Analysis of Contaminated Samples by DPiMS-2020 (1): Detection of Surfactants in Beverages

Importance of the Topic

The risk of beverage contamination by dishwashing detergents and other surfactants poses serious public health and quality control challenges. Rapid, sensitive screening methods are essential to ensure consumer safety and to meet regulatory requirements in food and beverage analysis.

Objectives and Study Overview

This work aimed to develop a fast, simple, high-sensitivity screening technique for detecting surfactant contaminants in beverages. The study evaluated the applicability of probe electrospray ionization mass spectrometry (PESI-MS) using the Shimadzu DPiMS-2020 direct probe ionization mass spectrometer to detect dishwashing detergent residues in various drink matrices.

Methodology and Instrumentation

Sample preparation involved spiking commercial beverages (barley tea, carbonated drink, sports drink, milk tea) and water with seven household detergents (A–G), diluting with equal volumes of 2-propanol, and depositing 9 μL onto a dedicated probe plate. The PESI method uses a fine metal probe thrust into the liquid sample to directly electrospray adhering compounds into the MS. Key analysis parameters included a probe speed of 250 mm/s, ionization at ±2.45 kV, DL temperature 250 °C, and dual-mode data acquisition (negative mode 0–1 min, positive mode 1–2 min).

Major Findings and Discussion

All tested surfactant ions (e.g., alkyl sulfates, ether sulfates, amine oxides) were detected with signal-to-noise ratios ≥3 at contaminant levels as low as 0.005 % (50 μL/L). Limits of detection in most beverages were below 0.001 % (10 μL/L). Matrix effects were minimal due to the direct ionization approach, allowing reliable identification of target ions without extraction or clean-up steps.

Benefits and Practical Applications

• Rapid analysis (<2 min per sample) without complex sample preparation
• High sensitivity for low-level surfactant detection in diverse beverage matrices
• Robust performance with minimal matrix interference

Future Trends and Potential Applications

The PESI-MS approach on DPiMS-2020 is expected to extend to other food and beverage contaminants, including dyes, pesticides, and toxic adulterants. Integration with automation and high-throughput screening, as well as coupling with data-driven workflows, will further enhance routine QA/QC and forensic applications.

Conclusion

The direct probe ionization method coupled with the DPiMS-2020 instrument delivers a highly efficient, sensitive screening tool for surfactant contamination in beverages. Its simplicity, speed, and low detection limits make it a promising technique for widespread adoption in food safety laboratories.

Reference

1. Nakano S., Kamata H., Sasaki N., et al. J. Mass Spectrom. Soc. Jpn., 67(2), 53–63, 2019.
2. Wada M., et al. Application of probe electrospray ionization mass spectrometry to the analysis of poisons and drugs in adulterated foods and beverages. Jpn. J. Forens. Sci. Technol.