Acetonitrile acetone mixture

Fig. 37A shows the chromatogram obtained in isocratic conditions for a mixture of homogeneous TG standards. The mobile phase is a mixture of CHC13 and acetonitrile (49 51). Tribehenin (BBB) is eluted easily in 18 min, while tristearin (SSS) could not be eluted without serious difficulties in previous studies where acetone/acetonitrile mixtures were used. This is certainly due to the use of a strong eluent, containing about half CHC13, a solvent in which fats are known to be very soluble. 

Information on vibrational spectra of thorium nitrate recorded in aqueous media is available in [2, 4, 7, 10 to 14] and details of NMR investigations of similar solutions will be found, for example, in [15 to 17]. An NMR study of Th(N03)4 4H20 in acetone-acetonitrile mixture has also been reported [18]. 

The most critical decision to be made is the choice of the best solvent to facilitate extraction of the drug residue while minimizing interference. A review of available solubility, logP, and pK /pKb data for the marker residue can become an important first step in the selection of the best extraction solvents to try. A selected list of solvents from the literature methods include individual solvents (n-hexane, " dichloromethane, ethyl acetate, acetone, acetonitrile, methanol, and water ) mixtures of solvents (dichloromethane-methanol-acetic acid, isooctane-ethyl acetate, methanol-water, and acetonitrile-water ), and aqueous buffer solutions (phosphate and sodium sulfate ). Hexane is a very nonpolar solvent and could be chosen as an extraction solvent if the analyte is also very nonpolar. For example, Serrano et al used n-hexane to extract the very nonpolar polychlorinated biphenyls (PCBs) from fat, liver, and kidney of whale. One advantage of using n-hexane as an extraction solvent for fat tissue is that the fat itself will be completely dissolved, but this will necessitate an additional cleanup step to remove the substantial fat matrix. The choice of chlorinated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride should be avoided owing to safety and environmental concerns with these solvents. Diethyl ether and ethyl acetate are other relatively nonpolar solvents that are appropriate for extraction of nonpolar analytes. Diethyl ether or ethyl acetate may also be combined with hexane (or other hydrocarbon solvent) to create an extraction solvent that has a polarity intermediate between the two solvents. For example, Gerhardt et a/. used a combination of isooctane and ethyl acetate for the extraction of several ionophores from various animal tissues. 

PCBs in biological samples are usually extracted by a Soxhlet column and with a nonpolar solvent such as hexane. The sample is first mixed with sodium sulfate to remove moisture. The extraction of PCBs from sediments was tested with sonication, with two sonications interspersed at a 24-h quiescent interval, with steam distillation, or with Soxhlet extraction (Dunnivant and Elzerman 1988). Comparison of the recoveries of various PCB mixtures from dry and wet sediments by the four techniques and the extraction efficiency of four solvents showed that the best overall recoveries were obtained by Soxhlet extraction and the two sonication procedures. In comparisons of solvent systems of acetone, acetonitrile, acetone-hexane (1+1), and water-acetone-isooctane (5+1.5+1), recoveries of lower chlorinated congeners (dichloro- to tetrachloro-) were usually higher with acetonitrile and recoveries of higher chlorinated congeners (tetrachloro- to heptachloro-) extracted with acetone were superior (Dunnivant and Elzerman 1988). The completeness of extraction from a sample matrix does not seem to discriminate against specific isomers however, discrimination in the cleanup and fractionation process may occur and must be tested (Duinker et al. 1988b). 

Solvents 1 and 2 are known to be good solvents for poly(methyl methacrylate) solvent 3 readily dissolves polystyrene.The solubility tests show that the radically polymerized sample is insoluble in all three solvents.The solubility isthusdifferentfrom that of both poly(methyl methacrylate) and polystyrene.The anionically polymerized product dissolves on warming in the acetone/methanol mixture and also in acetonitrile it is insoluble in cyclohexane/toluene.The solubility is thus similar to that of poly(methyl methacrylate). For the cationically initiated polymerization the product is only slightly soluble in acetone/methanol, insoluble in acetonitrile, but very readily soluble in cyclohexane/toluene.The solubility thus resembles that of polystyrene. 

HPLC analysis of TAGs was applied to olive oils and a limit for LLL was established at 0.5% of the total TAGs and enclosed in the European Commission (EC) Regulation on olive oils, as well as in the related international norms (International Olive Oil Trade Norm [2], Codex Alimentarius Standard [3]). The method performed the separation by RP-HPLC on a C18 Lichrosorb or Lichrosphere column, 25x0.46 cm, 5 J,m of particle size, isocratic elution with acetone/acetonitrile (50/50 v/v) and RI detection. Eigure 19.1 reproduced the HPLC traces annexed to the official method [4] chromatogram A refers to 100% soybean oil, B to a mixture 50/50 soybean and olive, C 100% olive oil. 

Several methods employ the homogenization of the plant material with aqueous acetonitrile (Hsu et al. 1991 Liao et al. 1991) or other polar organic solvents such as acetone/methanol mixtures (Hong et al. 

Plattner (82) briefly examined the effects of solvent composition upon TG separations. Mixtures of acetone/methanol and acetone/acetonitrile were examined. In this work, acetone/ acetonitrile mobile phases were reported to give less complex chromatograms of TG mixtures than acetone/methanol mixtures. 

Figure 26 shows the separation of a synthetic mixture of TG standards and an olive oil sample using two 3-//m C18 columns connected in series with NARP conditions. The mobile phase used was 7 3 acetone/acetonitrile at a flow rate of 2.5 ml/min. The analysis time was ca. 8 min. Attempts to duplicate this separation on several 5-/rmC18 columns packed with different packing materials were not successful. 

In addition to the above-listed systems, a minimum of the rate constant was observed for the Zn(II)/Zn(Hg) systems in water-methanol [232] and for the Mn(II)/Mn(Hg) systems in water-acetonitrile mixtures [230]. Electroreduction of T1(I), Zn(II) and maleic acid was also studied in water-acetone [273] and water-ethanol [274] mixtures. 

The reaction of amide chlorides with primary and secondary amines or amine derivatives yields amid-inium salts (134 Scheme IS). - In the course of the reactions HCl is produced, which converts the amino compound to its hydrochloride. The salt mixtures thus formed are difficult to separate. Provided the amidinium compound in the mixture is at most an N,A, -trisubstituted one, separation can be achieved via the free amidine, which, after separation, is easily converted to the desired amidinium salt (135) by acidification with water-free acids. From salt mixtures containing iV.. A -tetrasubstituted amidinium salts, the pure amidinium compound, e.g. (136) can sometimes be isolated via anion exchange by addition of HCIO4, NaC104 or Nal (in acetone/acetonitrile). 

The free acid shows an anomalous Stokes shift only in proton-accepting solvents (acetone, acetonitrile) or mixtures such as toluene/pyridine (36,35), whereas in benzene only normal fluorescence with its maximum near 23,700 cm" is observed. The system 3-hydroxy-2-naphthoic acid in toluene plus small amounts of pyridine has been studied in some detail by Hirota (36) and Ware... 

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