I analyzed glutaraldehyde by derivatizing with DNPH. Even though I have recrystallized the DNPH in acetonitrile/water I still get 5 peaks in my blank. one before the ACN peak and 3 after. My mobile phase is 60% ACN in 0.5% H3PO4. UV at 365nm.All peaks come out before the glutaraldehyde-DNPH peak. Column is Restek TO-11 at 35 C.

We assay glutaraldehyde in finished products using DNPH as well. We use deactivated C18 column at 365nm with ACN and H3PO4 as well (we use higher concentration of H3PO4). We obtain only the excess DNPH peak and the glutaraldehyde peak. Unfortunately, I'm not sure how to attach our chromatogram, it's in Word format.

What brand is your DNPH powdered chemical?Who sells them?

Aldrich D19,930-1

Also Mallinckrodt #2412 (my sample is over 20 years old though)

Are you talking about dinitrophenylhydrazine?
If so, CP Guy, what reaction conditions are you using? The old H2SO4 method we used years ago produced a multitude of products which mostly emerged with the solvent front, luckily. (We had another problem, though, and gave up: Ascorbic acid produces two osazone geometric isomers which interconvert at a slightly slower rate than the chrom time span. Nevertheless a problem, which, however, should not occur here).
Oh yes, we had a peak appearing, sometimes, at various retention times, never got it under control. Have any of you seen this type of thing in this reaction?

Yes, 2,4-dinitrophenylhydrazine; we've only used it for low levels of formaldehyde and glutaraldehyde, because those were the only aldehyde analytes of interest to my company. We haven't had any issues.

James R. Dahlgren and Melvin N. Jameson, “Determination of Formaldehyde and Other Aldehydes in Industrial Surfactants by Liquid Chromatographic Separation of Their Respective 2,4-Dinitrophenyl-hydrazone Derivatives,” Journal of the Association of Official Analytical Chemists (Vol. 71, No. 3, 1988), pp. 560-563.

EPA Method 8315, Revision 0, September 1994, EPA Test Methods for Evaluating Solid Waste, Field Manual, Physical/Chemical Methods, Volume II.

Folks at Union Carbide, part of DOW has published an article: Inactivation of Glutaraldehyde by Reaction with Sodium Bisulfite, Journal of Toxicology and Environmental Health, Volumre 47,Number3, February 23, 1996. They used a Spherisorb 3 CN 150cm column. The chromatogram shows 2 peaks before the DNPH peak. One of them may be glutaraldehyde bisulfite because I see that peak too in my chromatogram. My matrix contains sodium bisufite. It takes overnight sitting of the mixture or incubation for 30 minutes at 50C to derivatize the aldehyde completely.