Eluant hydrochloric acid

Radium in hydrochloric acid solution may be separated effectively by ion exchange methods using cation exchange-resin columns. A weak HCl solution is passed through the column. The absorbed metals on the ion-exchange column are eluted with ethylenediaminetetraacetic acid (EDTA) at pH 6.25 or with ammonium citrate at pH 7.8. With either eluant, radium is eluted last, after removing barium and then lanthanum, calcium, magnesium, and other metals. 

To a solution of 1.97 g (10 mmol) of 2-butynyl diisopropylcarbamate in 30 mL of diethyl ether under nitrogen at —78 °C are added 6.9 mL (11 mmol) of 1.6 M butyllithium via a syringe. After 15 min at — 70 °C, 3.12 g (11 mmol) of titanium(IV) isopropoxide in hexane are added and the mixture is stirred for 1.5 h at between — 70 and — 78 C. After raising the temperature to 0 °C the reaction mixture is poured into a mixture of 50 g of ice, 50 mL of 2 M hydrochloric acid and 100 mL of diethyl ether. The aqueous layer is extracted with two 50-mL portions of diethyl ether, and the ethereal solutions are washed with 50 mL of water, 50 mL of sat. aq NaHCOj/KCl and dried over MgS04. The solvent is evaporated in vacuo and the residue purified by column chromatography over silica with diethyl ether/hexane 1 5 as eluant yield 2.15 g (89%) mp 48 C. 

A solution of the amide of step 4 (10 g) in ethanol (300 ml), containing concentrated hydrochloric acid (5 ml), was refluxed for 8 hours. The reaction mixture was diluted with water and extracted into ethyl acetate. The extract was washed with water, dried and the solvent was evaporated to leave a dark brown semi-solid. This was chromatographed on a silica gel column, using ether as eluant to give 4.8 g of the required product whose structure was confirmed by mass and NMR spectral evidence mp 84-87°C. 

Examples of such a rapid "milking" technique can be found In the separation of 24-second Nb " 111 from Mo using Dowex-1 anion exchange resin and 6 N hydrochloric acid as eluant (171),... 

A modification of the elution technique, already referred to in section 4.6.3, is also used to good advantage. It depends on the alteration of the activities of the ions being separated by means of an eluting agent which will complex with them. A simple example is provided in experiment 4 in Chapter 9, where copper(II) and iron(III) ions are separated by elution with phosphoric acid. If this separation is tried with hydrochloric acid as the eluant, the copper(II) ions tend to move more rapidly down the column than the iron(III), because they carry a smaller charge and are therefore not so firmly held by the resin. A good separation will not be obtained. 

The separation involves the stepwise elution of iron(III) by phosphoric acid and then of copper(II) by hydrochloric acid, from a strongly acidic cation exchange resin such as ZeoKarb225, AmberliteIR-120 or Dowex50. If hydrochloric acid alone is used the order of removal of the ions from the columns is reversed, and poorer separation is obtained. The phosphoric acid eluant modifies the activities of the ions, possibly by complex formation, giving improved resolution. The order of elution is also reversed with a phosphate eluant, iron having the smaller retention volume. 

Lead has been found to adsorb more strongly onto De-acldlte PP anion exchange resin from 2 M hydrobromlc acid solution than from 2 M hydrochloric acid solution (M12). Hydrobromlc acid eluant has been used to separate lead frpm thoriian (M12). 

Put tracer Pb, Bl, Po onto the columnln 2ml of 1 M hydrochloric acid. Pass 3 ml of 1 M hydrochloric acid In 1 ml portions. Collect loading and wash eluants since this... 

In combination with a membrane-based suppressor (see Section 4.3) a mixture of 2,3-diaminopropionic add (DAP) and hydrochloric acid is frequently used for the separation of alkaline-earth metals. Using this eluant provides the advantage of being able to adjust the elution power via the dissociation equilibrium of 2,3-diaminopropionic acid see Eq. (104) in Section 4.1.1. With pJC = 1.33 for the dissociation of the carboxyl group, DAP may exist in the mobile phase as a monovalent cation, a divalent cation, or a mixture of both. In any case, the product of the suppressor reaction is the zwitterionic form, which has no intrinsic conductance ... 

---