Aqueous Chromatography

The isolation technique based on sequential aqueous chromatography was introduced by Stansell and Deutsch They used batch absorption of the nonhaemoglobin proteins on DEAE cellulose for the removal of haemoglobin. The overall procedure was very laborious and time consuming. Therefore, a more convenient method shorter in time was developed The yield of purified SOD was the same as obtained with the Tsuschihashi method. Compared to the latter technique the different operation 

---

Use non-aqueous chromatography (NAC) C,j and acetonitrile/THF/methanol mobile phase. Use a suitable C, column,. see below. 

Kobayashi J, Kikuchi A, Sakai K, Okano T. Aqueous chromatography utilizing pH-/temperature-responsive polymer stationary phases to separate ionic bioactive compounds. Anal Chem 2003 73 2027-2033. 

Kikuchi A, Okano T. InteUigent thermoresponsive polymeric stationary phases for aqueous chromatography of biological compounds. Prog Polym Sci 2002 27 1165-1193. 

HILIC is a strongly upcoming LC technique during the last years and was recently reviewed several times [23-25]. Briefly, it is understood as aqueous chromatography on normal phase materials and especially suitable for the separation of very polar, that is, hydrophilic compounds. As column materials, silica, modified silica, or functionalized polymer particles are available, which commonly provide a water-enriched liquid layer within the stationary phase. Separation is achieved by partitioning of polar analytes from the eluent into the hydrophilic environment. 

Kikuchi, A., Okano, T. (2002). Intelligent thennoresponsive polymeric stationary phases for aqueous chromatography of biological compounds. Progress in Polymer Science, 27, 1165-1193. http //dx.doi.org/10.1016/S0079-6700(02)00013-8. 

More information has appeared concerning the nature of the side reactions, such as acetoxylation, which occur when certain methylated aromatic hydrocarbons are treated with mixtures prepared from nitric acid and acetic anhydride. Blackstock, Fischer, Richards, Vaughan and Wright have provided excellent evidence in support of a suggested ( 5.3.5) addition-elimination route towards 3,4-dimethylphenyl acetate in the reaction of o-xylene. Two intermediates were isolated, both of which gave rise to 3,4-dimethylphenyl acetate in aqueous acidic media and when subjected to vapour phase chromatography. One was positively identified, by ultraviolet, infra-red, n.m.r., and mass spectrometric studies, as the compound (l). The other was less stable and less well identified, but could be (ll). 

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

I2O5 (400 mg 1.20 mmol) was added to a solution of a cycloalka[b]indole (l.OOmmol) in 80% aqueous THF (25 ml). The mixture was stirred at room temperature and the solvent removed in vacuo. The residue was extracted into EtOAc and the extract washed with water, 5% NaS203, saturated NaHCOj and brine and dried over Na2S04. The solvent was evaporated and the residue purified by silica gel chromatography. 

In reverse-phase chromatography, which is the more commonly encountered form of HPLC, the stationary phase is nonpolar and the mobile phase is polar. The most common nonpolar stationary phases use an organochlorosilane for which the R group is an -octyl (Cg) or -octyldecyl (Cig) hydrocarbon chain. Most reverse-phase separations are carried out using a buffered aqueous solution as a polar mobile phase. Because the silica substrate is subject to hydrolysis in basic solutions, the pH of the mobile phase must be less than 7.5. 

In many applications in mass spectrometry (MS), the sample to be analyzed is present as a solution in a solvent, such as methanol or acetonitrile, or an aqueous one, as with body fluids. The solution may be an effluent from a liquid chromatography (LC) column. In any case, a solution flows into the front end of a mass spectrometer, but before it can provide a mass spectrum, the bulk of the solvent must be removed without losing the sample (solute). If the solvent is not removed, then its vaporization as it enters the ion source would produce a large increase in pressure and stop the spectrometer from working. At the same time that the solvent is removed, the dissolved sample must be retained so that its mass spectrum can be measured. There are several means of effecting this differentiation between carrier solvent and the solute of interest, and thermospray is just one of them. Plasmaspray is a variant of thermospray in which the basic method of solvent removal is the same, but the number of ions obtained is enhanced (see below). 

Gel filtration chromatography (GFC) is the name used to describe this method of separation in the biochemical literature. Under this heading, the method is primarily applied to aqueous solutions of solutes of biological origin. 

The concentration of aqueous solutions of the acid can be deterrnined by titration with sodium hydroxide, and the concentration of formate ion by oxidation with permanganate and back titration. Volatile impurities can be estimated by gas—Hquid chromatography. Standard analytical methods are detailed in References 37 and 38. 

---