Nearly all methods of determining phosphate (P) concentrations in soil involve extraction of P into a
liquid phase followed by analysis by colorimetry (Murphy Riley) or inductively coupled plasma (ICP). An
alternative method for P analysis that has not yet shown wide use is electrospray ionization mass spectrometry
(ESI-MS). This research is an investigation of the viability of mass spectrometry (MS) as a method for P analysis
in soil extracts. P was extracted from soil samples using common soil extraction techniques: deionized water (DI)
and ammonium oxalate (AmOx). Colorimetry, MS, and ICP were used in the P analysis. Mass spectrometry measured
considerably more phosphate than colorimetric analysis following DI extraction and showed a good correlation with
ICP for P analysis following AmOx extraction. These results suggest that MS analysis may detect more than just
inorganic P in soil extracts, as ionization and ion transport in ESI-MS may convert organic P into detectable
phosphate ions. Thus, MS has promise as a technique for the analysis of P in soils. However, matrix effects,
likely due to components extracted from the soil and components of the extractants, may be a limitation in the
applicability of this technique.
A paper detailing the experiment and results, entitled "Mass Spectrometric Analysis for Phosphate in Soil Extracts; Comparison of Mass Spectrometry,
Colorimetry, and Inductively Coupled Plasma," was accepted by the
Analytical Sciences Digital Library on April 4, 2007.