Flow Injection Tutorial

Continuous flow injection is a mature technique for automation of a wide variety of reagent based assays. It has also been used as a “front end” to practically all spectroscopic and electrochemical detectors, of which UV-VIS spectroscopy, Atomic Absorption and Inductively Coupled Plasma Spectroscopy are the most prominent examples.

The chief advantage of cFI is the simplicity of its experimental setup, where sample injection, reagent addition and product detection follow a clear route, travelled by continuous forward flow. That allows automated assays to be carried out even without computer control, since it is the flow generated by the pump provides strict time framework necessary for reproducible reaction conditions. Such control of the mixing and timing allows reagent based assays to be carried out reproducibly, even if the chemical reactions involved do not reach completion.

A manually operated cFI setup is still an economical option for serial assays, when funds for automated instruments are not available. It is also a best tool for teaching the principles of flow analysis in any setting, as such a simple system allows students to focus on the kinetics of physical dispersion and chemical reactions, without distraction of composing software script.

Advances in computerization have enhanced cFI, mainly through automation of data collection, calibration routines and automated sample injection. In this way a routine laboratory, with aid of an auto sampler can assay up to 120s/hour on a single instrument.

Programmable flow injection, while still in its infancy, has already shown advantages, compared to continuous flow technique. Enabled by advances in microfluidics, fluid propulsion and computerization, it offers unprecedented versatility of automation of reagent based assays. The lab-on-valve based instrument (1.2.41.), has a small footprint, uses ten time less of sample and reagents, and generates a fraction of chemical waste, because flow is discontinued between individual assay cycles.

In this Tutorial, programmable Flow Injection is being introduced for the first time, and applied for automation of several reagent based assays (1.2.32. and Selected Publications). In Chapter 3, flow programming is used to automate sorbent extraction (3.2.1.), and in Chapter 4 to enhance performance of liquid chromatography (4.3.1.).