Eluents potassium citrate

Fig. 3-64. Separation of inorganic anions using potassium citrate as the eluent. - Separator column TSK Gel IC-SW eluent 0.001 mol/L potassium citrate, pH 5.2 flow rate 1.2 mL/min detection direct conductivity injection volume 100 pL solute concentrations 5 ppm chloride, 10 ppm bromide, iodide, thiocyanate, and sulfate.

The potassium salt of citric acid has an elution strength similar to potassium hydrogen phthalate. When fully dissociated, citrate as a trivalent ion exhibits a strong affinity toward the stationary phase and, therefore, may be used as an eluent at relatively low concentration. However, the elution order of standard inorganic anions that is obtained with potassium citrate depends on the stationary phase being used. When, for example, a poly(styrene-co-divinylbenzene)-... 

The eluents suitable for the separation of amino acids on latex cation exchangers do not comprise the classical citrate/borate buffers but mixtures of nitric acid and potassium oxalate. In comparison to buffers composed of sodium citrate and borate, these components may be obtained at much higher purity. The retention of the amino acids to be analyzed, however, is possibly affected by the sample pH due to the limited buffer capacity of the eluents that are based on nitric acid and potassium oxalate. Fig. 4-21 shows the separation of a calibration standard for collagen hydrolysates on an Amino Pac PA-1 latex cation exchanger at ambient temperature. The advantage is the short... 

The following procedure is a typical example [152]. To a stirred solution of 1 mmol aldehyde in 1.7 ml of 0.1 mol 1 sodium citrate buffer (pH 4.5), 2000 lU of (S)-oxynitrilase (1000 lU/ml) were added and the mixture was cooled down to ice bath temperature. Subsequently, 2.5 mmole equivalents of potassium cyanide adjusted to pH 4.5 with cold 0.1 mol 1 citric acid (17 ml), were added in one portion. After stirring for 1 h at 0-5 °C, the reaction mixture was extracted with methylene chloride (3 X 50 ml). The combined organic layers were dried over anhydrous sodium sulfate and the solvent was removed by evaporation to give the crude cyanohydrin, which was purified by column chromatography using petroleum ether/ethyl acetate (5/1 or 9/1) acidified with trace amounts of anhydrous HCl as the eluent. 

Sodium, potassium or ammonium orthophosphate, acetate, perchlorate or citrate salts are commonly used for buffering the eluent and should be of the highest... 

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