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Determination of methylene chloride acceptability and its "purification" for ethylenethiourea methodology
C A Sack1, D C Kendall, R T Krause
1U.S. Food and Drug Administration, Total Diet Research Center, Kansas City, MO 64106.
Abstract:
A liquid chromatographic-electrochemical method for the determination of ethylenethiourea (ETU) residues uses methylene chloride in the cleanup. Distilled-in-glass grade methylene chloride produced erratic ETU recoveries ranging from 0 to 106% for vacuum rotary evaporation of the solvent. ETU recoveries were found to be dependent on the bottle of methylene chloride used, not on supplier or lot. When GC2 grade methylene chloride from Burdick & Jackson Laboratories was used, ETU recoveries ranged from 92 to 110%. "Acceptable" ETU recoveries were defined as those values between 90 and 110%. Passing "unacceptable" methylene chloride through a column containing anhydrous sodium sulfate, sodium carbonate, and alumina was found to adequately purify methylene chloride. Treated methylene chloride provided acceptable ETU recoveries for up to 1 month after "purification."
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