ABSTRACT
Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) is an analytical technique for real-time quantification of trace gases in air or breath samples. SIFT-MS system thus offers unique potential for early, rapid detection of disease states. Identification of volatile organic compound (VOC) masses that contribute strongly towards a successful classification clearly highlights potential new biomarkers. A method utilising kernel density estimates is thus presented for classifying unknown samples. It is validated in a simple known case and a clinical setting before-after dialysis. The simple case with nitrogen in Tedlar bags returned a 100% success rate, as expected. The clinical proof-of-concept with seven tests on one patient had an ROC curve area of 0.89. These results validate the method presented and illustrate the emerging clinical potential of this technology.
Subject(s)
Algorithms , Diagnosis, Computer-Assisted/methods , Gases/analysis , Organic Chemicals/analysis , Pattern Recognition, Automated/methods , Spectrometry, Mass, Electrospray Ionization/methods , Artificial Intelligence , Biomarkers , Breath Tests/instrumentation , Breath Tests/methods , Computer Simulation , Humans , Kidney , Kidney Diseases/therapy , Nitrogen/chemistry , Renal Dialysis , Reproducibility of Results , Spectrometry, Mass, Electrospray Ionization/instrumentation , VolatilizationABSTRACT
The selected ion flow tube mass spectrometry (SIFT-MS) technique enables real time analysis of trace volatiles at ppb levels without preconcentration steps or chemical derivatization. Most previous studies of trace compounds on the breath were analyzed using gas chromatography where enhanced detection sensitivity was achieved by concentrating the breath using cryogenic or adsorption trapping techniques. In this paper, we have examined volatile organic substances, isoprene, acetone, ammonia and ethanol in breath before and after smoking a cigarette. It is interesting that isoprene levels increased in all the subjects after smoking one cigarette with a mean increase of 70%. The mean increase for acetone was found to be 22%. In contrast to isoprene, a decreasing ethanol level was observed in all the subjects except one with the negative mean decrease of 28%. Further SIFT-MS studies also have high-lighted some organic substances produced even by unburned cigarettes, US and New Zealand products. Certain US brands have shown much higher levels of volatile species than cigarettes produced in New Zealand.
Subject(s)
Acetone/analysis , Ammonia/analysis , Breath Tests/methods , Butadienes/analysis , Ethanol/analysis , Hemiterpenes , Mass Spectrometry/methods , Pentanes , Smoking/metabolism , Adult , Computer Systems , Female , Humans , Male , Methanol/analysis , Middle Aged , New Zealand , Propylene Glycol/analysis , United States , VolatilizationABSTRACT
We show how the concentration of the breath gases ammonia, acetone, and isoprene vary with time during exercise using the new selected ion flow tube mass spectrometry (SIFT-MS) technique. The expired breath concentrations of ammonia, acetone and isoprene were observed within the range of 50-500, 100-1400 and 5-400 ppb, respectively. Increasing acetone levels were observed for most subjects during the exercise period. However, isoprene levels decreased with time during exercise. Older subjects showed higher levels of isoprene compared with younger subjects. The ammonia time profile with exercise showed both decreasing and increasing patterns for different subjects.
