Improvement of Versatility and Analytical Range of AOAC Official Method 2015.06 for Selenium.

AOAC Official Method 2015.06 is not applicable for infant formula without selenium addition because of lack of sensitivity. In addition, Method 2015.06 specifies hydrogen gas as the cell gas of inductively coupled plasma (ICP)-MS instruments. There are only a few manufacturers who have formally adopted hydrogen gas. To expand the applicability of Method 2015.06 for infant formulas with lower selenium content and for ICP-MS instruments that do not use hydrogen gas as the cell gas, we modified the conditions of Method 2015.06. The results exhibited a good linearity (coefficient of determination >0.999) when the range of standard concentration was set from 0.4 to 16.0 μg/L and the cell gas was replaced with helium gas. The measurement precision was improved to an intermediate precision RSD value of 3.49%, and the recovery factor was 103.1%. This study demonstrates that helium gas can be used as the cell gas (easing restrictions in selecting an ICP-MS instrument) and expands the applicability of this method to infant formula samples with lower selenium content by modifying the sample preparation method.