Soru

Isotope ratio mass spectrometry sample preparation requires a rigorous procedural sequence to ensure valid forensic data. Before initiating the combustion sequence in the elemental analyzer, the organic sample must be thoroughly homogenized. However, the pulverization step required for this homogenization can only commence after the sample has been lyophilized. Once the sample is properly homogenized, it is encapsulated in a specialized tin receptacle, a step that immediately precedes the combustion sequence. Meanwhile, the mass spectrometer's reference gas calibration must be executed concurrently with the lyophilization phase, ensuring system equilibrium is achieved well before the sample enters the analyzer. Following combustion, the resulting gases are chromatographically separated prior to final isotopic measurement.

According to the protocol detailed above, which of the following actions is performed immediately after the phase that occurs concurrently with the reference gas calibration?