Use of contactless conductivity detection for non-invasive characterisation of monolithic stationary-phase coatings for application in capillary ion chromatography

Abstract

A capacitively-coupled contactless conductivity detector (C4D) has been utilised as an on-capillary detector within a capillary ion chromatograph, incorporating a reversed-phase monolithic silica capillary column semi-permanently modified with a suitable ionic surfactant. The monolithic capillary column (150 x 0.1 mm i.d.) was modified using sodium dioctyl sulfosuccinate (DOSS), an anionic surfactant, for the separation of small inorganic and organic cations. With the use of the on-capillary conductivity detector, the longitudinal homogeneity and temporal stability of the coating were investigated. The approach allowed a detailed non-invasive observation of the nature of the ion-exchange coating over time, and an example of an application of the technique to produce a longitudinal stationary-phase charge gradient is shown. An investigation of the basis of the measured on-capillary conductivity was carried out with a counter ion study, clearly showing the on-capillary detection technique could also distinguish between chemical forms of the immobilised ion exchanger. The above method was used to produce a stable and homogeneously-modified monolithic ion-exchange capillary column, for application to the separation of inorganic alkaline earth cations and amino acids.

Simultaneous Determination of Inorganic Cations by Capillary Ion Chromatography with a Non-suppressed Contactless Conductivity Detector

“…Since the description published by Rokushika et al in 1983, 3 capillary ion chromatography (IC) has proved itself to be a powerful technique for the determination of trace inorganic and organic ions in environmental, industrial and clinical samples, [4][5][6][7][8][9] due to potential benefits such as low reagent consumption, rapid and efficient separations, and analysis of small sample volumes of high matrix complexity. Capillary IC offers a versatile, selective, and sensitive analytical tool, and it is relatively low in cost.…”

Fabrication and characterisation of capillary polymeric monoliths incorporating continuous stationary phase gradients

“…More recently, contactless conductivity detection has been used in scanning mode (sC 4 D) for the characterisation of surface modifications to stationary phases and stationary phase longitudinal homogeneity in capillary formats [12,[21][22][23][24].…”

On‐column titration and investigation of metal complex formation for aminopolycarboxylate functionalised monoliths using scanning contactless conductivity detection

“…However, the characterisation of the modified stationary phases has relied on either indirect methods (EOF) [4] or destructive methods (electron microprobe) [4]. In 2006, Gillespie et al applied the use of scanning capacitively coupled contactless conductivity detection (SC characterisation of surfactant coated RP silica monolithic capillary columns [9,10]. From these studies SC 4 D emerged as a viable technique for the characterisation of modified capillary columns under a variety of conditions, both in a spatial and temporal nature.…”