A microprocessor controlled mass spectrometer for the fully automated purification and isotopic analysis of breath carbon dioxide.

Breath tests that measure the oxidative utilization of 13C labeled substrates have been shown to be clinically useful, but have failed to gain wide acceptance because of the slow and costly isotopic analysis of the breath samples. Therefore we have developed a fully automated, microprocessor controlled CO2 purification and isotopic analysis system. The breath CO2 is cryogenically purified by passage through cold traps of -94 degrees C and -196 degrees to condense water and CO2, respectively. The CO2 is intorduced into a dual inlet, peak-stepping mass spectrometer and analyzed for isotopic content by comparison with a known standard. Thirty samples can be analyzed without operator intervention. Analysis time average 14 minutes per sample, and the analysis has a precision of 0.3% which corresponds to 3 parts excess 13C per 10(6) parts CO2. The speed of analysis is comparable with scintillation counting and permits next day reporting of clinical breath test results. The precision is sufficient for clinical applications as it is less than 0.7% isotopic variation in basal breath CO2.