Valve switching applications are becoming popular in ion chromatography. Example applications include matrix diversion or matrix elimination prior to analysis of trace components. A conventional ion chromatograph is equipped with a single injection valve, and adding valves for various applications, such as two-dimensional separations and sample preparation applications, is cumbersome. However, the modular design of the ICS-3000 makes reconfiguration of the system for applications such as two-dimensional ion chromatography (2-D IC) easier than ever. The overall strategy for matrix removal and signal enhancement is shown graphically in the figure below.
There are several advantages of the 2-D matrix diversion approach. First, initial sample loading onto the 4-mm column allows a large sample injection volume (large amount of sample) due to the high capacity of the analytical column and higher selectivity for analytes of interest relative to the matrix ions. Second, it is possible to focus the analyte peak that is partially resolved in the first dimension onto a concentrator column in the second dimension. The suppressed effluent with hydroxide eluent is water, which provides the ideal environment for ion-exchange retention and focusing. Third, the second dimension column has a smaller cross-sectional area relative to the first dimension, thereby enhancing the detection sensitivity. Finally, this approach allows the potential of combining two different chemistries in two dimensions, which enables a selectivity not possible when using a single chemistry dimension.
As the figure below demonstrates, bromate, a carcinogen, is not resolved from the sample matrix in the first-dimensional separation (top chromatogram). However, when the fraction containing bromate is concentrated, then transferred to the second dimension and separated on the smaller column, the bromate peak is well resolved and quantifiable.
For examples of 2-D IC, see the publications below.
