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Lawrence K Wang deposited OIL AND GREASE DETERMINATION, SOLVENT HAZARDS AND WASTE DISPOSAL WHEN USING TRICHLOROETHANE FOR EXTRACTION in the group
Science, Technology, Engineering, Arts and Mathematics (STEAM) on Humanities Commons 3 years, 8 months ago A spectrophotometric procedure has been developed for determination of hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases and related oily organic matter in aqueous phase. The water sample is acidified to a low pH (less than or equal to 2) and extracted with trichloroethane (methyl chloroform). Under controlled conditions, the oil and grease are extractable into the selected organic solvent, where the intensity of yellow color is proportional to the oil and grease concentration. The color in the selected organic solvent (methyl chloroform) is measured by spectrophotometry at recommended wavelengths. The new analytical method uses a visible spectrophotometer or a filter photometer, which is available in almost any water quality laboratories. The oil and grease concentration as low as 0.1 mg/L can be quantitatively measured, provided that a quartz cell with light path length of 5 cm or longer is used. Colorimetry (instead of spectrophotometry) can also be used if a colorimeter is properly calibrated or color charts are properly developed. 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 with n-hexane and conclude that trichloroethane (methyl chloroform) is better than n-hexane considering the safety of both the laboratory workers and the laboratory although trichloroethane is an ozone-depleting substance (ODS). Solvent recycle and/or proper laboratory waste management will eliminate the opportunity of ODS release to the environment.