Development of a Dosimeter System for Unsymmetrical Dimethylhydrazine,Monomethylhydrazine and Hydrazine

摘要

A dosimeter for real-time, colorimetric detection of current and proposedthreshold limit value (TLV) levels of hydrazine, monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH)in air has been developed. The dosimeter consists of a replaceable dosimeter card and a reusable, polypropylene badge housing containing a clear, LTV adsorbent shield. The replaceable dosimeter card has two reaction sites, each containing one of two chemistries on a paper substrate. One chemistry uses 2,4-dinitrobenzaldehyde which is an excellent derivatization agent for UDMH, though less effective for hydrazine and MMH. Through a condensation reaction, 2,4-dinitrobenzaldehyde reacts with UDMH to form a colored product that absorbs in the visible region. The hydrazone formed in the reaction is yellow to golden yellow. The intensity of the color is proportional to the dose. When coated on porous filter paper and exposed passively to UDMH, the detection limit is <20 ppb-hrs. Actively drawing UDMH vapors through the paper gives a detection limit of <50 ppb-L. The second reaction utilized in the dosimeter system involves 3-methoxy-4hydroxbenzaldehyde (vanillin) for the detection of hydrazine and MMH (U.S. patent 4,900,681). In the reaction between vanillin and hydrazine or MMH, a yellow hydrazone is formed. When coated on porous filter paper and exposed to MMH or hydrazine, the detection limit is 7 ppb-hours. Neither chemistry is hindered by a sensitivity to relative humidity changes. Badges remain sensitive to hydrazines vapors for at least one year when stored in a freezer. Interferences with the chemistries are limited to tobacco smoke and sunlight for the vanillin and 2,4-dinitrobenzaldehyde chemistries, respectively.