DNPH vs recrystallized DNPH for Carbonyl determination

[TimGG]

Hey guys, I am not a Chemist and I hope i can get some advise~~

my colleague is using HPLC to determine the concentration of carbonyl by DNPH derivatization. I saw the standard method require recrystallize the DNPH, but he did not. I just wonder would it make a signifiant difference for determine Carbonyl~~ and why?

Thanks a lot.

[eg@aaclab]

It might. DNPH typically contains ~30 percent water and some levels of contaminants usually including formaldehyde-DNPH etc thus the purification process. EPA Soil and water method 0011 and CARB 430 or EPA TO-5 all give the cleaning procedure..if the impurities in the DNPH do not interfere with your compounds of interest (analyze a blank) than I don't think the DNPH needs to be cleaned...For most methods the blank levels of Formaldehye and other carbonyl-DNPHs are too high and the DNPH must be cleaned. Hope that helps.

[Bruce Hamilton]

I believe there are vendors of DNPH that sell grades specifically for carbonyl determination, and they may claim that you don't need to recrystallize before use.

As well as carbonyls, DNPH also reacts with NOx and some other volatile compounds so, as eg@aaclab notes, it depends on whether impurities will interfere with your assay. As your colleague will be running blanks and standards, he'll discover whether recrystallization is required.

Bruce Hamilton

[eg@aaclab]

http://www.cerilliant.com/ used to sell recrystallized DNPH but it's very expensive...the stuff can be slightly explosive thats why they sell it mostly with 20-40% water added....havent checked in a few years as we recrystalize our own..you can clean tens of grams or more at one time and it stores well so a batch can last a long time depending on your useage....keep from light and heat , i.e. amber bottle in a fridge works well.

[TimGG]

Thank you very much, it is very helpful, I guess I will look at the blank data first and see what my colleague want to do about it~~

[cody84]

What is the actual process of recrystallization??

[Bruce Hamilton]

What is the actual process of recrystallization??

http://www.epa.gov/osw/hazard/testmetho ... s/0100.pdf

Section 5.9 refers...

[cody84]

Thanks Bruce! So I can make a stock solution and keep it in the fridge?