High-speed Simultaneous Analysis of Passivators and Furanic Compounds in Insulating Liquid

Significance of the Topic

Monitoring both passivators and furanic degradation products in electrical insulating liquids is critical for assessing the condition and remaining life of high-voltage equipment. Traditional methods require separate analyses under British and ASTM standards, leading to increased turnaround time, labor, and consumable costs. A unified, high-speed approach enables more efficient health checks of transformers and other oil-filled devices.

Objectives and Study Overview

This study aimed to integrate two established HPLC methods into a single ultra-high-performance liquid chromatography (UHPLC) protocol on the Nexera X3 platform, achieving rapid and simultaneous quantification of benzotriazole-type passivators and five key furanic compounds in insulating oil.

Methodology and Used Instrumentation

Standard solutions of benzotriazole (BTA), tolutriazole derivatives (as Irgamet® 39), and five furanics (5HMF, 2FOL, 2FAL, 2ACF, 5MEF) were prepared in acetonitrile and water. Sample pretreatment followed the ASTM protocol: oil extraction with acetonitrile, vortex mixing, centrifugation, and aqueous dilution.

• UHPLC system: Shimadzu Nexera X3
• Column: Shim-pack XR-ODS III (75 × 2.0 mm I.D., 1.6 µm)
• Mobile phase: water (A) / acetonitrile (B), gradient from 20 % to 90 % B in 1 min, then to 100 % B
• Flow rate: 0.7 mL/min; column temp: 50 °C; injection: 5 µL
• Detection: PDA at 220, 260, 280 nm

Main Results and Discussion

The optimized method achieved baseline separation of all seven analytes within a 1 min run (5 min total cycle). Calibration curves showed excellent linearity (r2 > 0.9999) over 200–20 000 µg/L for passivators and 10–1000 µg/L for furanics. Repeatability RSDs were below 0.24 % for all compounds. Recovery tests in spiked white oil yielded 86–102 % with RSD ≤ 1.4 %, confirming the validity of the pretreatment.

Benefits and Practical Applications

By merging two analyses into one rapid protocol, laboratories can:

• Reduce total analysis time from 30 min to 5 min
• Minimize instrument downtime and method switching effort
• Lower solvent and consumable usage through combined pretreatment
• Enhance throughput for routine transformer oil monitoring

Future Trends and Application Potential

Potential developments include:

• Integration with automated online sampling for real-time condition monitoring
• Coupling with mass spectrometry for expanded analyte panels and lower detection limits
• Miniaturized or portable UHPLC systems for field diagnostics
• Data-driven alerts through AI models trained on large datasets of degradation markers

Conclusion

The UHPLC method on Nexera X3 delivers fast, reliable, and simultaneous quantification of passivators and furanic compounds in insulating oil. It streamlines laboratory workflows, reduces costs, and supports more frequent and informative condition assessments of electrical equipment.