Quantification of Persistent Organic Pollutants in Dietary Supplements Using Stir Bar Sorptive Extraction Coupled with GC-MS/MS and Isotope Dilution Mass Spectrometry

Importance of the Topic

A growing number of consumers rely on plant extract based dietary supplements for health benefits yet these products may contain persistent organic pollutants that bioaccumulate and pose risks to human health. Reliable methods for trace level quantification of PAHs and organochlorine pesticides in complex botanical matrices are essential to ensure product safety and regulatory compliance.

Objectives and Study Overview

The study aimed to develop and validate a stir bar sorptive extraction method coupled with GC-MS/MS and isotope dilution mass spectrometry for accurate, precise, and sensitive quantification of PAHs and OCPs in commercially available dietary supplements. Twelve products were screened to assess typical contaminant levels and compare daily intake estimates with health guidelines.

Methodology and Instrumentation

Sample Preparation

• Weighed 1 g of powdered supplement, added 2 mL acetonitrile and 8 mL water
• Extracted for 60 min at 1200 rpm using 10 mm × 0.5 mm PDMS stir bars
• Rinsed and dried stir bars prior to thermal desorption

Instrumental Setup

• GERSTEL MultiPurpose Sampler with Thermal Desorption Unit and CIS cooled injection
• Agilent 7890B GC coupled to 7010 triple quadrupole MS/MS
• HP-5 MS column, helium carrier at 1.2 mL/min, oven 40 °C to 290 °C at 10 °C/min
• Multiple reaction monitoring of native analytes and 13C or D-labelled analogues

Quantification Technique

• Isotope dilution mass spectrometry used to eliminate matrix effects and calibration curve preparation
• Direct calculation of analyte concentration from measured isotope ratios following EPA Method 6800 principles

Key Results and Discussion

Extraction Optimization

• Best recoveries obtained with 2 mL acetonitrile and 8 mL water, 60 min extraction
• Recoveries reached equilibrium after 60 min for most PAHs and OCPs

Method Performance

• IDMS accuracy error mean 7.2 %; RSD mean 8.3 %
• Calibration curves without internal standards exhibited errors > 30 % at low concentrations
• GC-MS/MS LOQs were 0.01–0.5 ng/g, roughly two orders of magnitude lower than GC-MS

Real Sample Screening

• Twelve commercial supplements contained on average 12 analytes each
• PAHs such as naphthalene, phenanthrene and benzo[a]pyrene frequently exceeded 1 ng/g
• DDT detected in 8 samples, other organochlorine pesticides less common
• Estimated daily intakes remained below ATSDR minimal risk and OEHHA Proposition 65 limits
• Some sample daily intakes of benzo[a]pyrene and benz[a]anthracene approached half of regulatory thresholds

Benefits and Practical Applications

• High sensitivity and accuracy at low ng/g levels supports toxicological risk assessment
• IDMS minimizes matrix effects and calibration steps, reducing analysis time sixfold
• Automated SBSE and thermal desorption streamlines sample throughput for quality control labs
• GC-MS/MS selectivity lowers interferences in complex botanical matrices

Future Trends and Potential Applications

Opportunities include extending SBSE-IDMS workflows to additional contaminants such as brominated flame retardants, adapting protocols for biological fluids or environmental samples, further miniaturizing stir bars for microextraction, and integrating high-throughput autosamplers for routine monitoring in pharmaceutical and food industries.

Conclusion

The developed SBSE-GC-MS/MS-IDMS method provides robust, efficient quantification of PAHs and OCPs in plant-based dietary supplements at trace levels. It demonstrated superior precision and accuracy over conventional calibration approaches and is suitable for regulatory testing and consumer safety assessment. None of the surveyed products exceeded established daily exposure limits, although some contaminants approached concern thresholds.

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