Analysis of Perchlorate in Infant Formula by Ion Chromatography-Electrospray-Tandem Mass Spectrometry (IC-ESI-MS/MS)

Importance of the Topic

Perchlorate is a persistent environmental contaminant that enters the food chain and can impair thyroid hormone production by blocking iodine uptake. Infants are particularly vulnerable to disrupted thyroid function, making the accurate determination of perchlorate in infant formula and milk essential for consumer safety and regulatory compliance.

Study Objectives and Overview

This study aimed to develop a streamlined and ultra-sensitive ion chromatography–electrospray tandem mass spectrometry (IC-ESI-MS/MS) method for quantifying perchlorate in powdered and liquid infant formula as well as milk. The approach emphasizes minimal sample preparation, rapid analysis, and reliable confirmation of analyte identity.

Methodology and Instrumentation

Sample Preparation

• Mix 4 mL of infant formula or milk with 4 mL of cold ethanol.
• Spike with isotope-labeled perchlorate internal standard (100 ng/mL).
• Vortex, centrifuge at 5000 rpm under refrigeration, and filter the supernatant.
• Collect filtrate in autosampler vials for direct IC-MS/MS injection.

Chromatographic Conditions

• System: Thermo Scientific Dionex ICS-3000 RFIC.
• Guard and analytical columns: AG16/AS16 hydroxide-selective anion exchange.
• Suppressor: Dionex ASRS 300 in external water mode.
• Eluent: isocratic 45 mM KOH (EGC III).
• Flow rate: 300 µL/min; column temperature: 30 °C; injection volume: 100 µL.
• Post-column addition of 150 µL/min acetonitrile for MS compatibility.

Mass Spectrometry Conditions

• Instrument: Thermo Scientific TSQ Quantum Access triple quadrupole with ESI source.
• Ion mode: negative; spray voltage: 4000 V; capillary temperature: 300 °C.
• Gas pressures: sheath 40, sweep 15, auxiliary 5 (arbitrary units); collision gas pressure: 1.8 mTorr.
• Scan mode: selected reaction monitoring (SRM) transitions:
  – m/z 99→83 (35ClO4−→35ClO3−) quantitative
  – m/z 101→85 (37ClO4−→37ClO3−) confirmatory
  – m/z 107→89 internal standard quantitation

Key Results and Discussion

The method achieved a detection limit of 5 pg/mL (S/N>10) and a linear calibration range from 20 pg/mL to 10 000 pg/mL with R2 values >0.9996. Recoveries in spiked samples ranged from 103% to 114%, and precision was high (RSD ≤3.6%). Analysis of commercial formulas and milk revealed perchlorate levels between 1.05 and 2.44 ng/mL in infant formulas and 4.64 ng/mL in milk, demonstrating the method’s capability to detect typical contamination levels without interferences.

Benefits and Practical Applications

By eliminating time-consuming solid phase extraction and employing a simple protein precipitation and filtration protocol, the workflow reduces preparation time by several hours. The high sensitivity and reproducibility make this IC-MS/MS approach suitable for routine monitoring in food safety laboratories, regulatory testing, and quality assurance of infant nutrition products.

Future Trends and Potential Applications

Continued advances may include automated high-throughput sample handling, further miniaturization, and coupling with high-resolution mass spectrometry for broader contaminant screening. Extension of this methodology to other anions and complex food matrices will enhance environmental and food quality surveillance.

Conclusion

An efficient IC-ESI-MS/MS procedure was established for the sensitive, accurate, and precise quantitation of perchlorate in infant formulas and milk. The streamlined sample preparation and robust analytical performance support its adoption for food safety monitoring and health risk assessment.

References

1. Schier JG, Wolkin AF, Valentin-Blasini L, Belson MG, Kieszak SM, Rubin CS, Blount BC. Perchlorate exposure from infant formula and comparisons with the perchlorate reference dose. Journal of Exposure Science and Environmental Epidemiology. 2009; advance online publication. doi:10.1038/jes.2009.18.