The separation of ionic and ionizable analytes can be effectively achieved using a reversed-phase high performance liquid chromatographic (RP-HPLC) technique called ion-pair chromatography (IPC). 

  • Used on reversed phase columns which are more efficient than columns used in ion exchange chromatography, resulting in better resolution 
  • Sharper peak shapes and highly reproducible results even with larger ion
  • Reduced separation times (vs. ion exchange)
  • Suited for separations of complex mixtures (unlike the ionic suppression method) 
  • Able to simultaneously separate both ionized and nonionized analytes   

In this type of chromatography, an ion-pair reagent (IPR) consisting of a hydrophobic tail and an ionic moiety is added to the mobile phase.  The ionic moiety selectively binds to the analyte of interest while the hydrophobic tail is retained by the non-polar stationary phase serving to increase the analyte’s retention time and improve peak shape and resolution. 

Two main types of (traditional) IPRs are commonly used based on the charge of the desired analyte: Straight-chain quaternary ammonium salts are used to attract anionic analytes while negatively charged alkyl sulfonate salts bind cationic ones. Other than the positively and negatively charged ion-pair reagents, chiral, volatile, chaotropic, and ionic liquid based IPRs have also been developed.

IPRs are extensively used in biomolecule, pharmaceutical, food, and environmental analyses since 1973Examples of relevant analytes are:  

Amino Acids  



Inorganic Ions

Nucleic Acids



Water-soluble Vitamins  


Carboxylic Acids


At J&K Scientific, our mobile phase reagents are manufactured under strict ISO 9001 standards. A filter test is used to confirm the absence of insoluble matter that may interfere with the analyte.  In addition, solvent associated impurity peaks are removed with additional purification steps. They are also subject to rigorous testing, meeting the requirements of modern RP-HPLC to guarantee the quality and performance of your application. Even at high concentrations, they exhibit UV transparency as low as 200 nm under UV detection. Volatile IPRs are also available for Mass spectrometry (MS) detectors which provide detailed structural information of the separated components. 

Related Articles

IPR Method Development Guide

IPR Application Examples


By Qinling Li


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