  Often a surface sensitive analytical technique in combination with sample
erosion by inert ion sputtering is used for compositional in-depth analysis of
solid state samples. Layer by layer the sample gets eroded and then the
composition of the actual surface is estimated. The elemental detection limits
can be increased by spending more time for the measurement in each sputter
depth of the profile measurement. But during this time a significant sample
surface recontamination with the element under investigation via adsorption
form the vacuum has to be avoided. Commonly the vacuum quality of an analytical
instrument is monitored using the base pressure of the UHV system. This article
presents a novel method, which improves this crude approach. The
recontamination of a sputtered Ti surface by adsorbed residual gas particles
was used to monitor the sputter depth profile specific vacuum condition of an
XPS microprobe Quantum 2000 over a 4 years period. This new method is suitable
to monitor the condition of every sputter depth profiling instrument.
