Eluents 7-cyanophenol

FIGURE 6 Effect of p-cyanophenol on the separation of perchlorate. Column 4x250mm lonPac ASII. Flow rate I.OmLmin. Injection volume 25pL. Detection suppressed conductivity utilizing the Anion Self Regenerating Suppressor (4mm), recycle mode. Ion I—perchlorate (20mgL" ). (a) Eluent lOOmM NaOH. (b) Eluent 50 mM NaOH and 5mM p-cyanophenol. 

Fig. 3-1. Representation of the sorption effects in the separation of bromide and nitrate. - Separator IonPac AS4 eluent 0.0043 mol/L NaHC03 + 0.0034 mol/L Na2C03 + 100 mg/L p-cyanophenol flow rate 2 mL/min detection suppressed conductivity injection volume 50 pL solute concentrations 3 ppm fluoride, 4 ppm chloride, 10 ppm nitrite, 10 ppm phosphate, 10 ppm bromide, 20 ppm nitrate, and 25 ppm sulfate.

The aromatic amino acid tyrosine has proved successful as an eluent for the simultaneous analysis of all halide anions, which also causes a reduction in the iodide retention at alkaline pH, while still allowing for the separation of bromide and nitrate in contrast to p-cyanophenol containing eluents. In the respective chromatogram obtained with tyrosine as the eluent, a reversed retention is observed for orthophosphate and sulfate. This is caused by the comparatively high pH value of the mobile phase. The... 

The introduction of the IonPac AS5 separator column significantly facilitated the analysis of polarizable anions. Reducing the hydrophobicity of the functional groups bonded to the latex beads makes it possible to elute polarizable anions using a standard mixture of sodium bicarbonate and sodium carbonate. To minimize adsorption phenomena, some p-cyanophenol is added to the eluent mixture. The influence of this species on the peak form is evident in Fig. 3-18. The peak broadening could also be greatly reduced because of the compatibility of the eluent with commercial membrane suppressors and the reduction in the void volume. 

Salts of other weak acids may also be employed as the eluent. For example, extensive investigations were performed with p-cyanophenolate ions [130] which, compared to hydroxide ions, exhibit a slightly stronger elution power. A high selectivity for aliphatic dicarboxylic acids is obtained with p-cyanophenolate in combination with a CarboPac PA-1 (IonPac AS6) anion exchanger. Nevertheless, this eluent has not gained acceptance because it is not commercially available in the required purity. 

Fig. 8-98. Separation of inositol-1,4,5-triphosphate in a rat brain extract. — Separator column IonPac AS4A eluent 0.0264 mol/ Lp-cyanophenol flow rate 2 mL/min detection suppressed conductivity injection 50 pL of a chloroform/methanol extract (2 1 v/v) (taken from [89]).

A similar example represents the determination of borate that is usually analyzed with ion-exclusion chromatography. However, when borate is converted into tetrafluoro-borate by reacting with hydrofluoric acid [107], upon application of an anion exchanger indirect borate determination together with other inorganic anions becomes possible. Tetrafluoroborate is a polarizable anion therefore, when using the suppressor technique some p-cyanophenol is added to the carbonate/bicarbonate eluent to improve the peak shape of the ion that elutes after sulfate. 

Figure 3.128 Separation of polarizable and nonpolarizable inorganic anions on a poly (styrene-co-divinylbenzene)-based stationary phase by adding p-cyanophenol. Separator column lonPac AS4A eluent 1.7 mmol/L NaHCOa + 1.8 mmol/L Na2C03 + 100 mg/L...

The introduction of the nanobead-agglomerated lonPac ASS many years ago significantly facilitated the analysis of polarizable anions. The hydrophobicity of the functional groups bonded to the nanobeads was lowered, so that polarizable anions could be eluted with a standard carbonate/bicarbonate eluent. To minimize adsorption effects, some / -cyanophenol was added to this eluent. The influence of / -cyanophenol on the peak shape is illustrated in Figure 3.55 (see Section 3.4.1.4). Due to the compatibility of this eluent with commercial membrane suppressors and the subsequent decrease in dead volume, peak broadening was significantly reduced. 

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