Colorimetric determination of epinephrine in blood and adrenal gland.

Various calorimetric methods of estimating epinephrine have been described by different workers using different chemical reagents such as potassium persulfate (I), mercuric chloride (2-4), potassium iodate (5), ammonium molybdate (6), diazobenzenesulfonic acid (7), and the ninhydrin test (8). None of the methods, however, is satisfactory for the estimation of epinephrine in blood. Some are not sufficiently sensitive, while with others it is either difficult to produce the color due to the presence of interfering substances or the color reaction is not specific. Barker and his associates (9) have investigated most of the color tests and have found that some of them are unreliable even for the qualitative estimation of epinephrine. They have estimated epinephrine with Folin’s reagent (10) and also with potassium persulfate and have observed that, although the former is 10 times more sensitive and gives better results with pure epinephrine, it is not sufficiently specific. The persulfate test, on the other hand, was specific and gave satisfactory results when applied to biological materials when conditions such as temperature and pH were controlled. We have confirmed the specificity of the persulfate test for epinephrine. However, this test is less sensitive. , Hence, it is not possible to determine low concentrations of epinephrine in blood. Further, the color is not easily developed, owing possibly to the presence of reducing substance like ascorbic acid which reduces the persulfate. The epinephrine content of adrenal glands has been determined with Folin’s reagent by several workers (11-14). Both epinephrine and ascorbic acid give a blue color with Folin’s reagent, and Rees (13) and Banerjee (14) have estimated the epinephrine content of adrenal glands by subtracting the blue value for ascorbic acid from the total blue value of the trichloroacetic acid extract of the gland. This process is, however, more or less suitable only when epinephrine concentration is either high or low as compared with the ascorbic acid content of the gland and when other interfering substances like glutathione, cysteine, uric acid, and ergothionine, which also give a blue color with Folin’s reagent, are known to be either absent or present in low concentrations. Using a Lumetron photoelectric calorimeter, we have observed that when a dilute solution of