Other Factors Influencing the Frequency Shift

Although Eq. (17.10) details six different factors that could affect the resonance frequency, there are additional phenomena that we might denote, somewhat 

If the surface of the sample is porous, small amounts of water may be occluded in the pores, influencing the observed frequency shift. Non-uniform current distribution during metal deposition leads to non-uniform thickness of the plated metal. These and some fine points in the design and operation of an electrochemical cell, where one side of the EQCM acts also as the working electrode, could all be lumped into the AJetc term, to interfere with the simple interpretation of the change in frequency observed as a change of mass. 

---