Separation and sensitive determination of i-urobilin and 1-stercobilin by high-performance liquid chromatography with fluorimetric detection

i-Urobilin and 1-stercobilin were separated by high-performance liquid chromatography on a reversed-phase octadecylsilane-bonded column and detected fluorimetrically through formation of phosphor with zinc ions in the eluent. The separation and the intensity of the fluorescence response were affected by concentrations of zinc acetate and sodium borate buffer, pH and methanol content in the eluent. The optimal eluent used consisted of 0.1% zinc acetate in 75 mM boric acid buffer (pH 6.0)-methanol (25:75). The detection limit was 0.2 microgram/l for both i-urobilin and 1-stercobilin (signal-to-noise ratio 2), which makes the method 250-2500 times more sensitive than conventional methods.

Quantitation of urobilinogen in feces, urine, bile and serum by direct spectrophotometry of zinc complex

Previous methods to quantitate urobilinogen lack precision due to either incomplete reduction of urobilin or to losses of pigment before the use of Ehrlich's aldehyde reaction or due to pigment precipitation, as occurs in Schlesinger's fluorescent assay. The present procedure modifies the latter assay to obviate described problems as it is based on direct spectrophotometry (or spectrofluorometry) of a zinc complex of urobilin in dimethylsulfoxide. The sample is extracted with dimethylsulfoxide to increase recovery of urobilinogen from samples of various origin (feces, urine, bile, serum etc.) and to prevent the precipitation of proteins. After oxidation of urobilinogen with iodine, the concentration of the resulting urobilin is directly determined from the absorption (or fluorescent) spectrum. High sensitivity and high specificity for the procedure result from the high value of absorption coefficient and by the characteristic absorption spectrum of zinc complex of urobilin, respectively. Within-day and day-to-day coefficients of variation of stool and bile samples range from 1.6 to 9.2%. The smallest concentration of urobilinogen measurable by spectrophotometry is approximately 0.5 mumol/l, by fluorometry it is 0.25 mumol/l. The recovery varies from 82.2 to 93.8% depending on re-extraction of the sample. The method is linear in the range of 1 to 35 mumol/l and of 0.5 to 17.5 mumol/l for spectrophotometric and fluorescent determinations, respectively. The results obtained with the present method correlated well with Ehrlich's determination (r2 = 0.912), but are approximately two-fold higher. Storage of the samples at -20 degrees C or extraction with dimethylsulfoxide prior to storage are good ways for sample preservation. Twenty stool samples from healthy adults were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased urinary urobilinogen following acute myocardial infarction

A study was conducted of the serial urinary urobilinogen excretion in patients with acute myocardial infarction, using Watson's semiquantitative method. Increased excretion was observed in some 90 per cent of the subjects with infarcts confirmed by the electrocardiogram and in more than half of the subjects where the electrocardiogram was not conclusive. The degree and duration of increased urinary urobilinogen had no apparent bearing upon prognosis. It is postulated that the altered urobilinogen excretion is induced by hepatic effects of the stress reaction incident to acute myocardial infarction.