Determination of myo-inositol hexakisphosphate (phytate) in urine by inductively coupled plasma atomic emission spectrometry

Myo-inositol hexakisphosphate (phytate) is a substance present in urine with an important role in preventing calcium renal calculi development. In spite of this, the use of urinary phytate levels on stone-formers’ evaluation and treatment is still notably restricted as a consequence of the enormous difficulty to analyze this substance in urine. In this paper, a simple procedure for routinary urinary phytate determination based on phosphorus determination through inductively coupled plasma atomic emission spectrometry is described. The method only requires a previous separation of phytate from other components by column anion exchange chromatography. The working linear range used was 0–2 mg l^-1 phosphorus (0–7 mg l^-1 phytate). The limit of detection was 64 (mu)g l^1 of phytate and the limit of quantification was 213 (mu)g l^-1. The relative standard deviation (R.S.D.) for 1.35 mg l^-1 phytate was 2.4%. Different urine samples were analyzed using an alternative analytical methodology based on gas chromatography (GC)/mass detection used for inositol determination (phytate was previously hydrolyzed), resulting both methods comparable using as criterion to assess statistical significance P<0.05.