Field intercomparison of a novel optical sensor for formaldehyde quantification

A one-week in situ intercomparison campaign was completed on the Rice Unive rsity campus for measuring HCHO using three different techniques, including a novel optical sensor based on difference frequency generation (DFG) oper ating at room temperature. Two chemical derivatization methods, 2,4-dinitro phenylhydrazine (DNPH) and o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PF BHA), were deployed during the daylight hours for three- to four-hour time- integrated samples. A real-time optical sensor based on laser absorption sp ectroscopy was operated simultaneously, including nighttime hours. This tun able spectroscopic source based on difference frequency mixing of two fiber -amplified diode lasers in periodically poled LiNbO3 (PPLN) was operated at 3.5315 mu m (2831.64 cm(-1)) to access a strong HCHO ro-vibrational transi tion free of interferences from other species. The results showed a bias of -1.7 and -1.2 ppbv and a gross error of 2.6 and 1.5 ppbv for DNPH and PFBH A measurements, respectively, compared with DFG measurements. These results validate the DFG sensor for time-resolved measurements of HCHO in urban ar eas.