Componential analysis of pepper of various origins using DART-MS using ultra-fast polarity switching

Significance of the topic

Direct Analysis in Real Time Mass Spectrometry (DART-MS) offers a fast, minimal-prep route to assess food components under ambient conditions. Incorporating ultra-fast polarity switching allows simultaneous detection of positive and negative ions, expanding the range of detectable compounds and enabling comprehensive quality control and origin authentication of agricultural and processed food products.

Objectives and study overview

This study aimed to evaluate the capability of a DART-MS platform with ultra-fast polarity switching to distinguish peppers, sauces, and oils of various origins. A chemometric approach was used to interpret the combined positive/negative ion data and assess differences in chemical profiles related to geographic provenance and ingredient composition.

Methodology and instrumentation

Samples of commercial peppers (seeds, exodermis, endodermis), olive oils, soy sauces, and fish sauces were introduced directly into the ionization region using tweezers, glass capillaries, or metal mesh as appropriate. A DART-SVP ion source was coupled to a Shimadzu LCMS-2020 single quadrupole mass spectrometer. Ultra-fast polarity switching (15 ms) and a scan speed up to 15 000 u/s over m/z 100–1000 were employed. DART gas heater temperatures were compared at 200 °C, 350 °C, and 500 °C to optimize ionization for key analytes.

Main results and discussion

• Peppers: Capsaicin ([M+H]+ m/z 306, [M–H]– m/z 304) was detected in both modes, with highest response at 350 °C. Seed samples yielded the strongest signals, reflecting placental tissue residues.
• Sauces: Soy and fish sauces exhibited distinct low-molecular-weight fingerprints in both polarities, corresponding to varying amino acid and peptide compositions.
• Oils: At 500 °C, high-mass triglycerides such as diolein and triolein, along with squalene and oleic acid, were more prominent. Multivariate analysis of these profiles enabled differentiation by origin.

Practical benefits and applications

The method delivers rapid screening without chromatography, detecting a broad polarity range. It supports quality assurance, fraud detection, and authentication of spices, condiments, and edible oils in research and industrial laboratories.

Future trends and applications

Further integration of DART-MS with advanced chemometric models and machine learning will enhance differentiation of complex food matrices. Expanding this approach to environmental, pharmaceutical, and forensic surface screening could provide similarly rapid, in-situ analyses.

Conclusion

Ultra-fast polarity switching significantly enhances the scope of DART-MS for food analysis. Optimal gas heater settings are analyte-dependent, with 350 °C favoring capsaicinoids and higher temperatures improving triglyceride detection. The combined platforms offer a powerful tool for rapid origin discrimination.

Instrumentation

• DART-SVP ion source (IonSense, MA, USA)
• Shimadzu LCMS-2020 single quadrupole mass spectrometer
• Ultra-fast polarity switching (15 ms) and scan rate up to 15 000 u/s
• DART gas heater: 200 °C, 350 °C, 500 °C