Application of water-in-oil microemulsions in microemulsion electrokinetic chromatography and as extractants of polar substances

We studied the use of water-in-oil (W/O) microemulsions as new pseudophases in microemulsion electrokinetic chromatography (MEEKC). It is shown that the method is suitable for the separation of complex mixtures of polar compounds. The effect of the microemulsion composition on the selectivity of separation of inorganic anions is examined. A new rapid method of sample preparation is proposed, which includes the complete dissolution of a mayonnaise sample in a reverse microemulsion for 2 min in an ultrasonic bath. Preservatives are determined by the MEEKC analysis of W/O microemulsion (MEEKC W/O). The developed procedure for determining preservatives in mayonnaise is simple and rapid: the duration of separation is 8 min and sample preparation takes 5 min. The repeatability of measurements is from 5.8 to 2.3%, and the intermediate precision is from 7.5 to 5.7%. The detection limit is 3.0 mg/kg for sorbic acid and 3.3 mg/kg for benzoic acid.