Quick Screening and Quantitative Analysis of Carcinogens in Medicinal Plants Using DPiMS™-8060

Significance of the Topic

Rapid and reliable detection of carcinogenic compounds in medicinal plants is crucial for safeguarding public health. Conventional LC and LC/MS methods require time-consuming chromatographic separation, extensive sample cleanup, and significant solvent consumption. Probe electrospray ionization (PESI) offers a direct, high-throughput alternative that simplifies pretreatment and accelerates analysis.

Objectives and Study Overview

This study aimed to develop and validate a rapid screening and quantitative method for four aristolochic acids (A–D) and their metabolite aristolactam I in Aristolochia debilis and Asiasarum sieboldii. Naproxen was employed as an internal standard to enable accurate quantitation using the Shimadzu DPiMS-8060 direct probe ionization mass spectrometer.

Methodology and Instrumentation

Sample preparation involved:

• Crushing 100 g of dried herb and sieving to <0.35 mm particles.
• Extracting 0.2 g of sample with 20 mL methanol/water (70/30, v/v) via 40 min ultrasonic treatment.
• Adjusting the extract to 25 mL, collecting 20 µL supernatant and diluting to 1 mL with ethanol/water (60/40, v/v) containing 2 mM ammonium formate and 10 ppb naproxen.
• Applying 10 µL of diluted sample directly onto the PESI plate for analysis.

Instrumentation Used

The DPiMS-8060 system integrates a probe electrospray ionization (PESI) source with a triple quadrupole LCMS-8060. Key parameters included a 2.3 kV positive/–3.0 kV negative interface voltage, 30 °C heat block temperature, and a probe cycle speed of 2.78 Hz. No chromatographic column or mobile phase was required.

Main Results and Discussion

Calibration curves for all analytes showed excellent linearity (R2 ≥ 0.999) over 0.05–50 µg/L. Limits of detection ranged from 0.04 to 0.66 µg/L, and limits of quantitation from 0.13 to 1.99 µg/L. Repeatability (n=6) yielded RSD values ≤ 15% for most conditions, reflecting acceptable precision for PESI measurements. Spike-recovery tests in both herbs produced recoveries of 85.5–146% at low spiking (1 µg/L) and 60.1–151% at high spiking (20 µg/L). Analysis time was approximately 20 s per sample. In real-sample measurements, H. aristolochiae contained high levels of aristolochic acid D (90.4 µg/g) and moderate amounts of A, B, C, and aristolactam I, while A. sieboldii showed elevated aristolactam I (82.0 µg/g) and acid D (36.5 µg/g).

Benefits and Practical Applications

The PESI-based method offers:

• Ultrafast analysis without chromatographic separation.
• Reduced solvent use and simplified sample workflow.
• High sensitivity and acceptable precision for trace carcinogen screening.
• Flexibility to measure a wide range of ESI-compatible compounds.

Future Trends and Opportunities

Advances may include integration with automated sampling platforms, expansion to other classes of harmful or bioactive compounds, and on-site field screening devices. Coupling PESI with high-resolution or hybrid mass analyzers could further enhance specificity and broaden application scope.

Conclusion

Probe electrospray ionization on the Shimadzu DPiMS-8060 enables rapid, sensitive, and straightforward quantitation of carcinogenic aristolochic acids and aristolactam I in medicinal herbs. This approach holds promise for routine high-throughput screening and quality control in natural product analysis.

Reference

Application No. B109, Shimadzu Corporation, 2020.