Chlorpyrifos

Single-component standards are available as stock items. They are supplied in methanol or in another solvent when appropriate. Additional solvents include methylene chloride, acetone, benzene, hexane, acetonitrile, THF, and water. You can inquire about the matrix for a particular item when ordering, of the matrix is important to your application, a substitution may be possible.
 
Concentrations other than these, as well as custom matrices, are readily available, but a minimum order of five ampules may be required in some cases.