Automated determination of formaldehyde in air without the use of tetrachloromercurate(II).

An existing modified (no mercury reagent) pararosaniline method for the determination of formaldehyde in air has been adapted for continuous monitoring using a CEA Instruments, Inc. Model 555 automated wet chemical analyzer. The adapted instrument was checked for linearity of response, formaldehyde collection efficiency, and drift. The instrument response was highly linear (r = 0.9996) in the 1-10 ppm formaldehyde concentration range tested. Formaldehyde collection efficiency of the analyzer increased from 64 to 88% as sample flow rate was increased from 0.25 to 1.0 Lpm. When the analyzer was connected to a constant 4.1 ppm formaldehyde permeation tube source, with careful control of ambient temperature and sample cell liquid levels, 3% instrument drift occurred over a 7 hour period.