With the entry into force of the new TRGS 552 “Carcinogenic N-nitrosamines Cat. 1A and 1B”, an acceptable concentration of 0.075 μg/m3 and a tolerable concentration of 0.75 μg/m3 were established for N-Nitrosodimethylamine. To comply with these concentrations, the measurement procedure for N-nitrosamines has been completely revised in 2018.

The revised IFA method, which will be presented here, includes the analysis of seven N-nitrosamines. Sampling is carried out with Thermosorb-N-cartridges specially designed for N-nitrosamine analysis. After elution of the N-nitrosamines, the analytical determination is achieved by gas chromatography with TEA detector (Thermal Energy Analyser), which is specially designed for the analysis of nitroso compounds and implies a high sensitivity.

A essential step in complying with the acceptable concentration was the doubling of the sampling time from previous 2 hours to 4 hours. As a result, a limit of quantification of 0.010 μg/m3 per N-nitrosamine (based on a 400 L air sample) was achieved.

However, this increased sampling time implicates the problem of breakthroughs occurring at relative humidities greater than 40% and simultaneously increased N-nitrosamine concentrations in the workplace air. This concerns especially the more volatile N-nitrosamines.

In order to enable sampling at workplaces with higher humidity levels, various tests were carried out on a dynamic test gas facility. Some changes in the sampling procedure finally made it possible to measure N-nitrosamines concentration-independent also in the air humidity range of 40% to 60%, although with minor restrictions. Unfortunately, sampling at a relative humidity greater than 60% is still not possible.