Glycol-based coolants are ubiquitous in automotive engines and industrial machinery. Recent European Union legislation has driven increased recycling of waste coolants, generating a need for quality control measures to assess the removal of various coolant additives, such as the alkali silicates used for corrosion inhibition. Capillary electrophoresis (CE) has previously been demonstrated to be an effective technique for the analysis of engine coolants, including both organic and inorganic analytes. Here, a CE method developed for analyzing geothermal brines was adapted for the determination of silicate in used and recycled engine coolants. Both waste and recycled coolants from a local manufacturer were used for method evaluation. Analyses were performed using an Agilent 7100 CE system coupled with Agilent OpenLab software. Separations were carried out in a fused silica capillary with a driving potential of 15 kV and a background electrolyte (BGE) of 10 mM Na2CrO4, 3 mM tetradecyltrimethylammonium bromide (TTAB), and 2 mM Na2CO3 adjusted to pH 11.0 ± 0.1 with NaOH. A facile and rapid sample treatment consisting of dilution, addition of an internal standard (methionine), and adjustment of pH to 11.0 ± 0.1 with NaOH was employed. Samples were introduced via pressure injection and silicate separation was achieved in ~6 min with high migration time reproducibility (%RSD = 1.23). Indirect UV detection at 254 nm was used to quantify silicate concentration. The method displayed high linearity (R2 = 0.99997) over a 40 mg L-1 range and limits of detection and quantification (~0.29 and ~0.95 mg L-1, respectively) were found to be sufficient for coolant analysis. Preliminary spike recovery tests display excellent recovery in some samples, though many waste coolants impose significant matrix effects that must be mitigated in future work.

Determination of silicate in waste and recycled engine coolants using capillary electrophoresis

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.