RESUMO
PURPOSE: In this study, we proposed a new sensitive quantitative method for detecting helium in human blood by gas chromatography-selected-ion monitoring (SIM)-mass spectrometry (GC-SIM-MS) using naturally existing neon-21 in air as internal standard (IS). METHODS: GC-SIM-MS analysis was performed on a double TC-Molsieve 5A capillary column (total length 60 m) for the separation of permanent gases by a single-run experiment. By using hydrogen as the carrier gas, the analyte (helium) and IS (neon-21) were separated on the double column, and detected at m/z 4 and 21, respectively. The ratio of the peak area of helium-to-neon-21 was used for obtaining the calibration curve for helium determination. RESULTS: The limits of detection and quantification of helium under the present GC-SIM-MS conditions were as low as 1.8 and 6.0 ppm, respectively. The proposed GC-SIM-MS method also showed high repeatability with relative standard deviation at 1.3-5.1%, indicating that the use of neon-21 as IS was valid for reliable helium assays. The successful quantification of helium in the headspace of vacuum blood collection tubes containing the whole blood from four humans who died of helium inhalation was achieved using the proposed neon-21-aided GC-SIM-MS method; the values obtained for helium were 24-497 ppm. CONCLUSIONS: The proposed GC-SIM-MS method in combination with the naturally existing neon-21 as IS is most recommendable for quantitative assays of helium in biological samples because of its simplicity and extremely high sensitivity.