Methanol hexane mixture

A methanol/hexane mixture is used in the best food (BF) method to extract the toxin from the substrate 100 g of sample is added to 500 ml of a methanol-water (55 45) mixture and 200 ml of hexane. After 1 min of vigorous shaking, the resulting solution is centrifuged for 5 min at 2000 rpm. Twenty-five ml of the methanol phase is used for the TLC assay. The method has been adopted by the AOAC Official Methods of Analysis in peanut and peanut products (17). 

Figure 11.3-3 shows the vapor-liquid and liquid-liquid equilibrium behavior computed for the system of methanol and n-hexane at various temperatures. Note that two liquid phases coexist in equilibrium to temperatures of about 43°C. Since liquids are relatively incompressible, the species liquid-phase fugacities are almost independent of pressure (see Illustrations 7.4-8 and 7.4-9), so that the liquid-liquid behavior is essentially independent of pressure, unless the pressure is very high, or low enough for the mixture to vaporize (this possibility will be considered shortly). The vapor-liquid equilibrium curves for this system at various pressures are also shown in the figure. Note that since the fugacity of a species in a vapor-phase mixture is directly proportional to pressure, the VLE curves are a function of pressure, even though the LLE curves are not. Also, since the methanol-hexane mixture is quite nonideal, and the pure component vapor pressures are similar in value, this system exhibits azeotropic behavior. 

Kim, Wang and Ma (1994) used 0.5% ammonium hydroxide in a water/ methanol/hexane mixture and a Cl8 column to resolve complex mixtures of molecular species of PLs, which were detected as protonated and sodiated molecular species. Samples were injected onto a C18 HPLC column (5 pm, 2.1 mm X 15 cm) and separated by means of the aforementioned mobile phase changing linearly from 12 88 0 to 0 88 12 in 17 min after holding at the initial composition for 3 min. The column flow rate was 0.5 ml min and the effluent was split 1 100. The capillary exit voltage was generally set at 200 V and raised up to 300 V for the detection of DG ions. 

Kim, Wang and Ma (1994) reported an improved technique for molecular species analysis of PLs including acidic PLs, with use of HPLC with an ES interface. By using 0.5% ammonium hydroxide in a water/methanol/hexane mixture and a Cl8 column, they separated complex mixtures of PL classes... 

At the earliest stage of LC-ESI/MS analysis of lipids, Kim et al. employed a C18 column (150x2.1 mm, 3-pm particle size) with a mobile phase consisting of the 0.5% ammonium hydroxide in a water-methanol-hexane mixture employing a linear gradient from 12 88 0 to 0 88 12 [69], They detected ions that were shown as the protonated or sodiated form in the positive-ion mode. They determined PI, PS, PC, PE, and SM with an SIM approach. 

Polymerization of triphenylmethyl methacrylate in the presence of a chiral anion catalyst results in a polymer with a helical structure that can be coated onto macroporous silica [742,804). Enantioselectivity in this case results from insertion and fitting of the analyte into the helical cavity. Aromatic compounds and molecules with a rigid nonplanar structure are often well resolved on this phase. The triphenylmethyl methacrylate polymers are normally used with eluents containing methanol or mixtures of hexane and 2-propanol. The polymers are soluble in aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran which, therefore, are not suitable eluents. 

We have previously reported results of the application of these procedures for the amination of poly(styryl)lithium (11). After an investigation of a variety of procedures, a 92% yield of poly(styryl)-amine was obtained using two equivalents of the amlnating reagent in a THF/Et20/hexane mixture of -78°C followed by slow warming to -15°C and quenching in methanol (eq. 2). 

Carotenoids A large number of solvents have been used for extraction of carotenoids from vegetables matrices, such as acetone, tetrahydrofuran, n-hexane, pentane, ethanol, methanol, chloroform [427-431], or solvent mixtures such as dichloromethane/methanol, tetrahydrofuran/methanol, -hexane/acetone, or toluene or ethyl acetate [424,432-435], SPE has been used as an additional purification step by some authors [422,426], Supercritical fluid extraction (SEE) has been widely used, as an alternative method, also adding CO2 modifiers (such as methanol, ethanol, -hexane, water, methylene chloride) to increase extraction efficiency [436-438], In addition, saponification can be carried out, but a loss of the total carotenoid content has been observed and, furthermore, direct solvent extraction has been proved to be a valid alternative [439],... 

The iridoids cerbinal, cerberic acid and cerberinic acid are found in the methanol extract of the bark of C. manghas [67]. The crude extract obtained by percolation from 4 kg of stem bark and 1.9 kg of root bark were diluted with water to 50% water methanol. The mixture was washed with hexane and partitioned with benzene. Benzene fractions were re-suspended in methanol and cerbinal (120 mg from stem bark extract and 300 mg from root bark extract) precipitated. 

Poly(styrene-co-acrylonitrile) samples (SAN) have been fractionated through methanol-acetone or methanol-dichloromethane mixtures of stepwise-altered composition 108) through methanol/dichloromethane, n-hexane/dichloromethane, or methanol/acetone gradients109), cyclohexane/methyl ethyl ketone gradients 110), or (toluene — 1-propanol 50 50)/dimethyl formamide gradients111. Mixtures of ethylene cyanohydrin — ethylene carbonate 112) or cyclohexane — methyl ethyl ketone 113 have also been used for the separation of SAN copolymers. Both the latter systems as well as the n-hexane/dichloromethane gradient109) had the efficacy of fractionating SAN copolymers by composition. 

Another paper describes a modified HPLC assay for the determination of TAP residues in spiked milk at levels as low as 30 /rg/kg (132). Milk spiked with TAP was extracted with ethyl acetate. Following the addition of hexane, the extract was cleaned up with a silica SPE cartridge. Just before use, the cartridge was pretreated by passing an ethyl acetate hexane mixture. The TAP was eluted with methanol. The eluate was collected and evaporated. The residues were dissolved in mobile phase and injected into an HPLC column. The recovery was found to range from 68.0% to 90.0%, and precision data suggested that RSD ranged from 7.0% to 9.4%. 

A monolithic hydrophobic polymer formed by photoinitiated polymerization for on-chip solid-phase extraction is shown in Figure 5.6. The polymer mixture includes butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA), with the pore size controlled by the composition of the hexane/methanol porogenic mixture. The degree of pre-concentration depends on the flow rate, as shown in the pre-concentration of GFP at three flow rates (see Figure 5.7). The factors of pre-concentration were 355, 756, and 1002 for the flow rates of 3, 1.03, and 0.53 rE/min, respectively [342]. 

A suspension of 22.8 g (0.05 mol) of 2-(N-propargyl)-phthalimidoacetamido-5-chlorobenzophenone in 250 ml ethanol containing 7.5 g hydrazine hydrate (0.15 mol) was heated under reflux for 2 hours, at the end of which time the reaction mixture was set aside overnight at ambient (25°C) temperature. Thereafter, the crystalline phthalyl hydrazide which had precipitated out was removed by filtration and washed with 3 x 50 ml aliquots of chloroform. The filtrate and washings were diluted with water and exhaustively extracted with chloroform. The chloroform extract was then evaporated and the residue washed with 100 ml hexane to promote crystallization. The crude 7-chloro-l-propargyl-3H-l,4-benzodiazepine-2(lH)-one was recrystallized from a methanol-water mixture to give 10.5 g (71.4%) of the pure product. Melting point 140°C to 142°C. 

A solution of the Step 1 product (0.75 mmol) in 7 ml of CCI3H was slowly added to a stirred mixture of Feds (2.47 mmol) in 3 ml of CCI3H and heated to 50°C for 1 hour and then to 40°C for 24 hours. After the polymerization, the mixture was diluted with 20 ml of toluene and washed three times with water. The separated organic phase was stirred with 200 ml of 7.5% NH4OH, washed three times with water, and poured into methanol to precipitate the crude poly thiophene. The residue was purified by Soxhlet extraction with methanol, hexane, and chlorobenzene, and the product was isolated with a M = 27,300 daltons and Mn= 16,900 daltons. 

On-column methylation of barbiturates, hydan-toins, and some carboxylic acids can be achieved by injecting the sample mixed with 0.2M trimethyl-anilinium hydroxide in methanol. For carboxylic acids, the sample can be dissolved in 14% boron trifluoride in methanol and heated at 60 to 100° for 30 minutes. After evaporation of the bulk of the methanol, the mixture is diluted with a few millilitres of water and the methyl derivative extracted with a small volume of hexane. 

Alternative LC methods in the separation of NPEO resulting in a separation based on EO number include the use of an alumina column using an ethylene oxide-n-hexane mixture as mobile phase [37], of a cyanosilica column and a mobile phase gradient of toluene and a 10 88 2 mixture of 0.5 mmol/1 sodium acetate in toluene, methanol, and water [38], and of a poly(vinyl alcohol) column and 10-55% acetonitrile in 30 mmol/1 aqueous ammonium acetate as mobile phase [39]. Ion-pair LC-MS, using 5 mmol/1 triethylamine in the mobile phase, was applied in the analysis of phenols and NPEC [33]. 

Before the advent of commercially available methods, it was common to use two-phase, liquid-liquid partition with organic solvents and solvent mixtures, including methylene chloride, hexane, diethyl ether, ethanoi/chloroform/water, methylene chloride/methanol, hexane/isopropanoi, and cydohexane/ethyl acetate. Ethanol and methanol... 

The pressure drop is markedly lower if low-viscosity organic solvents are used, e.g. hexane. In contrast to this, it is higher with methanol-water mixtures. 

To a well-stirred solution of 6.0 g (43 mmol) of acrylophenonef 1 in 110 mL ice-cooled methanol a mixture of 11 mL (0.11 mol) of 31% H2O2 and 11 mL (22 mmol) of 2 N NaOH was added slowly. Then this was poured into 200 mL of water and extracted with ether. The organic layer was washed with saturated NaCl solution and water, then dried over Na2S04 and conentrated. The oily residue was allowed to stand in a refirigerator overnight to become solid. The solid was filtered and washed with cold /i-hexane to give... 

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