Detection of Isoflavones and Its Metabolites in Foods by DPiMS QT and LCMS-9030

Importance of the Topic

With growing interest in functional foods and health supplements, reliable detection of soy isoflavones in food matrices is critical to ensure product quality and label accuracy. Traditional chromatographic techniques require time-consuming separation steps that slow analytical throughput.

Objectives and Study Overview

This study evaluates a rapid, direct analysis approach combining a DPiMS QT electrospray ionization probe and an LCMS-9030 quadrupole time-of-flight mass spectrometer to detect key soy isoflavones (daidzein, genistein, glycitein) and their glycosides in various soybean-based foods.

Methodology and Sample Preparation

Samples of tofu, boiled soybeans, soy milk, and a soybean processed chocolate snack (10 mg each) were extracted by vortexing with 1 mL of 50% ethanol for 1 minute and centrifuged. A 10 μL aliquot of the supernatant was deposited onto a sample plate. The DPiMS QT probe repeatedly sampled and ionized material directly from the plate under an applied voltage, introducing ions into the mass spectrometer without chromatographic separation. Measurement time per sample was 0.5 minutes, with total sample preparation under 5 minutes.

Used Instrumentation

• DPiMS QT electrospray ionization probe kit
• Shimadzu LCMS-9030 quadrupole time-of-flight mass spectrometer

Main Results and Discussion

All target isoflavones and glycosides were successfully detected in tofu, boiled soybeans, and soy milk. The processed chocolate snack yielded signals for aglycones only. Mass errors across all compounds ranged from –2.4 to +2.2 ppm, demonstrating stable mass accuracy in complex food matrices. The absence of chromatographic separation did not compromise selectivity or sensitivity.

Benefits and Practical Applications

• Rapid screening of isoflavones in processed foods with minimal sample prep
• Avoidance of lengthy column separations, increasing sample throughput
• High mass accuracy ensures reliable identification in diverse matrices
• Suitable for quality control in food manufacturing and research laboratories

Future Trends and Potential Applications

Further integration of direct sampling probes and high-resolution mass spectrometry may expand analysis to other bioactive compounds in complex matrices. Automation of sample handling and data processing could support routine high-throughput screening in food safety, nutraceutical development, and metabolomics.

Conclusion

The combination of a DPiMS QT probe and LCMS-9030 enables fast, accurate detection of soy isoflavones and glycosides in food products without chromatographic separation. The method delivers stable mass accuracy and significantly reduces analysis time compared to conventional LC/MS workflows, offering a powerful tool for quality assurance in the food industry.