Flow Injection Tutorial

Small internal volume of the flow path and its low flow resistance are the key features of lab-on-valve design. This is achieved by connecting LOV elements by a short, large bore (0.8mm I.D.) channel. In order to preserve this compact design, additional functions such as mixing, separations or reagent additions are accommodated by miniaturized units inserted into the flow path.

Mixing module (A) comprises a channel (10 mm long, 1,6mm I.D.) into which a shorter piece of 0.8 mm I.D. tubing is inserted. The resulting distortion of flow path creates a localized turbulence that facilitates radial mass transfer.

Confluence module combined with mixing coil (B) is the building block for a hybrid flow injection manifold. In this design reagents (R1,R2) are intermittently pumped, while sample and standards are injected by multiposition valve. The advantage of this design, compared to conventional FIA is reduced reagent consumption, by flow programming, and computer controlled selection of the volume of the injected sample.

Microcolumn inserted between LOV module and flow cell (C) will facilitate SPE separation/preconcentration of target analyte and the dervatization module (D) integrated with flowcell will allow reagent to be added to a separated analyte in post column fashion, as e.g, for assay of traces of Zn in sea water (Grand 2016).

Gas diffusion or dialysis module (E) mounted in close proximity to the long path flowcell is miniaturized, compared to conventional units. The acceptor (A) stream is stopped while the donor stream (D) is passed along the membrane (1.2.36.). This results in accumulation of target analyte, which is then transported undiluted into adjacent flow cell.