Development of Exact Matrix‐Matching Inductively Coupled Plasma‐Optical Emission Spectroscopy for the Analysis of Cu and K in Infant Formula

In the present study, we have developed an exact matrix‐matching inductively coupled plasma‐optical emission spectroscopy (ICP‐OES) as a low‐cost alternative to the isotope dilution inductively coupled plasma‐mass spectrometry (ICP‐MS) method for accurate and precise measurements of nutrient elements K and Cu in infant formula. In spite of its high precision and accuracy, ICP‐OES analysis of complex samples was not reliable due to biases originating from various matrix effects. The elaborated exact matrix‐matching approach tested here demonstrated its potential to minimize biases due to matrix mismatch. The exact matrix‐matching ICP‐OES method was successfully validated by comparing the results with those from an isotope dilution ICP‐MS method. Because the model provides reliable results without significant loss of precision, it will be an excellent choice for major element analysis in a complex sample, especially when isotope dilution is not applicable due to the lack of alternative isotopes or the high cost of enriched isotopes.