Technology - Amplified Geochemical Imaging
GeoChemTech Inc. provides Gore Amplified Geochemical Imaging™ which is an advanced geoscience tool used to measure and map compounds in diverse applications such as environmental site assessment, pipeline integrity management, petroleum exploration and field development and mineral exploration. Gore's unique and highly sensitive passive diffusion module (passive sampler) can detect these compounds in soil gas, air and water, at levels in the sub part per billion range.
The passive sampler contains a specially engineered hydrophobic adsorbent encased in a microporous expanded polytetrafluoroethylene (ePTFE) membrane. This membrane - known as GORE-TEX - has pores engineered small enough to keep soil particles and water from entering, but than the molecules of interest. As a result, the molecules of interest that are about 1000 times smaller, are unimpeded in their path to the adsorbent. This allows the module to be placed directly in dry or water saturated soils and even in water depths up to about 10 m.
The modules are manufactured in a cleanroom to eliminate ambient contamination and include a duplicate sorbent to be used if complications arise in the analysis. These modules uptake about 3-4 litres/hr in free air and, by placing them in the soil for weeks or months, they collect an integrated chemical signal. This boosts the mass collected by two to three orders of magnitude over an active sample and smoothes temporal variations due to barometric pressure, rainfall, and temperature variations.
When combined with a very sensitive state-of-the-art analytical method incorporating thermal desorption, gas chromatography, and mass spectroscopy, nanogram (10E-9 gram) levels of compounds can be detected relating to concentrations as low as 1 ppt. This high sensitivity allows detection in any soil type including saturated clays and sands, cemented rock, or even through thousands of feet of evaporates or volcanic rock.
Over 150 volatile compounds can be measured as needed for the application. These can be volatile gases like ethane, volatile liquids like benzene or low volatility liquids, and solids like pyrene, TNT, or sulfur as long as their vapour pressure is above 2E-6 mm Hg. In very moist environments it is also desirable for the compounds to have Henry’s Law constants >10E-7 atm/ cu m/mole. A few compounds of environmental interest, such as pentachlorophenol, 135TNB, VX, and RDX, fall outside this range. Molecules smaller than ethane are not adequately retained by the adsorbent, but natural gas with >99% methane can still be mapped by looking for the higher MW alkanes always associated with this gas.
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