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Select PDA Spectra

When you have imported DAD/PDA Spectra using the ChromSpec menu's Import Matrices option, all subsequent options that require a selection of a single or multiple spectra will display the following the dialog:

Automatic Creation of D1(wl) and D2(time) Matrices

When you import 3D chromatographic PDA/DAD spectra for any one of the three import methods, derivative matrices are also automatically created using an automated Savitzky-Golay algorithm that directly generates a first derivatives with respect to wavelength and a second derivative with respect to time.

Use the Spectra Only button to select just the spectral matrices as shown above. Use the D1(wl) Only button to select all first derivative spectra, and the D2(time) Only button to select all second derivative spectra. There are also Select All and Clear All options.

The main purpose of the D1 spectra is to find zones where the first derivatives of the various components pass through zero. Please see the Fitting Coeluting Peaks tutorial for using identified zero first derivative wavelength values for estimating the areas of coeluting peaks with slightly different UV-VIS spectra.

The D1(wl) and D2(time) spectra are designed for the S/N of a typical DAD/PDA spectral matrix. If your analysis has a low S/N due to very low concentrations or a very high sampling rate, or if you want a different partial derivative, you may need to import the spectra as opposed to the precomputed derivative spectra by extracting the wavelengths or times of interest for the chromatography or spectroscopy, and only then creating the first or second derivatives with the DSP menu's Smooth option.