The factors influencing direct spectral fluorimetry of some urine metabolites

Urine contains a variety of organic and inorganic chemicals including a number of natural fluorophores. Most of them are formed by tryptophan metabolites. But there are also metabolites of riboflavin, catecholamines and porphyrins. The alternation in the autofluorescence of urine and the alternation in the concentration of these substances are developed by both physiological and pathological changes such as disorder of body metabolism, dietary intake, age and etc. In this work we present fluorescent properties of chosen urine fluorophores - i.e. 5-hydroxyindole-3-acetic acid (5-HIAA), indoxyl sulphate (urine indican), serotonin (5-HT), vanillylmandelic (VMA) and homovanillic (HVA) acids typical for various diseases. Differences of fluorescent parameters of individual fluorophores measured in vitro in the water solutions and in natural environment of urine are significant and can lead to false results and conclusions. Therefore, we present the most common influence that can occur in urine (e.g. pH, ionic strength, proteins, and other fluorophores). The aim is to elaborate the exact "know-how" for direct complex fluorescent measurement in urine related to particular diagnoses.