Fluorescence determination of formaldehyde in air samples

Formaldehyde is a chemical compound with a pungent odor, irritating the mucous membranes, and has been classified as a Group 1 human carcinogen by the International Agency for Research on Cancer. Formaldehyde is a ubiquitous pollutant as numerous natural processes generate it. The main sources of exposure for the general population are combustion processes (cigarette smoke, cosmetics, stoves, vehicle exhaust, incinerators), paints, and preparation of smoked or fried foods; in the occupational field, it is mainly used in the medical-sanitary and veterinary fields as a disinfectant and preservative. The toxic characteristics of this chemical require particular attention during its handling and control and mitigation measures in all occupational sectors. Generally, formaldehyde in air is sampled with systems containing 2,4 dinitrophenylhydrazine (2,4-DNPH) solutions and subsequently analyzed by gas chromatography/FID or liquid chromatography/UV–VIS. However, chromatographic methods are slow, time-consuming and non-specific to formaldehyde. The present study describes a sensitive method for the selective determination of formaldehyde in air samples by fluorescence. The method is based on the reaction between formaldehyde and Fluoral P, which produces the fluorescent derivative 3,5-diacetyl-1,4-dihydrolutidine, which, when excited at 410 nm, emits light at 510 nm. The method was used in flow-injection mode or coupled with an HPLC and validated by comparison with an HPLC/UV-VIS method. After being eluted with acetonitrile, the cartridges with 2,4-DNPH were injected into the HPLC/fluorescence or HPLC/UV-VIS systems or analyzed directly by fluorescence using a small homemade straw and connected to a syringe. The main advantages of the new analytical procedure are low blank level, high selectivity, and low detection limits. In addition, very little sample preparation is required. Acknowledgements This research was funded by “Istituto Nazionale per l’Assicurazione Contro gli Infortuni sul Lavoro” grant BRIC-INAIL ID 05/2018 “Valutazione sperimentale dell’efficacia delle misure in atto per la mitigazione dell’esposizione a formaldeide nel comparto lavorativo sanitario e negli altri scenari occupazionali e sviluppo di sensoristica ad elevata innovatività tecnologica per gestire il rischio formaldeide in ambito lavorativo”, project number B86C19000070001.