The Characterization of Tentatively Identified Compounds (TICs) in Water Samples Collected from Public Water Systems in New Jersey

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Courtesy of NJDEP


This is a summary report of a detailed investigation in which the analysis of synthetic organic chemicals by Gas Chromatography (GC) and Liquid Chromatography (LC) was conducted on raw and finished water samples collected from public water supplies using ground water as a source of drinking water. All water systems sampled are known to be contaminated by volatile organic chemicals except for one (the “control” system). This work investigated the potential presence of non-volatile and semi-volatile organic chemicals in those water supplies. Five bottled waters were also sampled. Several generalizations can be made: 1) water serving systems impacted by identified hazardous waste sites have distinct and sometimes unique TICs associated with them; 2) TICs are generally low in concentration, most being estimated at a concentration below a part per billion (microgram per liter, mg/L); and 3) many organic chemicals reported as TICs were not actually in the water sampled but were found in the analysis due to sampling and/or laboratory contamination.


Presently, certain conventional analytical methods for analyzing drinking water samples from public water supplies for specific, or targeted, organic chemical contamination are required by the NJ Safe Drinking Water Act. For the most part, this routine testing is adequate for the determination of commonly occurring volatile organic chemicals (VOCs). It was always known that VOCs, which are the current regulatory focus of analysis for organics in drinking water, may serve as markers for the presence of mostly unregulated non- and semi-volatile contaminants in addition to being significant in their own right. In situations where impacted water is being used as a potable source, this issue is very important. In the past, reliable analytical methods were not available to determine the presence or the nature of many non-volatile (e.g., some pharmaceuticals, dyes, inks) and semi-volatile (e.g., plasticizers, fragrances, some components of fuel oils) contaminants, with the exception of certain types of semi-volatiles (i.e., some pesticides and plasticizers).

A volatile compound is defined chemically as one with a relatively low boiling point. That is, a volatile compound “evaporates” readily into the air. Whereas, a non-volatile compound evaporates much more slowly or not at all. A semi-volatile compound falls in between. Thus, due to the historical focus on VOCs, the full picture of exposure and health risk from contaminated drinking water may not have been adequately determined. With the emergence of more sensitive analytical capabilities for non- and semi-volatile organic contaminants, a more complete assessment of this additional contamination, if and where it exists, can be made, and appropriate steps can be taken to protect public health.

This study was able to address the potential detection of hundreds of chemicals because the instrumentation was set up to screen for tentatively identified compounds (TICs). A TIC is a compound that can be seen by the analytical testing method, but its identity and concentration cannot be confirmed without further analytical investigation. An analogy is when a photograph is taken of a subject. The picture also captures the information in the background, and often this information is fuzzy, but the focus of the picture is the subject. The subject (i.e., target item) is clear, but the background components (i.e., the tentatively identified items), while captured in the picture, are fuzzy.

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