If users know that their sample forms emulsion, they can add the salt to the sample before shaking with the solvent. If the emulsion occurs due to a surfactant, detergent or alkali soap, then reducing the pH to 2 with hydrochloric acid (HCl), or sulfuric acid (H 2SO 4), (as recommended in the grease and oil methods, mainly for preservation of the sample) will alter the surfactant’s charge such that it no longer serves as an emulsifier.ģ. Gently stirring the solvent and emulsion layer with a stir bar or tapping the side of the container can help accelerate the separation.Ģ. Ensure that the sample is covered tightly to reduce any evaporation of the solvent. The easiest way is to let the sample to sit for up to an hour and observe whether the emulsion decreases or remains stable. The following options may be useful for sufficiently reducing the emulsion to take a valid measurement.ġ. The best approach to reduce or break the emulsion depends on the sample matrix. If this type of emulsion cannot be broken by any attempted processes, the test method may not provide the representative results for the problem sample. EPA Method 1664, “if the emulsion is greater than one-third the volume of the solvent layer, the laboratory must employ emulsion-breaking techniques to complete the phase separation.” This is applicable to all oil in water measurements that employ liquid-liquid extraction, whether the analysis is performed by UV, gravimetric or infrared. The boundary between the sample and the solvent will have an emulsion layer that has a milky or cloudy appearance as shown in the below image. Particular types of samples, such as those containing detergent, may create emulsions when doing an oil-in-water extraction into a solvent. Sponsored by AMETEK Spectro Scientific May 17 2018

Oil in water emulsion