Chaotropic ions chromatograph

Thomlinson [78] was the first chromatographer to point out that the classical electrostatic ion-pair concept did not hold for IPRs that were usually bulky hydrophobic ions he also emphasized that in the interfacial region between the mobile and the stationary phases, the dielectric constant of the medium is far lower than that of the aqueous phase. Chaotropes that break the water structure around them and lipophilic ions that produce cages around their alkyl chains, thereby disturbing the ordinary water structnre, are both amenable to hydrophobic ion-pairing since they are both scarcely hydrated. The practical proof of such ion-pairing mode can be found in References 80 and 81 many examples of such pairing modes are reported in the literature [79-86],... 

The use of chaotropic counteranions for a chromatographic separation is beneficial as a method development strategy. These modiflers may replace the need for changing column type and/or addition of hydrophobic ion-pairing reagents for the more challenging separations. Further studies are needed to fully elucidate the detailed mechanism of chaotropic mobile-phase additives. 

---