PHOTOOXIDATION OF 3-SUBSTITUTED PYRROLES - A POSTCOLUMN REACTION DETECTION SYSTEM FOR SINGLET MOLECULAR-OXYGEN IN HPLC

A postcolumn photochemical reaction detection scheme, based on the rea ction of 3-substituted pyrroles with singlet molecular oxygen (O-1(2)) , has been developed. The method is selective and sensitive for the de termination of a class of organic compounds called O-1(2)-sensitizers and is readily coupled to HPLC, Following separation by HPLC, analytes (O-1(2)-sensitizers) are excited by a Hg pen-ray lamp. Analytes that are efficient O-1(2)-sensitizers promote groundstate O-2 ((3)Sigma(g)( -)) to an excited state ((1)Sigma(g)(+) Or (1)Delta(g)), which reacts rapidly with tert-butyl-3,4,5-trimethylpyrrolecarboxylate (BTMPC) or N -benzyl-3-methoxypyrrole-2-tert-carboxylate (BMPC), which is added to the mobile phase. Detection is based on the loss of pyrrole (BTMPC or BMPC). The reaction is catalytic in nature since one analyte molecule may absorb light many times, producing large amounts of O-1(2), Detect ion limits for several O-1(2)-sensitizers were improved by 1-2 orders of magnitude over optimized UV-absorbance detection. This paper discus ses the optimization of the reaction conditions for this photochemical reaction detection scheme and its application to the detection of PCB s, nitrogen heterocycles, nitro and chloro aromatics, and other substi tuted aromatic compounds.