Breath analysis by API/MS--human exposure to volatile organic solvents.

The expired breath of subjects, exposed for periods of ca. 90 min to atmospheres artificially contaminated with low levels of methanol, (ca. 100 ppm) toluene (ca. 50 ppm) or tetrachloroethylene, (ca. 50 ppm) was monitored during and after the exposure period using an atmospheric pressure ionization mass spectrometer, fitted with a direct breath analysis system. The retention of solvent by the subjects, estimated from steady state levels in the expired breath, averaged 82% of the inspired level for methanol, 83% for toluene and 87% for tetrachloroethylene. The elimination of unchanged solvent via respiration during the post exposure period followed first order kinetics with mean half life values of 24 min for methanol, 27 min for toluene and 79 min for tetrachloroethylene.

Applications of a versatile technique for trace analysis: atmospheric pressure negative chemical ionization.

The ability to use ambient air as a carrier and reagent gas in an atmospheric pressure chemical ionization source allows instantaneous air analysis to be combined with hypersensitivity toward a wide variety of compounds. The TAGA (Trace Atmospheric Gas Analyser) is an instrument which is designed to use both positive and negative atmospheric pressure chemical ionization (APCI) for trace gas analysis; this paper describes several applications of negative APCI which demonstrates that the technique is not limited to environmental monitoring. Examples are described which suggest that the TAGA can be used for the detection of illicit drugs and explosives, and for the analysis of breath or skin emissions, as well as for air pollution measurements. The applications are not restricted by the use of ambient air as a reagent gas; addition to the air carrier of various gases allows specific reagent ions such as Cl- or Br- to be generated. Furthermore, in certain situations pure gas carriers can be used to provide even more flexibility in the ion chemistry, with a short term absorber-desorber system used to transfer the sample from the ambient air into the ion source region. The potential uses for APCI are expanding continuously as the understanding of the complex ion-molecule chemistry grows. This paper underlines the complementary relation between the development of new negative chemical ionization (NCI) techniques and practical applications using the TAGA system.

Real-time analysis of breath using an atmospheric pressure ionization mass spectrometer.

A new technique is reported resulting in the direct, instantaneous analyses of trace compounds in breath. The analyses were performed using a commercial atmospheric pressure chemical ionization mass spectrometer (TAGA TM2000 APCI mass spectrometer). A known flow of breath sample is introduced into the ionization region of the mass spectrometer. The study includes the measurement and monitoring in real-time, of breath ammonia during a 24 hour and a 48 hour period. The ammonia profiles indicate a personalized daily pattern associated with each subject. This method appears to be of potential value in routine detection and treatment of hyperammonemia patients. Results also show that it is possible to obtain instantaneous analyses of several naturally occurring metabolites and other substances on breath in the ppm to ppt range, suggesting a number of diagnostic research applications.