Viagra � has quickly turn out to be one of the most popular in addition to traditionally used drugs inside the remedying of erectile dysfunction. 3 In parallel with typically the growth in their consumption, there is a great increase in the particular number of situations of adulteration plus falsification of this specific medication. 4 To date, it has an absence of a monograph and description of the official method with regard to its analysis in the Brazilian pharmacopoeia and in the main international works with this category. In watch of these considerations, it is best to guarantee the quality of the merchandise sold for the protection of consumers’ health.
The techniques described in typically the literature for sildenafil citrate analysis incorporate voltammetry, 5. 6 high performance water chromatography with AND ALSO 7-9 detection or coupled to mass spectrometry, 10 micellar electrokinetic chromatography, 10 gas chromatography, 13 capillary electrophoresis, tough luck spectroscopy of atómico magnetic resonance 14 and spectrophotometry. 15-17 Chromatographic methods are the most used inside the determination of sildenafil citrate within several matrices (pharmaceutical formulations, plasma and even urine), 7-9, 11as well such as the determination of pharmacokinetic parameters. They have reduced detection limits, which in turn justifies their work with in the examination of biological fluids. However, they need quite a while in the particular initial sample preparation steps, use increased amounts of solvents and the arrangement is far more expensive, which raises the ultimate cost of the particular analyzes. For typically the analysis of pharmaceutical formulations, it is usually desirable that strategies using inexpensive approaches and that give fast, precise plus accurate results are available.
Molecular absorption spectrophotometry is the instrumental technique of choice widely used for this purpose, having the benefits of being simple, involving the use of low-cost equipment in addition to being able to be able to be easily programmed. The methods defined inside the literature for the determination regarding sildenafil citrate simply by spectrophotometry 15-17 happen to be scarce found some disadvantages, as they need heating for color development in acetonitrile medium 16 or involve laborious processes with many levels of sample handling, including extractions along with chloroform. 15
This kind of work describes the introduction of a fast in addition to simple spectrophotometric method based on the reaction between sildenafil citrate and p-chloranil 16 accelerated by the addition involving hydrogen peroxide, immediately producing a secure violet complex (? max = 535 nm) at place temperature.
EXPERIMENTAL PART
Materials and products
The volume dimensions were created with class A burettes or even Eppendorf micropipette (100-1000 � L). Typically the glassware used in the preparation regarding the solutions has been grade A and the weighings were accomplished on an synthetic balance AG204, Mettler Toledo. Absorbance dimensions were made using some sort of Varian spectrophotometer model Cary 100 outfitted with glass or perhaps quartz cuvettes having an optical path of just one cm.
Reagents and even solutions
All reactants and solvents utilized in this work were of analytical level. Working solution 5. 68 x twelve -3 mol L -1 of sildenafil citrate (supplied simply by Pfizer, 95%) was initially prepared in methanol (Mallinckrodt, Xalostoc, Mexico). This solution will be stable for 12-15 days if kept in the fridge. 5 p-chloranil (Sigma, St. 비아그라 구입 , USA), working solution 1 . 00 x 10 -2 mol L -1 of p-chloranil (Sigma, St. John, USA) was ready in dioxane (Mallinckrodt, Xalostoc, Mexico). Hydrogen peroxide solution 5. 00 mol M -1was prepared by the right dilution regarding the Peridrol option (Merck, Darmstadt, Philippines, 30% w and w) with methanol, previously standardized based to the permanganimetric procedure. 18
and so that its last concentration went from 8. 52 x ten -5 to 1. 70 x 10 -3 mol L -1. The volume from the flasks was finished with methanol up to be able to the mark after which the absorbance sizes were made with 535 nm against a similarly well prepared blank, but with out the addition of sildenafil citrate. Typically the calibration curve was basically constructed by conspiring the absorbance principles?? measured as being a functionality of the sildenafil citrate concentration.
Test preparation and analysis
Samples of drugs containing sildenafil citrate available on the market were purchased coming from local pharmacies and analyzed by the proposed method, within their expiration dates.
Sixteen tablets, from the same order, were weighed with an analytical balance plus the mean mass price was determined. Subsequently, they were sprayed on agate cause until a great powder was acquired. A portion associated with sprayed sample similar to 20 mg of sildenafil citrate was exactly weighed in addition to subjected to mixing with 5 milliliters of methanol in a magnetic stirrer for 15 min. This solution was basically transferred to a ten mL volumetric flask and the volume comprised with methanol until the meniscus. In that case, the solution was filtered on Whatman 41 quantitative filter paper along with a 750 �L differential was taken plus analyzed according in order to the recommended treatment for the structure with the analytical competition.