Siberian Federal University

A procedure of sample preparation of oil samples for the determination of chloride ions, which are part of high-molecular organic compounds, has been developed. The procedure consists in the extraction of chloride ions from oil into the aqueous phase with a solution of sodium nitrate, followed by ionochromatographic detection. The work was performed on a high-performance LC‑20 Prominence liquid chromatograph with LC Solution software (Shimadzu, Japan), equipped with a conductometric detector (CDD‑10 Avp/10Asp), a 120×5 mm KanK-ASt14 μm separating column (GEOHI RAS, Russia) and a 200×6 mm SPS-SAC 50 suppression column μm (LLC PC «Aquilon», Russia). A carbonate buffer solution (2.5 mM Na2CO3 + 3.0 mM NaHCO3) was used as an eluent. The volume of the injected sample is 100 μl. The eluent flow rate was 2.0 ml/min. The temperature of the column thermostat is 33 °C. Under these conditions, satisfactory separation of fluoride, chloride, nitrate, and sulfate ions is achieved, and hydrogen sulfide does not have ionic forms and does not manifest ionochromatographically. Using the method of full factorial experiment, the main parameters determining the efficiency of extraction of chloride ions from the organic phase were optimized: extraction of 1 mM with an aqueous solution of NaNO3 at a temperature of 90 ± 2 °C, the volume ratio of oil and extractant 1:10, extraction time 20 min. The developed procedure of sample preparation has been tested on model solutions and real oil samples. In comparison with the known methods, the combination of extraction isolation of organic chlorides with ionochromatographic detection makes it possible to significantly simplify the procedure for determining the analyte due to the high selectivity of the method without loss in sensitivity and measurement accuracy