Optimization of a Slurry Dispersion Method for Minerals and Trace Elements Analysis in Infant Formulae by ICP OES and FAAS

摘要

Infant formula developed by manufacturers requires a rigorous control of composition,particularly those elements added routinely in an attempt to mimic the mineralcomposition of human milk. A total of 97 different types of powdered infant formulae(preterm, adapted starter, adapted follow-up, toddler, specialised and soy basedformulae) commercially available in Spain were studied. It is noteworthy greatdifferences in mineral (Ca, P, Mg) and trace element (Zn, Fe, Cu, Mn) contents foundbetween analysed and listed in label information. The development of a fast, simple anddirect slurry method for the determination of these essential micronutrients in infantformula by inductively coupled plasma optical emission spectrometry (ICP OES) andflame atomic absorption spectrometry (FAAS) was performed in order to help in qualitycontrol tasks. Infant formula samples were solubilised using different amounts ofseveral different solvents. An addition of 250 L of a solution 10 %tetramethylammonium hydroxide and 25 % ammonium hydroxide were required for theaccurate quantification of Ca and P, Mg, Zn, Fe, Cu and Mn, respectively. The standardreference material 1549 non-fat milk powder was solubilised to compare the validity ofassayed methodology following slurry nebulisation and traditional microwave-assistedacid digestion method. Good agreement of the analytical results by both ICP OES andFAAS, with the certified values was obtained. Method performance parameters(accuracy, precision and methodological detection limits) were determined for studiedelements to check the quality and usefulness of the optimised slurry method. Theanalytical procedure was applied successfully to the analysis of a representative groupof infant formulae. Levels of analysed elements were graphically represented, showingan acceptable comparability between slurry and acid-mineralisation method set by linearcorrelation coefficients and slopes close to the unit. The described simple and slurrymethod is appropriate, as an attractive alternative, for routine control analysis of addedessential elements in infant formulae regardless of predominant protein type used inmanufacture.