Air Monitoring 31


shown in a previous study that the other aldehydes react 1000– 10,000 times more slowly with Fluoral than formaldehyde, which means that they cannot interfere [7]. MicroF is thus an interference- free analyser, specifi c to formaldehyde and able to measure the range of concentration from 1 to 1000 µg m–3


, covering formaldehyde levels in domestic and professional environments.


2.2. The microF: a tool for continuous real-time formaldehyde monitoring


An example of airborne formaldehyde monitoring performed in a French primary school over 5 weeks is shown in Figure 4.


During the fi rst week, the room was empty from furniture. The analyser measured concentrations in the range of 7.8–40.9 μg m−3


with an average of 29.5 ± 5.0 μg m−3 . It showed that


building materials emit a signifi cant amount of formaldehyde. Subsequently, during the second week, formaldehyde concentration was monitored in the furnished classroom. The concentration levels were in the range of 18.8–56.4 μg m−3 an average concentration from 29.5 ± 5.0 to 33.8 ± 5.2 μg m−3


(3.4 to 40.1 μg m−3


(range 8.9 to 48.1 μg m−3 ), and 25.6 ± 7.7 μg m−3


, with .


), respectively. It corresponds to users following either: the usual ventilation protocol of the school, ventilation according to CO2


levels (windows opening when CO2 concentration


reach 1700 ppm), and ventilation according to Observatoire de la qualité de l’air intérieur (Observatory of indoor air quality) instructions (windows opened for approximately 30 min before and after class, every 2 h of class). MicroF was able to monitor formaldehyde concentrations in indoor air for several weeks and successfully reported concentration changes within 10 minutes, which cannot be highlighted with the off-line DNPH method.


3. Conclusion


In this article, we present a portable cost-effective solution for the measurement of formaldehyde concentration in the air. The analyser is free from potential interferences: whether other aldehydes as it has been demonstrated before, or humidity as it has been shown here. It shows a high sensitivity to the ambient formaldehyde level, with a detection limit as low as 1 µg m–3


During the 3rd, 4th and 5th week, concentrations measured were in average 31.0 ± 6.9 μg m−3 μg m−3 m−3


(6.4 to 41.3 μg ), 27.4 ± 6.3 Figure 3: Calibration curves obtained with the microF in laboratory-controlled setting in dry (RH<8%) and humid conditions (RH=50%)


, enabling precise measurements of concentration in the


indoor air (in private housing or public places). Furthermore, this sensitivity extends its utility for outdoor air analysis. It notices rapid changes of concentration within a 10-minute timeframe.


The on-line microF analyser provides precise time concentration change, as opposed to the reference method which gives averaged values (usually over 1 hour or more) after off-line analysis with sedentary laboratory equipment after manual elution of DNPH tube. The microF can autonomously monitor differences between night and day, events of window opening or specifi c activities involving formaldehyde emission in the air. People’s exposure can then be assessed accurately and potentially minimised by taking appropriate measures.


Since it is portable, it can be moved during an analysis to investigate either one room or different rooms in a same building in order to spatially map concentration levels and potentially identify the various formaldehyde sources. Additionally, thanks to its microfl uidic confi guration, it has an extremely low reagent consumption, so that 4.1 days of analysis can be carried out with only 100 mL of reagent.


Regarding the different formaldehyde uses, applications of the analyser can include advanced diagnostics for indoor environments and monitoring of employee’s exposure in industries for food-processing, construction materials, cosmetics and even hospital in thanatopraxy and anatomic pathology services, etc.


4. Bibliography


[1] World Health Organisation, Ed., Who guidelines for indoor air quality: selected pollutants. Copenhagen: WHO, 2010.


Figure 4: Formaldehyde concentration evolution during fi ve consecutive weeks in a French primary school. The data are obtained with either an on-line formaldehyde microanalyser operating with a time resolution of 2 seconds (raw data, blue) or the DNPH reference (adapted from [8]).


[2] L. Yu et al., “Association between indoor formaldehyde exposure and asthma: A systematic review and meta-analysis of observational studies,” Indoor Air, vol. 30, no. 4, Art. no. 4, Jul. 2020, doi: 10.1111/ina.12657.


[3] M. Guglielmino, P. Bernhardt, C. Trocquet, C. A. Serra, and S. Le Calvé, “On-line gaseous formaldehyde detection by a microfl uidic analytical method based on simultaneous uptake and derivatisation in a temperature controlled annular fl ow,” Talanta, vol. 172, pp. 102–108, Sep. 2017, doi: 10.1016/j. talanta.2017.05.038.


[4] A. Becker, N. Lohmann, C. A. Serra, and S. Le Calvé, “Development of a Portable and Modular Gas Generator: Application to Formaldehyde Analysis,” Chemosensors, vol. 10, no. 4, Art. no. 4, Apr. 2022, doi: 10.3390/ chemosensors10040131.


[5] A. Grandjean, D. Bazin, F. Amiet, and S. Le Calvé, “Comparison of Two Analytical Systems for Continuous Monitoring of Ppb to Ppm-


levels of Formaldehyde in Air,” Chemical Engineering Transactions, vol. 95, pp. 67–72, Oct. 2022, doi: 10.3303/CET2295012.


[6] “NF ISO 16000-3, Dosage du formaldéhyde et d’autres composés carbonylés dans l’air intérieur et dans l’air des chambres d’essai - Partie 3 : Méthode par échantillonnage actif.” Dec. 16, 2011.


[7] M. Guglielmino, “Développement d’une nouvelle méthode analytique du formaldéhyde dans l’air basée sur un dispositif microfl uidique,” PhD thesis, University of Strasbourg, Strasbourg, 2014.


[8] C. Trocquet et al., “Continuous real-time monitoring of formaldehyde over 5 weeks in two French primary schools: identifi cation of the relevant time resolution and the most appropriate ventilation scenario,” Air Qual Atmos Health, vol. 16, no. 6, pp. 1091–1115, Jun. 2023, doi: 10.1007/s11869- 023-01328-x.


Audrey Grandjean – Chromatotec Damien Bazin - Chromatotec


Stéphane Le Calvé – ICPEES – CNRS/ University of Strasbourg Anaïs Becker from ICPEES - CNRS / University of Strasbourg


15, rue d’artiguelongue – Saint-Antoine – 33240 VAL DE VIRVEE Tel: +33 557 940 626 Email: info@chromatotec.com Web : www.chromatotec.com


Audrey Grandjean Damien Bazin Anaïs Becker Stéphane Le Calvé


WWW.ENVIROTECH-ONLINE.COM


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