Separation of inositol phosphate isomers in environmental samples by ion-exchange chromatography coupled with electrospray ionization tandem mass spectrometry.

A method for isomeric separation of inositol phosphates (InsPn) in environmental samples originating from different sources such as soil, manure/compost, and aquatic sediments has been developed. The method includes a single NaOH-EDTA extraction step, centrifugation and direct injection of a particle free solution into an ion chromatographic column. Isomeric liquid chromatographic separation was achieved with an ammonium carbonate gradient compatible with electrospray ionization tandem mass spectrometric detection (LC-ESI-MS/MS). The detection limits of the LC-ESI-MS/MS method were between 0.03-0.16µM for the different InsPn, corresponding to 37-99ng P/g sample DW. The method has shown to be able to analyze more than 200 samples from soil, manure and sediment without any severe matrix effects. This will allow future studies of the fate of inositol phosphates in the environment.