Effect of Organic Solvent

It is quite common to add a low percentage of methanol or acetonitrile to an aqueous mobile phase in order to obtain sharper peaks for organic sample ions, and it is entirely feasible to perform cation chromatographic separations in an aqueous-organic mixture with a much higher proportion of the organic solvent Hoffman and coworkers [10, 11] have shown that two mechanisms occur in such cases ion exchange and hydrophobic interaction between the sample and the resin when the eluent contains 70% acetonitrile. This is due to lower hydrophobic interaction in the 70% acetonitrile. 

Dumont, Fritz and Schmidt studied cation chromatography in organic solvents containing Uttle if any water [12]. Under these conditions solvation of the Hpophi-Uc part of the cation should be sufficient to virtually eliminate the hydrophobic interaction between the sample cations and the ion-exchange resin. In this way the true ion-exchange selectivity could be measured. 

After trying several different inorganic acids, methanesulfonic acid was selected as the eluting acid for the separation of protonated amine cations. In IC of cations with as the eluting cation, k should vary according to the following equation  

The effect of solvent was studied by measuring the retention factor, k, for a series of protonated alkylamine cations with 25 mM methanesulfonic acid in the appropriate solvent as the eluent [12]. Ordinarily a plot of log k vs the number of carbon atoms in such a homologous series would be linear. The slope of such a plot is at least in part an indication of the effect of the carbon chain on the retention factor. The retention factors were measured under identical conditions in each of four organic solvents. The k values of the alkylamines increased according 

Metal cations usually form complexes with inorganic anions much more readily in organic solvents than in water. For example, the pink cobalt(II) cation requires around 4 or 5 M aqueous hydrochloric acid to be converted to a blue cobalt(II) chloride anion. In a predominantly acetone solution, the intensely blue cobalt(ll) is formed in very dilute hydrochloric acid. Thus, the scope of ion-exchange group separations is increased greatly by carrying out separations in a mixture of water and an organic solvent. 

Fritz and Rettig [18] showed that zinc(II), iron(lll), cobalt(II), copper(II) and manga-nese(II) can be separated from each other on a short cation-exchange column with eluents containing a fixed, low concentration of HQ and increasing the water-acetone proportion from 40 % to 95 % acetone in steps. Later Strelow et al. [19] published extensive lists of metal-ion distribution coefficients in water/acetone/hydrochloric acid systems. 

Korkisch and co-workers have studied the effect of ethanol, acetic acid, ethylene glycol, and many other solvents upon the ion-exchange behavior of metal ions in systems containing hydrochloric and other complexing acids [20]. 

The selectivity of low capacity cation columns for monovalent ions can be adjusted by the addition of an organic modifier to the eluent. Using a nitric acid eluent of pH 

for example, the elution order for monovalents is Li, Na, NH4, K. Simple amines elute in the order of the carbon number, after NH4, with the result that (CH3)NH3 (methylammonium) can co-elute with potassium. In most cases, this coelution is of little significance, because potassium and methylammonium are not often in the same sample. However, where the analysis of either of these species in the presence of the other is desired, the selectivity cjm be modified by the addition of 40 % methanol to the eluent [21]. The methanol causes the potassium to elute later but does not affect the elution time of methylammonium, and potassium peaks are now resolved from each other. 

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The protonation equilibria for nine hydroxamic acids in solutions have been studied pH-potentiometrically via a modified Irving and Rossotti technique. The dissociation constants (p/fa values) of hydroxamic acids and the thermodynamic functions (AG°, AH°, AS°, and 5) for the successive and overall protonation processes of hydroxamic acids have been derived at different temperatures in water and in three different mixtures of water and dioxane (the mole fractions of dioxane were 0.083, 0.174, and 0.33). Titrations were also carried out in water ionic strengths of (0.15, 0.20, and 0.25) mol dm NaNOg, and the resulting dissociation constants are reported. A detailed thermodynamic analysis of the effects of organic solvent (dioxane), temperature, and ionic strength on the protonation processes of hydroxamic acids is presented and discussed to determine the factors which control these processes. 

Kjellstrand P, Holmquist B, Jonsson I, etal Effects of organic solvents on motor activity in mice. Toxicology 35 35 6, 1983... 

Grasso P. 1988. Neurotoxic and neurobehavioral effects of organic solvents on the nervous system. Occupational Medicine State of the Art Reviews. 3 525-539. 

Based on a series of studies of the effect of organic solvent on the reaction of Ca-ATPase with Pj and ATP synthesis, De Meis et al. proposed that a different solvent structure in the phosphate microenvironment in Ej and E2 forms the basis for existence of high- and low-energy forms of the aspartyl phosphate [93]. Acyl phosphates have relatively low free energy of hydrolysis when the activity of water is reduced, due to the change of solvation energy. The covalently bound phosphate may also reside in a hydrophobic environment in E2P of Na,K-ATPase since increased partition of Pj into the site is observed in presence of organic solvent [6] in the same manner as in Ca-ATPase. 

McCalley, D. V., Effect of organic solvent modifier and nature of solute on the performance of bonded silica reversed-phase columns for the analysis of strongly basic compounds by high-performance liquid chromatography, /. Chromatogr A, 738(2), 169, 1996. 

Acetonitrile, methanol and DMSO had no apparent effect on umbelliferone glucuronidation in human hepatocytes at concentration up to 2% [32]. With HLMs or expressed UGTs, inhibitory effects of organic solvents on glucuronidation of 7-hydroxy-4-trifluoromethyl-coumarin (7-HFC) and estradiol generally followed the order acetonitrile > ethanol > methonal > DMSO [33], DMSO did not inhibit estradiol-3-glucuronidation activity at a concentration up... 

Easterbrook, J., Liu, C., Sakai, Y. and Li, A.P. (2001) Effects of organic solvents on the activities of cytochrome P450 isoforms, UDP-dependent glucuronyl transferase, and phenol sulfotransferase in human hepatocytes. Drug Metabolism and Disposition The Biological Fate of Chemicals, 29, 141-144. 

Qin S, Gan J (2007) Abiotic enantiomerization of permethrin and cypermethrin effects of organic solvents. J Agric Food Chem 55 5734—5739... 

Abrams K, Harvell JD, Shriner D, et al. 1993. Effect of organic solvents on in vitro human skin water barrier function. J Invest Dermatol 101(4) 609-613. 

Stefanovic J, Starsia Z, Murgasova 1, et al. 1987. In vitro effects of organic solvents on immunity indicators in semm. J Hyg Epidemiol Microbiol Immunol 31 1-7. 

Makkar HPS, Becker K (1993) Vamllin-HQ method for condensed tannins effect of organic solvents used for extraction of tannins. J Chem Ecol 19 613-621... 

Edelfors S, Raven-Jonsen A. 1992. Effect of organic solvents on nervous cell membrane as measured by changes in the calcium magnesium ATPase activity and fluidity of synaptosomal membrane. Pharmacology and Toxicology 70(3) 181-187. 

Estell RE, Anderson DM, Havstad KM, Effects of organic solvents on use of tarbush by sheep, / Chem Ecol 20 1137—1142, 1994. 

Synthesis of Z-Tyr-Gly-NH2 in Aqueous-DMF Solvent Media. Using this modified enzyme, we carried out the synAesis of "Z-Tyr-Gly-NH2", which has never been formed in 100% aqueous system (14), and compart with native chymotrypsin on the effect of organic solvent. To a solution of Z-Tyr-OH (315mg) in Tris buffer (pH 6.7,0.5ml), which contained N,N-dimethylformamide (DW) (0-100%), was added a solution of H-Gly-NH2 HC1 (1 Img) and native or modified chymotrypsin (2mg) in the same Tris buffer. The mixture was incubated at 20°C for 24 hours and heated at lOO C for IS minutes. The products were isolated by HPLC (ODS column, 278nm, 50% acetonitrile). Native chymotrypsin inactivated when concentration of DMF was 50%, while chemically modified chymotrypsin kept its activity even up to 80% (Table IV). 

At this point, it is instructive to notice that the numerical example given above for the minimal Michaelis-Menten scheme will probably be very relevant to the situation for the majority of the enzymes considered so far. In consequence, it appears that the effects of organic solvents on the enantioselectivity are not restricted to their relative effects on the ground state system and the transition state. Instead, substantial contributions from the diffusional process parameters have to be taken into account as well. Since these contributions are probably better described by the Einstein-Smoluchovski relation,... 

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