New detection cell for piezoelectric quartz crystals: frequency changes strictly follow Bruckenstein and Shay's equation in very dilute non-electrolyte aqueous solutions

Abstract

Using a newly designed detection cell called a ‘loading-free’ detection cell, the oscillation frequencies were measured in various non-electrolyte solutions, and the frequency changes from those in pure water, ΔF, were plotted against the changes of √ρη from those in pure water, Δ√ρη, where ρ and η, respectively, are the density and viscosity of the solution. For very dilute solutions of various non-electrolytes, the relationship between ΔF and Δ√ρη exactly follows Bruckenstein and Shay's equation [F=–2.26 × 10^–6nF_b^3/2√ρη where F_b is the basic frequency of the crystal and n the number of surfaces exposed to the solution (n= 1 or 2)]. The ρη values at which the data started to deviate from the equation depended on the solutes used. The relationship between ΔF and Δ√ρη for electrolyte solutions was also examined.