The Fluorimetric Determination of Noradrenaline

Abstract

SINCE Eulerl in 1946 demonstrated the important role played by (-)-noradrenaline (I) as a transmitter of adrenergic nerve impulses and later isolated it in pure form from the adrenal medulla2, this substance has found a wide clinical application. Exerting an overall vasoconstrictor effect, it is used, for instance, to maintain the blood pressure in surgical and traumatic shock and other acute hypotensive states. Because of its greater stability to oxidation it is progressively supplanting adrenaline in many instances, e.g. as a vasoconstrictor in injectable local anaesthetics, as a haemostatic and so on3. Tullar and c o -~o r k e r s~?~ have discussed the substance from different points of view.Noradrenaline is used mainly as the laevo-isomer, usually as the hydrochloride or the bitartrate, this isomer being about twice as active' as the racemic form. Several solutions containing the equivalent of 0.1 per cent. of (-)-noradrenaline are commercially available, but there is contemplated for inclusion in the Swedish Pharmacopceia a solution containing only 0.001 per cent. of noradrenaline as the bitartrate.For the chemical estimation of noradrenaline in solution one may utilise, with slight modifications, several methods originally intended for the determination of adrenaline, e.g. the adrenochrome methods and our fluorescence method with strong alkali. Moreover the absorption peak at 279 mp in the ultra-violet spectrum offers a possibility for the quantitative determination of noradrenaline, E: being 85.0 for a solution of 0.01 N hydrochloricacid in this laboratory. Thecondensation of the primary aliphatic amine moiety with a carbonyl compound implies a selective method', being capable of determining noradrenaline even in adrenaline.The solutions containing 0.1 per cent. of noradrenaline may be conveniently assayed by the methods mentioned, but in the case of the 0.001 per cent. solution only the fluorescence method seems to have a sufficient sensitivity. As noted by EhrlCn* and others, a drawback of the fluorescence method for adrenaline is the instability of the fluorescence. A great improvement was made, however, in 1949, when Natelson et aL9 introduced a method for the determination of adrenergic amines in blood involving oxidation and condensation in alkaline medium with a primary aliphatic amine. As proposed by Weil-Malherbe and Bonelo ethylene diamine may be employed as the amine, thus by cyclisation producing a fairly stable fluorescent compound (formula 111, below). However, this method does not work in the presence of pyrosulphite, a serious limitation to its usefulness, because noradrenaline solutions generally are stabilised with pyrosulphite.

The Estimation of Catecholamines in Urine by a Chemical Method

“…Bone, 1953). With the extension of the method to other catecholamines it became desirable to repeat these experiments with noradrenaline and hydroxytyramine, particularly in view of a report of Erne and Canback (1955), who recommend, for noradrenaline, heating at 1000 C. for 5 min. in the presence of ammonium molybdate solution as a catalyst.…”

Pharmaceuticals and Related Drugs

“…Using a circular horizontal technique and methanolic-aqueous tartaric acid solvent, Rf values of 0.75 and 0.68, respectively, were obtained. Noradrenaline develops a green fluorescence when condensed with ethylenediamine (148). Stock and Hinson (481) made spectrophotometric studies of the iodate and persulfate oxidation of adrenaline and noradrenaline.…”