Hexane, chrysene

The surrogate compounds were mono-, tetra-, octa-, deca- C-PCBs, dg-naphthalene, C-PCP and C-phenol. The soil samples were dried with Na2S04 (60 g) and then Soxhlet extracted with hexane acetone (9 1) for 16 h. The extract was dried with sodium sulfate, concentrated, and split. While one portion was held for other analyses, the other portion was placed on a 3% deactivated silica gel column and eluted with increasing solvent polarity systems [hexane, followed by methylene chloride hexane (1 1), and then methylene chloride acetone (95 5)]. The extracts were combined and reduced to 1 mL, split and two internal standards added (tetrafluorobiphenyl and di2 Chrysene). The extracts were chromatographed on a 15-m DB-5 fused silica capillary column and detected with flame ionization (FID). Sludge samples were extracted according to the EPA sludge protocol (2) developed at Midwest Research Institute. 

Prior to extraction, water samples were filtered through precleaned Whatman GF/F filters (using pure acetone/n-hexane) in order to remove suspended particulate matter from the aqueous phase. A sequential liquid/liquid extraction procedure was applied to approximately 1000-mL aliquots of the water samples using the solvents n-pentane, dichloromethane and dichloromethane after acidification to pFl 2. Each extraction step was carried out in a separating funnel with 50 mL of the solvent. The third extraction was applied to the pre-extracted water samples after addition of 2 mL of concentrated hydrochloric acid that was pre-cleaned by intense extraction with n-hexane. Subsequently the organic layers were separately dried by filtration over 1 g of anhydrous granulated sodium sulphate (Merck, Darmstadt, FRG) and 50 pL of an internal standard solution containing routinely d34- -hexadecane (6.0 ng/pL), dio-anthracene (5.1 ng/pL) and di2-chrysene (4.7 ng/pL) in n-hexane was added. Acidic compounds in the third extract were methylated by addition of a diazomethan solution and subsequent reconcentration. Prior to GC/MS analyses the extracts were reduced to a final volume of approximately 25 pL by rotary evaporation at room temperature. 

Figure 2. A 50-min portion of a typical HR (GCf chromatogram of a 40% benzene in hexane fraction of a Gulf of Mexico sediment sample collected off the south Texas coast. 1, Crnaphthalene 2, C2-naphthalene 3, biphenyl 4, C -naphthalenes 5, C5-naphthalene 6, fluoranthene 7, pyrene and 8, chrysene. IS represents internal standards (hexamethyl benzene and 3-methyl tricosane). Chromatographic conditions are described in the text.

In general terms, lignite and anthracite coals appear to contain much lower proportions of the volatile organic componnds (10) than the bituminous coals, although alkaline extraction of lignite (and bituminous coal) will yield organic acids of various types that can be characterized. On the other hand, the hexane-soluble portion of the pyridine extracts that were obtained at 50°C (120°F) from coal (carbon content 83.6% w/w) have been identified as alkylated chrysenes as well as alkylated picenes in addition to a mixture of C2g, C29, and C30 paraffins. There were also indicates of the presence of an alicyclic or methyl-substituted five-ring (cat-condensed) system as well as l,2,5,6-dibenzanthracene(s) (Table 10.1). 

Smith and Cooper [601] studied the retention of three nonpolar solutes (phenan-threne, chrysene, perylene) and four polar solutes (nitrobenzene, 1,2-dinitrobenzene, phenol, aniline) in hexane and hexane/x mobile phases (where x = chloroform, methyl r-butyl ether [MtBE], and dichloromethane at the 5%, 10%, 15%, and 20% levels) on cyanopropyl, aminopropyl, and diol columns. From this work, the solvent strength of each mixture was determined for use in predicting chromatographic retention. More importantly, complex solvent/solute/adsorbed solvent/stationary phase interactions were described highlighting important and unique selectivities offered by these combinations. For example, altering the mobile phase composition from 3% MtBE in hexane to 12% MtBE in hexane (on a cyanopropyl support) leads to a decrease in the retoition of phenol and aniline. What is imexpected is the concomitant reversal of the elution order (phenol/aniline to aniline/phenol). This type of reversal of elution order is rare in leversed-phase separations (ion-pair systems notably excluded) but may be a considerable advantage in normal-phase separations. 

Snyder and co-workers [606] studied the retention of benzyl alcohol, m-nitroacetophenone, 10 substituted naphthalenes, chrysene, and perylene on a 30°C diol column using a series of isocratic dichloromethane/hexane (0/100 to 35/65) mobile phases. Retention results for all compounds at various isocratic mobile phase compositions are tabulated. Five steroids (prednisone, corticosterone, adrenosterone, 4-androstene-17a-ol-3-one, and 4-androstene-17j5-ol-3-one) were similarly studied but at ranges of dichloromethane from 13% to 80%. Also presented in this work is an equation from which the eluotropic strength of an A -F B solvent mixture, i.e.. 

Figure 4 Rapid (a) fully off-line and (b) fully on-line OPLC separation, and (c) comparison of retention data. Operating parameters CHROMPRES 25, external pressure on membrane, 2.8 MPa temperature, 23 C layer, diol-modified HPTLC silica gel 60 eluent, n-hexane flow rate, 2.5 cm /min detection absorbance at 254 nm. Sample volume injected and streaked 3 xl, dissolved in carbon tetrachloride 1, carbon tetrachloride 2, toluene 3, acenaphthene 4, phenanthrene 5, pyrene 6, chrysene 7, benzopyrene 8, butter yellow 9, fat red. (Reproduced by permission of Dr. Alfred Huethig Verlag GmbH, from Ref, 42.)...

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