What is Micro Seg Flow?

Frequently Asked Questions, Misconceptions regarding µ-SFA vs. FIA

History

Leonard Skeggs, PhD, invented the first continuous flow analyzer back in 1957. With that invention and with the eventual development of the first Segmented Flow Analyzer (SFA), a revolution took place in wet chemistry analysis: Many labor-intensive tests could now be automated, thereby increasing a laboratory’s testing capabilities without the need for more personnel and supplies. As a result, hundreds of wet-chemistry methods were converted over to durable and reliable SFA.

The initial SFA systems were limited, however, and slow when compared to other technologies that followed. And although these first systems provided a considerable advantage over doing tests manually, faster and more sophisticated technologies began to appear and phase out the older systems. Of course the problem with many of these newer technologies (i.e. FIA) was that many laboratories would often have to sacrifice detection limits for speed and automation.

The Astoria and Astoria2 analyzers provide the modern laboratory with three advantages: (1) they have the detection capabilities of SFA, (2) they use far less reagent than both older SFA and FIA, and (3) they take up much less bench space.
Essentially, the differences are in the design: Astoria’s systems are micro-SFA. This means that the Astoria and Astoria2’s analysis rates are nearly twice as fast as older SFA systems and use a tenth less reagent!

Five primary components make up a micro-SFA system: (1) Sampling device, (2) peristaltic pump, (3) reaction cartridge, (4) colorimeter (or a detector of some type), and (5) data acquisition software. When a RUN is started, the sampling device–working in concert with the peristaltic pump–pulls some sample from a cup or test tube. The peristaltic pump pushes that sample, along with specific reagents of a particular method, into the reaction cartridge. The reaction cartridge, which consists of injection fittings, glass mixing coils, heating units, etc., not only brings the sample and reagents together but also introduces air-segmentation bubbles into the reagent stream to help facilitate the mixing of the sample and reagents. Then, once a detectable product is formed–i.e. a colorimetric test like Nitrite–the sample is then analyzed by a colorimeter using absorbance vs. time; therefore, in this case, the intensity of the color formation is directly proportional to the concentration of the analyte (Nitrite) you have configured the system to monitor. Overseeing the RUN, the data acquisition software collects the data from the colorimeter and also controls the various functions of the sampling device, peristaltic pump, and colorimeter.

Astoria’s micro-SFA systems allow the lab to run between one to several different parameters at the same time, depending on how many channels or number of detectors the system has. Most laboratories run anywhere between one to six methods (i.e. Nitrate, Nitrite, Ammonia, OP, Silicate and Urea in seawater) simultaneously.

In contrast to Discrete analyzers, the Astoria and Astoria2 are ideal units for labs that have only a few tests to run but have a lot of samples. Micro-SFA is also a good platform for alternative methods of analysis that use in-line dialysis, in-line distillation and/or UV digestion, fluorometry, UV detection, flame photometry, etc.

Consult with an API representative to determine the best automated platform (micro-SFA or Discrete) for your laboratory.