dinitrophenylhydrazine chloroacetaldehyde

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fembiochem
fembiochem's picture
dinitrophenylhydrazine chloroacetaldehyde

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.

Dr. Analytical
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I know this method well.  I

I know this method well.  I developed the original version of 8315 for EPA in 1988.
You should check your DNPH.  I have recently prepared solution in acetonitrile with no difficulty.  I was using the 50% suspension in water.  What concentration are you trying to dissolve?  You should be using the neutral version (DNPH), not the salt (DNPH.HCl). 
Please write back with more details.
 
 

Greg Pronger
Greg Pronger's picture
fembiochem wrote:

fembiochem wrote:

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.

 
1) The DNPH is not soluble in acetonitrile. See Appendix A; here you recrystalize the DNPH from acetonitrile (clearly indicating its not soluble).
2) Follow 7.3.5. with samples as acidic as yours, I may perform an initial 1:10 dilution so that when I adjust the pH I am less likely to get a violent reaction. It may also be beneficial to do this in a beaker which is sitting in an ice bath (simply a plastic pan with ice) to keep the temperature from going to high. Once the pH is adjusted you can then transfer the sample to the extraction equipment.
 
If I mis-interpretted your question, feel free to reply and clarify.
 
Greg