The Class 1 mixtures below reflect the requirements of USP23/NF18 effective January 1, 1995 to December 31, 1999. While these mixtures do not meet the current USP guidelines, many still use these mixtures to obtain a detectable benzene peak for the direct injection methods, Method I and Method V.
Chloroform (67-66-3), 60 µg/mL
1,4-Dioxane (123-91-1), 380 µg/mL
Methylene chloride (dichloromethane) (75-09-2), 600 µg/mL
Trichloroethene (79-01-6), 80 µg/mL
