Flow Injection Analyzer

Flow Injection Analysis – Nutrients

  • Manufacturer: Lachat Instruments Div., Zellweger Analytics, Inc.
  • Model: QuikChem 8000
  • Capabilities
    • Simultaneous determination of up to 5 analytes per sample
    • Random-access autosampler with racks for up to 120 samples per batch
    • Analytical manifolds available:
      • Nitrite
      • Nitrate plus Nitrite
      • ortho-Phosphate
      • Silicate
      • Ammonium

General Description

Flow injection analysis (FIA) is a continuous-flow technique for automated wet-chemical analysis. The methodology used by the flow injection analyzer is similar to that used by AutoAnalyzers, with continuously flowing reagent streams, reaction 'manifolds', and flow-through detectors. However, FIA does not use air-bubble segmentation to separate samples and promote mixing. Instead, small diameter tubing is used in the manifolds, resulting in laminar flow conditions in which mixing takes place by axial and radial diffusion, and the manifolds are self-cleaning. Diffusion (dilution and mixing) is controlled by manifold design. (A concise description of basic FIA principles is provided at Global FIA's 'Principles' web page, and a more extensive discussion is presented in their FIA Tutorial.) A major practical advantage of this technology over that of air-segmentation, is that analytical results are usually available within a minute or so from the time the sample is aspirated, so any problems in the system can be spotted quickly and corrected, with little wasted time. The overall analysis times also tend to be shorter with FIA, so more samples can typically be analyzed in a given period of time. Precision and detection limits are generally comparable between the two technologies.

The software that controls our instrument is Windows 95 based, and displays real-time graphical output of any or all of the active detectors. This is extremely useful for during-run monitoring of the instrument's performance. Data is stored on disk, and is available for post-run processing in a variety of formats. The software also provides a wide range of quality control options to ensure accurate and reliable results. These include check-standards and control samples (the measured concentrations of which can be compared to known values on either a relative or absolute basis), same-vial or different-vial replicates, and spikes.