Friedfeld, S.Fraser, M.Lancaster, D.Leleux, D.Rehle, D.Tittel, F.2010-08-172010-08-172000Geophysical Research Letters, 2000; 27(14):2093-20960094-82761944-8007http://hdl.handle.net/2440/59850<jats:p>A one‐week <jats:italic>in situ</jats:italic> intercomparison campaign was completed on the Rice University campus for measuring HCHO using three different techniques, including a novel optical sensor based on difference frequency generation (DFG) operating at room temperature. Two chemical derivatization methods, 2,4‐dinitrophenylhydrazine (DNPH) and <jats:italic>o</jats:italic>‐(2,3,4,5,6‐pentafluorobenzyl) hydroxylamine (PFBHA), were deployed during the daylight hours for three‐ to four‐hour time‐integrated samples. A real‐time optical sensor based on laser absorption spectroscopy was operated simultaneously, including nighttime hours. This tunable spectroscopic source based on difference frequency mixing of two fiber‐amplified diode lasers in periodically poled LiNbO<jats:sub>3</jats:sub> (PPLN) was operated at 3.5315 µm (2831.64 cm<jats:sup>−1</jats:sup>) to access a strong HCHO ro‐vibrational transition 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 PFBHA measurements, respectively, compared with DFG measurements. These results validate the DFG sensor for time‐resolved measurements of HCHO in urban areas.</jats:p>enCopyright 2000 by the American Geophysical UnionJournal article003000114910.1029/2000gl01152365155