Fast determination of inorganic cations and low mass amines in a spoiled grape juice sample using IC-MS

Significance of the Topic

The reliability of analytical methods is critical for food and beverage testing to meet labeling regulations, maintain product quality, and detect spoilage or contamination. Complex matrices such as spoiled grape juice present significant analytical challenges that require sensitive and selective techniques.

Objectives and Study Overview

This study aimed to develop a rapid ion chromatography–mass spectrometry method for the simultaneous determination of inorganic cations (sodium, ammonium, potassium, magnesium, calcium) and low-mass amines (dimethylamine, ethylamine, monoethanolamine, diethylamine, triethanolamine) in a moldy grape juice sample within a six-minute run time.

Methodology

• Sample preparation: 1000-fold dilution of spoiled grape juice with deionized water.
• Chromatographic separation: Thermo Scientific Dionex IonPac CG12A-5μm and CS12A-5μm columns (3 mm I.D.) using 33 mM methanesulfonic acid eluent at 0.5 mL/min and column temperature of 30 °C.
• Suppression: Thermo Scientific Dionex CERS 500e in external water mode at 0.7 mL/min.
• Detection: suppressed conductivity and Thermo Scientific ISQ EC single quadrupole MS with HESI II source in positive mode, acquiring full scan (18–250 m/z) and SIM data.

Used Instrumentation

• Dionex Integrion HPIC system with RFIC model, dual high-pressure divert valve, and conductivity detector.
• Dionex AS-AP autosampler and AXP-MS auxiliary pump for suppressor water supply.
• Thermo Scientific ISQ EC single quadrupole mass spectrometer with HESI II probe.
• Chromeleon CDS software v7.2 SR6 for data acquisition and processing.

Results and Discussion

• Successful baseline separation and detection of all target ions within six minutes.
• SIM mode delivered high sensitivity (E3–E5 ion counts), with calcium showing the lowest response (~3×10^2 counts).
• Monoethanolamine and diethylamine, undetectable by conductivity, were clearly identified by MS.
• Symmetric peaks and low baseline noise (<1 µS-min) demonstrate robustness in a complex sample matrix.

Benefits and Practical Applications

• High-throughput workflow suitable for QA/QC laboratories in the food and beverage industry.
• Enhanced selectivity and lower detection limits compared to conductivity-only detection.
• Comprehensive analysis of inorganic and organic ionic species in a single run to streamline testing.

Future Trends and Potential Applications

• Extension to a wider range of ionic analytes, including larger organic acids and emerging contaminants.
• Coupling with high-resolution mass spectrometry for non-target screening and structural characterization.
• Automation of sample prep and data handling to support large-scale regulatory testing.
• Application to other complex matrices such as fermented beverages, dairy products, and environmental samples.

Conclusion

The presented IC–MS method delivers a rapid, sensitive, and selective approach for simultaneous quantification of inorganic cations and low-mass amines in spoiled grape juice. The combination of suppressed conductivity and single quadrupole MS enhances detection capability, offering a valuable tool for routine food quality and safety monitoring.

Reference

1. Wang J and Schnute WC. Optimizing mass spectrometric detection for ion chromatographic analysis. Rapid Commun Mass Spectrom. 2009;23(21):3439–3447.
2. Thermo Fisher Scientific. Specific and Selective Detection for Food and Beverage Analysis by Ion Chromatography–Mass Spectrometric Detection. White Paper 70424; 2016.
3. Thermo Fisher Scientific. Identification and Quantification at ppb Levels of Common Cations and Amines by IC–MS. Application Note 269.