Sequential Injection Chromatography has come a long way since first proposed ten years ago. While its principle was established right from the beginning, what hindered its progress was the lack of a suitable drive that will propel the mobile phase reproducibly within a wide range of flow rates back and forth and at a high pressure.
Starting with convention syringe and short monolithic column (4.1.6.) the proof of concept and first comparisons with conventional LC development continued trough innovative use of new column materials (4.1.8.). Real life applications (4.2.7.) documented advantages and long time stability (4.2.6.) that makes SIC a suitable tool for continues monitoring of dynamic processes.
It is now established that SIC combines the advantages of multicomponent assay with the automated solution handling and versatility lent by flow programming. The combination of a selection valve with programmable flow gives the SIC technique an unprecedented flexibility in the choice of injected volumes, of elution gradients and stationary phases. The SIC instruments now operate at far higher pressure which widens the range of suitable columns and thus improves performance and resolution of this technique. SIC instruments are compact, with a footprint smaller than that of a laptop PC, and portable.
We have also seen progress in column technology. In addition to monolithic columns, fused core particle columns broaden the availability of stationary phases suitable for SIC.
Yet, an ideal drive for mobile phase is still missing, as bemoaned in the previous section. But it will become available one day in the future. There is no doubt about it. We saw this happening over the years. From manually operated injection valves and chart recorders, logarithmic tables and Indian ink ( for drawing graphs) to stepper motor driven valves, PC, Excell and Power Point.