Speciation analysis of orthophosphate and myo-inositol hexakisphosphate in soil- and plant-related samples by high-performance ion chromatography combined with inductively coupled plasma mass spectrometry

A novel method based on high-performance ion chromatography inductively coupled plasma mass spectrometry employing strong anion exchange chromatography with HNO3 gradient elution for simultaneous analysis of orthophosphate and myo-inositol hexakisphosphate (IP6) in soil solution and plant extracts is presented. As inductively coupled plasma mass spectrometry analysis of phosphorus at m/z 31 is hampered by N-based interferences, P-31 was measured as (PO+)-P-31-O-16 at m/z 47 employing dynamic reaction cell technique with O-2 as reaction gas. Orthophosphate and IP6 were separated within a total chromatographic run-time of 12min revealing a limit of detection of 0.3 mu mol/L. The coefficients of determination obtained in a working range of 1-100 and 1-30 mu mol/L were 0.9991 for orthophosphate and 0.9968 for IP6, respectively. The method was successfully applied to extracts from three different soils as well as root and shoot extracts of Brassica napus L. The precision of three independently prepared soil extracts was in the range of 4-10% relative standard deviation for PO43- and 3-8% relative standard deviation for IP6. Soil adsorption/desorption kinetics for IP6/orthophosphate were performed for investigating the sorption behavior of the two P species in the experimental soils.