The document describes the development of an autonomous in-situ total phosphorus analyzer for use in aquatic environments. The analyzer uses the colorimetric stannous chloride-molybdenum blue method to measure orthophosphate, organic phosphate, and assimilated phosphate in algal biomass. A fluorinated ethylene propylene tubing digester catalyzed by UV light and heated by a nickel chromium wire is developed to digest organic phosphorus into a measurable form. Water samples and reagents are delivered using microfluidics and syringes controlled by linear actuators. Absorbance measurements are taken using a photodiode and LED in a flow cell. Validation tests achieved a correlation of r2=0

1. Development of an In-Situ Total Phosphorus Analyzer in Aqueous
Environments
Christopher F. Pertsch V1,2, Dr. James Bonner3, Dr. Christopher Fuller3, Russell Nelson3,
Meaghan Lavin3
1ASSETS to Serve Humanity REU Program, Clarkson University
2Department of Systems Engineering and Operations Research, George Mason University
3Beacon Institute, Clarkson University
cpertsch@gmu.edu
Abstract- Ecosystems that contain high levels of phosphorus usually flourish and contain a large number of
flora and fauna. Anthropogenic factors, such as sewage effluent and run off from agricultural activities, can
cause an excess of phosphorus in the water leading to an uncontrolled growth of algae and plant life. This
uncontrolled growth causes a drastic decrease in the dissolved oxygen of the body of water creating a hypoxic
environment for the organisms. This is commonly known as eutrophication and is one of the major causes for
loss in biodiversity. An increase in phosphorus monitoring will provide a more efficient and accurate
determination of phosphorus levels over time, which can potentially lead to a better understanding of
phosphorus cycling and eutrophication. The performance of a prototype, autonomous t-phosphorus analyzer
will be evaluated with respect to its ability to measure: orthophosphate, organic phosphate, and assimilated
phosphate in algal biomass. The analyzer uses the colorimetric stannous chloride-molybdenum blue method to
calculate the phosphorus in the aqueous environment. Analysis of total phosphorus requires the digestion of
organic phosphorus into soluble phosphorus. To accomplish this a digester needs to be developed. To build the
digester a fluorinated ethylene propylene (FEB) tubing is wrapped around a 12W UV-light (254nm) to catalyze
the digestion process. A nickel chromium wire is added to heat the digester, which is controlled using a
temperature probe and a proportional-integral-derivative (PID) algorithm. Water samples and reagents are
delivered by using microfluidics and syringes controlled by linear actuators. Following the phosphorus
digestion and the addition of the colorimetric reagents the sample is then transferred to a flow cell (Z-Cell)
where a photodiode and an LED are usedto measure the absorbance of the sample. Validation of the chemistry
and overall behavior of the system was obtained using orthophosphate and organic phosphate (algae and
adenosine monophosphate). A linear regressionwas performed for concentrationvs. absorbance. The samples,
with ranging concentrations from 20-200g P/L, were randomized and repeated three times, the correlation
obtained was r2 = 0.960. Results for the different forms of phosphorus, assuming a successful digestion of the
material, are expected to be virtually the same. Definition and verification of process flow steps was done to
calculate the volumes flowing through the system, as well as to consider the mixing regimes by calculating
Reynolds numbers in different parts of the analyzer. The cost of the operating components of the system can
be purchased for under $3,000 compared to other commercially available nutrient analyzers that cost up to
$30,000.
Keywords- phosphorus, in-situ, micro-fluidics, Reynolds numbers
Acknowledgements: This project was supported in part by the National Science Foundation underGrant No. EEC-
1359256.
Mentors: Dr. James Bonner, Beacon Institute, Clarkson University
Dr. Christopher Fuller, Beacon Institute, Clarkson University
Mr. Russell Nelson, Beacon Institute, Clarkson University