Selective Monitoring of Formaldehyde in Air by Use of the Stopped-Flow Technique

摘要

Two kinetic methods based on the stopped-flow technique are proposed for the determination of formaldehyde in air by reaction with 3-methyl-2-benzothiazolone hydrazone (MBTH), followed by photometric detection at 620 nm, and with acetylacetone, followed by fluorimetric detection at #x3B4;cx= 410 nm and #x3B4;cm= 510 nm. Kinetic methodology considerably shortens the formaldehyde analysis time (measurements can be obtained within a few seconds) relative to existing methods based on these reactions and equilibrium measurements (ca. 30 and 60 min are needed for equilibrium to be reached in the photometric and fluorimetric method, respectively). One additional advantage of the kinetic methodology is its high selectivity, which was checked by studying the effect of various organic and inorganic species. Calibration graphs were linear over the ranges 20#x2013;600 and 20#x2013;1000 ng ml#x2212;1formaldehyde for the photometric and fluorimetric methods, respectively. Both methods were applied to the determination of formaldehyde in air from urban- areas; the accuracy of the results was confirmed by comparing them with those provided by the standard chromotropic acid method. The poposed kinetic methods were found to be more sensitive, rapid, reproducible and easier to use than the widely accepted standard method.