Aliquot 336, phase-transfer

To promote phase transfer in the toluene/H20 solvent system, 1 drop of Aliquat 336 (tricaprylmethylammonium chloride, Aldrich) was added. For kinetic studies, aliquots (0.1 ruL) were withdrawn by syringe at timed intervals (20-360 s)... 

Eight samples from each set (A and D) were split into two groups, one incubated in 0.15 M phosphate buffered solution (PBS) and the other in PBS containing 0.1% of the phase transfer catalyst, tricapryl methyl ammonium chloride (Aldrich Aliquot 336) (PBS, catalyzed), both at pH 7.4. The samples were suspended in centrifuge tubes with 10 mL of incubation solution by nylon string and the tubes were placed in a shaker bath at a constant temperature of 37°C. Periodically, the samples were taken out of the tubes, placed on lint free paper towels, allowed to dry for exactly one hour, weighed and placed in fresh incubation media. The total time of the study was 48 weeks (330 days). 

Emulsion Capacity and Stability. A 0.5 g sample of the freeze-dried protein fraction was redissolved in a minimum of 0.3 M citrate-phosphate buffer at pH 7.0 and mixed thoroughly with 50 ml of 1 M NaCl for 1 min in a Sorvall Omnimixer at 1000 rpm in a one pint Mason jar set in a water bath (20°C). Crisco oil (50 ml) was added to the jar and an emulsion formed by mixing at 500 rpm with simultaneous addition of oil at the rate of 1 ml/min until the emulsion broke. The endpoint was determined by monitoring electrical resistance with an ohmeter. As the emulsion broke a sharp increase (l KS2 to 35- 0 KSi) was noted. Emulsion capacity was expressed as the total volume of oil required to reach the inversion point per mg protein. This method is similar to that used by Carpenter and Saffle (8) for sausage emulsions. To establish emulsion stability the same procedure was used except that 100 ml of oil was added and a stable emulsion formed by blending at 1000 rpm for 1 min. A 100 ml aliquot was transferred to a graduate cylinder and allowed to stand at room temperature. Observations were made of the volume of the oil, emulsion and water phases at 30, 60, 90 and 180 min. 

Different parameters describing the principal properties of self-assemblies are mentioned in the literature. Critical micellization concentration (CMC) is described using the pyrene fluorescence method. From a stock solution of pyrene dissolved in chloroform, an aliquot is transferred with a micropipette into a series of dry test tubes the solvent is allowed to evaporate under vacuum by protecting it from light to obtain dry pyrene. Then, a series of polymer solutions in buffer solution (pH 7.4) are added to the pyrene. Mixtures are stirred in the dark for 24 h at 25°C and then filtered through a membrane filter for separation of undissolved pyrene crystals. The concentration of solubilized pyrene in the micellar phase is determined spectrofluorometrically at 339 nm wavelengths of excitation and 390 nm of emission. 

Model Studies. General Procedure. The theoretical amount of sodium or potassium hydroxide (corrected for the amount of water present), an equivalent amount of 4-methylphenol, 0.05 equivalent of the phase transfer catalyst, biphenyl (internal standard, 0.25 equivalents) and methylene chloride or a 3 to 1 mixture of chloro-benzene/methylene chloride were heated at reflux. The amount of solvent used was chosen to give a solution which would be 20% in final product (g of formal/ml of solvent X 100 = 20%). Aliquots were removed at timed intervals and were worked up with methylene chloride and 1.2N HCl. These samples were analyzed by vpc and the yields of the product were calculated, based on an internal standard... 

Traditionally, LC and GC are used as separate steps in the sample analysis sequence, with collection in between, and then followed by transfer. A major limitation of off-line LC-GC is that only a small aliquot of the LC fraction is injected into the GC p. (e.g. 1 - 2 p.1 from 1 ml). Therefore, increasing attention is now given to the on-line combination of LC and GC. This involves the transfer of large volumes of eluent into capillary GC. In order to achieve this, the so-called on-column interface (retention gap) or a programmed temperature vaporizor (PTV) in front of the GC column are used. Nearly all on-line LC-GC applications involve normal-phase (NP) LC, because the introduction of relatively large volumes of apolar, relatively volatile mobile phases into the GC unit is easier than for aqueous solvents. On-line LC-GC does not only increase the sensitivity but also saves time and improves precision. 

Quantitatively transfer the hydrolysis reaction solution to a 50-mL glass culture tube with a screw-cap by rinsing witli 3x5 mL of deionized water followed by 5 mL of 30% (v/v) sulfuric acid and one additional 5 mL of deionized water. Rinse the Teflon culture tube with acetone and transfer to the glass culture tube. Extract the acidic aqueous phase (pH 1) with 3 x 2.5 mL of toluene. Pass each upper toluene phase through approximately 3 g of anhydrous sodium sulfate contained in a 6-mL disposable filtration cartridge into a 10-mL volumetric flask. Adjust the volume of the solution to 10 mL with toluene. Condition a 3-mL diolsilane bonded silica gel SPE cartridge with two column volumes of toluene. Load a 5-mL aliquot of toluene solution and collect the eluate in a 125-mL round-bottom flask. Elute the column with an additional 50 mL of toluene (use the 75-mL reservoirs) and collect the eluate in the same round-bottom flask. Concentrate the toluene extract to approximately 3.0 mL at 40 °C under weak reduced pressure with a rotary evaporator. 

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

Lipid extraction 200 pL of plasma sample is mixed by brief vortexing with 200 pL of ethanol followed 1 min of vortexing with 800 pL hexane. After centrifugation for 5 min at 5000 rpm, 400 pL of upper (hexane) phase is transferred to a glass tube with screwed cap, dried under nitrogen, and kept at - 60°C until PCL analysis. For PCL analysis the sample is dissolved in 400 pL of MeOH by 30 s of vortexing, and 100 pL aliquots are taken for ACL assay. 

According to the modified procedure (602), milk is thoroughly mixed in its storage container immediately before transfer of the 1 ml aliquot in the extraction tube. This is necessary because approximately 50% of phenylbutazone in milk is associated with the cream. The sample is extracted with 2.4 ml diethyl ether and 2.4 ml petroleum ether in presence of 1 ml ethanol and 100 1 25% ammonia solution. The organic layer that contains the milk lipids is discarded. Five ml hexane-tetrahydro furan (4 1) is added to the aqueous layer, which is tiien acidified with hydrochloric acid and the layers are mixed. Under the acidic conditions, phenylbutazone partitions quantitatively into tlie organic layer, which is collected, evaporated, and dissolved in the mobile phase to be analyzed by liquid chromatography. Separation is performed on a reversed-phase column using an isocratic 0.02 M phosphate buffer/methanol mobile phase, and determination is by ultraviolet detection at 264 nm (Fig. 29.18.2). The limit of detection and limit of quantification were 3.0 and 5.4 ppb, respectively (Table 29.17). 

Evaporation and redissolving. The solvent of the combined upper layer is evaporated under nitrogen flow or low-temperature vacuum distillation. An oily material appears after it is dried. A precisely measured aliquot of mobile phase is normally used to redissolve theextract. These procedures are intended to not only increase the concentration of tocopherols and tocotrienols to the measurable level of the detector, but also to avoid uncertain volume change of organic layer during extraction, which results in inaccurate results. The redissolved sample is transferred to a vial for HPLC analysis. 

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