Isolation of anionics

The most convenient procedure depends on which other classes are present. When nonionics and sulphobetaines are absent, the preferred method is to remove all other species and leave only the anionics in the column effluent. When nonionics are present, the anionics must be sorbed and eluted. Use 80% methanol or aqueous ethanol or propan-2-ol as solvent. 

Nonionics and SW and SS amphoterics absent. Remove all cationics and amphoterics by retention on a strongly acidic cation exchanger, e.g. Bio-Rad AG 50W-X4 acid. The effluent contains all the anions, surfactant and otherwise, as the corresponding acids. 

Nonionics and/or sulphobetaines present, all other amphoterics absent. Retain all anionics on a strongly basic anion exchanger, e.g. Bio-Rad AG 1-X4 hydroxide, and elute with at least 25 bed-volumes of 

1M methanolic hydrochloric acid. The effluent contains all the anions, surfactant and otherwise, as the corresponding acids. 

Nonionics and WW or amphoterics present. The previous procedure would include all amphoterics with weakly basic nitrogen (WW and SW) in the anionic fraction. If a WW amphoteric is present the simplest procedure is to combine the two columns described, with the cation exchanger first. The WW amphoteric is retained on the cation exchanger and the anionics on the anion exchanger, from which they are eluted as described. 

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Hodge et al. [689] have described a method for the determination of platinum and iridium at picogram levels in marine samples, based upon an isolation of anionic forms of these elements using appropriate resins, with subsequent purification by uptake on a single ion-exchange bead. All steps are followed by radiotracers, and yields vary between 35 and 90%. Graphite furnace AAS was employed as the determinative step. 

Of particular significance in this respect has been the ability to prepare, characterize and study most intriguing species, the alkalides [2.79, 2.80] and the electrides [2.80, 2.81] containing an alkali metal anion and an electron, respectively, as counterion of the complexed cation. Thus, cryptates are able to stabilize species such as the sodide [Na+ c 9]Na- and the electride [K+ c 9]e-. They have also allowed the isolation of anionic clusters of the heavy post-transition metals, as in ([K+ c cryp-tand]2 Pb52-) [2.82]. 

Anion exchange Anion-exchange phase Isolation of anionic analytes in aqueous or nonaqueous solutions Extraction of acidic and weakly acidic proteins and enzymes Removal of acidic pigments from wines, fruit juices, and food extracts Removal of organic acids from water... 

Isolation of anionics and nonionics for IR analysis Silica Gel F-60, activated at 80- C for 5 min CHCl3/MeOH, various ratios Iodine vapor 139,140... 

The significance of phenoxy anions is well recognized in the isolation of kraft and other water-insoluble technical lignins by acid precipitation. The ioniza tion of phenoHc hydroxyl groups coupled with the reduction of molecular size renders native lignin soluble in the aqueous pulping solution, thus enabling its separation from the polysaccharide components of wood. 

Thorium compounds of anionic nitrogen-donating species such as [Th(NR2)4], where R = alkyl or sdyl, are weU-known. The nuclearity is highly dependent on the steric requirements of R. Amides are extremely reactive, readily undergoing protonation to form amines or insertion reactions with CO2, COS, CS2, and CSe2 to form carbamates. Tetravalent thorium thiocyanates have been isolated as hydrated species, eg, Th(NCS)4(H20)4 [17837-16-0] or as complex salts, eg, M4 Th(NCS)g] vvH20, where M = NH, Rb, or Cs. 

U(IV) nitrates have been obtained from aqueous solution, but a number of anionic complexes of general formula M2[U(N02)g], where M = NH Rb, Cs, and M[U(N02)g] 8H20, where M = Mg, Zn have been isolated and characterized. These soHds contain the 12 coordinate anionic U(IV) center shown in (2) (158). Neutral, U(IV) nitrate complexes of formula U(N02)4L2 (3) (L = OP(CgH )2, OP(NC4Hg)2) have also been isolated from aqueous solutions and stmcturaHy characterized (159). 

The majority of U(V1) coordination chemistry has been explored with the trans-ddo s.o uranyl cation, UO " 2- The simplest complexes are ammonia adducts, of importance because of the ease of their synthesis and their versatihty as starting materials for other complexes. In addition to ammonia, many of the ligand types mentioned ia the iatroduction have been complexed with U(V1) and usually have coordination numbers of either 6 or 8. As a result of these coordination environments a majority of the complexes have an octahedral or hexagonal bipyramidal coordination environment. Examples iuclude U02X2L (X = hahde, OR, NO3, RCO2, L = NH3, primary, secondary, and tertiary amines, py n = 2-4), U02(N03)2L (L = en, diamiaobenzene n = 1, 2). The use of thiocyanates has lead to the isolation of typically 6 or 8 coordinate neutral and anionic species, ie, [U02(NCS)J j)/H20 (x = 2-5). 

These species are also unusual iu that they are extremely hydrophobic anions which form very strong conjugate acids. This unique combination of features leads to a number of potential uses such as the extraction of organic compounds from extremely dilute solutions and the isolation of metal cations, including the quantitative separation of radionucUdes, eg, Cs (192). 

A particularly imaginative application of this concept has led to the isolation of compounds which contain monatomic alkali metal anions. For example, Na was reacted with cryptand in the presence of EtNHi to give the first example of a sodide salt of... 

Interconversion between two tautomeric structures can occur via discrete cationic or anionic intermediates (scheme 24, where T is an anion capable of reacting with a proton at a minimum of two distinct sites). Alternatively, interconversion can occur by simultaneous loss and gain of different protons (scheme 25, w here T has the same definition as in scheme 24). These mechanisms are well established for acyclic compounds, but they have been much less thoroughly investigated for heteroaromatic systems. The rate of interconversion of two tautomers is greatest when both of the alternative atoms to which the mobile proton can be attached arc hetero atoms, and isolation of the separate isomers is usually impossible in this case. If one of the alternative atoms involved in the tautomerization is carbon, the rate of interconversion is somewhat slower, but still fast. When both of the atoms in question are carbon, however, interconversion is... 

The chiral bicyclic imidazolidine 74 is deprotonated at the 2 position by s-BuLi and the resulting anion adds to alkyl halides, acid chlorides, chlorofor-mates, phenyl isocyanate, and aldehydes. The use of this compound as a chiral formyl anion equivalent seems to be limited, however, since the diastereoselectiv-ity in the addition to aldehydes is poor and hydrolysis of the products 75 to give aldehydes also produces cyclohexane-1,2-diamine, necessitating isolation of the aldehyde as its 2,4-dinitrophenylhydrazone (96SL1109 98T14255). 

Isolation of Inosine by Ion Exchange Method Half of the above clear centrifugate (1.15 liters) is treated with 250 cc of anion exchange (bicarbonate form) and stirred together therewith for 16 hours at room temperature. The pH value is increased thereby to about 4 to 5. The ion exchanger is filtered off under suction and washed 3 times, each time with 150 cc of water. The solution is brought to a pH value of 7 by means of normal sodium hydroxide (total volume of the solution about 1.55 liters), and concentrated to a volume of about 100 cc under vacuum. 

Thus, under suitable experimental conditions, all aromatic sulphones are cleaved, in most cases by a two-electron process summarized by equations 1 and 2. Such reactions have been established1-5 by means of coulometric titration, isolation of cleavage residues ArH and RH and chemical identification of the anion ArS02- (e.g. by treatment of the... 

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