Simultaneous Analysis of Benzotriazole, Tolutriazole Derivatives and Furanic Compounds: Passivators in Insulating Oil

Significance of the Topic

This study addresses the critical need to monitor both protective additives and degradation products in transformer and condenser insulating oils. Benzotriazole and tolutriazole derivatives prevent metal corrosion, while furanic compounds indicate cellulose breakdown in paper insulation. Simultaneous tracking of these markers ensures reliable maintenance and failure prevention.

Study Objectives and Overview

The main goal was to develop and validate a high-performance liquid chromatography (HPLC) protocol capable of quantifying benzotriazole (BTA), its derivative TTAA, and five key furanic compounds in a single run. Building on ASTM D5837-15 and BS148:2009 guidelines, the method was optimized for speed, sensitivity, and robustness.

Methodology and Instrumentation

Samples of insulating oil underwent a simple pretreatment: mixing with acetonitrile, centrifugation, dilution with water, then injection (15 µL). Chromatographic separation used a Prominence-i HPLC system equipped with a Shim-pack VP-ODS column (250 × 4.6 mm, 5 µm). A water/acetonitrile gradient (15–45% B over 0–10 min, 100% B hold to 20 min, return to 15% to 30 min) ran at 1.0 mL/min, 40 °C. Detection employed PDA at 220, 260 and 280 nm.

Key Results and Discussion

Chromatograms demonstrated baseline separation of BTA, TTAA isomers, and five furanic compounds within 11 minutes. Calibration curves showed excellent linearity (r² > 0.9999) over 100–20 000 µg/L for BTA/TTAA and 5–1 000 µg/L for furans. Recovery tests (n=3) yielded 79–122% with RSD < 2%. Accelerated aging at 150 °C for 48–96 h revealed increasing furanic levels and detectable BTA in select oil samples, confirming method applicability.

Benefits and Practical Applications

• Combines two standard analyses into one HPLC run, halving analysis time.
• Achieves high sensitivity and precision for both passivators and degradation markers.
• Supports preventive maintenance by providing a comprehensive oil quality assessment.

Future Trends and Applications

Advances may include coupling the protocol to mass spectrometry for lower detection limits and enhanced specificity, miniaturizing sample preparation with automated solid-phase extraction, and integrating inline monitoring for real-time transformer health diagnostics.

Conclusion

The optimized HPLC method reliably quantifies corrosion inhibitors and furanic degradation products in insulating oil in a single analysis. Its high accuracy, speed, and practicality make it a valuable tool for quality control and predictive maintenance in power equipment.

Reference

• BS148:2009 – British Standard for Passivator Analysis in Insulating Oil
• ASTM D5837-15 – Standard Test Method for Furanic Compounds in Insulating Oil