Abstract
<jats:p>The method of synchronous thermal analysis, combining thermogravimetry and differential scanning calorimetry, is widely used to study various processes and properties of materials. This method is based on the simultaneous recording of changes in sample characteristics upon heating. Mass spectrometry is most often used to analyze the evolved gases, which significantly expands the capabilities of this method. In this study a lag in the mass spectrometer signals for mass numbers 18 (water) and 44 (carbon dioxide) from the sample mass loss signal was detected in experiments on the thermal decomposition of sodium bicarbonate. This effect is presumably due to the time required for gaseous products to pass through the capillary before entering the ion source of the mass spectrometer. Although this lag is insignificant relative to the overall experimental time, some studies have taken this effect into account. In this study, this lag time was calculated based on a series of measurements of the thermal decomposition of sodium bicarbonate samples. The average ion current signal lag time for water was 21.68 s, while for carbon dioxide it was 8.64 s. These results are consistent with the velocity values typical of gas movement in capillary columns. It was also found that the signal lag time is independent of the initial sample mass. The results of this study can be used to supplement existing software packages for processing experimental data obtained using the system.</jats:p>