Page 10 - Shimadzu Journal vol.3 Issue1

Environmental Analysis

The headspace autosampler can be transferred to a GC-MS for 8. Acknowledgments
identification of unknown compounds detected by HS-GC-FID.
The authors would like to thank the Shimadzu Institute for
Analysis of compounds with a boiling point significantly higher
Research Technology (SIRT) and the Shimadzu Center for
than 90 °C may not be suitable for headspace sampling.
Advanced Analytical Chemistry (SCAAC) at The University of Texas
Analysis Conditions at Arlington for use and support of the aforementioned analytical
instruments. They would also like to thank Shimadzu Scientific
Instrument: GC-2010 Plus
Instruments, Inc. (Columbia MD) for the use of the TOC
Column: ZB-BAC2, 30 m L. x 0.32 mm I.D., df:1.2 µm
instrument featured in this work.
Column oven temp.: 40 °C (4.5 min.) ˠ (30 °C/min.) ˠ130 °C (2 min.)
ˠ(35 °C/min.) ˠ200 °C (0.5 min.)) 9. References
Carrier gas: He FID temp.: 200 °C 1 US EPA. Drinking Water Contaminants.
Carrier gas control: Linear velocity, Agitator temp.: 90 °C http://water.epa.gov/drink/contaminants/index.cfm#one
50 cm/s Agitator time: 15 min. (accessed October 28, 2014).
Split ratio: 10:1 Syringe temp.: 90 °C 2 US EPA. Private Drinking Water Wells.
Injection port temp.: 200 °C http://water.epa.gov/drink/info/well/ (accessed October 28,
Injection volume: 750 µL 2014).
3 Fontenot, B. E.; Hunt, L. R.; Hildenbrand, Z. L.; Carlton, D. D.,
6. TOC/ TN Jr.; Oka, H.; Walton, J. L.; Hopkins, D.; Osorio, A.; Bjorndal, B.;
Hu, Q. H.; Schug, K. A. An Evaluation of Water Quality in
Carbon and nitrogen content of the water were measured with
Private Drinking Water Wells Near Natural Gas Extraction Sites
the Shimadzu TOC-L outfitted with the TNM-L total nitrogen
in the Barnett Shale Formation. Environ. Sci. Technol. 2013, 47,
module. Samples were filtered with a 0.45 µm PTFE Luer lock
10032-10040.
syringe filter as needed and filled a 40 mL volatile organic analysis
4 Almasri, M. N.; Kaluarachchi, J. J. Modeling Nitrate
autosampler vial. Total Carbon (TC), Inorganic Carbon (IC),
Nonpurgable Organic Carbon (NPOC), Purgable Organic Carbon Contamination of Groundwater in Agricultural Watersheds. J.
(POC), and Total Nitrogen (TN) were measured. When TC-IC was Hydrol. 2007, 343, 211-229.
below 2 ppm, NPOC+POC was used for reporting TOC per 5 Boyer, E.W.; Clark, J.; Madden, M.; Rizzo, D.E. The impact of
manufacturer suggestions. In all other cases, TC-IC was used for Marcellus gas drilling on rural drinking water supplies. The
TOC. Center for Rural Pennsylvania. 2012.
TOC and TN are valuable to validate the presence of organic
compounds and amines or other nitrogen-containing organic
compounds determined by a more detailed analytical method. A
non-zero TN value does not confirm nitrogen-containing organic
compounds, as TN is also sensitive to nitrate, nitrite, and ammonia.
Agricultural contamination of groundwater results primarily in an
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increase of halogenated and nitrogen-containing compounds ,
while UOG contamination would result in the introduction of
carbon or carbon and nitrogen-containing compounds, depending
on the phase of the extraction operation. The detection of
compounds GC-MS/ HS-GC-FID should be accompanied by
nonzero TOC values. Many caveats such as analyte response
factors and volatility, can account for the lack of graphical linearity
of the GC and TOC measurements from sample to sample.
In addition to validating more targeted analytical methods, TOC/
TN can be utilized as an indicator for contaminated groundwater
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samples. It may be efficient to screen many samples with TOC/ TN
before applying more detailed and costly methods. A positive
correlation between HS-GC-FID and TOC data was found for an
arbitrary set of 14 groundwater samples selected for evaluation.
Four out of five of the samples with the highest total HS-GC-FID
peak areas had the highest TOC/ NPOC values.

7. Summary
Research involving the chemical analysis of groundwater is likely to
be highly scrutinized due to the potential for risks associated with
health and environmental impacts. Although the measurement of
general parameters such as conductivity and Total Organic Carbon
(TOC) may have analytical utility on their own, they can be even more
valuable for supporting findings using more targeted analytical
techniques such as ICP-OES and GC-MS.

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