Ion-pair high-performance liquid chromatography

Tomlinson, E.; Jefferies, T.M.; Riley, Christopher M.

doi:10.1016/s0021-9673(00)91700-x

Cited by 186 publications

(37 citation statements)

References 79 publications

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“…This increase is of utmost importance since it runs counter to the typical electrostatic ion-pairing behaviour (as already noted [36,40]) which can be stated as "the larger the ion, the lower its association constant", in compliance with Coulomb's law. Actually, a simple electrostatic, Bjerrum type [41 -43] modelling of K EH received a greater share of credit from model makers [6], but the present results confirm rare observations of the inadequacy of the classical ion pair concept in IIC [44]. For organic ions the increase of the ion-pairing constant with increasing chain length was already observed by non-chromatographic methods [35 -36, 45 -46] and this is comforting.…”

Section: Resultssupporting

confidence: 77%

Extended thermodynamic approach to ion interaction chromatography. Influence of the chain length of the solute ion: a chromatographic method for the determination of ion-pairing constants

Cecchi¹

2005

J. Sep. Science

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The influence of the chain length in Ion Interaction Chromatography (IIC), previously named Ion Pair Chromatography, was investigated. The system examined is a C18 stationary phase and a variable, salt-controlled, mixture of a phosphate buffer pH 2.1 in methanol containing tetrabutylammonium bromide as Ion Interaction Reagent. IIC proves to be a good alternative to the well established spectrophotometric and conductometric methods of obtaining thermodynamic ion-pairing constants. The latter increase with increasing analyte chain length and decrease with increasing methanol concentration in the eluent: both results support a physical chemical description of the hydrophobic ion-pairing process at variance with the classical, Bjerrum-type modelling of the purely electrostatic interaction between inorganic ions. The calculated deltaG(o) are reliable because they compare to non-chromatographic estimates of deltaG(o) for similar systems. The present extended thermodynamic approach is able to predict and explain why the purely electrostatic approach works better for lower analyte lipophilicity or higher organic modifier concentration.

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Section: Resultssupporting

confidence: 77%

Extended thermodynamic approach to ion interaction chromatography. Influence of the chain length of the solute ion: a chromatographic method for the determination of ion-pairing constants

Cecchi¹

2005

J. Sep. Science

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“…In this technique a suitable ion-pairing agent, added to the mobile phase, is forming with the sample ions ion-pairs, which may be separated by reversed phase HPLC. Alkylammonium ions and alkylsulphonates are the most commonly used pairing agents for detection of anions and cations respectively (Horvath et al, 1977;Reeve, 1979;Tomlinson et al, 1978). For detection of Ni-EDTA the following HPLC conditions were applied: the HPLC system comprised a liquid chromatograph, Varian 8500, a variable wavelength UV-visible Aerograph, Variscan LC detector (modified spectrophotometer Varian Techtron 635), a Valco loop injection valve (volume 50 pl) and a 25cm x 0.4cm (I.D.)…”

Section: Methodsmentioning

confidence: 99%

Biological effects of nickel species and their determination in plant and soil

Willaert

Verloo

1988

Plant Soil

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Chemical and biological behaviour of several Ni-forms was studied on different soil types with spinach as a test plant. For the positively charged forms, Ni-ions and Ni-TETREN-ions, extractability increased with decreasing pH and CEC values of the soil. On the other hand, Ni added as EDTA-complex resulted in an extremely high Ni mobility, enhancing extractable Ni in soils having higher pH and CEC values. Speciation of Ni in the saturation extracts of the soils revealed that the transformation of both added positive forms was dependent on the soil characteristics, while Ni added as EDTA-complex mainly remained in the negative form. This altered mobility, accompanied by variable modification of the original chemical form in the soil solution, affected plant uptake and appearance of phytotoxic effects. Speciation in the plant extracts indicated that regardless of the chemical form added to the soil, Ni was only found in neutral and negative complexes. Finally, using ion-pair reversed phase HPLC, Ni-EDTA-ions were quantified in both the soil solution and the plant extract.

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“…The paired-ion, reversed-phase, method (146) thus constitutes a considerable improvement over paper-chromatographic and paper-electrophoretic analysis of phenol sulfates, particularly those occurring in crude extracts of urine. Normal (polar), phase-adsorption LC (147)(148)(149) usually leads to poor retention characteristics and poor resolution of such strongly ionized compounds.…”

Section: Analysis Of Phenol In Human Urinementioning

confidence: 99%

Priority toxic pollutants in human urine :

Fatiadi¹

1983

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Ion-pair high-performance liquid chromatography

Cited by 186 publications

References 79 publications

Extended thermodynamic approach to ion interaction chromatography. Influence of the chain length of the solute ion: a chromatographic method for the determination of ion-pairing constants

Extended thermodynamic approach to ion interaction chromatography. Influence of the chain length of the solute ion: a chromatographic method for the determination of ion-pairing constants

Biological effects of nickel species and their determination in plant and soil

Priority toxic pollutants in human urine :

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