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Emulsion Breaking Techniques for Oil in Water Solvent Extractions
Certain types of samples, such as those containing detergent, may form emulsions when doing an oil in water extraction into a solvent. The boundary between the solvent and the sample will have an emulsion layer that has a cloudy or milky appearance as shown in this photo. According to U.S. 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 relevant to all oil in water measurements that use liquid-liquid extraction whether the analysis is done by infrared, gravimetric or UV. If such an emulsion cannot be broken by any attempted means, the test method may not give representative results for the problem sample. The best way to break or reduce the emulsion depends on the sample matrix.