Agriculture Reference
In-Depth Information
Technology
Measurement Device
Friedel-Crafts alkylation reaction and
colorimetry
RemediAid™ Total Petroleum Hydrocarbon
Starter Kit
Infracal® TOG/TPH Analyzer, Models CVH
and HATR-T; OCMA-350 Oil Content Analyzer
Emulsion turbidimetry PetroFLAG™ Hydrocarbon Test Kit for Soil
Ultraviolet fluorescence spectroscopy
Synchronous Scanning Luminoscope;
siteLAB® Analytical Test Kit UVF-3100A
Immunoassay and colorimetry EnSys Petro Test System
Table 2. Technology of TPH field-measurement kits
Infrared analysis
These technologies are thoroughly discussed in the report from the EPA field test
conducted in June 2000: while some of these tests produced good results, the kits were
found to be expensive and to require a knowledgeable operator (Tetra Tech EM Inc. for
EPA 2000).
All analytical methods, whether conducted in the laboratory or
in situ
, that are available for
the determination of TPH in soil samples have individual drawbacks, for example: shipping
of the sample to a distant laboratory (no
in-situ
availability), long waiting periods for results,
high cost per sample, inaccuracy, and the requirement of a skilled staff to perform the
measurement. Due to these drawbacks, a new low-cost
in-situ
method for assessing PHC
contamination, particularly at a new site, is greatly needed. Emphasized desired properties
of this new method are cost-effectiveness and its ability to be implemented by not only
highly trained personnel.
4.2 TPH and reflectance spectroscopy
4.2.1 Absorption features of organic compounds
Carbon-hydrogen bonds (C-H, C-H
2
, C-H
3
), hydroxy groups (O-H), double and triple bonds
of aliphatics and aromatics, carboxyl groups (C=O), ester groups (C-O-C), amino groups (N-
H) and other structural groups of organic chemicals exhibit characteristic fundamental
vibrations that are evident in the 2,500 to 6,670 nm wavelength region of the IR spectrum.
Furthermore, these compounds exhibit overtone and combination bands in the IR and
VNIR-SWIR spectrum between 500 and 6,670 nm. These fundamental vibrations can be
determined by IR spectroscopy and some of the overtone and combination bands can be
determined by VNIR-SWIR spectroscopy (Winkelmann 2005).
4.2.2 VNIR-SWIR spectroscopy of organic chemicals
As IR spectroscopy is the better choice for qualitative analysis, VNIR-SWIR spectroscopy is
primarily applied for quantitative analysis in many disciplines (termed “chemometrics”).
However, despite the fact that VNIR-SWIR spectra of organic chemicals are often highly
complex due to many overlapping overtone and combination absorption features, they still
contain information on the functional and structural groups of the chemicals under
investigation. During the past 10 years, a new quantitative methodology has been widely
developed that utilizes the reflected radiation in solids. Basically, this technology was
adopted 40 years ago from a strategy developed in the food science discipline (Ben-Gera &
Norris 1968a; Ben-Gera & Norris 1968b), whereas today it is widely utilized in many
industrial and scientific applications. In this approach, the radiation reflected across the
