PubMed · 15307773
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Douglas E Raynie. 2004-08-15. Modern extraction techniques.. https://doi.org/10.1021/ac040117w
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Two approaches for decreasing diesel hydrocarbon group-type separation times by normal phase supercritical fluid chromatography (SFC) are compared. Short (10-15 cm) columns with small 3 microm diameter packing are compared with monolithic Chromolith bare silica columns under high carbon dioxide flow rates approaching 5 ml min(-1). Elution times are reduced up to 13-fold on a 10 cm Chromolith column and 7-fold on the short packed columns compared with conventional length columns run at typical flow rates. Short packed columns, with their higher surface area and retention characteristics, offer higher resolutions compared with Chromolith columns. Diesel samples are separated into saturates, mono-, di-, tri-, and polyaromatics in as little as 2 min on a 10 cm packed silica column. Diesel group-type results on a 15 cm titania-silica coupled column compare favorably with results from longer columns.
Supercritical fluid extraction (SFE) and the use of aminopropyl solid-phase material for "in-line" cleanup was evaluated for residue analysis of 22 GC-amenable pesticides in wild- and white-rice samples with a fat content of 1.9 and 0.4%, respectively. After optimizing the extraction conditions on glass beads as inert material and evaluating the fat amount extracted from rice by SFE, the use of Florisil, Celite, Extrelut, Hydromatrix, and an aminopropyl material as fat-retention materials for SFE "in-line" cleanup was assessed, aminopropyl being the most suitable material for this cleanup of fat. Pesticide mean recoveries obtained from rice samples, at fortification levels around 0.5 mg/kg, by means of the SFE/in-line cleanup method finally proposed (15-mL CO2 volume, 50 degrees C temperature, 200 atm pressure, 200 muL of methanol static modifier, and a 1-cm layer of aminopropyl at the bottom of the extraction vessel), ranged between 74 and 98%, except for captafol and dimethoate for which mean recoveries lower than 21% were determined.
Supercritical fluid extraction (SFE) of orotinin, orotinin-5-methyl ether and licoagrochalcone B from Patrinia villosa was performed. The optimization of parameters including pressure, temperature, modifier and sample particle size on yield was carried out using an analytical-scale SFE system. The process was then scaled up by 100 times using a preparative SFE system under the optimized conditions of 25 MPa, 45 degrees C, a sample particle size 40-60 mesh and modified CO2 with 20% methanol. The yield of the preparative SFE was 2.82% (crude extract I) and the combined yield of orotinin, orotinin-5-methyl ether and licoagrochalcone B was 0.82 mg/g of dry sample mass. Then the crude extract I was re-dissolved in methanol and methanol soluble fraction (crude extract II, 0.17%) was obtained, which was successfully isolated and separated by a preparative high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:6:6:6, v/v/v/v) by increasing the flow-rate of the mobile phase stepwise from 1.0 to 2.0 ml/min after 3 h. The target compounds isolated and purified by HSCCC were analyzed by high performance liquid chromatography. The separation produced total of 38.2 mg of orotinin at 99.2% purity, 19.8 mg of orotinin-5-methyl ether at 98.5% purity and 21.5 mg of licoagrochalcone B at 97.6% purity from 400 mg of the crude extract in a one-step separation. The recoveries of orotinin, orotinin-5-methyl ether and licoagrochalcone B were 91.1, 91.6 and 90.3%, respectively, and the chemical structure identification was carried out by UV, IR, MS, 1H NMR and 13C NMR.