Regis Technologies

Ion Pair Chromatography is a method for improving the separation of charged analytes. In the resolution of organic ions with conventional HPLC methods, use of ion pair reagents can enhance peak shape and retention time when common remedies such as modifying eluent ratios or changing stationary phase fail.

 

Ion Pair Concentrates – Regis manufactures both ultrapure anionic Sulfonate (S-Series) and cationic Quaternary Amine (Q-Series) ion pair concentrates in the following alkyl chain lengths: pentyl, hexyl, heptyl, octyl, and dodecyl, represented by cardinal numbers in the naming of our products, i.e., 5, 6, 7, 8, and 12, respectively.

 

Sulfonate (S-Series)	Quaternary Amine (Q-Series)
ion pair concentrates for anionic separations	ion pair concentrates for cationic separations
S5 (1-pentylsodiumsulfonate)	Q5 (1-pentyltriethyl-ammonium phosphate)
S6 (1-hexylsodiumsulfonate)	Q6 (1-hexyltriethyl-ammonium phosphate)
S7 (1-heptylsodiumsulfonate)	Q7 (1-heptyltriethyl-ammonium phosphate)
S8 (1-octylsodiumsulfonate)	Q8 (1-octyltriethyl-ammonium phosphate)
S12 (1-dodecylsodiumsulfonate)	Q12 (1-dodecyltriethyl-ammonium phosphate)
CH3CN
CH3OH

 

Purity is of key importance in the manufacture of our Ion Pair Reagents. Regis S- and Q-Series products are synthesized in accordance with the industry's highest quality standards, resulting in exceptional purity and integrity as demonstrated in Table 1.

 

S - Series	200 nm	210 m	Q - Series	200 nm	210 nm
S5	0.006	0.002	Q5	0.060	0.001
S6	0.048	0.018	Q6	0.059	0.06
S7	0.008	0.001	Q7	0.022	0.009
S8	0.001	0.003	Q8	0.082	0.003
S12	0.002	0.003	Q12	0.102	0.013
CH3CN	0.076	0.013
CH3OH	0.940	0.510

Table 1. Typical Optical Absorbances (AUFS) at 0.005 M

 

UV transparency as low as 200 nm can be achieved for both the S- and Q-Series reagents. In most cases, these absorbances are lower than those for HPLC grade acetonitrile and methanol. Although the S- and Q-Series ion pair reagents can be used at wavelengths less than 210 nm, the crucial factors in determining what wavelength to use are the integrity of the detector optics and the purity of the organic modifiers.

Regis also supplies bulk Sulfonate and several additional bulk Ion Pair Reagents to complement the separation capabilities of the Sulfonate S-Series and Quaternary Amine Q-Series.

 

In the past, chromatographic separation of charged analytes has been achieved by ion suppression—the careful adjustment of the mobile phase pH to result in a nonionized analyte. Determining the optimum mobile phase pH in ion suppression, however, often requires extensive method development. Samples containing more than one ionizable component were often unusable. The limitations of ion suppression led to the development of a new, more generally applicable approach to separation of ionized components: ion pair chromatography.

Developed by Dr. Gordon Schill in 1973, ion pair chromatography relies upon the addition of ionic compounds to the mobile phase to promote the formation of ion pairs with charged analytes. These reagents are comprised of an alkyl chain with an ionizable terminus [Figure 1]. When used with common hydrophobic HPLC phases in the reversed-phase mode, ion pair reagents can be used to selectively increase the retention of charged analytes [Figure 2].

 

Figure 1. Quaternary Amine (Q-Series) Ion Pair Reagent

 

 

Figure 2. Quaternary Amine (Q-Series) Ion Pair Reagent Interacting with C-18 Support

 

Although ion exchange chromatography has become a popular mode of separation, it is not useful in all situations. The advantages of ion pair chromatography over ion exchange are: