Eluents carbonate/hydroxide

Eluent degassing is important due to trap in the check valve causing the prime loose of pump. Eoss of prime results in erratic eluent flow or no flow at all. Sometimes only one pump head will lose its prime and the pressure will fluctuate in rhythm with the pump stroke. Another reason for removing dissolved air from the eluent is because air can get result in changes in the effective concentration of the eluent. Carbon dioxide from air dissolved in water forms of carbonic add. Carbonic add can change the effective concentration of a basic eluent including solutions of sodium hydroxide, bicarbonate and carbonate. Usually degassed water is used to prepare eluents and efforts should be made... 

The sensitivity increase for some selective carbohydrates that is caused by the addition of Ba(II) is shown in Figure 3.229. While retention of the first three components remains practically the same when adding barium acetate, a slight retention decrease is observed for fructose and sucrose. At first view, this seems surprising one might suppose that the complete removal of carbonate would lead to a retention increase. However, since in this case Ba(II) has been added as acetate salt, and acetate is a stronger eluent than hydroxide, even traces of acetate in the mobile phase will result in a retention decrease. The sensitivity increase is attributed by Cataldi et al [219] to the inhibition of the gold oxide formation by alkaline-earth metals in the order Ca(ll) > Sr(II) > Ba(II) that, in turn, results in an increase of the electrocatalytic activity of the electrode. 

Other eluent systems in suppressed ion chromatography are typically chosen based on specific separation requirements. For routine analysis of monovalent and divalent anions, carbonate-based eluents represent a reasonable alternative to hydroxide-based eluent systems. Carbonate eluents are simple to prepare and can be useful in cases where anion analysis is only occasionally performed. It must be kept in mind, however, that carbonate lowers the detection sensitivity for anionic species and introduces significant nonlinearity into the analysis. ... 

In Fig. 2, the columns were IonPac ICE-AS6 (250X9-mm i.d.), AG9-HC (concentrator, 50X4-mm i.d.) and AG9-HC/AS9-HC (analytical, 250X2-mm i.d.). The ion exclusion sample treatment eluent was deionized water and the flow rate was 0.55 ml/min. The sample volume was 750 pi. The ion exchange eluent was 8.0 mM sodium carbonate and 1.5 mAf sodium hydroxide. The flow rate on the 2-mm analytical column was 0.25 ml/ min. Detection was by suppressed conductivity using the ASRS -I electrolytically regenerated suppressor in the external water mode. 

To a solution of previously dried l-[[2-carboxy-3-(2-dimethylaminoethyl)-5-indolyl]methanesulphonyl]-pyrrolidine (1.6 g 0.0442 moles) in anhydrous quinoline (75 ml) and under atmosphere of nitrogen, cuprous oxide (160 mg 0.0011 moles) was added. The reaction mixture was heated to 190°C for 15 minutes, stirred to room temperature, poured into a mixture of 1 N hydrochloric acid (150 ml) and ethyl acetate (50 ml), shaken and decanted. The aqueous solution was washed several times with ethyl acetate, then solid sodium bicarbonate was added until pH = 7.8, and washed with n-hexane to eliminate the quinoline. The aqueous solution was made alkaline with solid potassium carbonate and extracted with ethyl acetate. The organic solution was dried (Na2S04), the solvent removed under reduced pressure when a dark oil was obtained (1.3 g yield 92%). This product was purified by column chromatography with silica gel and methylene chloride ethanol ammonium hydroxide (60 8 1) as eluent and a white foam (0.8 g) of l-[[3-(2-dimethylaminoethyl)-5-indolyl]methanesulphonyl]-pyrrolidine was obtained. To a solution of the above product (0.8 g) in acetone (30 ml), a few drops of hydrogen chloride saturated dioxan solution, were added. The precipitated solid was collected by filtration, washed with acetone and dried to give l-[(3-(2-(dimethylamino)ethyl)-5-indolyl)methanesulphonyl]-pyrrolidine hydrochloride (0.75 g). Melting point 218°-220°C. 

Ion exchange chromatography is based upon the differential affinity of ions for the stationary phase. The rate of migration of the ion through the column is directly dependent upon the type and concentration of ions that constitute the eluent. Ions with low or moderate affinities for the packing generally prove to be the best eluents. Examples are hydroxide and carbonate eluents for anion separations. 

Oikawa and Saitoh [89] reported studies of the application of ion chromatography to the determination of fluoride, chloride, bromide, nitrite, nitrate, sulphate, sulphite and phosphate ions in 3 ml samples of rainwater. The results show that the most suitable eluent for this purpose is 2m mol L 1 sodium carbonate/5m mol L 1 sodium hydroxide. The reproducibility of the determination was satisfactory for standard solutions of all the ions except nitrite. This problem was solved by preparing standard and sample solutions with the same composition as the eluent. 

The second direct method depends on the ability of aqueous potassium chloride, adjusted to pH 4 with carbon dioxide, to selectively elute hydrogen ions from sulfonic acid groups in pulps that first have been converted to their hydrogen form with 0.1 M hydrochloric acid (Cappelen and Schoon 1966). Carbon dioxide is removed from the eluent by sparging with nitrogen and the remaining acid is titrated with 0.1 M sodium hydroxide. Again, a correction factor for interference from carboxylic acids is required. This factor, as before, is based on the protons eluted from bleached pulps by the eluent. As the results depend on the concentration of potassium chloride used, the letter is adjusted so that the sulfonate content corresponds to the sulfur content of pulps assumed to contain only acidic sulfur. 

The preferred eluents for anions are dilute carbonate-bicarbonate mixture, sodium hydroxide and, for common alkali metals and simple amines, dilute mineral acids (HCl, HNO3, BaCb, AgN03, amino acids, alkyl and aryl sulfonic acids). The most common... 

For the detection of mineral acids in the presence of an excessive amount of nitrate, the IonPac AS2 separator column was developed from which bromide and nitrate elute after sulfate. The selectivity of this stationary phase is based on the hydrophobic properties of the exchange groups bound to the latex beads (see Section 3.3.1.2). As shown in Fig. 3-47, small quantities of chloride, orthophosphate, and sulfate can be determined in the presence of high amounts of nitrate. The best separation is obtained with an eluent mixture of sodium carbonate and sodium hydroxide. 

Aliphatic tricarboxylic acids such as citric acid exhibit a remarkably high affinity toward the stationary phase of an anion exchanger. Hence, low ionic strength bicarbon-ate/carbonate buffer solutions are not particularly suited as eluents. However, when a sodium hydroxide solution at a comparatively high concentration (c 0.08 mol/L) is used, citric acid may be eluted, and may even be separated from its structural isomer isocitric acid. When the detection of these compounds is carried out via electrical con-... 

In preparing sodium hydroxide-based eluents, care must be taken to ensure that they are carbonate free. Because the carbonate ion exhibits a much higher elution strength than the hydroxide ion, the presence of even small traces of carbonate reduces the resolution. The eluents should, therefore, be prepared from a 50% NaOH concentrate which only contains minute amounts of carbonate. The de-ionized water being used to... 

Eluents and regenerents suitable for the analysis of organic acids when applying an AFS-2 hollow fiber membrane suppressor are listed in Table 4-2. For the analysis of borate and carbonate with octanesulfonic acid as the eluent, an ammonium hydroxide solution with a concentration c = 0.01 mol/L can also be used as the regenerent. 

The addition of even minute amounts of sodium carbonate has a particularly strong effect on the retention behavior of multivalent anions. These comprise, for example, the two iron cyanide complexes Fe(CN)63 and Fe(CN)64, whose separation is obtained with an eluent containing only 3 10 4 mol/L sodium carbonate (see Fig. 5-9), apart from tetrabutylammonium hydroxide and acetonitrile. Lowering the acetonitrile content in favor of sodium carbonate, the resolution between both signals will decrease drastically, although the peak shape of the iron(II) complex will be distinctly improved. 

Most emulsion polymerization is based on free-radical reactions, involving monomers (e.g., styrene, butadiene, vinyl acetate, vinyl chloride, methacrylic acid, methyl methacrylate, acrylic acid, etc.), surfactant (sodium dodecyl diphenyloxide disulfonate), initiator (potassium persulfate), water (18.2MQ/cm), and other chemicals and reagents such as sodium hydrogen carbonate, toluene, eluent solution, sodium chloride, and sodium hydroxide. 

In suppressed ion chromatography, anions are separated on a separator column that contains a low-capacity anion-exchange resin. A dilute solution of a base, such as sodium carbonate/sodium bicarbonate or sodium hydroxide is used as the eluent. Immediately following the anion-exchange separator column, a cation-exchange unit (called the suppressor) is used to convert the eluent to molecular carbonic acid. 

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