In OriginPro, the Peak Analyzer is capable of creating and subtracting baseline. There are various ways for baseline creation. You can generate baseline anchor points automatically or manually and then connect them with interpolation or fit them with a function.

Steps

Create baseline with 2nd Derivative method

1. Start a New Workbook and import the <Origin EXE Folder>\Samples\Spectroscopy\Baseline.dat. Highlight the second column. In the main menu, select Analysis: Peaks and Baseline: Peak Analyzerto open the dialog of the Peak Analyzer.
2. In the first page (the Goal page) of the Peak Analyzer, select Create Baseline as Goal. Click Next to go to the Baseline Mode page.
3. Next we are going to create an user defined baseline for this spectrum by defining anchor points. On the Baseline Mode page, select User defined from the Baseline Mode dropdown list. Check on Snap to Spectrum to make sure when you add or move a baseline anchor point, it will be pulled back onto the spectrum.
4. The first two methods in Anchor Points Finding are the most commonly used, and they can find anchor points automatically based on the derivative of the spectrum. If the baseline is approximately constant, 1st Derivative and 2nd Derivative is more powerful, otherwise, we should use 2nd Derivative. In this example, the baseline is more curly, so we use 2nd Derivative(zeros) method for locating anchor points.For other methods in Anchor Points Finding and related smoothing parameters, you can refer to the link: Baseline Mode Page.
5. Now click the Find button in the Baseline Anchor Points group. You can preview the anchor points in preview window.
6. Click Next to go to the Create Baseline page, select Interpolation in the Connect by drop-down list. In Interpolation method group, select Spline from the drop-down list. You can preview the spectrum in preview window, and then click Finish to get the baseline data.

Create baseline with ALS Method (Pro)

1. Start from the Baseline Mode page, and select the Asymmetric Least Squares Smoothing Baseline (ALS) as the baseline method. The ALS baseline can be tuned easily with a few parameters without pre-selecting any anchor points.
2. Click Next go to Asymmetric Least Squares Smoothing Baseline page, adjust the parameters to make the baseline optimal, then click Finish button to output the results table and graph.

Subtract Baseline from a Spectrum

1. If you want to subtract baseline, select Subtract Baseline as the Goal at start page.
2. After you created a baseline, click Next button to go to Subtract Baseline page.
3. Click Subtract button for previewing the subtracted data. The baseline data and subtracted spectrum will be outputted after clicking Finish button. The figures below displayed the Subtract Baselinepage and the preview of the subtracted spectrum.

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1. Determine the X-axis and the Y-axis of the spectrum. The X-axis of an IR spectrum is labeled as “Wavenumber” and ranges in number from 400 on the far right to 4,000 on the far left. The X-axis provides the absorption number. The Y-axis is labeled as “Percent Transmittance” and ranges in number from 0 on the bottom and 100 at the top.

2.Determine the characteristic peaks in the IR spectrum. All IR spectra contain many peaks. However, determine the large peaks on the spectrum because they will provide the data necessary to read the spectrum.

3. Determine the regions of the spectrum in which the characteristic peaks exist. The IR spectrum can be segregated into four regions. The first region ranges from 4,000 to 2,500. The second region ranges from 2,500 to 2,000. The third region ranges from 2,000 to 1,500. The fourth region ranges from 1,500 to 400.

4. Determine the functional groups absorbed in the first region. If the spectrum has a characteristic peak in the range of 4,000 to 2,500, the peak corresponds to absorption caused by N-H, C-H and O-H single bonds.

5. Determine the functional groups absorbed in the second region. If the spectrum has a characteristic peak in the range of 2,500 to 2,000, the peak corresponds to absorption caused by triple bonds.

6. Determine the functional groups absorbed in the third region. If the spectrum has a characteristic peak in the range of 2,000 to 1,500, the peak corresponds to absorption caused by double bonds such as C=O, C=N and C=C.

7. Compare the peaks in the fourth region to the peaks in the fourth region of another IR spectrum. The fourth is known as the fingerprint region of the IR spectrum and contains a large number of absorption peaks that account for a large variety of single bonds. If all the peaks in an IR spectrum, including those in the fourth region, are identical to the peaks of another spectrum, then you can be assured that the two compounds are identical.