Although reversed phase HPLC is one of the most important techniques in chromatography, by itself it is limited to separations of non-ionic (neutral) and non-polar compounds.
Polar or ionic substances tend to separate badly on reversed phase systems. So, bearing in mind that many compounds of biological interest are either ionic or highly polar, what can the HPLC analyst do to improve such separations? Either give up or reach for ROMIL-SpR™ Super Purity Reagents. The addition to the mobile phase of one of these high purity substances, as a counter-ion of opposite charge, enables the sample species to form a neutral 'ion pair' that will now readily interact with the reversed phase packing and thereby permit a clean separation.
Concentration of the ion-pair reagent should be around 0.005M. A slight change of concentration by 10-20% can alter retention time and thereby resolve overlapping peaks. Where detection is by UV, good UV transparency is important. Also, the ion-pair reagent if supplied in a powdered form should be easy to dissolve in small amounts. Equally the powder should be free from non-soluble particulate matter which can affect sensitive HPLC pumps and frits.
All these are standard features of ROMIL-SpR™ Super Purity Reagents. Available in bulk and laboratory quantities these reagents permit cost-effective separations in either high-volume routine quality control or specialist separations in research and development.