Nutrient Analytical Services Laboratory

Other Chemistries

Hardness – EDTA Titrimetric Method


EDTA forms a chelated soluble complex when added to a solution of certain metal cations. If a small amount of dye is added to a solution containing calcium and magnesium ions at a pH of 10 ± 0.1, the solution turns wine red. If EDTA then is added as a titrant, the calcium and magnesium are complexed. When all of the calcium and magnesium are complexed, the solution turns from wine red to blue.

APHA. 1975. Method 309 B. EDTA Titrimetric Method in Standard Methods for the Examination of Water and Wastewater, 14th Edition. American Public Health Association. Washington, D.C. 1193pp.




Carbonate Alkalinity


Dissolved inorganic carbon concentration is determined by the Shimadzu TOC 5000 analyzer. Refer to Total and Dissolved Organic and Inorganic Carbon methodology. Dissolved inorganic carbon concentration is also determined by method APHA #403.





Biochemical Oxygen Demand (BOD)


BOD is an indicator of how much oxygen is utilized by a natural water sample (phytoplankton and bacteria) in five days at 20 degrees C. Low utilization is good…. High utilization not so good.




Dissolved Metals










Sulfate, Chloride and Bromide


A small volume of filtered sample is introduced into an ion chromatograph (IC). The sample is pumped through a precolumn, separator column, suppressor column, and conductivity detector. Anions are separated in the precolumn and separator column based on their affinity for resin exchange sites in the columns. The suppressor column converts the sample anions to their acid form. The separated anions are measured by the conductivity detector. The concentration of anions is determined by comparing peak heights of unknowns to a calibration curve generated from known standards.

Pfaff, J.D., C.A. Brockhoff and J.W. O’Dell. August 1991. USEPA Test Method No. 300.0. The determination of inorganic anions in water by ion chromatography. Environmental Monitoring and Systems Laboratory, Cincinnati, OH 45268.

USEPA. 1987. Section 11.0 Determination of chloride, nitrate, and sulfate by ion chromatography in Handbook of methods for acid deposition studies: Laboratory analysis for surface water chemistry. United States Environmental Protection Agency, Office of Research and Development. Washington, D.C. Report No. EPA 600/4-87/026 September 1987. 336pp.








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