Quantification of phytic acid in baby foods by derivatization with (trimethylsilyl)diazomethane and liquid chromatography–mass spectrometry analysis

Rationale Phytic acid (PA) is both a naturally occurring nutrient and a widely-used food additive for conferring antioxidant properties to food. PA can be found in baby foods and it is essential to monitor PA content due to its antinutritional properties when present in excess. Current methods for determining PA content are unsatisfactory because interference from inositol phosphates and inorganic phosphates complicate PA quantification. Methods Baby foods were extracted by aqueous HCl, and the extractant was subjected to derivatization with (trimethylsilyl)diazomethane after de-metalation using a cation exchange resin. The PA derivative was quantified by liquid chromatography-mass spectrometry (LC-MS/MS) using a multi-response monitoring mode (m/z 829 -> 451). Results The linearity of the developed analytical method ranged from 10 to 1000 ng/mL for phytic acid with R2 > 0.999. Reasonable reproducibility was obtained with an intraday RSD (N=5) of 4.5% and an interday RSD (N=5) of 5.7% at a concentration of 10 ng/mL. The developed method was successfully applied to determine PA content in various baby foods, with PA recovery between 90.6 to 119.8%. Conclusions A robust and sensitive method for the determination of PA in baby foods has been developed by methyl esterification with (trimethylsilyl)diazomethane and LC-MS/MS analysis. The established method showed good anti-interference and precision, and it has been applied for the determination of phytic acid in various baby foods.