ICP-OES Analysis of Nutrient Elements for Labeling Compliance of Dietary Food Supplements

Importance of the Topic

Dietary supplements blend vitamins minerals herbs and other bioactive compounds that support health yet require stringent quality control to ensure label compliance and consumer safety. Accurate determination of major to trace elements addresses regulatory requirements under the US FDA EAM 4.4 and safeguards against contamination or misbranding.

Objectives and Study Overview

This study adapts the FDA Elemental Analysis Manual method EAM 4.4 for simultaneous measurement of 24 elements in dietary supplements using the Agilent 5900 vertical dual view ICP-OES. It evaluates method performance including calibration linearity detection limits recovery accuracy throughput and stability across a range of commercially available supplement formats.

Methodology and Instrumentation

Sample Preparation and Digestion
• Tablets capsules and powders were homogenized and digested via microwave assisted acid digestion following EAM 4.4 protocols.
• Each 0.5 g sample received HNO3 H2O2 and water then heated to 200 °C in a closed vessel system.

ICP-OES Analysis
• Agilent 5900 Synchronous Vertical Dual View ICP-OES in axial mode coupled with SPS 4 autosampler.
• Standard sample introduction system with SeaSpray concentric nebulizer cyclonic spray chamber and cooled cone interface.
• Solid state 27 MHz RF generator and high-speed Vista Chip III CCD detector.

Software Tools
• IntelliQuant Screening for rapid semiquantitative profiling and interference assessment.
• Intelligent Rinse to dynamically adjust wash times between samples optimizing argon consumption and throughput.
• MultiCal to merge multiple wavelengths per element for extended dynamic range in axial view.
• Fitted Background Correction and FACT algorithms to correct spectral overlaps.

Main Results and Discussion

Calibration and Detection Limits
• Linear calibration achieved for all 24 elements with correlation coefficients above 0.9998.
• Limits of quantification well below EAM 4.4 nominal requirements ensuring regulatory compliance.

Accuracy and Precision
• Recovery of certified elements in NIST SRM 3280 and 1570a ranged within ±10% of reference values.
• Spike recovery in fortified blanks and fortified analytical portions maintained within ±10% across low to high concentrations.
• Long-term stability over 7 hours showed QC recoveries within ±10% without recalibration.

Sample Analysis
• Five commercial supplements (spirulina plant iron berry concentrate St Johns wort herbal adaptogen) exhibited excellent reproducibility with RSD and RPD values below 7% and 20% respectively.

Benefits and Practical Use of the Method

• Comprehensive simultaneous analysis from major to trace elements in a single run.
• Robust interference management with background correction intelligent screening and optimized rinse cycles.
• Flexible dynamic range using MultiCal facilitates accurate quantification of widely varying elemental concentrations.
• High sample throughput and reduced argon usage support routine QC workflows.

Future Trends and Potential Applications

• Integration of automated sample preparation and on-line monitoring to further enhance throughput.
• Expansion to other food and botanical matrices requiring multielement profiling.
• Incorporation of machine learning algorithms in spectral deconvolution and method optimization.
• Development of portable plasma-based devices for field screening of supplements.

Conclusion

The adapted Agilent 5900 ICP-OES method following FDA EAM 4.4 delivers accurate reliable and high-throughput multielement analysis for dietary supplements. Key software tools and instrumentation features ensure regulatory compliance robust interference control and cost-effective operation making this approach ideal for routine QA/QC laboratories.

References

• US Food and Drug Administration Dietary Supplement Labeling Guide April 2005
• US Food and Drug Administration Dietary Supplements June 2022
• Grand View Research Dietary Supplements Market Size Report 2022-2030 March 2022
• Mindak WR Dolan SP FDA Elemental Analysis Manual EAM 4.4 2010
• Agilent 5900 Synchronous Vertical Dual View ICP-OES Application Note 5994-5874EN 2023
• Agilent ICP Expert Pro Software User Guide 2023
• Agilent Intelligent Rinse for ICP-OES Technical Overview 5991-8456EN
• Agilent IntelliQuant Screening Theory and Practice 5994-1518EN
• Agilent Background Correction Techniques for ICP-OES 5991-8452EN
• US FDA Elemental Analysis Manual Section 3.2 Version 3.0 December 2021