High-performance ion chromatography method for separation and quantification of inositol phosphates in diets and digesta

A gradient high-performance ion chromatographic method for separation and quantification of inositol phosphates (InsP2–InsP6) in feedstuffs, diets, gastric and ileal digesta from pigs was developed and validated. The InsP2–InsP6 were separated on a Dionex CarboPac™ PA1 column using a gradient with 1.5 mol L−1 methanesulfonic acid and water. The exchange of the commonly used HCl with methanesulfonic acid has two advantages: (i) the obtained baseline during the separation is almost horizontal and (ii) it is not necessary to use an inert HPIC equipment as the methanesulfonic acid is not as aggressive as HCl. Twenty-three of the 27 separated inositol phosphate isomers were isolated. ICP-MS was used for quantification of phosphorus in the isolated isomers and used for calculation of correction factors for each isomer allowing InsP6 to be used as calibration standard. The detection limits for InsP2–InsP6 were in the range of 0.9–4.4 mg phosphorus L−1. The recovery of the major part of the inositol phosphates was 80–100%, and the CV for repeatability and reproducibility were 1–17% and 1–14%, respectively.