Applicability of HR-ICP-OES in the Pharmacopoeial Assessment of the Uniformity of Elemental Dosages in Food Products for Medical Use

Abstract

Unlike medicinal products (MPs), dietary supplements (DSs), foods for special medical purposes (FSMPs) and fortified foods (FFs) available on the Polish market are not required to meet pharmacopoeial quality standards. Dose uniformity testing, a pharmacopoeial requirement for MPs, confirms both the accuracy of the declared dose and consistency between individual doses. As consumption of DSs, FSMPs, and FFs continues to increase, particularly among vulnerable populations, ensuring consistent intake of essential nutrients becomes increasingly important. Therefore, adapting pharmacopoeial dose uniformity criteria to elemental analysis may provide an additional quality assessment tool beyond the percentage of the label claim. Accordingly, this study aimed to (1) validate a multi-element High-Resolution Inductively Coupled Plasma Optical Emission Spectrometry (HR-ICP-OES) method for assessing dose uniformity and (2) evaluate the uniformity of elemental doses in one DS and four FSMPs according to pharmacopoeial guidelines, with MPs included as reference materials. To achieve this, the key parameters of the HR-ICP-OES measurement methodology were defined to ensure reliable results, and the uniformity of the doses of the seven preparations was determined by establishing a pharmacopoeial acceptance value. Although HR-ICP-OES is useful for multi-element analysis of products, limitations have been identified relating to chemical and spectral interference, and to the analysis of selenium at low levels. Of the DSs and FSMPs analysed, none complied with the pharmacopoeial requirements for uniformity.