A dynamic system for the generation of stable hydrogen peroxide test atmospheres was applied to the evaluation of samplers used for the determination of hydrogen peroxide in workplace air. The system is able to generate gas mixtures of between 0.1 and 10 ppm at different combinations of relative humidity (20-80%) and temperature (10-30 degrees C). Gaseous hydrogen peroxide is sampled on glass filters impregnated with Ti(IV) chloride and sulfuric acid and analyzed by UV spectroscopy. An interference was observed due to the acid catalyzed decomposition of peroxyacetic acid to hydrogen peroxide. This was significantly reduced by applying high sample flow rates and by lowering the concentration of sulfuric acid. The performance of the sampler and sources of uncertainties were tested according to the European Standard EN 1076.
A new method for the determination of peroxyacetic acid (PAA) in gas phase samples is described. It is based on the oxidation of ABTS (2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonate) by PAA with formation of a radical cation which is characterized by four strong absorption maxima between 405 nm and 810 nm. These allow for sensitive spectrophotometric determination of the peracid. The selectivity of the method towards hydrogen peroxide is strongly dependent on the sampling method used. Impinger sampling and sampling based on the use of coated solid sorbents (test tubes) was performed. Limits of detection are 10(-8) mol, limits of quantification are 5 x 10(-8) mol, the linear range consists of 1.5 concentration decades in both cases. Using ABTS-coated test tubes above 1 x 10(-7) mol, direct reading of the results is possible and may be used as rapid screening method for the PAA concentration.
The Nordic Network on Isocyanates (NORDNI) is financed by the Nordic Council of Ministers and is under the administration of Prof. Yngvar Thomassen and co-workers. National Institute of Occupational Health, Norway. The aim of NORDNI is to establish a broad network between the Nordic National Institutes of Occupational Health working within the field of isocyanate exposure and strategies for sampling and determination of isocyanates in workroom atmospheres. This viewpoint article summarizes the resolutions that were established at the 1st NORDNI consensus meeting arranged in Frøya, Norway, 31st August-2nd September, 2001. The consensus platform from the 1st NORDNI meeting was presented at the 4th International Symposium on Modern Principles of Air Monitoring, Lillehammer, Norway, 3-7 February, 2002.
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