Popular Science: The Devil’s Own
Formaldehyde is a volatile gas that is generally considered to be a dangerous contaminant that has been known to be a human carcinogen (it has been classified as Group 1 by the International Agency for Research on Cancer, which includes, for example, tobacco smoke and asbestos). Nevertheless, its global production amounts to more than 20 million tons per year (with almost half of the global production coming from Asia, followed by Europe – 23% and by North America – 17%). In addition to, for example, the production of pesticides and fertilizers, formaldehyde is widely used in the production of paints, varnishes, adhesives and stains, which are often used in carpets and furniture, from which toxic formaldehyde is further released in the space. This causes air pollution and staying in such areas for prolonged periods can be harmful to health.
Furniture made of plywood and chipboard usually contains the highest concentration of formaldehyde, though new wooden furniture made of ‘solid’ wood can also contain certain concentration of formaldehyde, if it is used, for example, for gluing. Its higher concentration in the interior air is also supported by the current efforts towards sealing the interiors (e.g. by using plastic windows), thanks to which there is no natural air circulation with the outside environment.
In Europe, the amount of formaldehyde released into the air from wood-based products is measured using several methods, which are based mainly on spectrophotometric analysis. However, most of the methods require the addition of cofactors to enable formaldehyde conversion, they often generate various by-products and are time-consuming.
This is why researchers from Charles University in Prague, in collaboration with colleagues from the University of Porto, came up with a new method that could significantly speed up and simplify the analysis of the detected formaldehyde release. The method is known as HLAS (Headspace Liquid Acceptor System) and is suitable for the detection of volatile and semi-volatile compounds which can be used with liquid and solid samples. This new method is inspired by the recently patented gas-diffusion microextraction (GDME) method, which is based on a combination of gas diffusion and microextraction. Simply put, a volatile substance is released from a heated sample and passes through a hydrophobic gas-permeable membrane into the acceptance solution, which was acetylacetone in this study. In the acceptance solution, formaldehyde is derivatised (its derived compound is formed) and subsequently the final amount released is determined. Electrochemical detection was performed using square-wave voltammetry (SWV) on unmodified screen-printed carbon electrodes (SPCEs). This was the initial use of unmodified screen-printed carbon electrodes in combination with electrochemical detection for the determination of formaldehyde extracted from wood-based products.
The authors used seven different wood-based products for the experiment. All samples were without any specific surface finish. The determined concentrations of formaldehyde in the analysed samples ranged from about 3.4 to 11.6 mg.kg−1, which (according to the limit values) should not significantly affect air quality in buildings – just to give you an idea: industrial LPG boilers can produce of 11.2 mg.kg−1 on average, cars produce about 16–115 mg of formaldehyde per 1 km of driving, and human intake from smoking 20 cigarettes a day amounts to 1 mg of formaldehyde per day. The sensitivity of people to formaldehyde is very individual, with children and the people with diseases being more sensitive. For a healthy person, increased irritation is generally reported at concentrations above 0.1 mg.m−3, life-threatening above 37 mg.m−3, and danger of death above 60 mg.m−3.
In order to validate the results of formaldehyde content in wood-based products obtained using the new methodology, the European standard method EN 717–3 was used, achieving statistically identical results. However, the new method was ten times faster than the current European standard.
Formaldehyde still poses a major health risk in today’s world. It is therefore very important to monitor its releasing. New research into the possibility of detecting formaldehyde in wood-based products shows a great way to determine its concentration release relatively easily, quickly and at a lower cost compared with older methods. At the same time, it represents a new option in the determination of formaldehyde content in wood-based products as well as in other solid and liquid samples.
Dvořák, P., Ramos, R.M., Vyskočil, V., Rodrigues, J.A. (2020): A new electroanalytical methodology for the determination of formaldehyde in wood-based products. Talanta, 217. https://doi.org/10.1016/j.talanta.2020.121068