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Procedure for determination of total formaldehyde concentration according to VdL-Guideline 03

Posted Date:2025/12/9

6.2. Determination of total formaldehyde concentration

6.2.1. Acid steam distillation

Approx. (10 ± 5) g of a sample (note initial sample weight to nearest 0.001 g) is weighed in the distillation flask on the analytical balance and approx. 50 ml of deionised water is added. After the careful addition of 20 - 30 ml of the 25% sulphuric acid solution (caution: causes foaming), the sample is subjected to steam distillation, whereby around 245 ml of solution is distilled over. The distillate is filled up to the 250 ml mark with deionised water.

6.2.2. Photometric determination with acetyl acetone reagent

A sample of (2.5 ± 0.5) g of the distillate is weighed into a graduated 25 ml cylinder, to which 10 ml acetyl acetone reagent is added. In parallel, a blind solution is prepared with deionised water and 10 ml acetyl acetone reagent in another 25 ml cylinder. Allow the solution to stand for 2 h at room temperature. Both solutions are measured against one another at 412 nm in the spectrophotometer.

6.2.3. Determination with the chromotropic acid method

There are commercially available test kits for the determination of the formaldehyde content using the chromotopic acid method (e.g. Merck KGaA). This method can be utilised as an alternative to the acetyl acetone method for determining the total formaldehyde content in samples following acid steam distillation. The method is not suitable for determining the free formaldehyde concentration.

6.3. Determining the in-film formaldehyde concentration

Determination of the in-film formaldehyde concentration is performed as follows. The paint or varnish is applied to a suitable substrate (glass, aluminium) using a squeegee/film applicator with a 250 µm gap height, and stored at 23 °C and 50% relative humidity. After the desired number of days – but no sooner than after completion of drying time – the paint or varnish film is removed from the substrateand shredded. Steam distillation is performed according to 6.2.1 to release the formaldehyde from the sample.

The formaldehyde concentration is determined using photometry by reacting with acetyl acetone (6.2.2) or alternatively by reacting with chromotropic acid (6.2.3).