Solid Sorbent Media for Collection of Formaldehyde in Air

Abstract

A new sampling method for monitoring personal exposure to formaldehyde is described. The method consists of drawing air through a solid sorbent tube containing silica gel impregnated with 20 percent sodium bisulfite. The formaldehyde collected reacts to form the sodium formaldehyde bisulfite addition product. This salt may then be desorbed with water and the resulting solution analyzed for formaldehyde using the chromotropic acid colorimetric method. The collection and desorption efficiency of the method were tested using an atmosphere generator capable of producing calibrated, dynamic atmospheres of formaldehyde. The new solid sorbent sampler gave results equivalent to a bubbler/H₂O collection method and to the formaldehyde concentration calculated for the atmosphere generator. The overall method was very simple, and the desorbed solutions did not require filtration prior to analysis. The capacity of this sorbent material for retaining formaldehyde before breakthrough occurred was much higher than untreated silica gel. High humidity in air sampled for formaldehyde had no adverse effect on sorbent breakthrough thresholds. In addition, this solid sorbent stabilized collected formaldehyde for over one month of storage at room temperature.