This is part 1 of a tour through PEAXACT - Software for Quantitative Spectroscopy from S-PACT. It explains the concept of models and samples, introduces the main window, and demonstrates the interactive what-you-see-is-what-you-get model editor.
Models and Samples
PEAXACT is an interactive Windows App for the quantitative analysis of UV/VIS/IR/Raman/NMR spectra. Its central element is a model. You create, edit, and train models, and then apply models to analyze measured samples. A PEAXACT model contains six sub-models:
- Data Pretreatment Model - provides options for the manipulation of sample spectra
- Integration Model - specifies peaks for peak integration
- Hard Model - a peak-based representation of spectra used by Spectral Hard Modeling methods (e.g., Indirect Hard Modeling and Hard Modeling Factor Analysis)
- Calibration Model - predicts numerical sample feature, e.g., concentrations
- Classification Model - identifies categorical sample features, e.g., for material class
- Custom Model - extends the built-in analyses by user-definable custom results
Other central elements in PEAXACT are samples. Samples consist of a measured signal (e.g., spectrum) and features associated with them, e.g., concentrations, temperature, measurement time, ... Samples are used for data visualization, model building, and of course, for analyses.
The PEAXACT Main Window
Use the PEAXACT main window to manage your models, create and edit new models, and conduct analyses to extract information from your spectra.
- The Model Tree Panel (top-left) displays models as trees. Use it to navigate through the model structure.
- The Samples Panel (bottom-left) displays a list of loaded samples.
- The Properties Panel (top-right) displays model parameters and allows you to edit them.
- The Plot Panel (bottom-right) displays the selected model and spectrum and offers a way to interactively edit the model with the mouse.
What you see is what you get
A nice concept of PEAXACT is its What-You-See-Is-What-You-Get (WYSIWYG) editor. For instance, if you make changes to the Pretreatment Model, you immediately see the effect on the selected spectrum. And if you drag an Integration Model Peak with the mouse, you immediately see how the peak area gets re-calculated. You will learn more about Integration Models in a later part.
You can even interactively build and modify peak models - so-called Hard Models - to deconvolve complex overlapping signals. You will learn more about Hard Models in a later part.
Many of the modeling steps are also automated, but just being able to see how a model fits your spectra is a great way to learn more about the measured system. It also makes modeling with PEAXACT a pleasant experience.