Spectrophotometric determination of sildenafil citrate in pharmaceutical drug formulations

Viagra � has quickly become one of the most popular plus widely used drugs inside the take care of erectile dysfunction. 3 Inside parallel with the growth in it is consumption, there was clearly a good increase in typically the number of situations of adulteration and even falsification of this particular medication. 4 In order to date, it comes with an absence of a monograph and description associated with an official method with regard to its analysis throughout the Brazilian pharmacopoeia and in the main international works within this category. In watch of these considerations, it is best to guarantee the particular quality of the merchandise sold for the particular protection of customers’ health.

The approaches described in the literature for sildenafil citrate analysis contain voltammetry, 5. six high performance chemical chromatography with UV 7-9 detection or perhaps coupled to size spectrometry, 10 micellar electrokinetic chromatography, eleven gas chromatography, 10 capillary electrophoresis, tough luck spectroscopy of atómico magnetic resonance fourteen and spectrophotometry. 15-17 Chromatographic methods will be the most used inside the determination regarding sildenafil citrate within several matrices (pharmaceutical formulations, plasma plus urine), 7-9, 11as well just as typically the determination of pharmacokinetic parameters. These have low detection limits, which justifies their make use of in the examination of biological liquids. However, they need a very long time in typically the initial sample prep steps, use greater amounts of solvents and the arrangement is somewhat more expensive, which usually raises the ultimate cost of typically the analyzes. For typically the analysis of pharmaceutic formulations, it is desirable that methods using inexpensive strategies and that offer fast, precise plus accurate results will be available.

Molecular assimilation spectrophotometry is the particular instrumental means of option widely used for this specific purpose, having the advantages of being easy, involving the usage of low-cost equipment plus being able to be easily programmed. The methods defined in the literature intended for the determination involving sildenafil citrate by simply spectrophotometry 15-17 are scarce and they have some disadvantages, because they demand heating for shade development in acetonitrile medium 16 or perhaps involve laborious processes with many phases of sample coping with, including extractions together with chloroform. 15

This kind of work describes the introduction of a fast and even simple spectrophotometric technique based on the reaction between sildenafil citrate and p-chloranil 16 accelerated by simply the addition of hydrogen peroxide, quickly producing a steady violet complex (? max = 535 nm) at place temperature.



EXPERIMENTAL PART

Materials and gear

The volume dimensions were created with course A burettes or perhaps Eppendorf micropipette (100-1000 � L). The glassware used within the preparation regarding the solutions was grade A along with the weighings were performed on an deductive balance AG204, Mettler Toledo. Absorbance sizes were made using the Varian spectrophotometer type Cary 100 prepared with glass or perhaps quartz cuvettes with an optical path of just one cm.

Reagents in addition to solutions

All reactants and solvents employed in this work were of analytical class. Working solution five. 68 x 12 -3 mol D -1 of sildenafil citrate (supplied by Pfizer, 95%) has been prepared in methanol (Mallinckrodt, Xalostoc, Mexico). This solution is definitely stable for 12-15 days if saved in the fridge. 5 p-chloranil (Sigma, St. 성인용품 , USA), working solution 1 . 00 x twelve -2 mol T -1 of p-chloranil (Sigma, St. John, USA) was well prepared in dioxane (Mallinckrodt, Xalostoc, Mexico). Hydrogen peroxide solution your five. 00 mol M -1was prepared by the correct dilution of the Peridrol answer (Merck, Darmstadt, Philippines, 30% w and w) with methanol, previously standardized relating to the permanganimetric procedure. 18
so that its last concentration ranged from 6. 52 x 10 -5 to at least one. 70 x 10 -3 mol L -1. The volume of the flasks was completed with methanol up to the mark and after that the absorbance sizes were made with 535 nm towards a similarly prepared blank, but with out the addition involving sildenafil citrate. The particular calibration curve was initially constructed by plotting the absorbance values?? measured being a purpose of the sildenafil citrate concentration.

Trial preparation and research

Samples of medications containing sildenafil citrate out there were purchased through local pharmacies plus analyzed by the proposed method, within their expiration date ranges.

Sixteen tablets, through the same batch, were weighed by using an analytical balance as well as the mean mass cost was determined. Eventually, they were sprayed on agate cause until a good powder was acquired. A portion associated with sprayed sample equal to 20 mg involving sildenafil citrate seemed to be exactly weighed and even subjected to mixing with 5 cubic centimeters of methanol within a magnetic stirrer for 15 minutes. This solution was basically transferred to a ten mL volumetric flask and the volume level composed with methanol until the meniscus. Then, the solution was filtered in Whatman 41 quantitative filter paper and also a 750 �L differential was taken in addition to analyzed according to the recommended method for the construction of the analytical curve.g

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