  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.
