Facile barometric calibration of photoluminescence-based oxygen sensors on a standard rotary evaporator system with a digital vacuum pump

A simple setup and methodology for barometric calibration of quenched phosphorescence oxygen sensors are described, which utilize a standard rotary evaporator (Rotavap) system equipped with a digital vacuum pump. They were demonstrated with a panel of different sensing materials based on PtBP dye, including solid-state sensor coatings on different substrates (membrane inserts, stickers or inner wall of the vacuum flask), as well as liquid sensor formulations. The sensors inside the flask were exposed to different conditions created by the Rotavap system (dry or humid air, water, temperatures ranging 2°C-40°C, residual total pressure), and their intensity, lifetime or phase shift signals were measured with handheld sensor readers Optech (Mocon) and Firesting (PyroScience) in a contact-less manner to generate multi-point calibration curves. Several critical points of the method, which require careful consideration, have been revealed, including sensor mounting inside the Rotavap, its temperature control during calibration, choice of the reader. Finally, a detailed characterization of several sensor types was carried out and their key operational parameters (τ₀, KSV, heterogeneity, T-coefficients), and calibration equations for the different conditions were determined and compared to each other and the results of conventional O₂ calibration. Overall, barometric calibration method using Rotavap provides a useful alternative to conventional O₂ calibration methods, being simple, accurate, convenient and versatile.