Indirect CE-UV detection for the characterization of organic and inorganic ions of a broad mobility and pK a range in engine coolants

An alternative CE-(indirect ultraviolet) method for the analysis of inorganic and organic anions in ethylene glycol-based engine coolants is presented using a BGE with 4 mM pyromellitic acid and 3.4 mM 1,6-hexamethylene diamine, pH 3. Baseline separation of six inorganic (e.g. nitrite, nitrate, and sulfate) and five organic anions (e.g. acetic and glycolic acid) was achieved. Quantification of 8 out of 11 specified anions was possible in stressed engine coolant samples after simple aqueous dilution. LODs between 0.8 and 15.1 mg/L with RSD values of peak areas between 2.6 and 11.9% were obtained. Some limitations due to matrix effects can be overcome with slight adaptations of the BGE. The flexibility of the method is vital regarding the increasing demands for the composition of engine coolants for pollution reduction.