Robust Hybrid Flow Analyzer for Formaldehyde

Abstract

We report fully automated self-calibrating formaldehyde analyzers relying on a hybrid flow format and include operational scheme and design details. Long-term operation is made possible with the use of syringe pumps. Four identical analyzers were built and showed low LODs of 120 pptv or better (S/N = 3) and good linearity over 0-50 ppbv HCHO concentration range (r2 > 0.9960), all concentrations refer to 10 min averaging times. The analyzer can resume normal operation after shortterm power failure with at most two cycles of data loss following restart. Good agreement between analyzers was observed for either indoor or outdoor measurements. The use of an integrated HCHO calibration source and full control by the host computer via a graphical user interface program enables the instrument to switch between zero, calibration, and sampling modes in a programmed automated manner. Detailed field data from deployment in three urban Texas locations from the summer of 2006 are presented. Features of the data, including an episode in which the HCHO concentration exceeded 50 ppbv, the highest reported ambient HCHO concentration in North America to our knowledge, are discussed in some detail.

Formaldehyde and its relation to CO, PAN, and SO<sub>2</sub> in the Houston-Galveston airshed

“…Relatively stable at night, HCHO rapidly photolyzes after sunrise and serves as an important source for early morning radicals. Some of the highest HCHO levels in North America have been reported for the HGA, in particular the HSC area, ranging from ∼35 to 52 ppbv (Dasgupta et al, 2005;Eom et al, 2008). Airborne HCHO measurements in HGA likewise exceeded 30 ppbv on some occasions; terminal olefins were identified as the most important precursors .…”

Near-source air quality impacts of large olefin flares

“…The peak mixing ratio in the plume exceeds 30 ppb. Such peaks are hardly unprecedented, as the maximum HCHO concentration measured in the Ship Channel during TexAQS II was 52 ppb (Eom et al, 2008).…”

A Multiple Processing Hybrid Flow System for Analysis of Formaldehyde Contamination in Food

“…In flow injection analysis (FIA), the Hantzsch reaction has been applied to the analysis of air, [14][15][16][17] 15,18 have been employed. Amongst these, 2,4-pentanedione is recommended as the best reagent due to its reactivity at lower temperature and low sensitivity to interferences.…”

“…16 In a recent flow system, 2,4-pentanedione and ammonium acetate solutions were arranged to mix together in one of the syringes prior to a reaction with HCHO. 17 This flow system for the analysis of HCHO in air is based on the concept of a hybrid flow analyzer. 22 The system is more robust than the conventional FI system due to using syringe pumps.…”

“…The procedure is different from one presented earlier by Eom et al for monitoring HCHO in air. 17 A new operating procedure has been designed that allows for the processing of 3 samples at one time to achieve a considerably improvement in the sample throughput. dissolving 38.5 g of ammonium acetate (Ajax, Australia) in 200 ml of water, followed by adjusting the pH to the range of 5.6 to 6.2 using glacial acetic acid (J. T. Baker, USA), and then diluted to 250 ml with water.…”