Volatile compounds released by Nalophan; implications for selected ion flow tube mass spectrometry and other chemical ionisation mass spectrometry analytical methods

Abstract

Rationale Nalophan bags are commonly used to collect breath samples for volatile metabolite analysis. Volatile organic compounds (VOCs) released from the polymer can, however, be mistaken as breath metabolites when analyses are performed by selected ion flow tube mass spectrometry, SIFT‐MS, or techniques that depend on a proper understanding of ion chemistry. Methods Three analytical techniques were used to analyse the VOCs released into the nitrogen used to expand Nalophan bags, viz. gas chromatography/mass spectrometry (GC/MS), secondary electrospray ionization mass spectrometry (SESI‐MS) and selected ion flow tube mass spectrometry (SIFT‐MS). The most significant VOCs were identified and quantified by SIFT‐MS as a function of storage time, temperature and humidity. Results The consistent results obtained by these three analytical methods identify 1,2‐ethanediol (ethylene glycol) and 2‐methyl‐1,3‐dioxolane as the major VOCs released by the Nalophan. Their concentrations are enhanced by increasing the bag storage temperature and time, reaching 170 parts‐per‐billion by volume (ppbv) for ethylene glycol and 34 ppbv for 2‐methyl‐1,3‐dioxolane in humid nitrogen (absolute humidity of 5%) contained in an 8‐L Nalophan bag stored at 37°C for 160 min. Conclusions Using H3O+ reagent ions for SIFT‐MS and SESI‐MS analyses, the following analyte ions (m/z values) are affected by the Nalophan impurities: 45, 63, 81, 89 and 99, which can compromise analyses of acetaldehyde, ethylene glycol, monoterpenes, acetoin, butyric acid, hexanal and heptane.

Determination of trace compounds and artifacts in nitrogen background measurements by proton transfer reaction time‐of‐flight mass spectrometry under dry and humid conditions

“…It appears as an artifact with a remarkably high humidity dependency with a signal increase under humid condition of a factor of 21 times. The peak at m/z 89 has been previously ascribed to 2‐methyl‐1,3‐dioxolane or butyric acid 105 . Figure 7E shows a peak at m/z 91 with positive humidity dependency, which appears to be a gas impurity and memory effect.…”

“…The 2-methyl-1,3-dioxolane or butyric acid. 105 Figure 7E shows a peak at m/z 91 with positive humidity dependency, which appears to be a gas impurity and memory effect. Figure 7E shows only two tentative assignments; however, at this m/z, the following isobars can contribute to the signal: C 7 H 7 + , 82 aromatics, 110 and it is assigned here to 1,2,4-trimethylbenzene.…”

Combination of Exhaled Breath Analysis with Parallel Lung Function and FeNO Measurements in Infants

“…It shows a tendency toward negative values, indicating that the signals tend to be reduced in the offline measurements, suggesting a general trend of adsorption and losses of the metabolites onto the surface of Nalophan bag. Positive values probably correspond to impurities released by the Nalophan bags, some of which have been previously characterized …”

A SIFT-MS study of positive and negative ion chemistry of theortho-,meta- andpara-isomers of cymene, cresol, and ethylphenol

“…A nalophan sample bag was therefore used in which the bags were filled with dry pure air (generated by zero air generator Parker Hannifin Manufacturing Ltd, Model 636273000) and were spiked separately with the 9 different aromatic compounds, used for SIFT-MS analysis. Nalophan is known to release ethylene glycol, 25 although it is not believed that this would interfere with the aromatic species investigated in this study. Nine different aromatic compounds were analysed, for which a large concentration of standards headspace (from a saturated atmosphere of having injected droplets of standard liquid in to a blank nalophan bag) of each species was injected using a syringe into the nalophan bags, followed by subsequent dilutions.…”