Flow Injection Tutorial

The unique design of flow cells detachable from LOV body, allows convenient change from spectrophotometry, to fluorescence or chemiluminescence. Flow cells are positioned in close proximity to port#2, and are connected to light sources and detectors by optical fibers. (2.3.5.).

For spectrophotometry, the unique design of Garth’s cell (2.3.6.) allows the length of the optical path, and thus sensitivity of measurement, to be chosen between 3cm and 50 cm. (A) The conventional flow cell (2.2.6.), also has adjustable optical light path between 1mm and 20mm. This is achievable by selecting the distance between optical fibers (encased in green PEEK tubing (B)) since O.D. of this tubing is slightly smaller then the O.D. of the flowcell. This design allows liquid to pass, even when fibers are not aligned with the inlet or outlet of the flowcell. Typical applications of long path flow cell are the assay of phosphate (2.2.25.) in SHC mode and high sensitivity phosphate in SFC mode (2.2.26.) where 15cm long flow cell was thermostatic at 40 C. The conventional flow cell was used to assay high concentrations of glucose (2.2.11.C.).

For fluorescence based assays (2.3.9.A.) the detachable flowcell is made from black polymer. The optical fibers are mounted at right angles (C) and the volume of monitored stream is about 2 microliters. The illuminating fiber is aimed towards LOV module. This flowcell was applied to assay of aluminum (2.3.9.B.).

For chemiluminescence based assays (2.3.11.) the linear flow cell (D) is similar to long path cell for spectrophotometry, albeit that it is thoroughly shielded from external illumination. This is achieved by using terminal blocks fabricated from a black polymer, and by positioning the ends of optical fibers short of inlet and outlet of the flowcell. The free flow of solution was facilitated in the same way as in the design of the conventional flow cell for spectrophotometry. The linear flow cell was used for the assay of hypochlorite by luminol (2.3.12.) and its performance was compared with the conventional spiral flow cell interfaced directly with a photomultiplier.