Composition acetonitrile

Bifenox, nitrofen and oxyfluorfen HPLC conditions withpost-columnfluorescence reactor system column, C-18 reversed-phase (25cmx4.6-mm i.d.) temperature, 40 °C flow rate, 1 mL min flow composition, acetonitrile-water (1 4, v/v) (2 min), with increase in acetonitrile at 5%min to 90% acetonitrile to acetonitrile-water... 

Kees et introduced the use of nitrile-bonded silica column packings in their methods for roxithromycin, clarithromycin and azithromycin by HPLC-ED. The eluent composition, acetonitrile-methanol-phosphate buffer (50nmiolL, pH 6.6-7.5), was varied according to the compounds being assayed and detection was at PGEs (Ei +0.5 to +0.6 V E2 +0.8 to +0.9 V vs Pd). Samples were prepared by LLE into MTBE. LLoQs (RSD, 0.5 mL plasma) were clarithromycin, 30 pg L ... 

The largest errors in predicted compositions occur for the systems acetic acid-formic acid-water and acetone-acetonitrile-water where experimental uncertainties are significantly greater than those for other systems. 

Figure 7-2. Conjugate liquid phase compositions for water-acrylonitrile-acetonitrile system calculated with subroutine ELIPS for feeds shown by . ...

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

The composition of PPG—PEG blends has been determined using gpc with coupled density and RI detectors. PEG and PPG have different response factors for the density and RI detectors which were exploited (173). An hplc system with CHROMPAC RP-18C2g column at 298°C and acetonitrile—water or methanol—water as the mobile phase has been used to gather information about the functionaUty of PPO (174). 

Although fluorocarbons are considered very stable compounds, they can be defluonnated to unsaturated denvatives under certain mild conditions. Hexa-decafluorobicyclo[4.4.0]dec-I(6)-ene reacts with activated zinc powder at 80-100 °C to yield partially and fully aromatized products [61] The final product composition depends on the solvent. Dioxane, acetonitrile, and dimethylform-amide, m this order, effect increasing unsaturation (equation 30). 

We had no good way to predict if they would be liquid, but we were lucky that many were. The class of cations that were the most attractive candidates was that of the dialkylimidazolium salts, and our particular favorite was l-ethyl-3-methylimid-azolium [EMIM]. [EMIMJCl mixed with AICI3 made ionic liquids with melting temperatures below room temperature over a wide range of compositions [8]. We determined chemical and physical properties once again, and demonstrated some new battery concepts based on this well behaved new electrolyte. We and others also tried some organic reactions, such as Eriedel-Crafts chemistry, and found the ionic liquids to be excellent both as solvents and as catalysts [9]. It appeared to act like acetonitrile, except that is was totally ionic and nonvolatile. 

The solvent in a bulk copolymerization comprises the monomers. The nature of the solvent will necessarily change with conversion from monomers to a mixture of monomers and polymers, and, in most cases, the ratio of monomers in the feed will also vary with conversion. For S-AN copolymerization, since the reactivity ratios are different in toluene and in acetonitrile, we should anticipate that the reactivity ratios are different in bulk copolymerizations when the monomer mix is either mostly AN or mostly S. This calls into question the usual method of measuring reactivity ratios by examining the copolymer composition for various monomer feed compositions at very low monomer conversion. We can note that reactivity ratios can be estimated for a single monomer feed composition by analyzing the monomer sequence distribution. Analysis of the dependence of reactivity ratios determined in this manner of monomer feed ratio should therefore provide evidence for solvent effects. These considerations should not be ignored in solution polymerization either. 

Figure 4. Log intensity vs. potential plots (Tafel plots) obtained from the voltammograms of a platinum electrode submitted to a 2 mV s l potential sweep polarized in a 0.1 M LiC104 acetonitrile solution having different thiophene concentrations. (Reprinted from T. F. Otero and J. Rodriguez, Parallel kinetic studies of the electrogeneration of conducting polymers mixed materials, composition, and kinetic control. Electrochim, Acta 39, 245, 1994, Figs. 2, 7. Copyright 1997. Reprinted with permission from Elsevier Science.)...

In general, the majority of separations are achieved by exploiting dispersive interactions in the stationary phase and modifying and controlling the absolute and relative retention of the solutes by adjusting the composition of the mobile phase. It is far easier to adjust the mobile phase by selecting different mixtures of water and the solvents methanol, acetonitrile and/or tetrahydrofuran than change from column to column. 

Dimethylformamide is also a suitable solvent [50], it has, however, the disadvantage of being oxidized at fairly low potentials to A-acyloxy-iV-methyl formamide [51]. The influence of the composition of the ternary system water/methanol/dimethyl-formamide on the material and current yield has been systematically studied in the electrolysis of co-acetoxy or -acetamido substituted carboxylates [32]. Acetonitrile can also be used, when some water is.added [52]. The influence of various solvents on the ratio of Kolbe to non-Kolbe products is shown in Table 1 [53]. 

The HPLC system used consisted of a 30 x 2 mm Luna CN column with linear gradient elution employing two mobile phases A and B (A, 90% H2O 10% acetonitrile B, 10% H2O 90% acetonittile) with both phases containing 5 mM ammonium acetate and 0.2% formic acid. The hnear gradient commenced with 50 50 A B increasing to 100% B after 1 min of the analysis this composition was maintained for 1 min before returning to 50 50 A B after 4 min. Positive-ion ionspray (pneumatically assisted electrospray) was used to obtain mass spectra, with the spectrometer operating at a resolution of 5000. 

Although some normal phase methods have been used, the majority of carotenoid separations reported in the literature were carried out by reversed phase HPLC. Among the Cjg columns employed for determination of complete carotenoid compositions in foods, the polymeric Vydac brand is preferably used for separation of cis isomers. Several examples of different C,g columns and mobile phases are cited in the literature, but not aU carotenoids are baseline separated in most systems. Table 6.2.1 shows some examples employing different brands of Cjg columns." Acetonitrile did not improve selectivity toward separation of carotene isomers in a Vydac 201TP column and resolution was strongly dependent on the Vydac column lot. ... 

Dry the organic solvent layer through 80 g of anhydrous sodium sulfate on a glass funnel and collect the dried solution in a 300-mL round-bottom flask. Evaporate the solvent under reduced pressure. Dissolve the residue in 150 mL of n-hexane and transfer the solution into a 300-mL separatory funnel. Extract twice with 100 mL of acetonitrile. Combine the acetonitrile extracts in a 500-mL round-bottom flask and evaporate the solvent under reduced pressure. Dissolve the residue in a small amount of column-eluting solvent (dichloromethane-n-hexane, 1 1, v/v) and transfer the solution to the top of the silica gel column. After eluting the column with 60 mL of solvent of the same composition (discard), elute orbencarb and I with 150mL of dichloromethane. Collect the eluate in a 300-mL flask and evaporate the solvent under reduced pressure. Dissolve the residue in an appropriate volume of acetone for analysis. 

Solvent A water containing 0.1% (v/v) formic acid Solvent B acetonitrile containing 0.1% (v/v) formic acid A gradient is run from 90% A to 10% A over 12 min. The solvent composition is taken back to 90% A at 12.5 min and equilibrated until 17.5 min (solvents degassed)... 

Solvent optimization in reversed-phase liquid chromatography is commenced by selecting a binary mobile phase of the correct solvent strength to elute the seuaple with an acceptable range of capacity. factor values (1 < k <10 in general or 1 < k < 20 when a larger separation capacity is required). Transfer rules (section 4.6.1) are then used to calculate the composition of other isoeluotropic binary solvents with complementary selectivity. In practice, methanol, acetonitrile and tetrahydrofuran are chosen as the selectivity adjusting solvents blended in different... 

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