Determination of Total Nitrogen and Phosphorus in Environmental Waters (By Using Alkaline Persulfate Digestion and Ion Chromatography with Suppressed Conductivity Detection)
Oral Presentation
Prepared by R. Jack, B. Deborba, J. Rohrer
Thermo Fisher Scientific, 1214 Oakmead Parkway, Sunnyvale, CA, 94085, United States
Contact Information: [email protected]; 408-481-4227
ABSTRACT
Nutrients (i.e., nitrogen and phosphorus) are a natural part of the aquatic ecosystems that help support the growth of algae and aquatic plants, which provide shelter and food for fish and other organisms. However, excess nitrogen and phosphorus in the waters, such as from anthropogenic sources, can cause serious environmental such as algal blooms. In addition, algal blooms can also cause health issues such as elevated toxins and bacterial growth can cause illnesses when coming in contact with the water, consuming tainted fish, or drinking contaminated water. Because a national numeric criteria doesn’t exist, the EPA requested that each state develop criteria for their water bodies. Simultaneous nitrogen and phosphorus determinations are typically accomplished by Kjeldahl digestion methods. This method has several drawbacks, 1) health and safety risks posed by concentrated acids, toxic reagents (mercury), and high temperatures (370°C); 2) Nitrate is not measured, 3) propensity of acidic digests to trap and become contaminated by ammonia vapors in ambient laboratory air; and 4) laboratory reporting limits (0.1 mg-N/L; 0.04 mg-P/L) higher than those of other inorganic nitrogen- and phosphorus-containing species, which limit the precision of mass balance estimates. In this report, alkaline persulfate digestion was used to convert nitrogen to nitrate and phosphorus to phosphate followed by determination using anion exchange chromatography with suppressed conductivity detection. To initially evaluate the method, several inorganic and organic nitrogen and phosphorus-containing compounds were digested and the recoveries were determined. For the nitrogen-containing compounds the recoveries ranged from 93-100% and from 85-99% for the phosphorus-containing compounds. The linearity, sensitivity, and recovery of nitrate and phosphate in environmental waters will be discussed. We will also show data comparisons with alkaline digested samples with colorimetric determination.
Oral Presentation
Prepared by R. Jack, B. Deborba, J. Rohrer
Thermo Fisher Scientific, 1214 Oakmead Parkway, Sunnyvale, CA, 94085, United States
Contact Information: [email protected]; 408-481-4227
ABSTRACT
Nutrients (i.e., nitrogen and phosphorus) are a natural part of the aquatic ecosystems that help support the growth of algae and aquatic plants, which provide shelter and food for fish and other organisms. However, excess nitrogen and phosphorus in the waters, such as from anthropogenic sources, can cause serious environmental such as algal blooms. In addition, algal blooms can also cause health issues such as elevated toxins and bacterial growth can cause illnesses when coming in contact with the water, consuming tainted fish, or drinking contaminated water. Because a national numeric criteria doesn’t exist, the EPA requested that each state develop criteria for their water bodies. Simultaneous nitrogen and phosphorus determinations are typically accomplished by Kjeldahl digestion methods. This method has several drawbacks, 1) health and safety risks posed by concentrated acids, toxic reagents (mercury), and high temperatures (370°C); 2) Nitrate is not measured, 3) propensity of acidic digests to trap and become contaminated by ammonia vapors in ambient laboratory air; and 4) laboratory reporting limits (0.1 mg-N/L; 0.04 mg-P/L) higher than those of other inorganic nitrogen- and phosphorus-containing species, which limit the precision of mass balance estimates. In this report, alkaline persulfate digestion was used to convert nitrogen to nitrate and phosphorus to phosphate followed by determination using anion exchange chromatography with suppressed conductivity detection. To initially evaluate the method, several inorganic and organic nitrogen and phosphorus-containing compounds were digested and the recoveries were determined. For the nitrogen-containing compounds the recoveries ranged from 93-100% and from 85-99% for the phosphorus-containing compounds. The linearity, sensitivity, and recovery of nitrate and phosphate in environmental waters will be discussed. We will also show data comparisons with alkaline digested samples with colorimetric determination.
