Variable-Capacitance Measurement System to Detect Sodium Dodecyl Sulfate in Pure Liquids

Sodium dodecyl sulfate (SDS) is an anionic surfactant and is listed as an emerging contaminant due to its excessive use in industrial settings and homes. Therefore, there is a need to develop new detection methods for SDS particles that provide easy-to-interpret responses at reasonable times, to complement the established analytical methods. In this letter, we introduce a variable-capacitance measurement system (VCMS) and its associated methodology for detecting the presence of SDS particles in pure liquids. Using a microliter liquid sample, the system records in terms of capacitance, the effects due to the presence of SDS on the evaporation kinetics and lifetime of a sample in vaporization. This unexplored electrical measurement perspective provides simple traces as a function of the volumetric changes of the droplet. The high resolution and sensitivity of the system, allow it to detect the presence of SDS particles in the order of 1 mgL
$^{-1}$
, complying with regulatory requirements. Finally, the proposed VCMS can provide information in a relatively short time and has potentiality in quality control applications.