Validation of passive samplers for monitoring of acetic and formic acid in museum environments

Abstract

Acetic acid and formic acid are volatile pollutants leading to degradation of some heritage materials. They are usually determined in museum environments with various types of passive samplers. In this work, SKC UMEx 200 passive samplers, originally intended for sampling of ${\text{NO}}_2$ and ${\text{SO}}_2$, have been validated for sampling of these organic acids. The sampling rates, extraction efficiency, loss through reverse diffusion or during storage, capacity, and detection limits were determined for both acids. For laboratory exposure, a known concentration of both acids was prepared in a flow-through reactor system at controlled temperature and humidity, the samplers were extracted, followed by analysis using ion chromatography. The sampling rates were determined to be 16.7 ml/min for acetic and 17.7 ml/min for formic acid and the detection limits for 7-day exposure were determined to be $2.1\mathrm{\mu }{\mathrm{g}/\mathrm{m}}^3$ for acetic and $1.9\mathrm{\mu }{\text{g/m}}^3$ for formic acid. The validated method was finally used for sampling of air in two case studies at the National Museum of Slovenia, where the concentrations in the range of 2–$54\mathrm{\mu }{\text{g/m}}^3$ were determined.