehyde content in the environment calculated according to 8.5
- Any deviations from this standard.
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