Cyclohexane extractables test

Previous research in this project dealt mainly with soxhlet extraction in general and related work as purification of solvents and extracts, testing several solvents in terms of extraction power to PAH, stability at boiling point and selectivity. Previously used solvents were methanol, dichloro-methane, trichloromethane, tetrachloromethane, cyclohexane, benzene, toluene, all xylenes, mesitylene, tetralin, tetrahydrofuran and acetic acid. 

Table 13.8 gives the results obtained in checks for the presence of DEA in synthetic liquid paraffin solutions of lauric diethanolamide after it had been heated for 10 days at 60 C. At the end of the extraction test, the solution (20 ppm w/v lauric diethanolamide) was diluted with cyclohexane and divided into two portions for determination of DEA and undegraded lauric diethanolamide. 

DEA is water-soluble and can be determined by applying the periodic acid method to a water extract of the liquid paraffin/cyclohexane mixture. A small amount of DEA was found in the liquid paraffin extractant (less than 20% of the 20 ppm w/v of lauric diethanolamide present in the liquid paraffin before the extraction test, see Table 13.8, some of which was present as an impurity in the original batch of lauric diethanolamide used in this work. 

Various extraction methods for phenolic compounds in plant material have been published (Ayres and Loike, 1990 Arts and Hollman, 1998 Andreasen et ah, 2000 Fernandez et al., 2000). In this case phenolic compounds were an important part of the plant material and all the published methods were optimised to remove those analytes from the matrix. Our interest was to find the solvents to modily the taste, but not to extract the phenolic compounds of interest. In each test the technical treatment of the sample was similar. Extraction was carried out at room temperature (approximately 23 °C) for 30 minutes in a horizontal shaker with 200 rpm. Samples were weighed into extraction vials and solvent was added. The vials were closed with caps to minimise the evaporation of the extraction solvent. After 30 minutes the samples were filtered to separate the solvent from the solid. Filter papers were placed on aluminium foil and, after the solvent evaporahon, were removed. Extracted samples were dried at 100°C for 30 minutes to evaporate all the solvent traces. The solvents tested were chloroform, ethanol, diethylether, butanol, ethylacetate, heptane, n-hexane and cyclohexane and they were tested with different solvent/solid ratios. Methanol (MeOH) and acetonitrile (ACN) were not considered because of the high solubility of catechins and lignans to MeOH and ACN. The extracted phloem samples were tasted in the same way as the heated ones. Detailed results from each extraction experiment are presented in Table 14.2. 

Oligomers in HDPE are readily determined gravi-metrically by using the so-called cyclohexane extracta-bles test. In this method, a small quantity of PE resin is Soxhlet extracted with cyclohexane and determined gravimetrically after drying. The test does not give the MW(D) of the extracted species. 

Despite the conflicting evidence, Heyes and Trahar (1984) believe there is sufficient evidence to confirm the presence of sulphur on mineral surface. They leached the surface of floated pyrrhotite from a typical test with cyclohexane and have examined the leach solution in a UV spectrophotometer. They found that sulphur could be extracted from the surface of pyrrhotite, which had been floated in the absence of collector. As can be seen from Fig. 2.26, the spectrum from the leached pyrrhotite was compared with the spectrum of sulphur dissolved in cyclohexane indicating that sulphur was present at the siuface. Kelebek and Smith (1989) used UV spectrophotometer to determine sulphur in the ethanol extract from the surface of floated galena and chalcopyrite showing that the amount of sulphur on the minerals can be correlated with their flotation rate which was found to be first order within the critical surface tension range. 

To 5.0 ml of an aqueous solution containing cocaine is added 1 ml of saturated sodium tetraborate solution and 2.0 ml of cyclohexane. The drug is extracted into the cyclohexane phase and this transferred to a test tube. 50 pi of a saturated LiAlH solution in diethyl ether are added. After 3 minutes 50 pi distilled water are added to the cyclohexane, and the mixture shaken. Next, 50 pi of heptafluorobutyric anhydride (or alternatively pentafluoropropionic anhydride) are added to the cyclohexane phase and allowed to stand for 3-5 minutes... 

Sub-samples of 1 g were taken for the analysis. The PAHs were extracted under reflux with toluene/acetone (1 1 v/v, 150 mL) for 30 minutes. The efficiency of the extraction procedure was tested by adding an internal standard (indeno[l,2,3-c t/]fluoranthene) and was found to be 95 99%. An additional extraction with tetrahydrofurane did not enhance the PAH yield. The extract was evaporated to about 2 mL. A cydohexane/dimethylformamide (DMF)/water (100 mL cyclohexane, 90 mL DMF and 10 mL water) partition was performed. The cyclohexane phase was discarded and the DMF/water phase diluted with 80 mL water. This phase was re-extracted with cyclohexane. The cyclohexane phase was evaporated to a volume of 2 mL and cleaned-up over a silica column (5 g, 9.1% water). The PAHs were eluted with 80 mL cyclohexane, which was evaporated afterwards to a volume of 0.1-0.5 mL. The obtained concentrate was placed on a Sephadex LH 20 column (10 g) and eluted with propanol-2. The fraction of 0-46 mL was discarded. The fraction from 46-170 mL was evaporated to a small volume and analysed by high resolution gas chromatography (on column injection) using a fused silica capillary column of which the conditions are described elsewhere [26]. 

A microchannel contactor has been developed and tested with water and cyclohexane streams extracting cyclohexanol [199]. Using this device, the relative importance of mass transfer resistance in the flow channels versus the contactor plate was explored. Both micromachined contactor plates and commercial polymeric membranes were configured with various channel heights both on the feed and solvent sides. Data indicate that contactor plate mass transfer becomes... 

ASTM D 5524 Standard Test Method for Determination of Phenolic Antioxidants in High-Density Polyethylene Using Liquid Chromatography The method technically is very similar to that described in ASTM D 1996, except HDPE samples are analyzed, and extraction is performed with cyclohexane. As the standard notes, besides Irganox 1010, Irganox 1076, and Isonox 129, the test method should be applicable for the determination of other antioxidants such as Cyanox 425, Cyanox 1790, Cyanox 2246, Ultranox 236, and Ultranox 246, but the applicability of this test method has not been investigated for these antioxidants. Precision of the procedure is slightly poorer compared to that of ASTM D 1996 6-13% for within-laboratory tests and 9-19% for between-laboratory tests with concentrations of antioxidants in HDPE from approximately 0.02 to 0.08%. 

According to Lury, xanthate compound extracted by organic solvent can be tested by using spectrophotometry. The adsorption curve of nickel xanthate extracted by toluol at pH 5.2 can be found from Fig. 6.5. As seen in Fig. 6.5, the absorption peak appears at 270 pm. It was also reported that nickel xanthate could be extracted by cyclohexane. And absorption peak appears at 420 pm. 

OUy and, to some extent, water-soluble concentrates can, for example, be directly diluted with cyclohexane or acetone, respectively. Preparations of the former type which contain little vitamin D must be largely freed from the large amount of fat-soluble ballast by dissolving in warm absolute alcohol and freezing out at 0° C. Products in powdered or pulverised form are best submitted to ammonia-cal or enzymatic digestion to liberate the vitamin D from the dry powder this is also done when added as an adsorbate or oily solution. Extraction with petrol ether is then carried out and the extract evaporated and dissolved in cyclohexane or chloroform. The most suitable procedure must be chosen and tested with every preparation. 

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