Setting up Libraries Using Search Plus

Author
John Arthur
Product Manager

PerkinElmer, Brandon Office Park, 530 – 540 Springvale Road,
Glen Waverley, VIC, 3150, Melbourne, Australia

Setting up Libraries Using Search Plus

Creating a New Library

The Create Library command, in the Search Plus option, enables you to create a new library. You can then add entries to this library with the Add to Library, Build Library, and Append Library commands.

Creating the library file

1. Display the Library Utils menu and choose Create Library.

2. In the Create Library dialog, type the name of the new search library, including the full path, in the Library Name text box, or choose Browse, and use the file selector to find the required search library.

3. Choose the library size.
The numbers in the Select Size area specify the maximum number of entries that can be added to the library.

4. Choose a library Type and Ordinate Type.
If you choose NIR, you can perform only a Euclidean Search.

5. You can only perform an interpretative search on mid-infrared spectra with an ordinate type %T %R or A. You cannot include mid and near infrared spectra in the same library. Spectra of different ordinate types cannot be included in the same library.



6. For Raman libraries, choose Type MIR and Ordinate Type INT.

7. Enter a Copyright Message of up to 60 characters and choose OK.
The Create Library dialog closes.

Adding spectra to your new library

Now you will add some spectra to the library.

1. Display the Library Utils menu and choose Build Library.
The Build Library dialog is displayed. Note that the Library Name is the library that you have just created.

2. In the Drive / Directory text box choose select the directory that contains the spectra you want to add to the library.

3. Choose Add All.
All the Source Spectra are copied to the Spectra to Add text box.

4. Choose OK.
Spectrum Search Plus starts to build the library.

NOTE: If any of the spectra do not have valid spectrum ids, a message is displayed. You must enter a spectrum ID before you can continue. The spectrum ID must be of the format ABNNNB, where A is a letter, B is either a letter or a number, but not V through Z, and N is a number.

5. If you use files of peak tables then you can only build a search library. The Build Library command automatically generates the PSU data required for a library entry.

Adding the current sample to a library

The Add to Library command enables you to add the current sample to a library. It is active as soon as a sample has been specified. A maximum of 127 peaks is allowed for a library peak table.

1. Display the Library Utilities menu and choose Add to Library.

2. In the Add to Library dialog, enter a spectrum id for the entry.
The spectrum ID must be of the format ABNNNB, where A is a letter, B is either a letter or a number, but not V through Z, and N is a number.

3. Type a Spectrum Name of up to 60 characters following the naming convention.

NOTE: If the spectrum id and name are available in the peak table, the Spectrum id: and Spectrum Name: text boxes defaults to those values.

4. Type the name of the new search library, including the full path, in the Library Name text box, or choose Browse and use the file selector to find the required search library.

5. Choose OK.
The entries are added to the Search Library.

What can I use Search for?

IR Search helps you to identify an unknown material. It will search through a library or libraries to find the spectra that best match your unknown sample. It can also interpret your unknown spectrum directly by determining from the pattern of peaks (and absences of peaks) which Possible Structural Units (functional groups) are likely to be present.

When should I use Compare and when should I use Search?

You should use IR Search when you do not know the identity of your sample, a search compares your sample spectrum with libraries that can contain many spectra, or compares the peaks in your spectrum with many Possible Structural Units to identify your sample.

Even if your sample is not in the libraries, an interpretation will give you information on what functional groups are present in your sample, and provide clues as to what it is.

If you know that your sample is one of a range of materials or if you want to measure how similar your spectrum is to another spectrum, you should use Compare; this compares your sample spectrum with one other spectrum or several spectra and reports the degree of similarity between the spectra.

What do the Different Search Types do?

There are three types of search available:

• Interpretation - an interpretation compares the peaks in your sample spectrum with the peaks that correspond to 896 PSUs (Possible Structural Units). A list of the PSUs in your sample spectrum is displayed. You do not need to have a search library to perform an interpretation.
• Euclidean - a Euclidean search compares every point in your sample spectrum with the points in spectra in a search library.
• Library search - a library search compares the position of the peaks in your sample spectrum with the position of peaks in the spectra in a search library.

What Type of Search should I use?

An interpretation is useful:

• If you think that your sample spectrum will not be present in a search library, the interpretative search will indicate what PSUs are present in the sample.

A library search is useful because:

• it is faster than an Euclidean search - it is comparing a relatively small number of peak positions whereas a Euclidean search compares a much larger number of points in the spectra;
• If you know that your sample contains a mixture of materials you can set up the search so that additional peaks from the other components are ignored.

A Euclidean search is useful where the search library spectra are not distinguishable from each other, for example:

• within classes of chemically-similar complex compounds where bands overlap strongly, the Euclidean search compares all the points in the spectrum and hence identifies peaks that are less-well separated;
• when you are searching for mixtures that are different in the proportions of their components, a Euclidean search takes account of peak intensity as well as position;
• When the signal-to-noise ratio of your spectrum is poor, a Euclidean search effectively ignores the noise in the spectrum.
• If you are searching for near infrared or Raman spectra, only a Euclidean search is available.
• A Euclidean search compares every point in a spectrum with spectra in a search library; the results from a Euclidean search are more reliable than a library search.

If you are using near infrared or Raman spectra only a Euclidean search is available.

If your spectra does not have an ordinate axis in %T, %R or A only a Euclidean search is available.

What do the Search Results Mean?

When a search finishes the results are displayed as hit lists. If you have chosen Display in the Graph Window section of the Display tab, a graph window displaying your sample spectrum and spectra of the top items in the hit list are also displayed.

The hit lists give the compounds that most closely match your sample spectrum. There are six different hit lists that use different methods for scoring.

Euclidean	A hit list of the best spectrum shape matches.
PSU/peak	A hit list based primarily on the PSU score. The peak match score is used only to rank those hits with identical PSU scores.
PEAK/psu	A hit list based primarily on the peak match score. The weight given to PSU matches is lower for high peak match scores.
MIX PSU	A hit list based on the PSU score, but allowing for the spectrum being that of a mixture of compounds.
MIX PEAK	A hit list based on peak matches, but allowing for the spectrum being that of a mixture of compounds.
Peak Match	A hit list based on the peak match score only.

The hit lists are a useful aid to identification. However, we recommend that you make a visual comparison of the sample and library spectra before accepting the identification.

To display the sample spectrum and an item in the hit list:

• Double-click on an item in a hit list.

Starting a Search

1. Display and select the spectrum or spectra that you want to identify.

2. Display the Process menu and choose IR Search.

The hit lists are displayed.

We advise you not to select several spectra and several hit lists simultaneously, because the display can become overcrowded and confusing.

Displaying unknown and library spectra

You can see how well the unknown spectrum matches a library spectrum by double-clicking on the spectrum name in a hit list. The two spectra are displayed.

IR Search Setup - Regions

You may want to search for your spectra over a limited abscissa range or to exclude specific regions of your spectrum from the search; the Regions tab enables you to specify the abscissa range and to exclude regions.

Range

If you choose Full Overlap, the entire range that overlaps is used in the search. If you choose Manual, you can enter your own Start and End abscissa values for the region to be searched.

Blanks

Specifies regions to be excluded from the search.