Oil and Grease Determination, Solvent Hazards, and Waste Disposal When Using Trichloromethane (Chloroform) for Extraction

This publication introduces a new oil and grease (O&G) determination method that involves the use of a visible spectrophotometer or a filter photometer and chloroform for oil and grease extraction. The laboratory equipment and chloroform are available in all water quality laboratories. The oil and grease concentration in the aqueous phase as low as 0.1 mg/L can be quantitatively measured, provided that a quartz cell with a light path length of 5 cm or longer is used. Selection of an appropriate organic solvent for oil and grease analysis is discussed in terms of chemist contact risk and hazardous solvent disposal. Current Standard Methods 5520B, 5520D, 5520E, and 5520G for oil and grease analysis adopt n-hexane for solvent extraction. The authors compare the selected solvent (chloroform) with n-hexane and conclude that chloroform is better than n-hexane considering fire and accident prevention because n-hexane is very flammable, but chloroform is not flammable. In terms of the worker’s health hazard, both chloroform and n-hexane are at the same level, but chloroform is a “select carcinogen” that needs additional personal protective equipment (PPE) and laboratory protective equipment (LPE). This new analytical method using popular chloroform for oil and grease extraction will provide extra flexibility. It is recommended that chloroform in analytical chemistry be eventually replaced by another solvent that is not a “select carcinogen” type.