o-phthalaldehyde-N-acetylcysteine polyamine derivatives: formation and stability in solution and in C-18 supports

A comparative study of different derivatization procedures has been perform ed in order to improve the stability of the reaction products o-phthalaldeh yde-N-acetylcysteine (OPA-NAC) polyamines. Procedures such as solution deri vatization, solution derivatization followed by retention on a packing supp ort, derivatization on different packing supports and on-column derivatizat ion, have been optimized and compared. The degradation rate constant (k) of the derivative was dependent on the procedure used and on the analyte. For the spermine (the most unstable isoindol tested) k was 8 +/- 2X10(-2) min( -1) in solution versus 7.7 +/-1.1x10(-4) min(-1) on the (C-18) solid suppor t. The results obtained showed that forming the derivative on the packing s upport (C-18) gave the best results following this procedure: conditioning the cartridges with berate buffer (1 ml, 0.5 M, pH 8), retention of the ana lyte, addition of 0.8 ml of OPA-NAC reagent, 0.2 ml borate buffer 0.8 M (pH 8) and elution of the isoindol with 3 ml of MeOH-borate buffer (9:1). The different derivatization procedures have been used to study the stability o f the reaction products OPA-NAC polyamines formed in urine matrix using spe rmine as model compound. Similar results were obtained for standard solutio ns and urine samples. (C) 2001 Elsevier Science B.V. All rights reserved.