We describe direct analysis of self-assembled monolayers (
SAMs) on
copper surfaces by low temperature plasma (LTP) mass spectroscopy (MS). Two kinds of
SAMs formed from n-
dodecylmercaptan (NDM) and l-phenyl-5-mercaptotetrazole (PMTA) were prepared on
copper by spontaneous chemisorption. With the LTP probe, desorption and ionization of the
SAMs was easily achieved, and the
ions produced were introduced into MS for analysis. Characteristic fragment
ions from NDM
SAMs, mainly [M + M - H](+) (M is the NDM molecule) and from PMTA
SAMs, mainly [M + H - S](+) (M is the PMTA molecule), were both absent in the MS spectra of neat NDM and PMTA samples. This provided evidence of the formation of
SAMs on
copper. As a supplementary method, LTP-MS is helpful in obtaining information on the barrier properties of
SAMs on
copper, such as inhibitor efficiency (IE) and the surface adsorption concentration of
corrosive electrolyte (Γ*) surrounding
copper. Aiming for an evaluation of the reliability of LTP-MS, a comparative study of our method and the traditional method of cyclic voltammetry (CV) showed a correlation coefficient higher than 0.97. In addition, a rough, simple procedure for imaging of the distribution of the molecules adsorbed on
copper surface was presented. The study supplied a rapid and simple method for direct investigation of
SAMs on
copper.