OPTIMIZATION OF POSTCOLUMN PHOTOLYSIS AND ELECTROCHEMICAL DETECTION FOR THE LIQUID-CHROMATOGRAPHIC DETERMINATION OF 3-NITRO-L-TYROSINE

A new post-column photolysis technology has been developed based on th e use of a low pressure, low temperature UV lamp and TiO2 coated knitt ed reaction coil. As a test case the developed technique was used for the determination of 3-nitro-L-tyrosine by liquid chromatography with electrochemical detection. Different photolysis lamps and reactor tubi ng lengths were evaluated in terms of their effect on the separation e fficiency and/or photolysis efficiency. A detection limit of 0.5 nM (1 0 fmol) for 3-nitro-L-tyrosine was achieved under optimized conditions , with a linear correlation coefficient of R-2=0.9898 over a concentra tion range of 2-100 mu M. Pre-injection photolysis of 3-nitro-L-tyrosi ne indicated that dihydroxyphenylalanine is the main photolysis produc t. In general, use of the photoreactor prior to liquid chromatography is an excellent method for exploring photodegradation products of an a nalyte in conjunction with the full range of available liquid chromato graphy detectors. (C) 1998 Elsevier Science B.V. All rights reserved.