Ion Pair Chromatography Reagents

It was the Russian botanist Mikhail Tswett who discovered the principle of chromatography in 1901. More than 100 years later, chromatography is omnipresent in analytical research and far from being out of fashion. Even nowadays, it is part of the latest hi-tech development of instruments with extreme ranges of sensitivity and selectivity. Despite the many modern computer-assisted instruments currently available, several traditional variations of chromatography are still widely used. One such chromatographic variation is Ion Pair Chromatography (IPC).

In the past, the approach used to separate charged analytes was ionic suppression. By changing the pH value of the mobile phase, charged analytes become non-ionised. This approach of method development can be time consuming and is better suited for single analytes or simple mixtures where pKA’s of the analytes are close together.

On the other hand, IPC is a more general and applicable approach that allows the separation of complex mixtures of very polar and ionic molecules. The mobile phase is supplemented with an ion-pairing reagent. Ion-pairing reagents consist of large ionic molecules having a charge opposite to the analyte of interest as well as a substantial hydrophobic region that allows interacting with the stationary phase, plus associated counter-ions. In total, IPC results in different retention of analytes, thus facilitating separation. IPC is an established and reliable technique that provides:

  • Reduced separation times
  • Highly reproducible results
  • Sharper peak shapes
  • Simultaneous separation of ionized and non-ionized analytes
  • Wide choice of additives to improve separation

The more sensitive modern instruments become, the easier they will detect any impurity added by auxiliaries in addition to the analytes of interest. Therefore, the purity of any kind of eluent additives will influence performance and accuracy. Only products that have been tested for suitability and that have been carefully analysed for purity will guarantee the quality and performance for your application.

Figure 1 shows an example of polar compounds that have been successfully separated using IPC additives on a Supelco Ascentis Express C18 column. The analytes are imidazolium and pyridinium derivatives. The column was subsequently rinsed with solvent in order to prevent ion pair reagent agglomeration.
Figure 1.Separation of polar compounds on a Supelco Ascentis Express C18, 2.7 μm, 7.5 cm x 4.6 mm I.D. (Supelco 53819-U).
Figure 1. Separation of polar compounds on a Supelco Ascentis Express C18, 2.7 μm, 7.5 cm x 4.6 mm I.D. (53819-U). Acetonitrile was used as a gradient with a buffer of 1.1 g Sodium 1-heptanesulfonate monohydrate (51832) and 700 μL Phosphoric acid 85% (49685) in 1 L Water. Sample volume 5 μL, flow rate 1.0 mL/min, T = 25°C, UV detection = 210 nm, gradient: t = 0 2% acetonitrile, t = 1 min to 10 min 2–20% and t = 15 min 35% acetonitrile. Analytes: anions (1), 1-(3-Cyanopropyl)-3-methylimidazolium dicyanamide (2), 1-Methyl-2-vinylpyridinium triflate (3), 1-Butyl-3-methylimidazolium bromide (4), 1-Butyl-2,3-dimethylimidazolium tetrafluoroborate (5), 1-Benzyl-3- methylimidazolium tetrafluoroborate (6), 1-Hexyl-3-methylimidazolium chloride (7)

We offer an outstanding range of tailor-made reagents for anionic (quaternary ammonium salts) and cationic (alkanesulfonate salts) determination. We have followed a well-established, reliable technique and can provide you with a broad range of products and application notes to help you to resolve your samples. All mobile phase additives are subject to rigorous testing with special emphasis on the requirements of modern reversed phase HPLC. UV-absorption test: Our reagents are of the highest purity and exhibit minimal extinction in the low UV. They have excellent transparency down to 200 nm, even at high concentrations. Filter test: confirms the absence of insoluble matter. Redox test: Non-absorbing impurities like redox traces, which may interfere with the sample, are also tested by measuring a cyclic voltammogram. HPLC gradient grade test: This suitability test is carefully performed, using a very steep gradient.

Acidic Ion Pair Reagents (Anionic)

Acidic samples can be separated with straight-chain alkyl quaternary ammonium salts. The pH of the mobile phase needs to be ajdusted to 7.5 and diluted with the HPLC solvents (acetonitrile/water or methanol/water) to 5 mM.

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73345 Dibutylammonium acetate solution 0.5 M in H2O, LiChropur, for ion pair chromatography
93645 Dihexylammonium acetate solution 0.5 M in H2O, for ion pair chromatography, LiChropur
89789 Dipropylammonium acetate solution 0.5 M in H2O, for ion pair chromatography
44239 Dodecyltrimethylammonium bromide for ion pair chromatography, LiChropur, ≥98.5% (AT)
44243 Dodecyltrimethylammonium hydrogen sulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
52371 Hexadecyltrimethylammonium bisulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
52367 Hexadecyltrimethylammonium bromide for ion pair chromatography, LiChropur
87208 Myristyltrimethylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
86853 Tetrabutylammonium bisulfate for ion pair chromatography, LiChropur, ≥99.0%
86857 Tetrabutylammonium bromide for ion pair chromatography, LiChropur, ≥99.0%
86852 Tetrabutylammonium chloride for ion pair chromatography, LiChropur, ≥99.0%
86854 Tetrabutylammonium hydroxide solution ~40% in water, for ion chromatography
86903 Tetrabutylammonium iodide for ion pair chromatography, LiChropur, ≥99.0%
86899 Tetrabutylammonium phosphate monobasic solution for ion pair chromatography, LiChropur, concentrate, ampule
86608 Tetraethylammonium bromide for ion pair chromatography, LiChropur, ≥99.0%
86626 Tetraethylammonium hydrogen sulfate for ion pair chromatography, LiChropur, ≥99.0%
87296 Tetraheptylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
87297 Tetrahexylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
87299 Tetrahexylammonium hydrogensulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
87578 Tetrakis(decyl)ammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
87724 Tetramethylammonium bisulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
87708 Tetramethylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
74202 Tetramethylammonium chloride for ion pair chromatography, LiChropur, ≥99.0% (AT)
02799 Tetramethylammonium sulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
87996 Tetraoctylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
87997 Tetrapentylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)
88106 Tetrapropylammonium bisulfate for ion pair chromatography, LiChropur, ≥99.0%
88103 Tetrapropylammonium bromide for ion pair chromatography, LiChropur, ≥99.0% (AT)

Basic Ion Pair Reagents (Cationic)

Basic samples can be separated by addition of a straight-chain alkylsulfonic acid to the mobile phase. The pH of the mobile phase is adjusted to 3-4 and diluted with the HPLC solvents (acetonitrile/water or methanol/water) to 5 mM.

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49540 Heptafluorobutyric acid solution 0.5 M in H2O, LiChropur, for ion pair chromatography
19022 Sodium 1-butanesulfonate for ion pair chromatography, LiChropur, ≥99.0% (T)
30631 Sodium 1-decanesulfonate for ion pair chromatography, LiChropur, ≥99.0%
71443 Sodium decyl sulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
71726 Sodium dodecyl sulfate for ion pair chromatography, LiChropur, ≥99.0%
02374 Sodium 1,2-ethanedisulfonate for ion pair chromatography, ≥99.0% (T)
51832 Sodium 1-heptanesulfonate monohydrate for ion pair chromatography, LiChropur, ≥99.0% (T)
51834 Sodium 1-heptanesulfonate solution for ion pair chromatography, concentrate, LiChropur, ampule
52862 Sodium 1-hexanesulfonate monohydrate for ion pair chromatography, LiChropur, ≥99.0% (T)
52864 Sodium 1-hexanesulfonate solution for ion pair chromatography, concentrate, LiChropur, ampule
70289 Sodium 2-naphthalenesulfonate for ion pair chromatography, LiChropur, ≥99.0% (HPLC)
74316 Sodium 1-nonanesulfonate for ion pair chromatography, LiChropur, ≥99.0% (T)
74882 Sodium 1-octanesulfonate monohydrate for ion pair chromatography, LiChropur, ≥99.0% (T)
74886 Sodium 1-octanesulfonate solution for ion pair chromatography, LiChropur, concentrate, ampule
75073 Sodium octyl sulfate for ion pair chromatography, LiChropur, ≥99.0% (T)
76952 Sodium 1-pentanesulfonate monohydrate for ion pair chromatography, LiChropur, ≥99.0% (T)
76954 Sodium 1-pentanesulfonate solution for ion pair chromatography, LiChropur, concentrate, ampule
81806 Sodium 1-propanesulfonate monohydrate for ion pair chromatography, LiChropur, 98.0-102.0% (T)
87191 Sodium 1-tetradecanesulfonate for ion pair chromatography, LiChropur, ≥99.0%