Abstract
A photometric flow titration based on the redox reaction between KMnO4 and minoxidil is described. The best titration results were observed at 3.20 x 10-4 mol L-1 KMnO4 and 1.00 x 10-3 mol L-1 minoxidil, using the minoxidil solutions as titrant. The flow rate was fixed at 17 mL min-1 and the titrant was added to the system in aliquots of 500 µL, the color changes were monitored at 550 nm. The method was applied to commercial samples and compared with the results from a chromatographic procedure. Recoveries from 97.6 to 102.8 % were observed depending on the sample. Comparison with the chromatographic procedure reveled relative errors of 3.5 - 4.0 %.
Highlights
Minoxidil (2,4-diamino-6-piperidinopyrimidine3-oxide, structure in Eq 1) is an odorless white crystalline powder, insoluble in water, acetone or alkaline solutions, slightly soluble in alcohols, and freely soluble in acidic solutions [1].Minoxidil has been used as a peripheral vasodilatator drug orally administrated, applied in the treatment of refractory hypertension patients [2]
In order to determine the stoichiometric coefficient of the reaction between minoxidil and KMnO4, standard solutions of both reagents were titrated as described in the experimental section
The KMnO4 solution exhibits absorption between 450 and 600 nm, while minoxidil solution and commercial formulation do not absorbs in the visible region
Summary
Minoxidil has been used as a peripheral vasodilatator drug orally administrated, applied in the treatment of refractory hypertension patients [2]. Excessive oral administration of this drug to patient should cause liquid retention and hirsutism [3]. Described as an antihypertensive drug, minoxidil have shown new applications in dermatology, especially in the treatment of androgenic alopecia [3,4]. In this case, this drug has been topically applied in order to stimulate hair growth by inducing vasodilatation and increasing the local irrigation and blood flow [4]. Available products contain 2% minoxidil (20 mg mL-1), in topic use formulations, containing ethanol, and propylene glycol, or their mixture with 2-n-nonyl-1,3dioxolane as a vehicle [5,6]
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