STP957

    Recent Developments in the Sampling and Analysis of Isocyanates in Air

    Published: Jan 1987


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    Abstract

    In the past decade (1975 to 1985) there has been a considerable amount of research activity in the field of sampling and analysis of isocyanates in air. The general trend has been to move away from impinger sampling to solid sorbent or coated filter techniques or both, and the method of analysis has shifted from spectrophotometric to chromatographic techniques.

    Dynamic atmospheres of various isocyanates were generated in the laboratory and several sampling and analysis methods for isocyanates were evaluated. The sampling media tested include impingers containing p-nitrobenzyl propylamine (nitroreagent) and Marcali solutions, nitroreagent coated glasswool and glassifiber filters coated with nitroreagent, 1-(2-pyridyl)piperazine (PP), and sulfuric acid. The particle size distribution of the 4,41 diphenylmethane diisocyanate (MDI) atmosphere was also determined.

    The studies show that isocyanates having significant vapor pressure such as toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and phenyl isocyanate (PI), are usually present as a vapor in the ambient atmosphere and generally the impinger, the solid sorbent, and the coated filter methods sample them efficiently. However, it has been found in the laboratory generated airborne atmospheres of nonvolatile isocyanates such as MDI and 4,4′ dicyclohexylmethane diisocyanate (Des W or hydrogenated MDI) that the coated filter methods have better collection efficiency than the impingers. Nevertheless, a study from a Swedish team has found quite the opposite results in the field for MDI. In an MDI based polyurethane insulation spraying operation, the impingers collected more than the coated filters in simultaneous sampling.

    This paper summarizes our evaluations of the various methods for the sampling and analysis of isocyanates and propose a hypothesis to explain the apparently contradictory finding of the collection efficiency of the filter and impinger method for MDI in the laboratory-generated atmosphere and in the field.

    Keywords:

    isocyanates, diisocyanates, sampling media, analytical methods, industrial hygiene, methods evaluation, sampling, air quality, calibration, atmospheric measurements


    Author Information:

    Dharmarajan, V
    Industrial hygiene specialist, industrial hygiene laboratory supervisor, industrial hygiene specialist, and industrial hygiene manager, Mobay Corporation, Pittsburgh, PA

    Lingg, RD
    Industrial hygiene specialist, industrial hygiene laboratory supervisor, industrial hygiene specialist, and industrial hygiene manager, Mobay Corporation, Pittsburgh, PA

    Booth, KS
    Industrial hygiene specialist, industrial hygiene laboratory supervisor, industrial hygiene specialist, and industrial hygiene manager, Mobay Corporation, Pittsburgh, PA

    Hackathorn, DR
    Industrial hygiene specialist, industrial hygiene laboratory supervisor, industrial hygiene specialist, and industrial hygiene manager, Mobay Corporation, Pittsburgh, PA


    Paper ID: STP25713S

    Committee/Subcommittee: D22.01

    DOI: 10.1520/STP25713S


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