Investigation of the inaccuracy of NIOSH Method 5505 for estimating the concentration of isocyanate in air.
Seymour MJ; O'Connor PF; Teass AW
Appl Occup Environ Hyg 1990 Feb; 5(2):115-122
The accuracy of NIOSH Method 5505 for estimating isocyanate concentrations in air was evaluated. The impetus for the study was the discovery that field samples gave high estimates of isocyanate concentrations in the sampled air. The purpose of the study was to test the hypothesis that loss of 1-(2-methoxyphenyl)piperazine (MPP), used as the reagent in the impinger solution, after sampling was the source of the problem. Up to 740 liters of isocyanate, free air, or nitrogen at flow rates of 0.4 to 1.6 liters per minute were drawn through impingers containing MPP and backup bubblers containing no MPP. The exit air from the impingers and the bubblers was analyzed for MPP by high performance liquid chromatography and mass spectrometry. Seventeen to 42% of the MPP was lost from the impingers. Less than 13% of the amount of MPP lost was found in the backup bubblers. Significant amounts of MPP were detected in the gas stream exiting the impingers. The amount of MPP entrained in the exit air increased with the volume of air sampled. The authors conclude that Method 5505 suffers from loss of MPP reagent. Since estimating isocyanate concentrations in a sample depends on the analyte reacting with the MPP and measuring the amount of MPP reacted, loss of MPP causes an unacceptably high bias in the result. Loss of MPP during sampling is related to the volume of air sampled. Method 5505 should no longer be used.
AIHYEX; NIOSH-Author; Isocyanates; Air-sampling; Reagents; Laboratory-testing; Analytical-methods; Chemical-analysis
Applied Occupational and Environmental Hygiene