3.2.9.7. Conclusion

Nephelometry and turbidimetry are almost always carried out in batch format, where each sample is assigned to its own container with a volume of anywhere between 0,1 and 10 mL.  In contrast, flow-based methods, where samples are sequentially analyzed while they travel through a tubular conduit, are seldom used to automate nephelometry or turbidimetry. According to Hansens Database, the first paper on Flow Injection Turbidimetry was published in 1977 by a group from Brazil (F. J. Krug, et.al,  Analyst,102 (1977) 503 on the determination of sulphate precipitated by barium chloride. Since then, over 24.000 papers were published on various FIA related topics, but only ten (10!) on FI turbidimetry (or nephelometry), all of them based on precipitation reactions, and none of them, as far as we could find, on the determination of Suspended Matter. Yet quantification of suspensions is, as mentioned in the Introduction, widely used in many fields of manufacturing and exploration.

Turbidity of water is an important parameter in the evaluation of aquatic systems, as it affects the activity of bioprocesses driven by the intensity of light. Increasing turbidity of sea water decreases its transparency to light and decreases the rate of photosynthesis while impacting aquatic life in many other ways. Therefore, measurement of turbidity in well defined NTU is preferable. While turbidity is routinely monitored in situ, it is not usually associated with analyzed samples, although information on the presence or quantity of Suspended Matter in individual samples may be important for their quantification. As an example, presence of 1 NTU of Suspended Mater in a sample will simulate concentration of 49 nM P when this sample will be analyzed by PMoB spetrophotometry (Appendix 3).

Acknowledgment

The authors wish to thank M. Hatta for critical comments. M. Davis was partially supported by the University of Hawaii.