Eluents citrate buffer

Figure 6 Separation of amino acids on conventional ion exchange Beckman 120B Amino Acid Analyzer. Column 15 cm. Eluent 0.35 M sodium citrate buffer, pH 5.28. Flow rate 30 ml/hr. Temperature 50°C. Note that the separation requires approximately 6 hours. Compare to a modern separation shown in Figure 7. (Reproduced with permission from Beckman Instruments Fullerton, CA.)...

Analysis of adrenaline (adr), noradrenaline (nadr) and dopamine (DA) in urine using (A) An ODS column with ionpairing agent in citrate buffer pH 5.0 with 2% tetrahydrofuran (THF) as the mobile phase (B) a strong cation exchange column with citrate buffer pH 5.0 with 7% THF as the mobile phase. The eluent was monitored by electrochemical detection at a potential of 0.7 V. Methyidopamine (MDA) was used as an internal standard and added to the urine before extraction. Reproduced with permission from J. Chromatogr. Biomed. Apps. (see Reference 10). 

Capacity factors for three solutes separated on a Cg nonpolar stationary phase are listed in the table. Eluent was a 70 30 (vol/vol) mixture of 50 mM citrate buffer (adjusted to pH with NH3) plus methanol. Draw the dominant species of each compound at each pH in the table and explain the behavior of the capacity factors. 

In Hamilton s early work, the sample was placed on the ion-exchange resin by removal of liquid at the top of the column and injection of the sample directly onto the top of the resin bed while the eluent flow was stopped. This is an adequate means of sample introduction, although an automated system can probably also be used. The chromatogram was developed with the stepwise elution by sodium citrate buffers of varying concentrations and pH from a typical sample of 0.5 ml of the body fluid (Fig. 15). 

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. 

Figure 11 Chromatogram of the imprinted stationary phase. This imprinted polymer does work in aqueous solvents and chromatographic characterizations are performed using an aqueous mobile phase (25 mM sodium citrate, pH 3.0) containing 10% MeCN at a flow rate of 1 mL/min and chromatograms, run in isocratic mode and recorded at 280 nm. Injections of 20 luL of 2 mM racemic isoproterenol HCl (40 pmol) dissolved in the mobile phase are done in order to evaluate the enantioselectivity towards its imprinted print molecule isoproterenol. Eluent used was a sodium citrate buffer (pH 3.0, 25 mM citrate, 10% MeCN) flow rate 1 ml/min, peak detection at 280 nm, injection of 20 pL of a racemic isoproterenol hydrochloride solution (2 mM), acetone was used as void marker. The structures of + and - isoproterenol are given in Fig. 8.

Fig.6 Enzyme extract from yeast. Conditions column, Finepak SIL AF-102 eluent, 10 mM citrate buffer containing 0.2 M NagSOa (pH 6.8) flow rate, 0.4 mL/min detection, UV 280 nm. Reproduceo with permission of JASCO.

Figure 4.1 Comparison of a typical voltammogram with changes in signal ( ) background noise (a) and signal to noise ratio (o) far noradrenaline (0.5 pmol injected). Column 5 pm ODS Hypersil (100x4.6 mm i.d.) Eluent phosphate/citrate buffer (50 mmol L" , pH 3.3)-octanesulfanic acid (OSA) (3 mmolL 7 methanol-water (15 85) Flow rate ...

Felice et al used a GCE (+0.7 to +0.9 V vs Ag/AgCl) in the analysis of polycyclic aromatic amines, such as 2-aminonaphthalene, 4-aminobiphenyl, and 2-aminoanthracene, in rodent skin samples after topical application of these compounds. The HPLC system used consisted of an ODS-modified silica column with acetonitrile-aq. citrate/perchlorate buffer (7 + 3 or thereabouts) as eluent - the buffer composition and the proportion of acetonitrile were varied in different experiments. A LoD of 0.1 pmol on column could be expected. 

Figure 5.29 Separation of a hydrolysate standard on a totally sulfonated cation exchanger. Column 1154110T temperature program 46°C from 0-4 min, 46-70 °C from 4-9 min, 70 °C from 9-32 min, 70-46 °C from 32-33 min eluent sodium citrate buffers gradient linear between pH 3.15,4.25, and 6.40 flow rate 0.60mL/min ...

The determination of amino acids in physiological samples is one of the most demanding tasks in the field of amino acid analysis. Often, more than 40 components have to be quantified in complex biological matrices such as serum or urine. For such separations, lithium citrate buffers are used as the eluent The separation of asparagine, glutamic acid, and glutamine, important for... 

C eluent sodium citrate buffers gradient step gradient between pFI 2.70 and 6.40 flow... 

Figure 5.32 Separation of a standard of physiologically relevant amino acids on a totally sulfonated cation exchanger 0354675T. Column temperature three-step temperature program from 34 to 70 °C eluent 3 lithium citrate buffers pH 2.80, 3.65, and 3.70 flow rate 0.55 mlVmin detection see Figure 5.28 peaks 0.25 pmol/mL each of P-Ser (1), Tau (2), Pea (3), Urea (4), Gaa (5), Asp (6), OH-Pro...

Fig. 8. Retention as a function of eluent pH for strongly basic or cationic substances on three different stationary phases. Conditions acetonitrile/60 mi citrate buffer (1 1, v/v), 35 °C (from [17]).

Eluent buffers A 0.067 M sodium citrate, 0.33 mM thymol, pH 3.0, except pH 5.0 for furosine analysis B 0.25 M sodium nifrafe, 0.024 M boric acid, pH 10.2 (pH adjusted with NaOH and HNO3). 

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... 

Fig. 4-20. Separation of a hydrolysate standard on a totally sulfonated cation exchanger BTC 2710 (Biotronik, Maintal, Germany). — Column temperature four-step temperature program from 48 °C to 70 °C eluent 5 sodium citrate/borate buffers flow rate 0.3 mL/min for all other chromatographic conditions and elution order see Fig. 4-19.

D. R. Jenke, Quantitation of oxalate and citrate by ion chromatography with a buffered, strong acid eluent, J. Chromatogr., 437,231,1988. 

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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