PUBLICATIONS:  Reporting of Tentatively Identified Organic Compounds

WGS-Mail Stop 412                                May 16, 1990




OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 90.11

SUBJECT:  PUBLICATIONS:  Reporting of Tentatively Identified
                         Organic Compounds


                          BACKGROUND

Extracts of water and sediment samples are routinely analyzed 
by gas chromatography/mass spectrometry (GC/MS) to identify 
and quantify synthetic organic compounds.  In this procedure, 
the MS spectra of specific GC peaks are computer compared to 
spectra of reference standards of compounds analyzed--
inhouse--on the same instrument under identical conditions.  
When specific GC peak retention times and MS spectra match, 
the sample compound is considered identified.  Furthermore, 
the concentration of the compound can then be quantified.  

Some samples produce additional spectral data representing 
compounds that do not match the GC retention times and the 
MS spectra of reference standards run inhouse.  Some of these 
compounds can be tentatively identified using a computerized 
library search, wherein the compound spectral data are 
compared with spectra produced previously by analysis of 
reference standards in other laboratories.  This process 
results in a "tentatively identified organic compound" (TIOC) 
that is neither confirmed nor quantified by direct comparison 
with reference standards.

The National Water Quality Laboratory (NWQL) continually adds 
spectra of reference standards to its own GC/MS library.  
However, because of the vast number of synthetic organic 
compounds, and the high cost of some reference standards, the 
NWQL has run references for only a small part of the existing 
manmade compounds.  

In addition to identified and tentatively identified organic 
compounds, MS spectra sometimes occur in samples that do 
not match any spectra in the computerized library.  These 
compounds are true unknowns and receive no tentative 
identification.  Such spectra, however, are computer stored 
for future interpretation.


                            POLICY

1.  U.S. Geological Survey publications will use the term 
tentatively identified organic compounds (TIOCs) to refer to: 
compounds identified by GC/MS library search, followed by 
visual examination by GC/MS analysts, but not confirmed or 
quantified by direct comparison with reference standards.

2.  Data for TIOCs are unconfirmed and, therefore, can not be 
entered into the NWIS/WATSTORE data bases or published in 
Annual Data Reports.

3.  Data for TIOCs can be published in USGS technical reports 
when accompanied by the following footnotes at the specified 
locations:

     A.  To be used as a footnote to the text at the location 
         where TIOCs are first mentioned:

	    "Data for tentatively identified organic compounds 
         (TIOCs) in this report are based on comparison of
         sample spectra with library spectra followed by
         visual examination by GC/MS analysts.  TIOC data
         have not been confirmed by direct comparison with 
         reference standards.  Therefore, TIOC identification 
         is tentative, and reported concentrations are
         semiquantitative."


     B.  To be used as a footnote to each table or to 
         specific columns or rows of tables that report 
         TIOCs:

         "Tentatively identified organic compound: the 
         reported concentration generally is accurate to  
         one order of magnitude."


FUTURE DATA BASE FOR TENTATIVELY IDENTIFIED ORGANIC COMPOUNDS

Because use of data for TIOCs is increasing, the Water 
Resources Division has prepared guidelines for the 
development of a separate data base to store, retrieve, and 
tabulate such data.  We anticipate that the new data base 
will be operational in 1991.  Until the system becomes 
operational, District offices will continue to receive TIOC 
results by paper copy from the NWQL.  Spectral data for 
unknown compounds will be retained indefinitely by NWQL for 
future attempts at additional spectral matching.

Questions regarding TIOC data or the proposed TIOC data base 
should be referred to Steve Zaugg (SDZAUGG - FTS 776-5345) at 
the NWQL, or to Jim Schornick (JCSCHORNICK - FTS 959-6867) in 
the Office of Water Quality.



                               David A. Rickert
                               Chief, Office of Water Quality

This memorandum does not supersede any previous Office of 
Water Quality memorandum.

Key Words:  nontarget, organics, data base

WRD Distribution: A, B, S, FO, PO