Analytical advances in the determination of calcium in bovine milk, dairy products and milk-based infant formulas

Background: Milk, dairy products and milk-based infant formulas (MIF) are major sources of calcium in humans' diet, especially in certain groups of population. The knowledge of the amount of this essential mineral in such complex matrices is a major concern to several areas such as health, quality control and research. Scope and approach: Through years, laboratory methods for calcium measurement have evolved into instrumental techniques, which brought to significant enhancements in analytical performances and sample throughput. Standardization bodies encourage keeping updated methods of analysis for nutrients. In this review, we gather knowledge on both the conventional and the promising analytical approaches of calcium measurement, highlighting their advantages and limitations. Key findings and conclusions: A wide array of techniques is available for calcium measurement and official international bodies have standardized several procedures. Classic sample pre-treatments, consisting in ashing or wet digestion, were joined by other effective and green-friendly solutions such as slurry sampling or direct solid sampling, when made feasible by the subsequent detection technique. Atomic spectrometry methods, complying with several standardized acceptability criteria, are nowadays largely used. In particular, flame atomic absorption spectrometry is well established together with inductively coupled plasma techniques, the latter being advantaged in terms of sensitiveness and multi-analyte capability. More recently, the interest in other approaches, such as instrumental neutron activation analysis and infrared techniques, has increased. X-ray fluorescence spectroscopy and laser-induced breakdown spectroscopy are suitable alternatives for routine at-line applications.