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Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated. |
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Note: This information is provided for reference purposes only. Although the information provided here was accurate and current when first created, it is now outdated. |
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The most inert system for the analysis of volatile organics in soils, aqueous media, impregnated solids, and crude oil.
The easy to load-and-unload 24 sample tray allows for continuous operation. The sample vial is heated to a pre-selected temperature (RT to 200 oC), it is pressurized with inert carrier gas (He, N2, H2, or other gases), it is introduced into the capillary column via a variable volume injection loop, and detected by either a flame ionization detector (FID) or a thermal conductivity detector (TCD).
Some of the work analyzed on this system is:
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One of the best methods for confirming the presence of suspected pollutants is the analysis of samples via gas chromatography - mass spectrometry; GED has two such systems.
After some sample clean-up, the samples are injected onto a capillary column and sample componants are separated by gas chromatography. The detection is achieved by quadrupolar mass spectroscopy and verified either by a library search from the on-board library of mass data or by analyzing known composition standards. The system can quantitate samples and, under selective mass ion operation, samples with parts per billion (ppB) of pesticides can be quantitated.
Some of the work analyzed on this system is:
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The single most versatile method for analysis, gas chromatography (GC) separates volatile mixtures.
The GC vaporizes a sample in a stream of carrier gas and passes it through a capillary column. Components separate in time according to their relative affinities to the stationary material coated inside the capillary column.
Several manufacturers offer a variety of capillary columns; from the most non-polar (for separating aliphatic hydrocarbons) to the most polar (for separating polyols and carboxylic acids), specialty columns that separate chiral or optically active isomers (such as the sugars) and columns that separate gases.
The column resides inside an oven whose temperature can be pre-programmed so as to selectively volatilize the components of a sample mixture. Coupled with electronic pressure control the carrier gas flow can be pre-programmed to aid in the separation of components of very similar chemical characteristics.
The crowning glory of GC is the versatility of detectors that can be utilized. The afore mentioned mass spectrometer (MS), the atomic emission detector (AED), the electron capture detector (ECD), the flame ionization detector (FID), infra red detector (FTIR), thermal conductivity detector (TCD), and a variety of specific detectors aimed at unique analytical schemes.
GED has over 15 GCs; from the latest PC controlled to the old work-horses of a decade ago. Some are configured for EPA's "Dual Column Self-Confirmatory" analyses for organo chlorine pesticides and PCBs, some are configured for mixed detector work (single split column with FID and ECD) to determine halogen content in complex mixtures from Superfund sites, and some are single detector units with detection in the nano-gram range (parts per billion).
GED has three of these GCs, fitted with a very polar and a very non-polar set of capillary columns ending in dual ECDs. It is routinely used to detect, quantitate, and confirm the presence of 15 organo chlorine pesticides, 17 PCBs, and endosulfans from potable water, salt water, marine sediments, aquatic plants, fish, crabs, and invertebrates.
GED has one GC that is fitted with a medium polarity capillary column that is split at the detector end and the sample is simultaneously analyzed by FID and ECD. In a soil extract sample, with dozens of components, this system can quickly pin-point the organic volatiles that have halogens in them (most probably organo chlorine pesticides or PCBs) and direct the analyst to the proper sample celan-up needed to obtain acceptable data.
GED has one GC that has, as its detector, an AED. The AED can simultaneously detect elements present in the componant mixture and aid in pin pointing the elution time of target compounds (i.e. if one is only interested in locating the number of sulfur containing volatile species from a sample of contaminated soil, or of one is interested in locating the particular species that has a chlorine and a phosphorus in it). The system can detect 19 elements and can be invaluable in elucidating structures.
Still the most common GC detector, GED has four GCs with FID for quantitation of hydrocarbons in complex mixtures from contaminated soil, oil spill waters, tainted potable water, and for "fingerprinting" crude oils in order to determine origin, age, wethering, and affects of bacterial aided biodegradation. One of the systems is configured with dual column dual FID for self-confirmatory detection and quantitation of polyaromatic hydrocarbons (PAHs).
GED has two such units, used primarily for the detection and quantitation of the organo phosphorus pesticides, and for propriatory research projects.
GED has an FTIR unit. When coupled to the GC/MS, this nondestructive detector is ideal for helping determine the structure of unknown species.
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Designed for the compounds that are either not volatile enough to be separated by a gas chromatograph (GC) or are thermally labile, HPLC has come of age in the last decade to where its ease of use and versatility of detectors has made it rival GC analyses.
GED has half a dozen HPLC units, some with only fixed pre-selected Diode Array Detectors (DAD), and some with tunable multi-frequency DADs.
One unit has Fluorescence Detector and Electrochemical Detector (as well as DAD).
Some of the work analyzed on this system is:
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A hybrid system bridging the gap between GC and HPLC, CcFC relies on carbon dioxide in the liquid state to elute components through a HPLC column.
Separations of thermally labile species can be achieved in one tenth of the time it takes to perform the analyses on the HPLC.
The sample can be split between a DAD and an ECD, making it an ideal detection method for organo-chlorine pesticides.
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