I am trying to derivatize chloroacetaldehyde (CAA) with 2,4 dinitrophenylhydrazine (DNPH) according to EPA method 8315A. Two problems that I'm having are 1). The DNPH is not soluble in acetonitrile. What else can I use to solublize the DNPH that wont interfere with the CAA reaction? 2). The sample matrix is very acidic (20% HCL, ph 0). Suggestions for sample prep would be welcome.