PTR-MS in Italy: a multipurpose sensor with applications in environmental, agri-food and health science

Abstract

Proton Transfer Reaction Mass Spectrometry (PTR-MS) has evolved in the last decade as a fast and high sensitivity sensor for the real-time monitoring of volatile compounds. Its applications range from environmental sciences to medical sciences, from food technology to bioprocess monitoring. Italian scientists and institutions participated from the very beginning in fundamental and applied research aiming at exploiting the potentialities of this technique and providing relevant methodological advances and new fundamental indications. In this review we describe this activity on the basis of the available literature. The Italian scientific community has been active mostly in food science and technology, plant physiology and environmental studies and also pioneered the applications of the recently released PTR-ToF-MS (Proton Transfer Reaction-Time of Flight-Mass Spectrometry) in food science and in plant physiology. In the very last years new results related to bioprocess monitoring and health science have been published as well. PTR-MS data analysis, particularly in the case of the ToF based version, and the application of advanced chemometrics and data mining are also aspects characterising the activity of the Italian community.

Figure 1.

Absolute VOC concentration determination with PTR-TOF-MS. Predicted and measured decrease of alpha-pinene concentrations in a flowtube along with the production of the dominant first order generation product pinonaldehyde upon exposure to ozone. Comparison between model prediction (solid lines) of mixing ratios for alpha-pinene (blue) and pinonaldehyde (red) and measured values by PTR-ToF-MS using Equation 4 (squares) showing an agreement within 10%. Reprinted with permission from ref [23]. Copyright 2012 American Chemical Society.

Figure 2.

PTR-TOF-MS spectrum of a cheese sample headspace. The upper panel shows the mass region (20–100 Th). The lower panels enlarge the regions around few selected peaks. Reprinted with permission from ref. [60]. Copyright 2010 John Wiley & Sons, Ltd.

Figure 3.

Dry cured ham headspace. Exemplificative peaks related to aldehydes and ketones measured by PTR-ToF-MS using different reagent ions. a: H₃O⁺; b: NO⁺; c: O₂⁺. Reprinted with permission from reference [63]. Copyright 2012 Elsevier Ltd.

Figure 4.

Evolution of endogenous ethylene emission for Breaburn, Gold Rush and Golden Delicious apples during shelf life at 20 °C under ambient air room conditions. Reprinted with permission from [65]. Copyright 2012 Springer Science+Business Media, LLC.

Figure 5.

Headspace VOC analysis of apple clones with PTR-ToF-MS. Random Forest graphical output for the discriminant analysis of the PTR-ToF-MS data of apple clone samples. Reprinted with permission from [54]. Copyright 2012 Springer Science+Business Media, LLC.

Figure 6.

Excerpt of the PTR-TOF-MS spectra of six samples collected upstream (dotted lines) and downstream (continuous lines) a biofilter. The upper panel is a detail of the peak at m/z = 60. Numbers indicate the expected exact mass of protonated monosubstituted acetone isotope (60.053) and of protonated trimethylamine (60.0813). At mass 61.0784 the mono substituted isotope of trimethylamine is also indicated. Reprinted from [129], with permission from the copyright holders, IWA Publishing.