Analytical methods for phenyltin compounds in polychlorinated biphenyl-based transformer oil samples

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Polychlorinated biphenyl (PCB)-based transformer oils may contain tetraphenyltin (TePhT) as a stabilizer.
• Long-term use of TePhT can lead to the formation of other phenyltin compounds (PTs) like monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TrPhT).

Purpose of the Study:

• To develop and validate analytical methods for quantifying PTs in PCB-based transformer oils.
• To investigate the presence of PTs in used transformer oil samples.

Main Methods:

• Direct measurement of TePhT using gas chromatography (GC) with mass spectrometry (MS), flame photometric detection (FPD), or atomic emission detection (AED).
• Propylation of MPhT, DPhT, and TrPhT using a Grignard reagent followed by GC analysis.
• Comparison of detector sensitivity and selectivity for PT analysis, with MS showing the lowest detection limits.

Main Results:

• The mass spectrometer (MS) offered the highest sensitivity for PTs, with detection limits ranging from 0.60 ng/ml (TePhT) to 30 ng/ml (MPhT).
• Despite lower selectivity, MS provided acceptable analysis with minimal interference from the PCB matrix under typical conditions.
• Analysis of two used transformer oil samples confirmed the presence of TePhT and TrPhT.

Conclusions:

• The developed analytical methods are effective for determining PTs in transformer oil.
• TePhT and TrPhT are present in aged transformer oils, suggesting degradation of TePhT over time.