The chief advantage of SI is its versatility, based on programmable flow. The SI concept allows a wide variety of assay protocols to be accommodated in the same manifold, because all experimental parameters (sample volume, sample dilution, mixing ratios and reaction times) can be modified and controlled by flow programming.
Conventional SI was conceived as a tool for process analysis, where robustness and reliability is important, while high sampling frequency and low sample and reagent consumption are secondary issues. This legacy might have initially hindered wider acceptance of SI in a laboratory setting, where speed of assay and volumes of sample and reagents are critical parameters, yet the conventional Sequential Injection has gained acceptance as a front end to a broad variety of instrumental techniques. An early comprehensive review (Barnett 2002) lists over 300 references, documenting uses of conventional SI in fields ranging from environmental to industrial, and from chemistry to pharmacy and biology.
Miniaturization of the flow path and integration of key manifold components into a single compact unit are the key features of the new generation of SIA technique This changes expanded the scope and versatility of SIA and lead to numerous, unexpected applications. Therefore, this chapter focused on the updated miniSIA methodology which has now achieved the same high sampling frequency as flow injection. In combination with the long light path flowcell miniSIA based nutrient assays reached LOD in 1 ppB range. This limit od detection obtained by SFC technique is applicable to many other reagent based assays. By operating on a low microliter scale, miniSIA is positioned between traditional assays based on processing of milliliter volumes and futuristic nanoliter systems (such as microTAS), that still have a long way to go before becoming useful for real life applications (Mukhopadhyay 2009).