Most spectrophotometers can be controlled by a program provided by the manufacturer – an SCP (used here as an abbreviation f for Spectrophotometer Control Program).
Generally, the SCP can be set to report data (e.g., single absorbance or fluorescence values) at a specified time interval and to save the resultant data to a file. By specifying the same reporting interval for both T-App and the SCP, and starting the two processes at the same time, the resulting data can be moved into a program such as Microsoft Excel to obtain absorbance or fluorescence as a function of temperature.
Most SCP programs can also be set to collect scans at a specified time interval and save the resultant scans to a file or files. By stepping or ramping the temperature, scans collected at a series of temperatures can be correlated with those temperatures.
The box below is an example procedure for manually using T-App in coordination with an SCP:
1. Turn the temperature controller on.
2. Start T-App. The application connects to the controller automatically. It also commands the controller to begin sending temperature reports automatically every 3 seconds and begins plotting CT (the Cell holder Temperature) in the graph window. If a thermistor probe is connected to the controller, it also automatically begins to plot PT (the Probe Temperature). Although HT (the Heat exchanger Temperature) is automatically reported, those data are not plotted unless the user chooses to have them included in the graph.
3. Set the target temperature (TT) to 10 ⁰C.
4. Turn temperature control on.
5. Wait until CT is stable (indicated by a change from flashing to always on of an LED on the controller and of a simulated LED in the T-App control panel. Then allow about 10 minutes for the sample temperature to “catch up”.
6. Select the Plot>(Time Interval …) menu item. In the “Plot Time-Interval” dialog presented, enter 30 in the sec (seconds) text box and click on the OK button.
7. Set the SCP to report every 30 seconds (but do not start the collection immediately).
8. Select the Tools>(Temperature Ramping …) menu item. In the “Ramping Parameters” dialog presented, enter 60 in the End (⁰C) text box and enter 2.0 in the Rate (⁰C/min) text box. When the OK button is clicked a temperature ramp at 2.0 ⁰C/min to end at 60 ⁰C starts immediately.
9. Select the Plot>(Clear & Restart) menu item, to clear the graph and reset the time to 0, and then immediately start the SCP data collection.
10. When the ramp reaches 60 ⁰C, select the Plot>Stop menu item and stop data collection by the SCP.
11. Copy the time/temperature data and paste it into Excel starting at cell A1 (or save it to a file for later use). Column A will contain time in minutes and Column B will be temperature in ⁰C. If a time stamp is included in Column C either delete the column.
12. Copy the SCP data and paste it into Excel starting at cell C1 (or save it to a file for later use). The following assumes Column C contains time and Column D the absorbance or fluorescence intensity.
13. Columns A and C should match closely (perhaps not exactly). Delete columns A and C, leaving temperatures in column A and SCP results in column B.
14. Save the Excel file as a text file.
15. Select the Data>(Load from File into)>(Sample Holder) and, in the “Open File” dialog presented, locate and select the file created in step 14. Click on the small black rectangle near the upper left corner of the graph, enter a new vertical axis label, and press the Enter key. Similarly, use the small black rectangle near the lower right corner of the graph to modify the horizontal axis label to “temperature (⁰C)”.
See Using Scripts with T-App for an example of a Script that would automate steps 3 – 10.