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DEVELOPMENT OF REAL-TIME MONITORS FOR GASEOUS FORMALDEHYDE
Citation:
Kelly, T. AND R. Barnes. DEVELOPMENT OF REAL-TIME MONITORS FOR GASEOUS FORMALDEHYDE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-90/088.
Description:
Two new methods for real-time measurement of gaseous formaldehyde have been developed. ne is a spectroscopic method based on direct fluorescence detection of gaseous formaldehyde following excitation with UV light. his method has been develop to the prototype stage by modifications of a commercial fluorescence SO2 detector to convert it to formaldehyde detection. he prototype spectroscopic formaldehyde monitor exhibits a detection limit of < 30 ppbv, with a time response of about one minute. he second method is based on derivatization of formaldehyde in aqueous solution to form a fluorescent product. he detection of fluorescent product was made more sensitive by using intense 254 nm light from a mercury lamp for excitation, thereby allowing use of a simple and efficient glass coil scrubber for collection of gaseous formaldehyde. he wet chemical formaldehyde monitor incorporating these improvements exhibits a detection limit for gaseous formaldehyde of 0.2 ppbv and for aqueous formaldehyde of 0.2 uM, with time response of about one minute, following a lag time of 2 minutes. oth instrument were tested in the laboratory with gaseous formaldehyde standards, and the aqueous scrubbing/analysis method was field tested by continuous operation over a 10-day period in which outdoor and indoor air were sampled for alternate half-hour periods. omparison of real-time (aqueous scrubbing/analysis) and integrated measurements, using dinitrophenylhydrazine (DNPH) impingers, showed close agreement between the real-time and DNPH data, even at concentrations as low as 1 ppbv.