Speciation of Inositol Phosphates in Lake Sediments by Ion-Exchange Chromatography Coupled with Mass Spectrometry, Inductively Coupled Plasma Atomic Emission Spectroscopy, and 31P NMR Spectroscopy

A method for the detection and speciation of inositol phosphates (InsPn) in sediment samples was tested, utilizing oxalate–oxalic acid extraction followed by determination by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) using electrospray ionization (ESI) in negative mode. The chromatographic separation was carried out using water and ammonium bicarbonate as mobile phase in gradient mode. Data acquisition under MS/MS was attained by multiple reaction monitoring. The technique provided a sensitive and selective detection of InsPn in sediment samples. Several forms of InsPn in the oxalate–oxalic acid extracted sediment were identified. InsP6 was the dominating form constituting 0.250 mg P/g DW (dry weight); InsP5 and InsP4 constituted 0.045 and 0.014 mg P/g DW, respectively. The detection limit of the LC–ESI-MS/MS method was 0.03 μM InsPn, which is superior to the currently used method for the identification of InsPn, 31P nuclear magnetic resonance spectroscopy (...