Supercritical Fluid Extraction (SFE) for the Removal of Lipid ... - Isco

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Syringe Pump Application Note AN30Figure 1: Photo and Schematic of the SupercriticalFluid Cleaning of Archaeological ArtifactsResults and DiscussionAs indicated earlier, the spiking experiments weredone to study the efficacy of modified supercritical CO 2in removing certain contaminants from the archaeologicalartifacts. The spiking experiments indicated thatsupercritical CO 2 modified with 10% (v/v) methanolremoved the beeswax, coconut oil, and humic acidsfrom linen. There was no significant effect of pressure onthe removal of coconut oil and beeswax from linen, butmore humic acids were removed at a pressure of 6000psi when compared with that at 3000 psi. This removalof humic acids from linen was not complete at thehigher pressure, since there were still traces of humicacid left behind in the cell and in the linen samples afterextraction. Gravimetric analysis indicated that at 40°Cand 6000 psi, modified SC-CO 2 was capable of removingabout 25.2% beeswax, 18.4% coconut oil, 5.80% humicacids, and 0.6% frankincense oil (by weight) from therespective spiked linen samples.The extracts from SFE cleaning of the Egyptianmummy gauzes and the Russian textiles were characterizedwith respect to their organic constituents.MALDI-TOF spectra mass spectroscopy study of theEgyptian mummy burial gauzes measured between500-5000 Da, indicating the presence of a polymer in thecollected extracts that contain repeating oligomericunits differing by 74 Da, which is characteristic of thepolymer, polyglycerol.In addition, GC/MS analysis (Table 1) showed thepresence of fatty acid moieties as their methyl esters inthe Egyptian burial cloths. The fatty acid methyl esters(FAMES) range from C14:0 through C18:3, and arisethrough the use of vegetable oils and/or wax esters inthe preparation of the mummy for burial [3]. The occurrenceof FAME derivatives in the SC-CO 2 – methanolextract is indicative of possible in-situ reaction betweenthe extraction solvent mixture and the lipophilic oils inthe burial gauze. The presence of odd- carbon numberedacids is also indicative of a ruminant fat beingused in burial preparation. One of the authors has in thepast reported in-situ methylation of vegetable oilsduring SFE [4,5]; other investigators such as McDaniel etal [6], Wyatt and Haas [7], and others [8] cite the synthesisof FAMEs under supercritical CO 2 in the presenceof methanol. It should be noted that both potash andnatron were widely used by the Egyptians—which couldserve as a source of alkali metal salts as possible catalystsfor producing FAMEs. If our rationale is correct,then a number of materials associated with archeologicalartifacts could be identified based on theirmethylated products [9, 10].
Syringe Pump Application Note AN30Table 1: Database fit from mass spectrophotometric characterization of FAMEcontent in Egyptian mummy gauzes extracted with SC-CO 2 modified with 10%(v/v) methanol at 40°C and 3000 psi. (nd = not defined.)Compound T r (min) Child Mummy Child Mummy (2) Bovine MummyC 14:0 20.3 nd 95 ndC 15:0 22.2 95 97 ndC 16:0 24.1 98 99 95C 16:0 (isomer) 24.7 nd nd 72C 18:0 27.5 nd 96 ndC 18:1 28.2 nd 98 ndC 18:2 29.3 nd 98 ndC 18:3 30.6 98 91 ndSimilar experiments performed with the Russian textilesamples indicated the presence of a polymericmoiety in the MALDI-TOF spectra with repeating oligomericunits differing by 58 Da. The assignment ofstructure and the origin of this compound are stillpending. The Russian textile samples were then treatedwith modified SC-CO 2 at 40°C under different pressuresof 3000, 6000 and 9000 psi, and the effectiveness of SFEcleaning was obtained by gravimetric analysis of thesamples. The efficiency of contaminant removal fromthe Russian textiles using modified SC-CO 2 at 40°C wasfound to increase linearly as a function of pressure(Figure 2).0.20.16% Weight Removed0.120.08y = 1E-05x + 0.0407R² = 0.97840.0400 2000 4000 6000 8000 10000Pressure (psi)Figure 2: Weight percent of organic matter extracted from the Russian mummy sample at 3000, 6000 and9000 psi and 40°C using SC-CO 2 modified with 10% (v/v) methanol
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Supercritical Fluid Extraction (SFE) for the Removal of Lipid ... - Isco

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