Measuring Oil in Water

摘要

Certain types of water samples, such as those containing detergent, may form emulsions when performing an oil-in-water extraction into a sol-vent, and impact the final readings. The boundary between the solvent and the sample will have an emulsion layer that has a cloudy or milky appearance as shown in the photo. According to 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 ultraviolet instrumentation.