Determination of chlorate and perchlorate in powdered infant formula using ion chromatography-mass spectrometry

Importance of the Topic

Trace levels of chlorate and perchlorate in food pose health concerns for infants and young children. Chlorate can arise from disinfectants such as sodium hypochlorite and chlorine dioxide used in dairy processing, while perchlorate can enter the food chain via agricultural fertilizers. Excessive intake of these oxychlorine anions may interfere with iodine uptake and thyroid function. Robust analytical methods are required to monitor contaminant levels in powdered infant formula and ensure compliance with emerging regulatory limits.

Goals and Study Overview

This study aimed to establish and validate a sensitive, accurate ion chromatography–mass spectrometry (IC-MS) method for simultaneous quantification of chlorate and perchlorate in powdered infant formula. The objectives included optimizing sample preparation, chromatographic separation, mass spectrometric detection, calibration strategy, and demonstrating method performance through recovery, precision, and real-sample analysis.

Methodology

Sample preparation involved spiking 0.1 g of formula powder with ^18O-labeled internal standards for chlorate and perchlorate, dissolution in 0.02 % NaOH, and ultrafiltration. A potassium hydroxide gradient (5–80 mM) was generated electrolytically and delivered at 0.25 mL/min through a Dionex IonPac AS20 column. Suppressed conductivity detection was combined with negative-mode electrospray ionization on an ISQ EC single quadrupole mass spectrometer. Selected ion monitoring (SIM) targeted m/z 83/85 for chlorate, m/z 99/101 for perchlorate, and corresponding m/z 89 and 107 for internal standards. A standard addition calibration was used to compensate for matrix effects.

Instrumentation

• Thermo Scientific Integrion HPIC system with eluent generator, pump, degasser, conductivity detector, column oven
• Dionex IonPac AG20 guard and AS20 analytical columns
• Dionex ADRS 600 suppressor and CR-ATC 600 trap column
• Autosampler with 250 µL syringe
• Thermo Scientific ISQ EC single quadrupole MS with auxiliary pump and nitrogen generator

Main Results and Discussion

Baseline separation of chlorate and perchlorate was achieved within a 50 min run time. Isotopic ratio confirmation ensured specificity. Calibration curves were linear from 0.05 to 2 mg/kg (r2 > 0.9998). Method detection limits reached 0.05 mg/kg (equivalent to 0.25 µg/L). Recoveries ranged from 99.6 to 105 % across three fortification levels. Intra- and inter-day precision exhibited RSDs below 5 %. Analysis of six formula brands revealed chlorate levels between 0.0656 and 2.16 mg/kg; perchlorate was not detected above the method limit.

Benefits and Practical Applications

• The IC-MS approach offers high sensitivity, selectivity, and accuracy for routine quality control.
• Standard addition calibration compensates for complex matrix effects typical of food samples.
• Matrix diversion and suppressor regeneration limited MS source contamination and extended uptime.
• Suitable for compliance monitoring under evolving regulatory standards.

Future Trends and Opportunities

Advances may include coupling with high-resolution MS for further specificity, automating sample workflows for higher throughput, miniaturizing systems for on-site monitoring, and extending the method to other complex food and environmental matrices. Evolving regulations will drive demand for increasingly sensitive and rapid screening tools.

Conclusion

A robust IC-MS method was developed and validated for determination of chlorate and perchlorate in powdered infant formula. It demonstrated excellent sensitivity, linearity, precision, and recovery. The approach can support regulatory compliance and routine quality assurance in dairy and food industries.

References

• McCarthy W. et al. Chlorate and other oxychlorine contaminants within the dairy supply chain. Compr. Rev. Food Sci. Food Saf. 2018, 17, 1561–1575.
• European Commission. Chlorate. https://ec.europa.eu/food/plant/pesticides/chlorate_en (2015).
• Lange’s Handbook of Chemistry, 15th Ed., Dean J. A., McGraw-Hill, New York, 1999.
• Thermo Scientific App. Update 72507. Determination of perchlorate in environmental waters by IC–MS. 2020.