Breath-by-breath measurement of exhaled ammonia by acetone-modifier positive photoionization ion mobility spectrometry via online dilution and purging sampling.

Exhaled ammonia (NH3) is an essential noninvasive biomarker for disease diagnosis. In this study, an acetone-modifier positive photoionization ion mobility spectrometry (AM-PIMS) method was developed for accurate qualitative and quantitative analysis of exhaled NH3 with high selectivity and sensitivity. Acetone was introduced into the drift tube along with the drift gas as a modifier, and the characteristic NH3 product ion peak of (C3H6O)4NH4+ (K0 = 1.45 cm2/V·s) was obtained through the ion-molecule reaction with acetone reactant ions (C3H6O)2H+ (K0 = 1.87 cm2/V·s), which significantly increased the peak-to-peak resolution and improved the accuracy of exhaled NH3 qualitative identification. Moreover, the interference of high humidity and the memory effect of NH3 molecules were significantly reduced via online dilution and purging sampling, thus realizing breath-by-breath measurement. As a result, a wide quantitative range of 5.87-140.92 µmol/L with a response time of 40 ms was achieved, and the exhaled NH3 profile could be synchronized with the concentration curve of exhaled CO2. Finally, the analytical capacity of AM-PIMS was demonstrated by measuring the exhaled NH3 of healthy subjects, demonstrating its great potential for clinical disease diagnosis.

Breath-by-breath measurement of exhaled ammonia by acetone-modifier positive photoionization ion mobility spectrometry via online dilution and purging sampling / 药物分析学报

Exhaled ammonia(NH3)is an essential noninvasive biomarker for disease diagnosis.In this study,an acetone-modifier positive photoionization ion mobility spectrometry(AM-PIMS)method was developed for accurate qualitative and quantitative analysis of exhaled NH3 with high selectivity and sensitivity.Acetone was introduced into the drift tube along with the drift gas as a modifier,and the characteristic NH3 product ion peak of(C3H6O)4NH4+(K0=1.45 cm2/V·s)was obtained through the ion-molecule reaction with acetone reactant ions(C3H6O)2H+(K0=1.87 cm2/V·s),which significantly increased the peak-to-peak resolution and improved the accuracy of exhaled NH3 qualitative identification.Moreover,the interference of high humidity and the memory effect of NH3 molecules were significantly reduced via online dilution and purging sampling,thus realizing breath-by-breath measurement.As a result,a wide quantitative range of 5.87-140.92 μmol/L with a response time of 40 ms was achieved,and the exhaled NH3 profile could be synchronized with the concentration curve of exhaled CO2.Finally,the analytical capacity of AM-PIMS was demonstrated by measuring the exhaled NH3 of healthy subjects,demon-strating its great potential for clinical disease diagnosis.

Rapid volatiles fingerprinting by dopant-assisted positive photoionization ion mobility spectrometry for discrimination and characterization of Green Tea aromas.

Aroma is one major concern of tea flavor and represents an essential criterion for quality evaluation. Herein, we presented a novel approach for rapid, non-destructive and real-time fingerprinting of green tea aromas using ion mobility spectrometry (IMS) without prior sample treatment. Positive photoionization with acetone as dopant was selected as suitable source for tea volatiles analysis in comparison to other sources. To demonstrate the effectiveness of presented method, chestnut-like aroma, an indicator of high-quality green teas, was distinguished from others using IMS fingerprinting. In particular, three sub-types with subtle difference in sensory evaluation, i.e., tender, pure and roasted chestnut-like aroma, were classified by IMS fingerprinting in combination with chemometrics with an overall predictive accuracy of 95.6%. Furthermore, we demonstrated a strategy of two-dimensional IMS profiling for capturing the "dynamics" of tea volatiles. To our knowledge this is the first report of tea aroma analysis using IMS-based tool, which may serve as a complement to the conventional tea sensory evaluation and is promising for process monitoring during tea manufacture.