Mixed solvent acetonitrile-water

Kumamoto, M., Sonda, T., Takedomi, K., and Tabata, M. 2000. Enhanced separation and elution of catechins in HPLC using mixed-solvents of water, acetonitrile and ethyl acetate as the mobile phase. Anal. Sci. 16 139-44. 

This high dielectric constant with its ease of handling, low corrosivity, and low toxicity have made ethylene carbonate suitable as a solvent for specialized applications and for the preparation of binary mixed solvents with water, methanol, acetonitrile, sulpholane, and acetone. It is also used as an electrolyte in nonaqueous batteries, as a plasticizer, as a monomerer or reagent for the synthesis and modification... 

Mixed solvent systems are often used to probe solvent effects and in this context the molecular composition of the metal-ion solvation sphere is critical. NMR measurements in acetonitrile/water systems show that for Li, where the coordination number is four, water replaces acetonitrile completely until the waterrU" " ratio is 4 1. For Na" and K, water replaces acetonitrile completely until the watenmetal ion ratio is around 1 1 and then the NMR signal parallels the shift in the bulk solvent acetonitrile/water mixture. 

Purification of the activation products (PMs). The methylamine activation product dissolved in methanol is purified by chromatography, first on a column of silica gel using a mixed solvent of chloroform/ethanol, followed by reversed-phase HPLC on a column of divinylbenzene resin (such as Jordi Reversed-Phase and Hamilton PRP-1) using various solvent systems suitable for the target substance (for example, acetonitrile/water containing 0.15% acetic acid). 

While water has been used as a solvent more than any other media, nonaqueous solvents [e.g., acetonitrile, propylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or methanol] have also frequently been used. Mixed solvents may also be considered for certain applications. Double-distilled water is adequate for most work in aqueous media. Triple-distilled water is often required when trace (stripping) analysis is concerned. Organic solvents often require drying or purification procedures. These and other solvent-related considerations have been reviewed by Mann (3). 

Transfer the residue with 1 g of Florisil PR on to the top of the column packed with 9 g of Florisil PR with the aid of hexane. Rinse the column with 150 mL of hexane-acetone (4 1, v/v). Elute acetamiprid with 120 mL of a mixed solvent of acetone-hexane (1 1, v/v) and concentrate the eluate to near dryness by rotary evaporation at 40 °C. Dissolve the residue with 5 mL of distilled water and apply the solution to the top of the packed Sep-Pak Ci8 column pretreated with 20 mL each of methanol and distilled water. Elute acetamiprid with 30 mL of a mixed solution of water-acetonitrile (17 3, v/v). Concentrate to dryness on a water-bath at ca 40 °C by rotary evaporation. Prepare the GC-ready sample by dissolving the residue in acetone. 

The pKs value of acetic acid is about the same as that of water therefore, in order to obtain high accuracy and greater differentiation in potentiometric titrations, Pifer and Wollish91 preferred to use acetic acid mixed with dioxan in the solvent and also in the perchloric acid titrant in view of the possible presence of peroxide, the previous purification requires great care40. Similarly, Fritz92 recommended acetic acid mixed with acetonitrile (pKs = 19.5 at 25° C)93 in both the solution and the titrant. 

The rate of decarboxylation of benzoylacetic acid is also accelerated in mixed dioxane-water (Hay and Tate, 1970) and acetonitrile-water (Straub and Bender, 1972) solutions. In no case, however, has an acceleration greater than 2.5 been observed. In aprotic solvents, such as benzene, decarboxylation rates are depressed (Swain et al., 1961). 

Halcinonide was partitioned between hexanes and methanol, and between hexanes and aqueous acetonitrile at apparent pH values of 2,4,6(unadjusted), and 10. After one hour of mixing, the steroid content was determined by ultraviolet spectrometry of both phases. In all cases, absorbance at the peak maximum of 239 nm was detected only in the acetonitrile-water or methanol layer. The aqueous acetonitrile (pH 6) result was verified- using 14C-halcinonide labeled at the 2- carbon of the acetonide moiety. Thus, the halcinonide is completely retained in either the acetonitrile-water or methanol layers, indicating the utility of these solvent systems for extracting the steroid from formulations. 

Recently, Sivakolundu and Mabrouk published an NMR solution structure of horse heart ferrocytochrome c in which the heme contains an Fe(II) ion. This solution structure was the first in which the cytochrome c protein was dissolved in a nonaqueous solvent a solvent mix of 70% water and 30% acetonitrile (ACN). The data obtained from the NMR study are deposited in the protein data bank (PDB) as (1) ILCl, the minimized average NMR structure and (2) 1LC2, the 30 lowest energy NMR structures. 

The kinetics of the alkaline hydrolysis of 2-methylpentyl salicylate (24) have been studied in various aqueous propanol and r-butanol mixtures and in mixtures of water and ethane-l,2-diol. ° Further smdies of the aminolysis of ionized phenyl salicylate (25) have been reported, in which it was observed that, in mixed acetonitrile-water solvents, glycine, 1,2-diaminoethane and 3-aminopropanol all reacted as did simple amines, via an intramolecular general-base-catalysed process. ... 

Fig. 18 Top CD spectra. Oligomer 15 (solid line) oligomer 15 in the presence of 100 equiv of (-)-a-pinene (dotted line) and 100 equiv of (+)-a-pinene (dashed line) in a mixed solvent of 40% water in acetonitrile (by volume) at 295 K. [15]=4.2 pmol. Bottom Plot of IniCn for 15 against the solvent composition. The solid line is the least-squares linear fit (correlation coefficient=0.9987), and the dotted line is the extrapolation to 100% water. Error bars are from the nonlinear fitting of the data to...

A protective influence of commercial coatings [335] and chromates [335, 336] as well as surface coating formation in water-acetonitrile mixed solvents [227] was analyzed. 

Heats of solution of lithium perchlorate in 20, 40, 60, 80, 90, and 100 wt % acetronitrile-water mixtures at 298.16°K are reported. The heats of dilution were measured for lithium perchlorate in the mixed solvent containing 90 wt % CH CN. The heats of transfer (AHtr) of lithium perchlorate from water to aqueous acetonitrile were calculated. The results are discussed in terms of the structure of the solvent system and selective solvation properties of the lithium ion. 

Lithium perchlorate was purified as described earlier (6). Acetonitrile was Fisher ACS reagent grade and was used without further purification. Water was distilled twice, the second time in a Corning AG-2 all glass still, and had a specific conductivity at 25°C of 8 X 10 7 ohm-1 cm-1. The mixed solvents were prepared by weight as shortly as possible before heat measurements were made. 

Fig. 4.15. Thickness of the double layer as a function of acetonitrile concentration in a water-acetonitrile mixture, as per Equation 4.1. Constants for the mixed solvents were obtained from ref. [49,129].

Most polymers belonging to this class are water-soluble only in their protonated form. As a consequence, most potentiometric titrations of these polymers have been performed with OH starting from their hydrochlorides, either in water or in mixed solvents, such as water/dioxane, water/sulfolane, water/acetonitrile 64). Many poly[thio-l-(N,N-dialkyl-aminomethyl)ethylene]s are optically active, and in these cases ORD and CD techniques may be used to study their protonation behaviour, in addition to potentiometric techniques. 

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