Spectrophotometric determination of sildenafil citrate in pharmaceutical formulations
Viagra � has quickly become just about the most popular plus popular drugs inside the take care of lovemaking dysfunction. 3 Inside parallel with the particular growth in their consumption, there was a great increase in the particular number of circumstances of adulteration and even falsification of this medication. 4 In order to date, there is an absence of a monograph and description of your official method regarding its analysis within the Brazilian pharmacopoeia and in the primary international works in this category. In look at of these factors, it is of paramount importance to guarantee the particular quality of the items sold for the particular protection of consumers' health.
The approaches described in the particular literature for sildenafil citrate analysis consist of voltammetry, 5. 6th high performance chemical chromatography with UV 7-9 detection or coupled to size spectrometry, 10 micellar electrokinetic chromatography, 10 gas chromatography, 12 capillary electrophoresis, 13 spectroscopy of nuclear magnetic resonance fourteen and spectrophotometry. 15-17 Chromatographic methods would be the most used throughout the determination involving sildenafil citrate in several matrices (pharmaceutical formulations, plasma and urine), 7-9, 11as well such as the particular determination of pharmacokinetic parameters. They have low detection limits, which usually justifies their use in the analysis of biological fluids. However, they demand quite a long time in the initial sample prep steps, use increased amounts of solvents and the instrumentation much more expensive, which in turn raises the last cost of the analyzes. For the particular analysis of pharmaceutical formulations, it is desirable that procedures using low cost methods and that provide fast, precise in addition to accurate results happen to be available.
Molecular consumption spectrophotometry is the particular instrumental technique of choice widely used for this specific purpose, having the positive aspects of being very simple, involving the utilization of low-cost equipment in addition to being able in order to be easily programmed. The methods defined in the literature intended for the determination regarding sildenafil citrate simply by spectrophotometry 15-17 are usually scarce and they have many disadvantages, as they require heating for coloring development in acetonitrile medium 16 or even involve laborious procedures with many periods of sample handling, including extractions together with chloroform. 15
This specific work describes the introduction of a fast in addition to simple spectrophotometric approach based on typically the reaction between sildenafil citrate and p-chloranil 16 accelerated simply by the addition regarding hydrogen peroxide, immediately producing a secure violet complex (? max = 535 nm) at area temperature.
EXPERIMENTAL PART
Materials and tools
The volume proportions were created with class A burettes or Eppendorf micropipette (100-1000 � L). Typically the glassware used throughout the preparation associated with the solutions was grade A as well as the weighings were completed on an conditional balance AG204, Mettler Toledo. Absorbance dimensions were made using a new Varian spectrophotometer type Cary 100 outfitted with glass or quartz cuvettes by having an optical path of just one cm.
Reagents and solutions
All reagents and solvents utilized in this work were of analytical class. Working solution five. 68 x twelve -3 mol M -1 of sildenafil citrate (supplied simply by Pfizer, 95%) was basically prepared in methanol (Mallinckrodt, Xalostoc, Mexico). This solution is definitely stable for fifteen days if kept in the refrigerator. 5 p-chloranil (Sigma, St. Louis, USA), working solution one 00 x ten -2 mol M -1 of p-chloranil (Sigma, St. John, USA) was prepared in dioxane (Mallinckrodt, Xalostoc, Mexico). Hydrogen peroxide solution 5. 00 mol L -1was prepared simply by the correct dilution involving the Peridrol answer (Merck, Darmstadt, Germany, 30% w and w) with methanol, previously standardized in accordance to the permanganimetric procedure. 18
thus that its last concentration went from eight. 52 x ten -5 to 1. 80 x 10 -3 mol L -1. The volume of the flasks was completed with methanol up in order to the mark after which the absorbance proportions were made at 535 nm in opposition to a similarly well prepared blank, but without the addition associated with sildenafil citrate. The calibration curve was basically constructed by conspiring the absorbance beliefs?? measured as a performance of the sildenafil citrate concentration.
Test preparation and research
Samples of medications containing sildenafil citrate in the marketplace were purchased from local pharmacies and analyzed by typically the proposed method, within just their expiration date ranges.
비아그라 구입 , from the same set, were weighed with an analytical balance along with the mean mass price was determined. Eventually, they were dispersed on agate grain until a fine powder was obtained. A portion associated with sprayed sample similar to 20 mg involving sildenafil citrate seemed to be exactly weighed in addition to subjected to stir with 5 ml of methanol throughout a magnetic stirrer for 15 minutes. This solution has been transferred to a 10 mL volumetric flask and the amount constructed with methanol until the meniscus. Then, the answer was filtered about Whatman 41 quantitative filter paper and also a 750 �L aliquot was taken plus analyzed according to the recommended treatment for the building from the analytical competition.