Separation and Determination of Diol Pollutants Come from Demulsifier in the Produced Water of Oil Fields

This paper introduced a novel test method for determination of the main demulsifier‐based pollutants in the produced water of oil wells, before draining to seawater. The type, concentration and distribution of diols depend on the demulsifier of interest; however, the main chemical species are the same. The novelty of this work is selective extraction and preconcentration of low chain diols in the produced water of oil fields. In this extraction method, dispersive solvent (1.2 mL, acetonitrile) containing extraction solvent (10.0 μL, carbon tetrachloride) was rapidly injected into the water sample containing analytes, and a cloudy solution was formed. After centrifugation (2 min at 3,000 rpm), these droplets were sedimented in the bottom of the conical test tube. Then 2.0 mL of sedimented phase containing preconcentrated analytes was injected into the gas chromatograph with flame ionization detector. The parameters affecting the extraction efficiency were evaluated and optimized. Factors such as the kind and volume of both extraction and disperser solvents, extraction and centrifugation times, pH and temperature, and salt effect were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 39.0 to 44.4 and 78.9 to 92.2%, respectively, within very short extraction time. The linearity (and limit of detection) of the method ranged 4.0‐100.0 (2.0) ng/mL for 1,2‐ethandiol, 6.0‐80.0 (4.0) ng/mL for 1,3‐propandiol, 2.0‐90.0 (1.0) ng/mL ng/mL for 1,4‐butanediol, 5.0‐120.0 (2.0) ng/mL for 1,5‐pentandiol. The relative standard deviations (RSD) for the concentration of diols, 5.0 ng/mL in water by using the internal standard were in the range of 1.5–4.5% (n = 5) and without the internal standard was in the range of 2.6–9.0% (n = 5). It is concluded that this method is successful for determination of diols in produced water samples.