Posted by: tvasailor | May 1, 2011

Searching TSCA for “Known Unknowns”

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Searching TSCA (Toxic Substances Control Act) Database for Non-Targeted Species

tsca

Previously, we primarily searched the TSCA database using the NIST search (Poster Sessions, ASMS 2001, 2004) by molecular formulae, nominal molecular weight, and monoisotopic mass to identify unknowns in commercial products.  This “spectra-less” database in NIST binary format contained names, CAS Number, molecular weights, and molecular formulae.  We refer to this type of database as “spectra-less” because it contains no computer-searchable EI or CID mass spectra.

We no longer update copies of the TSCA database in NIST format since we have found SciFinder or ChemSpider searches to be better approaches.  However, others might still find the TSCA/NIST approach useful and thus, a copy is made available on this website.

A problem with the NIST search of the TSCA database was that structures were only shown for compounds which were present in the NIST database.  The structures in the NIST EI database were correlated to TSCA entries by  CAS numbers since the TSCA database did not include structural connection tables.  Thus, the absence of structures for many TSCA entries in the hit list made data review tedious.

In addition, there was no way to prioritize the resulting hit list by the number of associated references as we can do with SciFinder and ChemSpider searches.  The number of associated references usually correlates very well with the probability that a component is found in a commercial sample.  Furthermore, SciFinder search results can also be prioritized by proper selection of key words.

We purchased the TSCA database on CD and converted it into NIST binary format for searching.  Originally we could only search by molecular formula and nominal molecular weight, but the current NIST software allows the TSCA database to be searched by monoisotopic mass with an error window.  This would be useful if there is some doubt in determining a unique molecular formula from the accurate mass data.

Documentation concerning the TSCA approach for identifying “known unknowns” can be found in the following link:

TSCA_documentation

In the link below, I have included a copy of the TSCA library in NIST format.  However, I have not updated the TSCA/NIST library in many years and there have been new entries to the TSCA database in that time period.  Nevertheless, it could still be useful for the identification of “known unknowns” and to demonstrate the process.  Be sure to put the files in a folder named TSCA in your NIST directory where other libraries such as mainlib and replib folders are found.

TSCA_NIST_Binary_Format

I also have included the entries in an Excel spreadsheet.

excel_spreadsheet_tsca_monomers

Here is a link to the executable used to convert the TSCA CD file to a NIST MSP format.  This NIST MSP ASCII-formatted file can then be converted to NIST binary format with the NIST Lib2NIST.exe utility.

TSCA_MSP_file_converter

One can purchase the TSCA file on CD from Solutions Software if you would like to create an updated copy:

Solutions_Software_TSCA_CD

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