Freon extractable material

Freon-extractable material is reported as total organic material from which polar components may be removed by treatment with silica gel, and the material remaining, as determined by infrared (IR) spectrometry, is defined as total recoverable petroleum hydrocarbons (TRPHs, or total petroleum hydrocarbons-IR). A number of modifications of these methods exist, but one particular method (EPA 418.1 see also EPA 8000 and 8100) has been one of the most widely used for the determination of total petroleum hydrocarbons in soils. Many states use or permit the use of this method (EPA 418.1) for identification of petroleum products and during remediation of sites. This method is subject to limitations, such as interlaboratory variations and inherent inaccuracies. In addition, methods that use Preon-113 as the extraction solvent are being phased out and the method is being replaced by a more recent method (EPA 1664) in which n-hexane is used as the solvent and the n-hexane extractable material (HEM) is treated with silica gel to yield the total petroleum hydrocarbons. 

This method (EPA 1664) is a liquid-liquid extraction gravimetric procedure that employs n-hexane as the extraction solvent, in place of 1,1,2-trichloroethane (CFC-113) and/or 1,2,2-trifluoroethane (Freon-113), for determination of the conventional pollutant oil and grease. Because the nature and amount of material determined are defined by the solvent and by the details of the method used for extraction, oil and grease method-defined analytes are used. The method may be modified to reduce interferences and take advantage of advances in instrumentation provided that all method equivalency and performance criteria are met. However, n-hexane is a poor solvent for high-molecular-weight petroleum constituents (Speight, 1999, 2001). Thus, the method will produce erroneous data for samples contaminated with heavy oils. 

Extractables were further identified by a Hewlett-Packard Model No.5993 GC/MS spectrometry. Solvent extractables were further diluted with Freon TA before GC/MS analysis. Six foot long, 0.3% SP2250 OV17 type material was used as the GC column, with 20-30 cc/min flow rate of helium as the carrier gas. Mass/charge (m/e) units were scanned from 30-800 atomic mass units (amu). Three-dimensional spectra GC/MS were printed out at the end of each run. Results of the GC/MS are shown in Figure 7. 

The Freon TA Soxhlet extraction of the RTV silicone sample at different curing times with Freon reveals the degree of curing of the material. At time zero, when the RTV material was first coated for room temperature cure, almost 100% extractables were obtained (except residue of fillers). This 100% extractable indicates a 0% cure of the material. After 16 hrs. of room temperature cure at 50% relative humidity, most of the RTV material (>90%) was cured. After the second day, almost all of the RTVs studied were fully cured, and they seem to reach an extraction equilibrium. Further curing time shows no noticeable change in amount of extractables. For the fully cured RTV silicone, the level of extractables at their equilibrium extraction was a good indication of the unreactive cyclics present in this material. In Figure 5, the RTV silicone extractable is approximately 4%. 

Certain aqueous materials can be extracted directly with a solvent to prodice an aroma concentrate. This technique has found utility in studies on wine aroma (3 ). The investigators studied model wine systems containing 12% ethanol and 4.4% sucrose. Extractions were performed manually, and the organic solutions were concentrated under vacuum. They concluded that Freon 11 (bp 24°) was the solvent of choice if the organic essence is to be stored for an extended period of time, they recommended methylene chloride as the solvent. The presence of sugar did not create any difficulties. 

For IR-based methods, TPH is defined as any compound extractable by a solvent (Freon 113 or tetrachloroethylene), which is not removed by silica gel or florisil clean-up and which can be measured at a specified wavelength. This definition is similar to that of mineral oil discussed previously. The method most referred to is the EPA Method 418.1 which is used for recoverable petroleum hydrocarbons. This method often suffers from poor accuracy and precision, especially for heterogeneous soil samples. This method gives neither the information on petroleum type nor the presence or absence of toxic materials, and is thus of little use in risk estimation. 

Chloroform (trichloromethane) is a chlorinated hydrocarbon solvent used as a raw material in the production of freon and as an extractant and solvent in the chemical and pharmaceutical industry. Because of its hepatic toxicity, it is no longer used as a general anesthetic or anthelmintic agent. Chronic low-level exposure may occur in some municipal water supplies owing to chlorination of biologic methanes (tri-halomethanes). 

Even though the extraction efficiency for some analytes can be increased by change of extraction fluid, carbon dioxide is by far the most common compound used (98% of all applications). It has low critical parameters, it is nonexplosive, nontoxic, and environmentally benign. Alternatives have been proposed such as alkanes and freons but they have never been widely accepted due to health and safety risks for the former and ozone depletion by the latter. One of the few competitors to carbon dioxide is nitrous oxide, however, it might cause explosion in contact with high amounts of organic material. Supercritical carbon dioxide has a polarity similar to that of n-hexane, and consequently for the extraction of more polar analytes an organic modifier such as methanol or acetonitrile (1-5%) has to be added to increase the polarity (see the section Modifiers ). To maintain supercriticality for two-component fluids, somewhat different conditions have to be applied, but normally there is no problem at the conditions under which SFE is normally carried out. 

The second sample appeared to be black sooty metallic shavings. Following solvent extractions of this material with xylene and Freon, the solvents were evaporated, and the residues were analyzed by FTIR spectrometry. Because chlorinated solvents attack the epoxy that secures the zinc selenide crystal to the horizontal attenuated total reflectance (HATR) boat. Freon was air dried from the residue. The residue was resolvated in acetone for mounting purposes. 

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