1.9 Peak Analysis

GSB-pa-tutorial

In this lesson we will perform fitting, including deconvolution of overlapping peaks and baseline correction.

Multiple Peak Fit with Deconvolution

1. Let's continue with the project file we saved in the previous lesson. Create a new folder in Project Explorer, rename it as Peak Analysis, then go to the empty folder.
2. In a new workbook, import the file <Origin EXE Path>\Samples\Spectroscopy\HiddenPeaks.dat.
3. Highlight column B and create a line plot.
4. With the graph window active, click Analysis: Peaks and Baseline: Multiple Peak Fit. This will open the Multiple Peak Fit dialog. Set the Peak Function drop-down as Gauss and click OK.
5. A Get Points dialog will open within the graph window. Note that you can re-position this dialog within the window. Double-click on a peak center to select it. Select a total of 7 peaks as in the following image, including two hidden peaks:
   

If you click the Open NLFit button in the Get Points dialog, the NLFit dialog will open with the peak centers initialized with your selection. You can further control the fitting process as desired.

6. After selecting all seven peaks, click the Fit button. A fit report will be added to the workbook.

Fit Peaks with Baseline

1. This part of the lesson assumes you have OriginPro. Start with a new workbook and import the file <Origin EXE Path>\Samples\Spectroscopy\Peaks_on_Exponential_Baseline.dat.
2. Highlight column B and then click Analysis: Peaks and Baseline: Peak Analyzer. This will open the Peak Analyzer dialog, and a preview window displaying the selected data.
3. In the bottom panel, select the Fit Peaks (Pro) choice under Goal. The top panel will update, displaying a map of the steps involved in the peak fitting process.
4. Click Next. On the Baseline Mode page, select User Defined for Baseline Mode. Click Next to go to the Create Baseline page. You can then see in the preview window that 8 anchor points connected by a red line, are added to the spectrum. This is the baseline created using the current settings. Now click the Prev button to go back to the Baseline Mode page to adjust the baseline mode settings.
5. Click the Find button below Number of Points to Find, to find the baseline anchor points in the spectrum. Eight (8) anchor points are added.
   
6. Clear the Enable Auto Find checkbox and then click the Add button to add one or more anchor points on the spectrum. Double-click on the tail of the spectrum like the following image to add 1 anchor point.
   
7. Note that you can also select and delete anchor points. Click Done to return to the Peak Analyzer.
8. Select the Snap to Spectrum checkbox to force anchor points to snap to the closest data point in the spectrum. Click Next.
9. On the Create Baseline page, select Fitting in the Connect by option. Select ExpDec2 for Function under the Fitting branch. Click Next twice to go to the Find Peaks page.
10. Click the Find button. Two (2) peaks are found in the preview.

There are several options available for peak finding including a 2nd derivative method to find overlapping peaks. You can also view the 2nd derivative curve, and turn on smoothing to help find peaks in noisy data.

11. Click Next to go to the Fit Peaks page. Accept defaults and click Finish to perform peak fitting. A graph containing fitting results is generated.

You can click the Fit Control button to control the fitting process including fixing and sharing parameters, and specifying bounds and constraints.

12. Now, let's customize the Fitting Results table to hide some peak properties we don't want to display. Right-click on the table and select Peak Report Field... from the context menu. The Peak Report Field dialog will open, listing all properties that can be included in the table. You can remove or change the order properties in this dialog. Select Peak Gravity Center and click the Remove button to hide it. Do the same for Peak Area by Integrating Data(%). Press OK to update the table in the graph.
    

Save your project file.