Liquid-solid chromatography aqueous mobile phases

The focus is on concepts in reversed-phase liquid chromatography (RPLC), though the same concepts are usually applicable to other modes of HPLC. International Union of Pure and Applied Chemistry (IUPAC)10 nomenclature is used. The term sample component is often used interchangeably with analyte and solute in the context of this book. As mentioned in Chapter 1, the most common stationary phase is a hydrophobic C18-bonded phase on a silica support used with a mixed organic and aqueous mobile phase. The terms packing and sorbent often refer to the bonded phase whereas solid support refers to the unbonded silica material. 

The indirect detection technique is used mainly in reversed phase liquid-solid chromatography and it can be applied to charged as well as non-charged analytes. An ion with detectable properties and with affinity for the solid phase is included in the aqueous mobile phase. Analytes that are injected into the system will give rise to equilibrium disturbances and influence the distribution of the detectable ionic component ( the probe ). The response pattern is quite different from that given by... 

Ion-exchange chromatography inductively coupled plasma—mass spectrometry (IC-ICP-MS) uses anion or cation ion-exchange resins or other solid phases with ion-exchange properties to separate ionic species prior to their sequential introduction into the ICP. Ions are separated according to their ionic affinity to the resin, rather than their differences in solubihty, which is the principle used in liquid chromatography. Separations are also highly dependent on the properties of the mobile phase. The mobile phase is usually composed of an aqueous-salt solution, which competes for the weakly electrostatically bonded analyte species. 

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