Dietary Supplements Analysis

Importance of the Topic

Dietary supplements must meet regulatory requirements for uniformity, purity and accurate labeling to protect public health and ensure consumer confidence. In the United States, FDA’s cGMP regulation (21 CFR Part 111) and USP–NF standards define official test methods for vitamins and minerals. With a growing global supplement market, reliable analytical methods are crucial for quality control, regulatory compliance and product development.

Objectives and Study Overview

This application note demonstrates USP-compliant analytical procedures for multivitamin and multimineral tablets. It reviews methods for quantifying fat-soluble vitamins (A, D, E), water-soluble vitamins (B complex, C), and essential minerals using HPLC and atomic absorption spectrometry. The study uses commercially available “Multivitamin & Mineral” tablets to illustrate sample preparation, system suitability tests, quantitation and comparison with labeled values.

Methodology and Instrumentation

All procedures follow USP32-NF27 official test chapters. Key instrumentation included:

• HPLC systems (Shimadzu Prominence, LC-2010CHT) with SPD-M20A photodiode array detector for vitamin analysis
• Shimpack VP-ODS or Luna NH2 columns for reversed-phase or normal-phase separations
• Shimadzu AA-7000 atomic absorption spectrophotometer for mineral quantitation

Sample preparation varied by analyte category:

• Fat-soluble vitamins: organic extraction, hexane partitioning, sample heating and HPLC injection
• Water-soluble B vitamins: acid-water/acetonitrile extraction, ion-pair reversed-phase HPLC
• Minerals: ashing or wet digestion (HCl or HNO₃/HClO₄), matrix modifiers for Ca/Mg, followed by AAS measurement

Main Results and Discussion

System suitability criteria (resolution, tailing factor, RSD) met USP requirements for all analytes. Quantitative findings for the test tablets showed:

• Vitamin A content higher than label due to presence of β-carotene contribution
• Vitamin D, E, B group vitamins and vitamin C within 90–110% of declared values
• Essential minerals (Ca, Cu, Fe, Mg, Mn, K, Se, Zn) aligned with label claims; molybdenum was below detection limits in the sample

The results highlight the importance of choosing appropriate methods (normal vs. reversed phase for fat-soluble vitamins) and verifying label claims, especially for provitamin contributors.

Benefits and Practical Applications

By applying USP official methods, laboratories can ensure:

• Regulatory compliance with FDA cGMP requirements
• High accuracy and reproducibility of vitamin and mineral assays
• Detection of labeling discrepancies, enhancing consumer safety
• Standardized approaches enabling cross-laboratory comparability

Future Trends and Opportunities

Advances are expected in several areas:

• Hyphenated techniques (e.g., LC-MS) for improved sensitivity and selectivity
• Miniaturized and automated sample preparation for higher throughput
• Green chemistry approaches reducing solvent use
• Expanding USP methods to novel matrices (gummies, liquids, botanical extracts)
• Data integration with informatics and AI for method optimization

Conclusion

USP-guided HPLC and atomic absorption methods provide robust, validated protocols for comprehensive dietary supplement analysis. These procedures support quality assurance, regulatory adherence and accurate product labeling. Adapting and harmonizing such standards globally will strengthen consumer protection and drive innovation in supplement testing.

Reference

• FDA Code of Federal Regulations Title 21, Part 111 “cGMP for Dietary Supplements”
• United States Pharmacopeia–National Formulary (USP32–NF27) Official Test Methods
• Shimadzu Application Note LAAN-C-XX-E008, Dietary Supplements Analysis