Determination of phytic acid and its degradation products by ion-pair chromatography (IPC) coupled to inductively coupled plasma-sector field-mass spectrometry (ICP-SF-MS)

Abstract

We developed a method for the determination of phytic acid (IP6) and its degradation products (IP1-IP5) by ion-pair chromatography coupled to a double focussing inductively coupled plasma-sector field-mass spectrometer (ICP-SF-MS). For the detection of the phosphorus species a mass resolution (m/Δm) of 4000 was needed in order to separate the 31P+ signal from the interfering clusterions. The separation of the six phosphorus species was enabled by a gradient elution using tetrabutylammonium hydroxide (TBA) as ion-pair reagent. Calibration data were reported and a detection limit of 230 ng g−1 for IP6 could be obtained. The method was firstly proved for a hydrolyzate of commercially available phytic acid and then applied to various real samples like nuts, cereals, legumes, beer etc. In all samples different pattern of inositol phosphates could be detected. The compositional comparison of inositol phosphates in a malt and a beer sample showed that during the brewing process IP6 is completely degraded to IP2 and IP3.