Trennung von Sulfonsäuren durch Flüssigkeits-Chromatographie (HPLC)

Ehmcke, H. U.; Kelker, H.; König, K. H.; Ullner, H.

doi:10.1007/bf00481647

Cited by 28 publications

(2 citation statements)

References 25 publications

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“…Although the separation schemes are widely varied, they generally involve a preliminary separation according to functional groups such as acids, bases, and neutrals (hydrocarbons) followed by subsequent fractionation of the functional-group types into compound classes (1)(2)(3). Highperformance liquid chromatographic (HPLC) fractionation of the neutral compounds in liquid fossil fuels into compound classes has received considerable attention (4)(5)(6)(7)(8)(9)(10). However, even with the large effort expended on these HPLC separations, the aromatic-ring number separation of high boiling or residuum hydrocarbons/neutrals from petroleum, coal liquids, and shale oils still represents a formidable task.…”

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confidence: 99%

Ion interaction chromatography of organic anions in the presence of tetraalkylammonium salts

Iskandarani¹,

Pietrzyk²

1982

Anal. Chem.

108

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The major equilibria that contribute to the retention of an organic analyte anion on PRP-1 (a nonpolar poly(styrenedlvlnylberizene) adsorbent) In the presence of a tetraalkylammonlum cation (R4N+), a coanlon, and OH' are identified and used to derive an equation describing the analyte retention which was experimentally verified. The significant parameters are structure and concentration of R4N+, mobile phase solvent composition and pH, analyte concentration, and type and concentration of coanlon. The ability of a R,,N+ salt to enhance analyte retention changes significantly as the coanlon Is changed. The analyte retention, referred to as Ion Interaction, Is suggested to follow a double layer model where the R4N+ salt occupies a primary layer at the stationary phase while the analyte anion and other anions in the system compete for the secondary layer. A major equilibrium is the selectivity of one anion over another. Several applications are Illustrated.Adding: hydrophobic counterions to a mobile phase to enhance retention and resolution has been widely used in the liquid chromatographic (LC) separation of charged organic species on alkyl-modified silica (1-3). Other studies have focused on identifying the interactions that occur in the presence of the counterions, and several retention mechanisms have been proposed (1-12).The ion pair mechanism is one where it is suggested that ion pairs form between analyte ions and the hydrophobic counterions prior to sorption on a hydrophobic alkyl-modified silica stationary phase. Experimental evidence supporting this are isotherm measurements and correlation of retention with counterion concentration. Other workers suggested an ion exchange mechanism, where the counterions are first sorbed and these charge sites serve as exchange sites for the analyte ions. Retention of counterion on the stationary phase and correlation of this to analyte retention has been the major supporting evidence for an ion exchange mechanism. It has also been suggested that both occur and the extent to which one is more significant than the other is a function of the conditions employed in the LC separation. If very longchained, bulky, hydrophobic counterions are used, micelle formation and molecular size factors are significant parameters that influence retention.Because neither the ion pair nor ion exchange mechanism individually explains all the experimental results, retention models that are broader in scope and which attempt to account for all equilibria have been suggested (2, 4, 5,10-14). Thus, Biddlingmeyer et al. (2,5) proposed a model that does not require ion pair formation in either phase and is not based on classical ion exchange. This model assumes dynamic equilibrium which is affected by electrostatic, eluophilic, eluphobic, adsorbophilic, and adsorbophobic forces. Although this study was done on a C-18 bonded phase the model is very similar to the double layer model proposed by Cantwell and

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confidence: 99%

Ion interaction chromatography of organic anions in the presence of tetraalkylammonium salts

Iskandarani¹,

Pietrzyk²

1982

Anal. Chem.

108

View full text Add to dashboard Cite

show abstract

“…Although tetraalkylammonium salt (R4N+) have been widely used as countercations to enhance selectivity and improve resolution of separations on alkylbonded reversed stationary phases, little has been done with these countercations on the XAD stationary phases. For the alkyl-bonded type columns, the enhanced retention in the presence of R4N+ salts has been suggested to be due to an ion-pair and/or ion-exchange type sorption mechanism (6)(7)(8)(9)(10)(11)(12)(13).…”

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confidence: 99%