Advancements in Electrochemical and Optical Detection, Quantification, and Characterization of Cosmetic/Industrial Polyelectrolytes

Polyions are polymers that contain significant numbers of positive and/or negative charges dispersed along their polymeric chains. Polyquaternary ammonium salts (i.e., polyquaterniums (PQs)) are cationic polyions (polycations) that derive their positive charges from quaternary ammonium groups. These polycations have found increased use in various cosmetic and industrial applications (e.g., hair conditioning formulations, lotion formulations, water treatment processes, etc.). As PQs are used in many applications it is imperative to develop simple devices/methods to quantitate and characterize these species. This dissertation examines the application of various electrochemical and optical sensing technologies to the study of four PQs (i.e., PQ-2, PQ-6, PQ-10, and poly(2-methacryloxyethyltrimethylammonium) chloride (PMETAC)). Chapter 1 provides an overview of the most significant advancements in electrochemical and optical polyion sensing technologies and applications over the last 25+ years. Chapter 2 explores the application of established electrochemical polyion sensing technology for the detection of PQ-10 in commercially relevant sample mixtures. These samples contain both sodium lauryl sulfate (SLS) and PQ-10. However, SLS can generate significant negative response signals when using single-use polyanion-sensitive ion-selective electrodes (ISEs) as detectors to detect PQ-10 indirectly via potentiometric titrations. However, it was determined that subjecting SLS/PQ-10 mixtures to an anion-exchange resin reduces the amount of SLS to a level at which there is negligible interference observed. Further, the remaining PQ-10 is shown to be detectable within the range of 0 – 80 µg/mL by titration with dextran sulfate (DS). Chapter 3 describes the application of single-use polyion-sensitive ISEs to the quantification and characterization of PQ-2 PQ-6, PQ-10, and PMETAC. Both direct (dose-response) and indirect (titrimetric) detection methods were explored. Limits of detection (3σ) for these species were found to be 7.7, 6.9, 21.5, and 9.0 µg/mL, respectively, using the preferred titration method. PQ-6 was also quantified in partially treated drinking water from a water treatment plant. Chapter 4 demonstrates the application of fully reversible (pulstrode) polyion-sensitive ISEs to the same PQ species discussed in Chapter 3 using direct and indirect detection methods. Limits of detection for PQ-2, PQ-6, PQ-10, and PMETAC were found to be 8.0, 7.9, 35.5, and 10.3 µg/mL, respectively, using the preferred titration method. Chapter 5 explores the application of the first polymer-/plasticizer-free polycation-sensitive ion-selective optode (ISO) for the direct detection of PQ-2, PQ-6, PQ-10, and PMETAC. Each PQ was found to yield sigmoidal response curves when average hue values were plotted against the logarithm of the PQ concentration. These polycation-sensitive ISOs were found to be useful in quantifying PQ-6 in recreational swimming pool water. Chapter 6 describes the construction and application of the first all-solid-contact paper-based polyanion-sensitive ISE to the direct detection of polyanions and the indirect detection of PQs. These sensors are found to yield similar dose-response and titration data to the single-use ISEs described in Chapter 3. Slope values for each PQ calibration curve are in excellent agreement with calibration curves reported in Chapter 3. Finally, an overview of the accomplishments of this thesis work and potential new directions for polyion sensor research/applications are discussed in Chapter 7.PhDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/147628/1/safergus_1.pd