2.3. Quantitative analysis
The amount of acetylene in a sample was estimated using a mass
chromatogram reconstructed with a molecular ion at m/z 26 for
acetylene and a fragment ion at m/z 43 for isobutane.
Calibration curves were prepared using the peak area ratios of
acetylene to isobutane against acetylene amounts added to blank
blood (1.08–8.63 g per 0.2 ml) and blank urine (2.16–10.8 g per
1.0 ml), by plotting five concentrations for each. Then, 9.64 g of
isobutane was added to each sample, and calculated using the ideal
gas law under the atmospheric pressure 1010 hPa and temperature
20 ◦C. To prevent acetylene from being volatilized, we divided the
samples into two bottles for storage. One was used to establish
measurement conditions, and the other for measuring concentration.
We decided the calibration concentrations from the results of
sample injections from one group of bottles.
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