A TECHNIQUE FOR ASSESSING THE EFFECTS OF PH AND PHOTODEGRADATION ON THE STABILITY OF THE IRON CHELATE OF ETHYL N-METHYL-4-HYDROXY-5-OXO-3-PYRROLINE-3-CARBOXYLATE

Ethyl N-methyl-4-hydroxy-5-oxo-3-pyrroline-3-carboxylate forms a deep red chelate with iron salts. The color intensity is directly related t o the iron concentration. The photostability of the red color was dete rmined at pH 1,2 and 5 by spectrophotometric assay at 484 nm at interv als during irradiation by tungsten light at 1020 mu W/cm(2). After 528 hr of continuous irradiation in deionized water, 90.9% of the iron ch elate had decomposed. The reaction followed zero order kinetics. Maxim al stability was observed at pH 5 at both 10(-1) and 10(-2) molar conc entrations of the iron chelate; no detectable decomposition occurred a fter 192 hr of continuous irradiation. The iron chelate in biological tissues is stable for 18 months. The staining technique is superior to other histological methods for estimating low concentrations of iron in tissue.