title: Synthesis and detection of oxygen-18 labeled phosphate.
abstract: Phosphorus (P) has only one stable isotope and therefore tracking P dynamics in ecosystems and inferring sources of P loading to water bodies have been difficult. Researchers have recently employed the natural abundance of the ratio of (18)O/(16)O of phosphate to elucidate P dynamics. In addition, phosphate highly enriched in oxygen-18 also has potential to be an effective tool for tracking specific sources of P in the environment, but has so far been used sparingly, possibly due to unavailability of oxygen-18 labeled phosphate (OLP) and uncertainty in synthesis and detection. One objective of this research was to develop a simple procedure to synthesize highly enriched OLP. Synthesized OLP is made up of a collection of species that contain between zero and four oxygen-18 atoms and, as a result, the second objective of this research was to develop a method to detect and quantify each OLP species. OLP was synthesized by reacting either PCl(5) or POCl(3) with water enriched with 97 atom % oxygen-18 in ambient atmosphere under a fume hood. Unlike previous reports, we observed no loss of oxygen-18 enrichment during synthesis. Electrospray ionization mass spectrometry (ESI-MS) was used to detect and quantify each species present in OLP. OLP synthesized from POCl(3) contained 1.2% P(18)O(16)O(3), 18.2% P(18)O(2) (16)O(2), 67.7% P(18)O(3) (16)O, and 12.9% P(18)O(4), and OLP synthesized from PCl(5) contained 0.7% P(16)O(4), 9.3% P(18)O(3) (16)O, and 90.0% P(18)O(4). We found that OLP can be synthesized using a simple procedure in ambient atmosphere without the loss of oxygen-18 enrichment and ESI-MS is an effective tool to detect and quantify OLP that sheds light on the dynamics of synthesis in ways that standard detection methods cannot.
authors.affiliation: Department of Soil Science, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Melby
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Soldat
authors.forename: Phillip
authors.initials: P
authors.lastname: Barak
mesh_terms: D004356:Drug Storage; D007553:Isotope Labeling; D010103:Oxygen Isotopes / Q000737:chemistry; D010710:Phosphates / Q000032:analysis* / Q000138:chemical synthesis* / Q000737:chemistry; D017553:Phosphorus Compounds / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D010103:Oxygen Isotopes; D010710:Phosphates; D017553:Phosphorus Compounds; C013196:phosphoryl chloride