Flow Injection Analysis is an analytical technique based on microfluidic manipulation of samples and reagents. Samples are injected into a carrier/reagent solution which transports the sample zone into a detector while desired (bio)chemical reactions take place. Detector response (absorbance, fluorescence, mass spectra, etc) yield a calibration curve quantifying the target analyte.

Microfluidics for automated sample processing can be based either on continuous flow, or on programmable flow.  Continuous flow techniques, such as Flow Injection (FI) and chromatography, use constant forward motion of the carrier to transport sample from injector to detector.  Programmable flow techniques, such as Sequential Injection (SI) and emerging Sequential Injection Chromatography (SIC) use flow reversals, and flow  acceleration to mix sample with reagents, and stop flow to accommodate reaction time, and to monitor the reaction rate based response. The advantage of continuous flow techniques is transparency of operation, while programmable flow techniques are more versatile, since assay protocols are controlled by software script.