Zusammen

Spectroscopy databases are useful in a number of situations - from tracking down impurities to identifying unknowns. Although we've previously covered other spectra databases, today's stop on our continuing tour of free chemistry databases an Web services offers something different still. Spectra Online hosts a diverse collection of spectral data of various types. From the about page:

Spectra Online is a FREE web-based spectral database service for the chemical research community. The spectra in the database are comprised of collections of public domain and other data generously submitted by various institutions and individuals. The database spans many different classes of compounds including drugs, common chemicals, polymers, petroleum products among others. It includes spectral data from many different instrument types such as FT-IR, UV-Vis, NIR, Raman, MS, NMR (13C, 1H and others), XRD and more. Please note that Thermo Electron Corporation does not review the data in the collections; all spectra and related compound information are presented "as-is" in the form they we received.

You'll need to create a free account before viewing any of the spectra on Spectra Online. I found the process to be relatively painless.

Spectra Online's dataset consists mainly of mass- and FT-IR spectra and associated structural data. Spectra have been assembled from a variety of free and proprietary sources. Records can be searched by compound name, CAS Number, molecular formula, and by molecular weight.

A potentially very useful way to search Spectra Online is through a spectrum match. By uploading your own spectrum, it's possible to perform a match based on a variety of criteria such as correlation and Euclidean distance. With such a large assortment of searching methods, an brief explanation of each would be helfpul. When browsing the search results, both the search spectrum and the target spectrum are shown with overlapping x-axes, making identification straightforward.

One thing to be aware of: at various times in my testing, the service seemed to malfunction during queries, giving repeated error messages. Each instance was resolved within a few hours.

Spectra Online hosts many spectra that may be of use. If you're ever looking for match to a chemical unknown, or trying to track down an impurity in your sample, Spectra Online makes a good resource.

Kudos

• Large collection of spectra viewable in graphical format online.
• Spectra referenced to original source collection.

Ideas for Improvement

• Add structure search.
• Enable spectra and structure browsing.
• Promote offline use by offering spectra in JCAMP-DX format.
• Encourage use by eliminating login requirement for viewing spectra.