Type of Document Dissertation Author Heerboth, Matthew Seth URN etd-08222007-232654 Title Speciation of Organic Phosphorus in Soils and Surface Waters By Liquid Chromatography With High Resolution Mass Spectrometry Detection Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title William T. Cooper Committee Chair John G. Dorsey Committee Member Naresh Dalal Committee Member Vincent J. M. Salters Committee Member Keywords
- Organic Phosphorus
- Time of Flight
- Inositol Phosphates
- Ion Chromatography
- Mass Spectrometry
- Size Exclusion Chromatography
Date of Defense 2007-07-24 Availability unrestricted AbstractPhosphorous is one of the most important nutrients in the natural environment. It is often the limiting nutrient in many environmental systems. Recently, it has been recognized that organic phosphorus compounds play a more important role in the environmental phosphorus cycle than once believed. Despite this realization, scientific knowledge of these compounds remains relatively low. A major reason for this is the lack of reliable analytical methods available for this class of compounds.
A prime example of the above problem is a class of organic phosphorus compounds known as inositol phosphates. Inositol phosphates are the most abundant form of organic phosphorus in soils, and also have a significant concentration in natural waters. However, their role in the global phosphorous cycle remains poorly understood principally because there is a lack of development in their analytical chemistry.
This work is an effort to improve the analytical methods available for analyzing organic phosphorus in environmental samples. Liquid chromatography separation with mass spectrometric detection was used to attack this problem on several fronts.
A major portion of this work is devoted to the above mentioned inositol phosphates. For the first time, electrospray ionization (ESI) time of flight-mass spectrometry (TOF-MS) has been used to detect molecular ion peaks of all six inositol phosphate congeners. Size exclusion chromatography (SEC) was used combined with TOF-MS in an effort to obtain separation of the congeners. Using selected ion monitoring (SIM) we are able to extract the SEC chromatograms attributable to each inositol phosphate molecular ion peak. However, because of in-source fragmentation in the mass spectrometer, a separation step was needed that could fully resolve all six congeners. Despite this drawback, we have used
SEC-MS to identify inositol phosphates in soil extracts from an everglades tree island for the first time. Inositol phosphates in these samples are known to be present at extremely low concentrations and had not previously been detected using other techniques.
Ion chromatography (IC) has the ability to separate the six inositol phosphate congeners with sufficient resolution. When the separation is combined with an ion suppressor, the IC eluent is compatible with ESI-MS. We have used IC-MS to develop a method for the rapid analysis of phytic acid. Through this method we were able to quantify the phytic acid content in the tree island soil extracts as well as pasture soils from the United Kingdom.
We have also developed the first size-based analysis for organic phosphorus extracts from surface water samples. Using samples from a water treatment facility in the Florida Everglades, size fractions were collected using an SEC column and the organic phosphorus concentrations determined using inductively-coupled plasma mass spectrometry.
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