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, ³¹P was measured as ³¹P¹⁶O⁺ at m/z 47 employing dynamic reaction cell technique with O₂ as reaction gas. Orthophosphate and IP₆ were separated within a total chromatographic run‐time of 12 min revealing a limit of detection of 0.3 μmol/L. The coefficients of determination obtained in a working range of 1–100 and 1–30 μmol/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 PO₄^3? 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.