nSalt gradient and ion-pair mediated anion exchange of intact messenger ribonucleic acids

•Ion pairing anion exchange “IPAX” method was developed for mRNA analysis.•Ion-pairing mediated salt gradients were tested and provided sharp peaks.•Column temperature was found to be a very important factor.•Elution with a classical salt gradient seemed to be an entropy dominant process.•IPAX separation was seen to be enthalpy controlled at higher temperatures.