Loop Calibration for TCD Analyzers Tutorial

Septum

Each loop must be calibrated prior to its first use to determine its precise volume under local conditions. Calibration consists of:

  • Determining the average area of a series of peaks generated by injections of a known volume of gas through the analyzer septum using a syringe.
  • Determining the average area of a series of peaks generated by injections of the same gas using the analyzer’s internal loop.
  • Calculating the volume of the loop by comparing the average peak area generated by the loop injections with that generated by the syringe injections.
  • Entering the calculated loop volume under Unit [n] > Unit Configuration.

Step 1: Create a Sample File

Create the sample file and insert a Loop Calibration experiment on the Analysis Conditions tab.

  A loop calibration must be created for each loop. For Loop Calibration, select a carrier gas, flow rate, and loop gas that will commonly be used for sample analyses.

Step 2: Perform the Analysis

  1. Install the correct injection loop.
  2. Go to Unit > Sample Analysis and select the sample file for the loop calibration.
  3. Click Next to accept the default values, then click Start.
  4. Inject 80% of the loop volume. For example, if calibrating the 1 cm3 loop, inject as close to 0.8 cm3 of gas as possible.
 

Pay close attention to the instructions provided in each prompt and perform the steps in the order given. Most accurate data results from keeping injection size as consistent as possible. Injection errors may be evident in the data and may make it necessary to repeat the experiment.

After the last manual injection, the analyzer automatically makes the same number of injections using the loop.

Step 3: Generate the Report

Peak Editor

When properly performed, each manual and automatic injection results in a peak. When the Results view of the Start Analysis window is selected, each peak can be viewed as it is collected. The area under the peak corresponds to the amount of gas injected.

  1. Go to File > Open > [.SMP]. Open the .SMP file containing the calibration experiment. Verify the defined peaks are properly marked (or correct them) using the Peak Editor.
  2. On the Reports tab, select only the Loop Calibration report option. Click Preview to view the results, including the Loop Volume.

  3. Go to Unit [n] > Unit Configuration. In the Loop Volume field, enter the Loop Volume.

 

Generate the Pulse Chemisorption Report

Peak Editor

Open the Peak Editor and ensure that peaks are properly marked.

There are three possibilities for each dose of gas injected during Pulse chemisorption :

  • all of the gas is taken up by the sample,
  • some of the gas is taken up by the sample, or
  • none of the gas is taken up by the sample.

When pulse chemisorption is properly performed, there will be some injections of each type. When the data is viewed using the Peak Editor, however, only those injections in which some or none of the gas is taken up will appear as peaks. When all of the gas is taken up by the sample, none of it reaches the detector and, therefore, the peak area is zero. These types of peaks are detected automatically by the application and do not require marking.

  1. Go to File > Open > .SMP file.
  2. Select the sample file used with this analysis. Click OK.
  3. On the Sample Description tab, click Active Metals.
  4. Verify that the Stoichiometry Factor and the % of Sample Mass values are correct.
  5. Click OK.
  6. Open the Peak Editor and click Calibration.
  7. Verify that the values for the loop (or manual injection) volume, ambient temperature, atmospheric pressure, and active concentration are accurate.
  8. Go to Report Options > Pulse Chemisorption to set the report options. Click OK, then click Preview to preview the report, or go to Reports > Start Report > SMP file to generate the report.