Accurate low-dose exposure assessment of benzene and monoaromatic compounds by diffusive sampling: Sampling and analytical method validation according to ISO 23320 for radiello® samplers packed with graphitised charcoal and suitable for thermal desorption

Abstract

This research was aimed at providing an accurate low-dose benzene exposure assessment method, prospectively suitable to exposure limit values in the low ppb range, such as in the present-day chemical, petrochemical, foundry and pharmaceutical industry. The project addresses the need for a robust and fully validated method of personal exposure measurements considering that the Occupational Exposure Limit Value for benzene will be significantly lowered in the next few years. Diffusive sampling offers a reliable alternative to pumped sampling methods, intrinsic safety in potentially explosive atmospheres, lightness and ease of use. The tested diffusive sampler is radiello® with the RAD145 adsorption substrate. This configuration is packed with graphitised charcoal suitable for thermal desorption and analysis by HRGC-FID or HRGC-MS.

The experiments have been conducted following the ISO 23320 standard in the range from 0.005 to 0.1 ppm (16 to 320 µg/m³), yielding a full validation of the sampling and analytical method. The sampler performances have fulfilled all requisites of the ISO 23320 standard, in particular: bias due to the selection of a non-ideal sorbent is lower than 10 % (no significant back diffusion of benzene due to concentration change in the atmosphere); bias due to storage of samples for up to 2 months is lower than 10 %; nominal uptake rate for benzene on RAD145 is 32.3 mL/min; expanded uncertainty of the sampling and analytical method is 22.1 % in the concentration range from 80 to 320 µg/m³. The sampling and analytical method is therefore fit-for-purpose for the personal exposure measurements aimed at testing compliance with lowered occupational exposure limit values for benzene. The method is also fit for short duration exposure monitoring related to specific tasks, and other volatile organic compounds, usually found in the same workplaces, such as aliphatic and aromatic hydrocarbons and some oxygenated compounds, have been also studied. In particular, n-hexane and isopropyl benzene (also known as cumene), whose classification is currently under revision, can be efficiently monitored by this technique.