Gas Concentration Calibration
After performing an analysis, peak area data can be converted to volume data. The application can perform this conversion when additional information is provided.
In some cases (such as in TPR analyses), the analyzer needs to know how to correlate the signal readings collected in the analysis with the volume of gas uptake at any given point in the analysis. If the analyzer is provided with a series of known gas concentrations, and it records the signal associated with each known concentration, then it can use this information to calculate the concentrations associated with the signals it recorded during the analysis. From that point, it can also calculate the volume of gas associated with each peak in the data.
- Prepare and install a clean, empty sample tube.
- Ensure the correct gases are connected.
- Create the sample file:
- Go to File > New Sample.
- Complete the fields on the Sample Description tab as needed.
- Select the Analysis Conditions tab.
- Click Insert and select Gas Calibration.
- Click OK.
- Select Hydrogen-Argon for Carrier.
- Select Argon for Loop.
- Enter 50 as the Flow rate.
- Click Zones to set the temperature for the analyzer’s heated zones.
- Complete the fields in the Set Temperature Zones window using the following table:
Field | Enter |
---|---|
Analysis | 110 °C |
Block Zone | 100 °C |
Cold Trap | 110 °C |
Filament | 175 °C |
- Click OK to close the Zones window.
- Click OK again to close the Calibration window.
- Click Save As, provide a new file name, then click Close.
- Go to Unit [n] > Sample Analysis.
- Click Browse to locate sample file previously created.
- Click Next three times in this sample file.
- Click Start to start the analysis. Use the other views of the analysis window to observe the progress of the analysis.
During the automatic analysis, the analyzer decreases the proportion of the analysis gas in 10% increments, beginning with 100% and ending with 0%. The resultant data should appear as a series of ten stepwise changes in the TCD signal.
- When the analysis ends, close the Analysis window.
- When the displayed sample temperature reaches the ambient temperature, open the furnace and remove the sample tube.
- Go to Options > Signal Calibration > Open. Select the calibration file, then click OK.
- Click Load Calibration Data then select the sample file for this calibration, then click OK.
- Click OK. The data in the sample file are automatically inserted into the appropriate fields of the Signal Calibration window
Use the cotton gloves provided in the accessory kit when handling heated surfaces. These cotton gloves are not intended to protect hands when heated surfaces are above 60 °C. |
- Assess the data listed in the table. In the Concentrations column, enter the starting and ending gas mixture percentages. The application calculates the percentages for the rest of the table.
- Assess the gas concentration plot, Goodness of Fit, and Coefficients to determine if the calibration file is acceptable. Use your laboratory’s standards to determine what level of linearity is acceptable. As a general guideline, use a calibration file with a very low value for Goodness of Fit (less than 1/2% of the maximum concentration) when 1st or 2nd Degree is specified.
Data points that deviate significantly from linear can be deleted. Evaluate the results when the degree is changed (select a different degree from the drop-down list).
- When satisfied with the calibration file, enter a descriptive name in the Description field.
- Click Save, then click Close.
- Go to Options > Signal Calibration > Report to select a report to generate.