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Ion Pair Reagents [HPLC]

  Ion-exchange chromatography systems have previously been utilized in HPLC analysis of ionic samples. Recently, reversed phase partition chromatography using ion-pair reagents has been developed and utilized. The ionic samples form an ion-pair with ion-pair reagents in the mobile phase to become electrically neutral. The increase in hydrophobic character of the ion-pair results in a greater affinity for the reverse stationary phase and leads to sample resolution.
 
  UV and fluorescence detectors are widely used. Therefore ion-pair reagents must lack UV absorption and fluorescence themselves to obtain highly sensitive detection of samples. The UV absorption of sodium alkanesulfonates and quaternary ammonium salts is minimal so that these reagents can be used for reliable HPLC analysis.  On the other hand, when a sample lacks sufficient UV absorption or fluorescence, the use of sodium 9,10-dimethoxyanthracene-2-sulfonate allows for high-sensitivity detection as a fluorimetric ion-pair reagent. 
 Recently, use of LC-MS in which mass spectrometry is incorporated in HPLC as a detector has become widespread.  Sodium alkanesulfonates, a general ion-pair reagent, being non-volatile crystals pose a problem in that they contaminate the interface. The IPC-PFFA series is made of highly volatile ion-pair reagents allowing for continuous LC-MS analysis without contaminating the interfaces.
  
• Ion-Pair Chromatography for Acidic Samples

¶Analysis is performed with pH adjusted to 7.5 with the addition of quaternary ammonium salts to the mobile phase.
¶Acidic samples form an electrically neutral ion-pair with the quaternary ammonium salt and are retained in the reverse phase systems.
¶The ion-pair reagents for acidic samples for LC-MS are supplied as 0.5M aqueous solutions and were adjusted to pH7.5. The solution can be used as a neutral mobile phase after dilution with the LC solvents (acetonitrile/water or methanol/water) to 5mM. Since the acidic substances are ionized under the neutral conditions, they are facilitated to form an ion-pair.

—Examples—
1. When 0.5mol/L Tetrabutylammonium Phosphate is used: The reagent (10mL) is diluted to 1L with an aqueous solvent such as methanol - water. (pH adjustment is not required because the reagent is already buffered.)
2. When Tetrabutylammonium Hydroxide is to be used:
1) The reagent (12.5mL) is diluted to 1L with an aqueous solvent such as methanol - water.
2) The pH is adjusted to 7.5 by the addition of an aqueous phosphoric acid (10%).


• Ion-Pair Chromatography for Basic Samples

¶Analysis is performed by the addition of sodium alkanesulfonate to the mobile phase.
¶The basic samples form an electrically neutral ion-pair with sodium alkanesulfonate and are retained in the reverse phase system.
¶In the case of sodium alkanesulfonate, the greater the number of carbons in the alkyl group, the greater the partition ratio.
¶The solubility of the products such as sodium 1-decanesulfonate (IPC-ALKS-10) may decrease depending upon the composition of the mobile phase solvents; especially after the addition of the buffer for pH adjustment. Resulted turbidity of the mobile phase and crystal formation may interfere with the analysis. To avoid the trouble, modification of the solvent system composition should be considered.
¶The ion-pair reagents for basic samples in LC-MS analysis are supplied as 0.5M aqueous solutions. The solution can be used as an acidic mobile phase after dilution with the LC solvents (acetonitrile/water or methanol/water) to 5mM. Since the basic substances are ionized under the acidic conditions, they are facilitated to form an ion-pair.
¶We launched the high-quality products of PFFA-6, 7 and 8 (A5722, A5721, A5720) for high-sensitive detections.


—Examples—
1) Sodium 1-Heptanesulfonate 1.011g (0.005mol) is weighed out.
2) The reagent is dissolved in 1L of an aqueous solvent such as methanol - water.
3) The pH is adjusted to 3.5 by the addition of aqueous phosphoric acid (50%).
A5701
Sodium 9,10-Dimethoxyanthracene-2-sulfonate [Fluorimetric Ion-Pair Reagent for Amines]
A5702
Dibutylammonium Acetate (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5703
Dipropylammonium Acetate (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5704
Diamylammonium Acetate (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5705
Dihexylammonium Acetate (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5711
Trifluoroacetic Acid (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5712
Pentafluoropropionic Acid (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5713
Heptafluorobutyric Acid (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5714
Nonafluorovaleric Acid (ca. 0.5mol/L in Water) [Ion-Pair Reagent for LC-MS]
A5715
Undecafluorohexanoic Acid (ca. 5mmol) [Ion-Pair Reagent for LC-MS]
A5716
Tridecafluoroheptanoic Acid (ca. 5mmol) [Ion-Pair Reagent for LC-MS]
A5717
Pentadecafluorooctanoic Acid (ca. 5mmol) [Ion-Pair Reagent for LC-MS]
A5720
Pentadecafluorooctanoic Acid High Grade [Ion-Pair Reagent for LC-MS]
A5721
Tridecafluoroheptanoic Acid High Grade [Ion-Pair Reagent for LC-MS]
A5722
Undecafluorohexanoic Acid High Grade [Ion-Pair Reagent for LC-MS]
I0341
Sodium 1-Propanesulfonate [Reagent for Ion-Pair Chromatography]
I0342
Sodium 1-Butanesulfonate [Reagent for Ion-Pair Chromatography]
I0343
Sodium 1-Pentanesulfonate [Reagent for Ion-Pair Chromatography]
I0344
Sodium 1-Hexanesulfonate [Reagent for Ion-Pair Chromatography]
I0345
Sodium 1-Heptanesulfonate [Reagent for Ion-Pair Chromatography]
I0346
Sodium 1-Octanesulfonate [Reagent for Ion-Pair Chromatography]
I0347
Sodium 1-Nonanesulfonate [Reagent for Ion-Pair Chromatography]
I0348
Sodium 1-Decanesulfonate [Reagent for Ion-Pair Chromatography]
I0349
Sodium 1-Undecanesulfonate [Reagent for Ion-Pair Chromatography]
I0350
Sodium 1-Dodecanesulfonate [Reagent for Ion-Pair Chromatography]
I0351
Sodium 1-Tridecanesulfonate [Reagent for Ion-Pair Chromatography]
I0352
Sodium Dodecyl Sulfate [Reagent for Ion-Pair Chromatography]
I0363
Tetraethylammonium Hydroxide (10% in Water) [Reagent for Ion-Pair Chromatography]
I0364
Tetrabutylammonium Hydroxide (10% in Water) [Reagent for Ion-Pair Chromatography]
I0365
Tetrabutylammonium Bromide [Reagent for Ion-Pair Chromatography]
I0366
Tetrabutylammonium Chloride [Reagent for Ion-Pair Chromatography]
I0367
Tetrabutylammonium Phosphate (0.5mol/L in Water) [Reagent for Ion-Pair Chromatography]
I0368
Tetrabutylammonium Hydrogen Sulfate [Reagent for Ion-Pair Chromatography]
I0453
Dodecyltrimethylammonium Chloride [Reagent for Ion-Pair Chromatography]

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