One of the most topical subjects in conventional HPLC is the increase of sample throughput without sacrificing resolution by utilizing UHPLC techniques. This is typically achieved by packing separator columns of shorter length and smaller internal diameter with separation materials of smaller particle sizes. However, even at optimal flow rates the resulting back pressure often exceeds the pressure tolerance of traditional HPLC hardware. Therefore, we currently witness the development of HPLC instruments with significantly improved back pressure tolerance well above 80 MPa. Although the stress on wear parts is very high at these high pressures, this development is facilitated with working materials in pumps and valves based on stainless steel.

Since ion chromatography is part of liquid chromatography, it is not surprising that a similar solution for IC is demanded as well. The fundamental difference in instrument design, however, is the fact that the fluidic pathways in ion chromatography instruments are made of metal-free components with a significantly lower pressure tolerance which excludes the use of particle sizes of around 2 µm (or smaller) typically employed in UHPLC separations. While particle sizes of common ion-exchange materials used in analytical IC are typically around 8.5 µm, so-called fast ion-exchange columns do exist, featuring 5 µm particle sizes in smaller column formats (150 mm × 3 mm ID). Thus, the analysis times for anion and cation profiles could be decreased by 50% as compared with conventional ion exchangers. But even under these conditions, typical anion or cation profiles are characterized by a run time of around eight minutes.

One possibility for further decreasing analysis times in IC is a flow rate increase beyond the van Deemter optimum, which goes along with a loss of resolution due the relatively large particle size of the ion-exchange material. Thus, this approach is only feasible for samples with a simple analyte composition and little or no matrix contamination. Doubling the linear velocity of the mobile phase through the separator column cuts the analysis time in half, while keeping the back pressure of the separator column well below the maximum pressure tolerance of the system.

The latest development in ion chromatography hardware design is the expanded pressure tolerance of electrolytic eluent generation in capillary and analytical IC systems up to 34.5 MPa (5000 psi). This allows the use of higher linear velocities of the mobile phase in conventional ion exchangers or the use of separator columns packed with a resin of smaller particle size (4 µm). On the other hand, it also facilitates high-resolution separations of complex samples through the use of longer conventional or 4 µm separator columns with standard length.

Besides the two major detection techniques for ion chromatography (conductivity and amperometry), a new type of detection mode based on charge measurements will be presented showing increased sensitivity and linear calibration behavior for weakly dissociated anions and cations.