Advances in computerization, electronics, optics and communication improved tools we use at home and at work. Accordingly over last 60 years flow based analysis evolved from air segmented continuous flow method, to miniaturized, programmable flow technique. The evolution from the traditional concept of homogenous mixing and reaction equilibrium, embodied in Skeggs's revolutionary idea, into present Flow Injection method, based on concentration gradients and ongoing kinetics, was enabled by availability of pumps, optical fibers, new materials and other components. Yet it is a relevant to ask if the new technique is “better” than what has been successfully used for so many years.
“There is much good and much new in this work. Unfortunately what is good is not new and what is new is not good" J.N.Bronsted
Let us consider what a well designed automated analyzer should do:
Provide reproducible and accurate results
Achieve a high sampling frequency
Minimize reagent consumption and waste generation
Perform assays that can not otherwise be performed ( by manual or batch technique)
Simplify the assay protocol, while making the system transparent to the user.
Be versatile, by accommodating reagent based assays, and simple sample preparation
The unquestionable success of Skegg’s AutoAnalyzer® was due to its ability to fulfill almost all of the above requirements, thus making flow based assays widely accepted in clinical and industrial laboratories. Yet, over the last fifty years technological advances and changes in perception of the role of chemistry led to two major changes.
Computerization revolutionized data processing and allowed flow programming to emerge as an important tool for assay optimization .
Concept of green chemistry and increased cost of disposal of chemical waste led to efforts to minimize reagent consumption and waste generation. As a result continuous flow techniques are steadily loosing ground to methods, where sample processing is “digitalized” in a way, that each sample is allocated a precise and minimized volume of reagent. In other words, reagents are only consumed when an individual sample is being processed. This is why a continuous pumping, at a constant flow rate, is the Achilles Heel of both CFA and of traditional Flow Injection Analysis.
Programmable Flow injection and Sequential Injection in lab-on-valve format operate in a “digitalized” way by using different microfluidic manipulations to suit requirements of individual steps of an assay protocol. These methods are accommodated in a versatile instrument that can perform a multitude of microfluidic operations and automate a variety of reagent based assays, without need for physical reconfiguration. The apparatus uses microliter volumes of sample and reagents and being portable, has the footprint of size of an iPAD. (1.2.41. and 2.3.3.). Compared to CFA analyzer or the traditional Flow Injection analyzer the new generation of miniaturized instruments, is as much advanced as smart phone is, compared to a landline phone. I do realize that even CFA analyzers are still being produced, and used in routine laboratories, as much as many wall mounted phones are still in use, for whatever reason. But the change is inevitable.