Analysis of ZDDP content and thermal decomposition in motor oils using NAA and NMR

TL;DR

This study compares neutron activation analysis and NMR techniques to measure ZDDP content and thermal decomposition in motor oils, offering potentially more accurate analysis methods for additive quantification.

Contribution

It introduces the use of NAA and 31P-NMR for analyzing ZDDP content and thermal decomposition in motor oils, providing alternative methods to traditional ICP-AES.

Findings

NAA can determine Zn concentrations with potentially higher accuracy.

31P-NMR reveals thermal decomposition behavior of ZDDPs.

Analysis of commercial oils and additives demonstrates method applicability.

Abstract

Zinc dialkyldithiophosphates (ZDDPs) are one of the most common anti-wear additives present in commercially-available motor oils. The ZDDP concentrations of motor oils are most commonly determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). As part of an undergraduate research project, we have determined the Zn concentrations of eight commercially-available motor oils and one oil additive using neutron activation analysis (NAA), which has potential for greater accuracy and less sensitivity to matrix effects as compared to ICP-AES. The 31P nuclear magnetic resonance (31P-NMR) spectra were also obtained for several oil additive samples which have been heated to various temperatures in order to study the thermal decomposition of ZDDPs.