The total trans fatty acid content of 18 food products was determined, after acid hydrolysis, extraction and methylation of fatty acids, by gas chromatography with a polar 100% cyanopropylsiloxane capillary column and by singlebounce horizontal attenuated total reflection spectroscopy (SB-HATR). The trans fatty acid methyl esters (FAME) of 9-hexadecenoate (9t-I 6:1 ), 9-octadecenoate (9t-I 8:1 ), and 9,12-octadecadienoate (9t,12t-18:2) were identified by comparison of their retention times with those of known standards and quantitated. The isomers c,t-and t,c-18:2 were identified from their published retention times and included in the quantitation of trans FAME. Neat 50-1aL portions of the FAME that were used for gas-chromatographic analysis also were analyzed by SB-HATR. This technique requires neither weighing nor quantitative dilution of test portions prior to spectroscopic quantitation of isolated double bonds of trans configuration. A symmetric 966-cm -] absorption band on a horizontal background was obtained from unhydrogenated soybean oil FAME as the reference material. For 9 of 11 products with trans fat content >5% of total fat, results obtained by SB-HATR were higher than those obtained by gas chromatography. Results obtained by the gaschromatographic procedure were slightly to significantly higher than those obtained by SB-HATR for the six foods in which trans fat content was <5% of total fat. JAOCS 73, 1699-I 705 (I 996).
This paper presents the largest In Situ Thermal Desorption (ISTD) project completed to date. The redevelopment of a former aerospace manufacturing facility adjacent to a commercial airport was the main driver, requiring relatively rapid reduction of several chlorinated volatile organic compounds (CVOC) in a 3.2‐acre source zone. The source zone was divided into four quadrants with differing treatment depths, heated simultaneously using a total of 907 thermal conduction heater wells. Five different depths were selected across the area, according to the depth of contaminant impact. Prior to implementation, a risk and optimization study led to placement of a vertical sheet‐pile wall around the treatment zone to minimize groundwater flow, and a pilot test of a novel direct‐drive method for installation of the heater casings. Because of a shallow water table, a layer of clean fill was placed over the treatment zone, and partial dewatering was necessary prior to heating. A network of vertical multiphase extraction wells and horizontal vapor extraction wells was used to establish hydraulic and pneumatic control and to capture the contaminants. The site was split into four decision units, each with a rigorous soil sampling program which included collecting a total of 270 confirmatory soil samples from locations with the highest pretreatment CVOC concentrations requiring reduction to below 1 mg/kg for each contaminant. Temperature monitoring and mass removal trends were used to trigger the sampling events. Eventually, a small area near the center of the site required the installation of four additional heaters before the soil goals were reached after 238 days of heating. The total energy usage for heating and treating the source area was 23 million kWh—slightly lower than the estimated 26.5 million kWh. Actual energy losses and the energy removal associated with the extracted steam were lower than anticipated. An estimated 13,400 kg (29,800 lbs) of CVOC mass was removed, and all soil goals were met. This paper presents the challenges associated with a project of this scale and describes the solutions to successfully complete the ISTD remedy.
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