FIA methods are limited by the amount of time necessary to obtain a measurable signal since travel time through the tubing tends to broaden peaks to the point where samples can merge with each other. As a general rule, FIA methods should not be used if an adequate signal cannot be obtained within two minutes, and preferably less than one. Reactions that need longer reaction times should be segmented. However, considering the number of FIA publications and wide variety of uses of FIA for serial assays, the "one minute" time limitation does not seem to be a serious limitation for most real life assays. Yet, assays based on slow chemical reactions have to be carried either in stopped flow mode ( SIA) or by segmenting the flow.