A method for the determination of aromatic isocyanates in air in the presence of primary aromatic amines

Abstract

A method is described for the determination of aromatic isocyanates in air in the presence of primary aromatic amines. Samples of the test atmosphere are drawn simultaneously through two different absorbing solutions a t 1 1 minute-1 for 10 minutes. One sample is collected in a dimethylformamide solution of 1,6-diaminohexane and the other in a dimethylformamidehydrochloric acid solution of 1,6-diarninohexane. The aromatic amine present, or produced, in each absorbing solution is diazotised and coupled with N-( 1-naphthyl) ethylenediamine to form a coloured complex, the optical density of which is measured spectrophotometrically. The difference between the resulting optical densities gives a measure of the isocyanate content of the air. A complete analysis requires about 30 minutes.

Determination of polymethylenepolyphenylene isocyanate in air by size exclusion chromatography

“…Standard atmospheres of PAPI were produced as aerosols ® Based on a 45-L air sample. Value was determined by colorimetric impinger method used for corroboration (7). 6 Average of six samples.…”

“…Miskovich has shown that trace level NMP can be quickly and accurately determined by dissolving extracts or raffinates in hydrocarbon solvents and analyzing the solutions by gas chromatography using a nitrogen-phosphorus detector (NPD) (7). However, after several analyses, detector response from the elution of the high molecular weight hydrocarbons forces purging the column at elevated temperatures for several hours to remove these hydrocarbons and stabilize the background interference.…”

“…The method was validated by the collection, workup, and analysis of six aerosol samples of PAPI at each of five concentration levels from 2 to 155 ppb (29-2300 µg m"3) for a 45-L air sample (29-2300 µg m"3). A colorimetric impinger method was used simultaneously with the treated filter method to corroborate the results (7). Colorimetric determinations were performed on a Bausch & Lomb (Rochester, NY) Spectronic 100 spectrophotometer.…”

“…Early work involved colorimetric test papers or midget impingers (4)(5)(6)(7)(8)(9)(10) while more recent methods have used derivatizing agents coated on solid sorbents (11,12). These solid-state derivatization techniques offer the advantage of ease of use.…”

Specific Inhibition of Contact Sensitivity in the Guinea Pig following Tolylene Diisocyanate Inhalation

“…The air containing TDI vapour was led into the exposure chamber after dilution with clean, dry air to achieve appropriate at mospheric concentrations. The concentration of TDI in the atmos phere was determined by Marcali's method as modified by Meddle and Wood [1970], Air from the chamber was drawn through two sintered glass bubblers in series containing an acid-absorbing solu tion in which the TDI was hydrolysed to the amine. The amine was subsequently diazotised and coupled to form a coloured complex, the intensity of which is a measure of the concentration of the TDI originally present in the air.…”