An in vitro method was used to determine the availability of Zn from infant foods containing increasing amounts of phytate, and to quantify the effect of the phytate:Zn molar ratio on the availability. During the in vitro assay, digestive conditions of infants, younger and older than 4 months of age, were carefully simulated since the solubility of phytate -Zn complexes during digestion is pH dependent. Availability was measured with a continuous flow dialysis in vitro procedure with previous intralumen digestive stage. Zn concentrations were determined with flame atomic absorption spectrometry. Phytic acid content was measured with HPLC. Adding phytate to infant formula lowered Zn availability to 2 : 84 (SD 0 : 17) % when the phytate:Zn molar ratio increased to 2 : 2 ðP , 0 : 05Þ; as compared with cows' milk-based formula (6 : 65 (SD 0 : 55) %). Availability from vegetables (23 : 83 (SD 2 : 17) %) significantly decreased ðP , 0 : 05Þ at a ratio . 7 : 9 (15 : 12 (SD 1 : 63) %). Zn availability from soyabean-based formula (2 : 26 (SD 0 : 36) %) was lower ðP , 0 : 05Þ compared with cows' milk-based formula (6 : 65 (SD 0 : 55) %). Availability between soyabean-and cows' milk-based formula was similar ðP . 0 : 05Þ when a phytate:Zn ratio of 2 : 2 (2 : 84 (SD 0 : 17) %) was obtained in the cows' milk formula. The negative effect of phytic acid on Zn availability was dependent on the type of the food and the phytate content, and should be considered when using soyabean-based formulas during early infancy.

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The contents of transition metal ions iron, copper, zinc, and manganese were simultaneously determined in pig feed using an ion chromatographic technique (IC) preceded by dry ashing. Employing ion exchange, the ions were separated on an IonPac CS5A column used in combination with a pyridine-2,6-dicarboxylic acid based eluent. The separation was followed by spectrophotometric detection after postcolumn reaction with 4-(2-pyridylazo)resorcinol. Dry ashing parameters were varied to assess their role in potential analyte loss. Quantitative recoveries (>95%) were obtained for all analytes with a dry ashing method that included a moderate temperature-time regime and ash leaching support in the form of sonication and heat treatment. The use of HCl as leaching acid and the presence of alkaline earths in the matrix solution did not interfere with the chromatographic separation.

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