Use Of Subcritical Water Research Articles

Hidrólise do óleo de Azadirachta indica em água subcrítica e determinação da composição dos triacilglicerídeos e ácidos graxos por cromatografia gasosa de alta resolução a alta temperatura e cromatografia gasosa de alta resolução acoplada à espectrometria de massas

The development of modern analytical tools plays an important role in quality control. The main purpose of this study was to explore the use of subcritical water as a versatile analytical tool, employed simultaneously as a reagent and solvent, as well as the application of high temperature-high resolution gas chromatography (HT-HRGC) to develop a procedure for the analysis of triacylglycerides and fatty acids in Azadirachta indica A. Juss. (Neem) oil without the need for solvents, chemical reagents, or catalytic agents. The developed method presented satisfactory results and is in agreement with the concepts of Green Analytical Chemistry (GAC).

Oxygen-induced efficient mineralization of perfluoroalkylether sulfonates in subcritical water

The decomposition of perfluoroalkylether sulfonates C 2 F 5 OC 2 F 4 SO 3 - and C 3 F 7 OC 2 F 4 SO 3 - in subcritical water was investigated, and the results were compared with those for perfluorobutanesulfonate ( C 4 F 9 SO 3 - ), which has no ether linkage. This is the first report on the use of subcritical water to decompose perfluoroalkylether sulfonates, which are being developed as alternative surfactants to environmentally persistent and bioaccumulative perfluoroalkylsulfonates. Whereas C 4 F 9 SO 3 - showed little reactivity in subcritical water, C 2 F 5 OC 2 F 4 SO 3 - decomposed efficiently in subcritical water (∼350 °C) in the presence of oxygen gas to form F − and SO 4 2 - in the aqueous phase and CO 2 in the gas phase as major products. Trifluoroacetic acid (CF 3COOH, TFA) and trifluoromethane (CF 3H) were also detected as minor products in the aqueous and gas phases, respectively. Similar decomposition behavior was observed for C 3 F 7 OC 2 F 4 SO 3 - , which decomposed at a rate that was somewhat higher than that of C 2 F 5 OC 2 F 4 SO 3 - . When argon was used in place of oxygen gas, the time profile of the decrease in the amount of C 2 F 5 OC 2 F 4 SO 3 - remained almost unchanged, but the product distribution changed markedly: the amounts of F −, SO 4 2 - , and CO 2 dramatically decreased, the amounts of TFA and CF 3H increased, and a new product, HCF 2 SO 3 - , was detected. These results clearly indicate that treatment with subcritical water in the presence of oxygen gas effectively mineralized perfluoroalkylether sulfonates to F −, SO 4 2 - , and CO 2. On the basis of a product analysis, we propose a decomposition mechanism.

Determination of pyrrolizidine alkaloids in comfrey by liquid chromatography–electrospray ionization mass spectrometry

Symphytum officinale L. (comfrey) is a medicinal plant commonly used in decoctions and aliments. Besides therapeutic bioactive compounds present in the herb, it is found to contain hepatotoxic pyrrolizidine alkaloids (PAs), such as lycopsamine and others. In the present study, PAs such as lycopsamine, echimidine and lasiocarpine were determined using electrospray liquid chromatography–mass spectrometry (LC–MS) with the method precision (relative standard deviation, RSD) <10%. Detection of lycopsamine, symviridine and their N-oxides could be confirmed with a newly developed method based on HPLC ion-trap and orbitrap MS with electrospray ionization interface. With LC–MS, quantitative analysis of lycopsamine in the botanical extract was carried out. The effect of extraction solvent was optimized by sonication and methanol: H 2O (50:50) was selected. Then a rapid method based on pressurized hot water extraction (PHWE) was employed for the extraction of lycopsamine from comfrey followed by the comparison with heating under reflux with the RSD ranging from 2.49% to 19.32%. Our results showed a higher extraction efficiency for heating under reflux compared with PHWE. It was proposed that the lower extraction efficiency for PHWE was attributable to dissolved nitrogen from air which caused the reduction in the solubility of lycopsamine in the compressed hot solvent. In this study, quantitative analysis of PAs in comfrey was demonstrated. In addition, it was found that the use of subcritical water for extractions depended on the physical properties of the dissolved solutes and their tendency to degrade under the chosen extraction conditions.

Hydrolysis of corn oil using subcritical water

This work presents the results of a study on the use of subcritical water as both solvent and reactant for the hydrolysis of corn oil without the use of acids or alkalis at temperatures of 150-280 °C. Corn oil hydrolysis leads to the formation of its respective fatty acids with the same efficiency of conventional methods. Fatty acids form an important group of products, which are used in a range of applications. The confirmation and identification of the hydrolysis products was done by HT-HRGC-FID and HRGC/MS.

Continuous subcritical water extraction as a useful tool for isolation of edible essential oils

A method for extraction of oregano oil based on the use of subcritical water is proposed. Ground oregano (ca. 1.8 g accurately weighed) was extracted with water at 2.0 MPa, 125 °C and 1 ml min −1 for 24 min. The extracted compounds were removed from the aqueous extract by a single extraction with 4 ml hexane, determined by gas-chromatography-flame ionisation (GC-FID) and identified by mass spectrometry (MS). Hydrodistillation was performed on 30 g of ground oregano with 500 ml water for 3 h for comparison of the results with those provided by the proposed method. The subcritical water extraction-based method is clearly quicker and more efficient than the conventional: yields from the former for eight of the 11 major compounds in the extract are higher after 15-min extraction than after hydrodistillation for 3 h. This enables substantial cost savings of both energy and raw material. In addition, the proposed method has the possibility of manipulating the composition of the oil and thus its quality. The aqueous-oil extract was investigated for essential oil preparative purposes and several fast, cheap and clean alternatives for breaking the emulsion and separating the phases are proposed.

Extraction of Tricyclazole from Soil and Sediment with Subcritical Water

The use of subcritical water to extract tricyclazole from soils and sediments was examined. Extraction efficiency and kinetics were determined as a function of temperature, sample age, sample matrix, sample size, and flow rate. Extraction temperature was the most influential experimental factor affecting extraction efficiency and kinetics, with increasing temperature (up to 150 degrees C) yielding faster and higher efficiency extractions. Higher extraction temperatures were also important for quantitative recovery of tricyclazole from aged samples. Extraction at 50 degrees C yielded 97% recoveries from samples aged 1 day but only 30% recoveries for samples aged 202 days, whereas extraction at 150 degrees C yielded recoveries of 85-100% that were independent of incubation time and sample matrix, with the exception of one sediment that contained a large amount of organic matter. Sample extracts from subcritical water extraction were generally a pale yellow color, contrasted with a dark brown color from organic solvent extractions of the same matrixes. Less sample cleanup was therefore required prior to analysis, with the total time for the extraction and analysis of a single sample being approximately 2 h. Subcritical water extraction is an effective technique for the rapid and quantitative extraction of tricyclazole from soils and sediments.