ANALYSIS OF VOLATILE ORGANICS BY SUPERCRITICAL-FLUID EXTRACTION COUPLED TO GAS-CHROMATOGRAPHY .2. QUANTITATION OF PETROLEUM-HYDROCARBONS FROM ENVIRONMENTAL SAMPLE

A coupled supercritical fluid extraction-gas chromatography (SFE-GC) m ethod has been developed for the quantitative extraction and analysis of gasoline and diesel range organics from rear world environmental sa mples. Petroleum-contaminated samples containing gasoline- to diesel- and motor oil-range hydrocarbons (total hydrocarbon content typically ranging from 2 to 26 mg/g) could be quantitatively extracted by a 15-m in SFE-GC extraction using 400 atm (1 atm = 101 325 Pa), 60 degrees C CO2. The SFE-GC hydrocarbon recoveries from real-world samples were co mparable to those obtained by sonicating the samples in methylene chlo ride for 14 h, except for the gasoline recovery which was higher by SF E-GC analysis due to the more efficient collection of the more volatil e analytes. Reproducibilities for replicate SFE-GC extractions and ana lyses were typically <5% (R.S.D.) for the quantitation of both individ ual organics and total hydrocarbon content. Gasoline- to diesel-range organics (as volatile as n-pentane) could be quantitatively retained d uring the SFE step of the SFE-GC analysis using a thick-him (30 m x 0. 32 mm I.D., 5 mu m film thickness) DB-1 column operated at a cryogenic trapping temperature of -25 degrees C. Using split SFE-GC operated at a high split ratio (100:1) relatively large l-g sample sizes could be extracted, and by using a drying agent (molecular sieve 3A) very wet (25%, w/w, water) samples could be analyzed without extracted water fr eezing and plugging in the GC column during the SFE step.