A simple analytical method for determining inorganic anions and formate in virgin olive oils by capillary electrophoresis with capacitively coupled contactless conductivity detection

- By the first time, CE was applied to determination of anions in olive oils.
- Direct detection of anions by contactless conductivity detection.
- Simple sample preparation using ultrasound-assisted liquid-liquid extraction.
- Commercial olive oil samples were analyzed by the proposed method.

This paper describes a novel and simple method for determining chloride, nitrate, sulfate, fluoride, and formate in virgin olive oil (VOO) by capillary electrophoresis with capacitively coupled contactless conductivity detection. The anions were extracted from VOO by a simple ultrasound-assisted aqueous liquid-liquid extraction procedure. The anions were separated in less than 3 min with good peak resolutions using a background electrolyte composed of 15 mmol L−1 histidine solution at pH 4.0, adjusted with lactic acid, and 0.6 mmol L−1 cetyltrimethylammonium hydroxide as electrosmotic flow (EOF) modifier. Tartrate was used as internal standard (I.S.). The proposed method showed good linearity and had coefficients of determination (R2) ranging from 0.9984 to 0.9999. The limits of quantification (LOQ) were between 0.01 and 0.7 mg kg−1. Recovery tests were used to evaluate the efficiency of the extraction procedure; the recovery percentages ranged from 70.2 to 118%, with a relative standard deviation (RSD) varying from 0.7 to 19.4%. The proposed method was applied to the determination of the anions in five different commercial samples of VOO.