Carbonate/hydroxide mixtures, analysis

The accuracy of analytical methods for solutions containing mixtures of carbonate and hydrogen carbonate ions or carbonate and hydroxide ions can be greatly improved by taking advantage of the limited solubility of barium carbonate in neutral and basic solutions. For example, in the Winkler method for the analysis of carbonate/hydroxide mixtures, both components are titrated with a standard acid to... 

The most popular device for fluoride analysis is the ion-selective electrode (see Electro analytical techniques). Analysis usiag the electrode is rapid and this is especially useful for dilute solutions and water analysis. Because the electrode responds only to free fluoride ion, care must be taken to convert complexed fluoride ions to free fluoride to obtain the total fluoride value (8). The fluoride electrode also can be used as an end poiat detector ia titration of fluoride usiag lanthanum nitrate [10099-59-9]. Often volumetric analysis by titration with thorium nitrate [13823-29-5] or lanthanum nitrate is the method of choice. The fluoride is preferably steam distilled from perchloric or sulfuric acid to prevent iaterference (9,10). Fusion with a sodium carbonate—sodium hydroxide mixture or sodium maybe required if the samples are covalent or iasoluble. 

The chemical composition with respect to Si and metallic impurities (mainly Fe, Ca, Al) is generally determined by wet chemical methods in combination with standard spectroscopic techniques (AAS, AES, XRF) (Table 8) [224-226]. A precondition is the dissolution of the powder. Typical dissolving processes are fusion with sodium carbonate or mixtures of sodium carbonate and boric acid, with alkaline hydroxides [225, 226] and special acid treatments [225]. A more effective analysis based on optical emission spectroscopy allows the direct analysis of impurities in the solid state and requires no dissolution step [227]. 

In their recent publication. Tucker et al. [73] describe the analysis of iodide in ground water and soil extracts on lonPac ASH using suppressed conductivity detection and a sodium hydroxide/methanol eluant. The soil samples to be analyzed were extracted with a carbonate/bicarbonate mixture and the resulting extracts diluted with de-ionized water after membrane filtration. As expected, the minimum detection limit for iodide with suppressed conductivity detection is in the mid-pg/L range. 

DETERMINATION DF A MIXTURE DF CARBONATE AND HYDROXIDE (ANALYSIS DF COMMERCIAL CAUSTIC SDDA) 10.32... 

DETERMINATION OF A MIXTURE OF CARBONATE AND HYDROXIDE (ANALYSIS OF COMMERCIAL CAUSTIC SODA)... 

During the performance of a CIEF analysis, the capillary is first filled with the sample and ampholyte mixture. The focusing step begins with the immersion of the capillary in the anolyte (dilute phosphoric acid) and catholyte (dilute sodium hydroxide) solutions followed by application of high voltage. Typically, the catholyte solution is 20 to 40 mM NaOH, and the anolyte is half the catholyte molarity, e.g., 10 to 20 mM phosphoric acid. It is important that the catholyte be prepared fresh because sodium hydroxide solutions will gradually take up carbon dioxide from the atmosphere. 

Alkaline hydrolysis with barium, sodium, or lithium hydroxides (0.2-4 M) at 110°C for 18-70 h126-291 requires special reaction vessels and handling. Reaction mixtures are neutralized after hydrolysis and barium ions have to be removed by precipitation as their carbonate or sulfate salts prior to analysis which leads to loss of hydrolysate. Correspondingly, peptide contents are difficult to perform by this procedure. Preferred conditions for alkaline hydrolysis are 4M LiOH at 145 °C for 4-8 h where >95% of tryptophan is recovered 291 An additional inconvenience of the alkaline hydrolysis procedure is the dilution effect in the neutralization step and thus the difficult application to the analyzer if micro-scale analysis is to be performed. The main advantage is the good recovery of tryptophan and of acid-labile amino acid derivatives such as tyrosine-0-sulfate1261 (Section 6.6) as well as partial recovery of phosphoamino acids, particularly of threonine- and tyrosine-O-phosphate (Section 6.5). 

A mixture of 3.44 g (9.63 mmoles) of 4-(2-di-n-propylaminoethyl)-7-hydroxy-2(3H)-indolone hydrobromide (U. S. Pat. No. 4,314,944), 22 cc of dimethylformamide, 1.79 g (9.91 mmoles) of 5-chloro-l-phenyl-lH-tetrazole, 220 cc of acetone, 10 cc of water and 2.90 g (21 mmoles) of anhydrous potassium carbonate was refluxed for about 3 hours at which time thin layer chromatographic analysis (silica gel GF, 75-23-2 ethyl acetate-methanol-conc. ammonium hydroxide) indicated that the reaction was complete. 

In a closed system equipped with an oil bubbler, 30 ml of tetrahydrofuran were added to a mixture of 4-amino-5-chloro-2-methoxybenzoic acid, 2.02 g (0.010 mole) and l,l -carbonyldiimidazole, 1.62 g (0.010 mole) with stirring. When evolution of carbon dioxide ceased, nitrogen was bubbled through the reaction mixture for 1 hr. A solution of 3-aminoquinuclidine, 1.26 g (0.010 mole) in 10 ml tetrahydrofuran was added dropwise to the stirred reaction mixture and stirring at room temperature continued for 3 hrs. TLC analysis (3% cone, ammonium hydroxide solution in methanol) showed some product formation. The mixture was heated at reflux temperature for 18 hours and then concentraded to an oil. TLC analysis showed the presence of the product, imidazole and 3-aminoquinuclidine. The oil was dissolved in methylene chloride (75 ml) and washed twice with 50 ml portions of aqueous sodium bicarbonate solution. The methylene chloride layer was dried over anhydrous magnesium sulfate and concentrated to yield 2.0 g (67%) of a glassy amorphous solid, the free base of the title compound. 

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