Determination of melamine in milk powder by HPLC-tandem mass spectrometry

Importance of the topic

Ensuring the safety and quality of dairy products is a critical concern in food analysis. Melamine contamination in milk powder poses serious health risks, and its detection at trace levels is essential to protect consumers and comply with regulatory standards. A reliable assay for melamine enables timely screening and ensures product integrity in both industrial and quality-control laboratories.

Objectives and study overview

This study aimed to develop and validate an HPLC-tandem mass spectrometry method for quantifying melamine in milk powder. Using a Shimadzu LCMS-8030 triple-quadrupole system, the procedure covers sample extraction, chromatographic separation, and detection by multiple reaction monitoring (MRM) to achieve high selectivity and sensitivity.

Methodology and instrumentation

The analytical workflow followed China’s GB/T22388-2008 standard for dairy products.

• Instrument configuration: Shimadzu UFLC (LC-30A series) coupled to LCMS-8030 triple-quadrupole mass spectrometer with LabSolutions software.
• Chromatography: CAPCELL PAK CR (2.0 × 150 mm, 5 µm) column at 40 °C; isocratic elution with 10 mM ammonium acetate/2 mL acetic acid in water (40 %) and acetonitrile (60 %); flow rate 0.2 mL/min; injection volume 10 µL.
• Mass spectrometry: Electrospray ionization in positive mode; MRM transitions m/z 127.10→85.05 (quantifier) and 127.10→68.00 (qualifier); dwell time 300 ms; collision gas argon.
• Sample preparation: Milk powder samples were extracted and cleaned according to GB/T22388-2008. Calibration standards ranged from 0.01 to 0.5 mg/L prepared in blank matrix extract.

Main results and discussion

Linearity was demonstrated over 0.01–0.50 mg/L with a calibration curve correlation coefficient of 0.9998. Precision tests on standards at 0.01, 0.10, and 0.50 mg/L yielded retention-time RSDs below 0.64 % and peak-area RSDs below 4.34 %. Spike recovery at 0.01 mg/kg in milk powder averaged 104.0 %, meeting the 80–110 % requirement. Sensitivity evaluation returned a limit of detection of 0.0017 mg/L (S/N=3) and a limit of quantitation of 0.005 mg/L (S/N=10), corresponding to 0.005 mg/kg in the prepared sample.

Benefits and practical applications

This HPLC-MS/MS approach offers rapid analysis, high specificity via MRM, and the ability to quantify melamine at regulatory threshold levels. It is well suited for routine monitoring in food safety laboratories, supporting quality assurance and compliance with national and international standards.

Future trends and opportunities

Advancements may include integration of high-resolution mass spectrometry for improved compound identification, miniaturized or online sample preparation to increase throughput, and application of data-processing algorithms and machine learning to enhance peak detection and automate result interpretation.

Conclusion

The described method using the Shimadzu LCMS-8030 meets national requirements for melamine determination in milk powder, combining excellent linearity, precision, recovery, and sensitivity. It provides a robust tool for safeguarding dairy product quality.

References

• GB/T22388-2008 Determination of Melamine in Raw Milk and Dairy Products—Part II: LC-MS/MS Method