CFA manifold

Fig. 10-14. CFA manifold for nitrate with LED-photometer and twin photometer amplifier (Institut fiir...

Coils for mixing and flow delay are the second dominating components in a CFA manifold. 

The tubing material that connects CFA systems is either glass or Teflon tubing. Tubing is used for the mixing coils that make up the analytical manifold, which is the junction box that contains all the connections between the different streams. The output from the manifold is then passed through a flow-through detector. 

Hydrazine (Bernhard and Wilhelms, 1967) or ascorbic acid are the common reductants in the flow-analysis of phosphate. The hydrazine method seems to reduce dye coating of the flow cell window but is equivalent to the ascorbic acid method described below. In continuous flow analysers (CFA) the same manifold can be used for both methods. 

Analyser systems are available commercially but may also be constructed from single components according to individual requirements. A typical system for the automated analysis of seawater constituents consists of a sampler, proportioning pump, the analytical manifold (a delay and reaction system), a flow-through spectrophotometer and a data acquisition system. Fig. 10-13 shows a 4-channel CFA system built and used in the Institute of Marine Research in Kiel (Germany). One example manifold (nitrate) including a flow-through-spectrophotometer is displayed in Fig.10-14. 

---