Determination Of Sildenafil Research Articles

Simple, Miniaturized, Adaptable, Robust and Transportable (SMART) 3D-printed electrochemical cell: A friendly tool for on-site and forensic analysis

In this work, we introduce the SMART-EC3D (Simple to mount, Miniaturized, Adaptable to several electrodes, Robust and Transportable 3D-printed electrochemical cell). This device consists of a lid with a mini solution reservoir (volume between 100 and 1000 μL) promptly attached through strong magnets to a base containing an adjustable bolt. This innovative and user-friendly configuration ensures the compatibility of the cell with any planar working electrode without solution leakage or electrode rupture. The cell was printed using different materials for FDM (ABS, PLA and PETG) and DLP (resin), which exhibited excellent stability in several supporting electrolytes (acid, basic and aqueous-organic). To demonstrate the versatility of SMART-EC3D for forensic analysis, we performed electrochemical screening of some seized illicit drugs (MDMA, LSD and 25I-NBOH) using typical working electrodes (gold, glassy carbon and boron-doped diamond, respectively) and a direct-on-solid screening protocol for the detection of the tadalafil in seized samples using a low-cost 3D-printed-based carbon electrode. Additionally, the determination of sildenafil citrate and paracetamol in pharmaceutical tablets using promising low-cost electrodes (graphite sheet and laser induced graphene, respectively) was demonstrated as examples of quantitative analysis. The fully portable system (SMART-EC3D plus wireless potentiostat and smartphone) has great potential for on-site electroanalyses and forensic applications.

Determination of sildenafil and tadalafil adulteration by LC-MS/MS and 23 elements by ICP-MS in food supplements

Determination of sildenafil and tadalafil adulteration by LC-MS/MS and 23 elements by ICP-MS in food supplements

Extraction and Determination of Sildenafil Citrate by Spectrophotometry: Classical Versus Factorial Design Optimization

In this work, the complexation and extraction processes of sildenafil citrate (SC) were evaluated by using classical optimization versus factorial design methodology. The selected factors were based on the reaction of sildenafil with methyl orange (MO) as a chromogenic reagent via the formation of ion-association complex in acidic buffer media, followed by extraction with chloroform and quantitatively measured by visible spectrophotometry at λmax of 427 nm. The optimization step was first carried out by classical one-factor-at-a-time (OFAT) from which the extracted results were exploited in the experimental design optimization by using 24-1 fractional factorial and 32 full factorial designs for the chosen variables such as pH, concentration of reagent, reaction time, extraction time and temperature. Results obtained from fractional factorial design 24-1 showed that only the variables pH, MO concentration and their interaction based on analysis of variance (ANOVA) in term of Pareto chart, were statistically significant at 95% confidence level. Under the optimized conditions, the assay method of SC was validated in term of the analytical figures of merit. SC can be determined in concentration range of 0.5-40 µg mL-1 with correlation coefficient of 0.9991, detection limit (S/N) of 0.15 µg mL-1, RSD (n=10) of 1.43%, accuracy as %Erel of -2.23% and mean percent recovery of 97.77±0.87. The proposed method was applied for the determination of SC in commercial medicaments without fear from excipients interferences with the assay procedure.

Rapid Quantitative Determination Control Male Sexual Dysfunction Drug Content of Sildenafil and Tramadol Mixture by Spectrophotometry Along With Smart Chemometrics Approaches Compared to the HPLC Reference Method.

There are reports for the simultaneous estimation of sildenafil (SIL) and tramadol (TM) using chromatographic techniques. Some limitations of these methods are high cost and time, more usage of pollutant solvents, and complicated instruments. Simultaneous determination of SIL and TM in the anti-sexual dysfunction pharmaceutical formulation using rapid and smart chemometrics approaches along with spectrophotometry. In this study, a spectrophotometric analysis method based on continuous wavelet transform (CWT), partial least-squares (PLS), and radial basis function neural network (RBF-NN) was presented. In the CWT method, the Symlet (Sym2) and Daubechies (db2) wavelet families with wavelengths of 268 and 221 nm were considered the best families for SIL and TM, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) values were found to be 0.0185, 0.0054 μg/mL and 0.0458, 0.3092 μg/mL for SIL and TM, respectively. The mean recovery values were 101.06 and 101.49% for SIL and TM, respectively. The results of PLS revealed that the root-mean-square error (RMSE) of SIL and TM was 0.0286 and 0.0635, respectively. Also, the mean recovery of both drugs was obtained over 99%. The mean square error (MSE) of RBF-NN was 5.88 × 10-29 and 4.61 × 10-27 for SIL and TM, respectively. A statistical comparative study conducted for the proposed methods with the high-performance liquid chromatography (HPLC) technique demonstrated no significant difference between these methods. The suggested approaches were simple, fast, accurate, and affordable. Three smart UV spectrophotometric methods based on chemometrics were presented to determine SIL and TM simultaneously. The efficient chemometrics methods, including CWT, PLS, and RBF-NN, were used. The mentioned methods are rapid, simple, inexpensive, and accurate. The comparison was performed between the proposed models and HPLC technique.

Smart spectrophotometric methods for enhancement spectral resolution and rapid simultaneous determination of dapoxetine and sildenafil in commercial tablets using fuzzy inference system and continuous wavelet transform

Dapoxetine (DAP) and sildenafil (SIL) have been clinically prescribed for the treatment of premature ejaculation and erectile dysfunction. The analysis of the combination of DAP and SIL has a challenge due to the high overlap spectra of these compounds. In this study, fuzzy inference system (FIS) along with principal component analysis (PCA) and continuous wavelet transform (CWT) methods were combined with UV–Vis spectrophotometry for solving such a challenging overlap and spectral resolution. Hence, simultaneous determination of DAP and SIL was performed in mixtures and pharmaceutical samples using these methods. The mean recovery percentage values of FIS were 98.22% and 98.44% for DAP and SIL, respectively. In addition, the root mean square error (RMSE) of DAP and SIL was found to be 0.158 and 0.933, respectively. The detection limits (LOD) of CWT were 1.134 and 0.179 μg mL−1 for DAP and SIL, respectively. Also, the limit of quantification (LOQ) values of DAP and SIL were 1.169 and 0.238 μg mL−1, respectively. Relative standard deviation (RSD) values related to the real samples were lower than 0.5% for both methods. Statistically, there was no significant difference between results found for the proposed and the high-performance liquid chromatography (HPLC) methods. The result obtained revealed that the suggested methods were found to be precise, accurate, simple, cost-effective, and robust. The present study provides an excellent approach for the concurrent determination of DAP and SIL in combined tablet formulation.

Metal-organic framework modified by silver nanoparticles for SERS-based determination of sildenafil and pioglitazone hydrochloride.

Aversatile surface-enhanced Raman scattering (SERS) assay has been establishedthat can realize rapid and sensitive determination of sildenafil (SIL) and pioglitazone hydrochloride (PIO) adulteration in healthcare products. Metal-organic frameworks-silver nanoparticles (MOFs-AgNPs) with SERS activity were successfully preparedvia in situ synthesis AgNPs on the MOFs surface. By virtue of the adsorptivity of MOFs, the MOFs-AgNPs could effectively concentrate the drug molecules on the electromagnetic enhancement areas of AgNPs. Moreover, the MOFs-AgNPs substrate exhibited more sensitive SERS activity than classical AgNPs with linear range of 1.0 × 10-7-1.0 × 10-5mol L-1 for SIL and 8.0 × 10-7-3.0 × 10-5mol L-1 for PIO and limit of detection (LOD) of 4.8 × 10-8mol L-1 for SIL and 1.4 × 10-7mol L-1 for PIO. The designed method realized the determination of SIL and PIO in commercial tablets and healthcare products with recoveries of 93.8-108.0% and 93.0-104.0%, respectively, with relative standard deviation (RSD) of 2.7-4.1% and 2.2-4.2%, respectively. The present system displayed littleinterference effect on determination. This work provides a multifunctional route for the determination of other drugs via the SERS technology.

Development and Validation of a Simple, Green Infrared Spectroscopic Method for Quantitation of Sildenafil Citrate in Siloflam Tablets of Unknown Manufacturing Formula.

A simple, easy-to-implement, and green infrared spectroscopic method was developed and validated for the quantitative determination of sildenafil citrate in tablets of unknown manufacturing formula. Homogenized tablet powder with known mass content (%, m/m) of sildenafil citrate was mixed with paracetamol to form standard mixtures with different percentages of sildenafil citrate on the total quantity of sildenafil citrate and paracetamol (designated as R). Unknown tablet samples were finely ground and mixed with paracetamol to form test mixtures having R values about 50%. Infrared spectra of standard mixtures, measured in attenuated total reflectance mode, in the wavenumber zone from 1800 cm−1 to 1300 cm−1 were selected and processed by partial least square regression to form the calibration model for quantitation of sildenafil citrate in unknown samples. Spectral responses of test mixtures and the calibration model were used to determine the exact mass content (%, m/m) of sildenafil citrate in the powder of unknown tablet samples. The method was fully validated in terms of linearity, precision, and accuracy according to the requirements of current guidelines and was proved as reliable and suitable for the intended application.

UPLC-MS/MS for the Simultaneous Determination of Sildenafil and N-Desmethyl Sildenafil.

A sensitive high-performance liquid chromatography-tandem mass spectrometry method was established for the simultaneous determination of sildenafil and N-desmethyl sildenafil in human plasma. The protein precipitation was used for extraction and the gradient elution of the mobile phase A of water (containing 0.01% formic acid) and the mobile phase B of acetonitrile, and methanol (V:V=1:1, containing 0.01% formic acid) was used for chromatographic separation on a C18 column. Quantification was performed by multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 475.4→m/z 283.3 for sildenafil, m/z 461.4→m/z 283.2 for N-desmethyl sildenafil, m/z 483.3→m/z 108.1 for sildenafil-d8 (IS) and m/z 469.2→m/z 283.3 for N-desmethyl sildenafil-d8 (IS) at the positive ionization mode. The intra- and inter-day relative standard deviations were less than 6.8% and 4.1% for sildenafil and N-desmethyl sildenafil, respectively. Accuracy at four levels ranged from 93.1% to 115.9% for sildenafil and 95.6% to 112.5% for N-desmethyl sildenafil. The present method was sensitive and reliable for simultaneous quantification of sildenafil and its active metabolite and was successfully applied to a pharmacokinetic study of an oral low dose of sildenafil in Chinese healthy volunteers.

HPLC DETERMINATION OF SILDENAFIL IN TABLETS

Objective: The popularity of Sildenafil, the widespread distribution of various products and dietary supplements with added synthetic drugs, requires reliable analysis methods. This research study aimed to develop a simple isocratic HPLC method for the determination of Sildenafil in tablet dosage forms from the local market.
 Methods: Separation was carried out at 30 °C, using column LiChrosorb® RP-18 (150 x 4.0 mm, 5 μm) with mobile phase consisting of acetonitrile: methanol: 0.5% triethylamine (15: 26: 59 v/v/v). The detector was set at 290 nm. The flow rate was 1.0 ml/min and the injection volume was 20 μl.
 Results: Linear correlation was obtained within the range 6.25–50.0 μg/ml with correlation coefficient (R2) 0.9998. The achieved limits of detection and quantitation were 0.7 and 2.2 μg/ml, respectively.
 Conclusion: The developed method can be applied for the quality control of Sildenafil preparations.

Фармакокинетические особенности силденафила в форме спрея для здоровых мужчин в зависимости от приема пищи

In order to evaluate the bioequivalence and benefits of a new dosage form of the type 5 phosphodiesterase inhibitor, sildenafil, two open-label studies in healthy male volunteers were carried out.An open, randomized, crossover study to compare the pharmacokinetics after a single dose of sildenafil at a dosage of 50 mg on an empty stomach in a new spray form (test drug) and in a traditional tablet form (comparison drug) on 44 volunteers (18 to 43 years old) was done. To assess the effect of food intake on pharmacokinetics, an open, non-randomized study was conducted on 6 healthy male volunteers (from 23 to 35 years old) who received sildenafil (50 mg) after a meal in timely fashion: 1) spray, under the tongue, without drinking, 2) spray , in the mouth, drinking water and 3) the tablet form, drinking water. For pharmacokinetic analysis, blood was analyzed for 24 hours. Plasma concentration of sildenafil was determined by high performance liquid chromatography with tandem mass spectrometric detection (HPLC/TM/SD). The main parameters were the rate (maximum concentration; Cmax) and the degree of absorption (area under the pharmacokinetic curve "concentration-time" during the observation period; AUC0-t) after a single dose of drugs. In addition, the pharmacokinetic profiles of the bioavailability of sildenafil and its active metabolite, N-desmethyl sildenafil, as well as the safety of the different dosage forms, were evaluated.When comparing taking drugs on an empty stomach, the 90% confidence intervals (CI) of the ratios of the mean Cmax and AUC0-t values of sildenafil were 82-106% and 82-101%, respectively. An earlier achievement of the maximum concentration of sildenafil was detected when taking the test drug compared with the standard form (51 and 62 minutes, respectively, Z-value=-2.25, p-value=0.0244). In addition, it was shown that when taking Viagra after a meal, the determination of sildenafil in plasma was delayed (after 30 minutes) compared to the tested drugs (after 10 minutes), however, significant differences in Tmax between the dosage forms were not seen. In two studies, most adverse events were mild to moderate and resolved uneventfully.The bioavailability of the new dosage form, the sildenafil spray, is equivalent to the traditional form, however, it has an advantage in terms of onset of action. For example, when taking a spray, an earlier achievement of the maximum concentration of sildenafil and an earlier detection of sildenafil in plasma are shown compared to the traditional tablet form.Our results suggest that the new dosage form of sildenafil is a reliable alternative therapeutic option for the treatment of erectile dysfunction.

Simultaneous determination and determination of sildenafil and its active metabolite in human plasma using LC-MS/MS method.

A sensitive and selective high-performance liquid chromatography-tandam mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous quantification of sildenafil and its metabolite N-desmethyl sildenafil in human plasma. Sildenafil-d8 was used as an internal standard. The analytes were extracted by precipitation extraction and chromatographed on a C18 column using mobile phase A of water (containing 0.1% formic acid) and mobile phase B of acetonitrile (containing 0.1% formic acid) with gradient elution. Quantification was done using multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 475.4 → m/z 283.3 for sildenafil, m/z 461.4 → m/z 283.2 for N-desmethyl sildenafil and m/z 483.3 → m/z 108.1 for IS in positive ionization mode. The calibration curve was established over the range of 2.00-1,000 ng/ml and the correlation coefficient was >0.99. The intra-day and inter-day relative standard deviations were <6.5% for sildenafil and 6.3% for N-desmethyl sildenafil respectively. Accuracy determinaed at four concentrations was 86.50-105.67% for sildenafil and 96.83-114.40% for N-desmethyl sildenafil. This method was successfully applied to a pharmacokinetic description of sildenafil and the effect of food intake on the pharmacokinetics of sildenafil was also demonstrated in healthy Chinese volunteers.

Influence of Energy Drinks on Pharmacokinetic Parameters of Sildenafil in Rats

Both sildenafil and RED BULL®(energy drink) are claimed to boost up energy.RED BULL®, one of the most commonly used energy drinks and its easily and widely available for daily use, the idea of this research work had arisen from observations about the concomitant use of sildenafil with RED BULL® by men seeking for better sexual performance. To study the effect of RED BULL® on the pharmacokinetic profile of sildenafil by using HPLC.The pharmacokinetic parameters (Cmax, Tmax and AUC) were determined in 10 rats following oral administration of 0.57 mg/ml sildenafil with and without RED BULL® in crossover design, to achieve this purpose,simple, rapid and accurate method for validation and determination of sildenafil in rat plasma in the presence of RED BULL® has been developed. This was performed using High-Performance Liquid Chromatography- Ultra Violet (HPLC-UV). The pharmacokinetic data showed that sildenafil plasma level was lower when combined with RED BULL® According to the results obtained, maximum concentration (Cmax) for sildenafil alone was (162.05 ng/ml) after 0.5 hours of administration. The Cmax decreased to (44.68 ng/ml) after 0.5 hoursof administration RED BULL® concomitantly with sildenafil which showed a significant effect on sildenafil plasma level (P&lt;0.001). The area under the curve (AUC) decreased significantly from (370.53 ng/ml*hr) for sildenafil alone to (87.74 ng/ml*hr) when combined with RED BULL®. RED BULL® can alter sildenafil pharmacokinetic if they were taken together.

A new magnetic nanodiamond/graphene oxide hybrid (Fe3O4@ND@GO) material for pre-concentration and sensitive determination of sildenafil in alleged herbal aphrodisiacs by HPLC-DAD system

A sensitive analytical methodology was investigated to concentrate and determine of sildenafil citrate (SLC) present at trace level in herbal supplementary products. The proposed method is based on simple and sensitive pre-concentration of SLC by using magnetic solid phase extraction with new developed magnetic nanodiamond/graphene oxide hybrid (Fe3O4@ND@GO) material as a sorbent. Experimental variables affecting the extraction efficiency of SLC like; pH, sample volume, eluent type and volume, extraction time and amount of adsorbent were studied and optimized in detail. Determination of sildenafil citrate after magnetic solid phase extraction (MSPE) was carried out by HPLC-DAD system. The morphology, composition, and properties of the synthesized hybrid material was characterized by Fourier transform infrared spectrometry (FT-IR), Raman spectrometry (Raman), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), mapping photographs, zeta potential analyzer, and BET surface area analysis. Under optimized conditions, linear range was ranged from 5.00 to 250.00 ng mL−1 with R2 of 0.9952. The limit of detection (LOD) was 1.49 ng mL−1 and the recoveries at two spiked levels were ranged from 94.0 to 104.1% with the relative standard deviation (RSD) < 7.1% (n = 5). The enhancement factor (EF) was 86.9. The results show that the combination MSPE with HPLC-DAD is a suitable and sensitive method for the determination of SLC in real samples.

Development of Disposable Immunosensors for Rapid Determination of Sildenafil and Vardenafil in Functional Foods

본 연구의 목적은 screen printed 탄소계 전극에 기반하여 기능성 식품중에 포함된 소량의 Sildenafil과 Vardenafil(SDF 및 VDF)을 쉽게 검출하기 위한 전류계 면역센서를 개발하고자 하였다. 본 연구에서 개발한 면역센서는 horseradish peroxidase로 labeling 시킨 후 비경쟁적 샌드위치ELISA 측정법에 의한 원리를 이용하였다. 개발된 센서는 그래핀 산화물 및 키토산(ErGO-CS) 복합체를 단순한 전기화학적 증착에 의해 screen printed 탄소계 전극을 이용하는 원리이며, 감지된 화학물질을 평가하고 센서특성을 최적화하기 위해 전기 화학적 임피던스분광법, 순환 전압전류법 등을 포함한 일련의 전기화학적 실험방법에 기초하여 완성되었다. 본 연구에서 개발된 센서는 100 pg/mL ~300 ng/mL 농도의 SDF 및 VDF에 대하여 직선상의 농도-의존적인 반응을 나타내었다. 또한 최저 검출 한계는 55 pg/mL이었으며, 센서의 민감도는 1.02 μAng/mL/cm2로 산출되었다. 센서의 성능은 7.1%의 상대 표준편차로 매우 우수한 재현성을 나타내었다. 본 연구에서 개발된 센서의 전략적 가치는 향후 건강기능식품중에 함유된 SDF 및 VDF과 같은 의약품의 미량을 현장에서 쉽게 분석 할 수 있어서 비용-효과적 측면에서 그 가치가 우수하다는 것을 제시한다.

Development and validation of method for quantitative determination of sildenafil and n-desmethyl sildenafil by HPLC-MS/MS in human blood plasma

Aim. To assess bioequivalence of sildenafil citrate tablet formulation produced by pharmaceutical company “Microkhim” (Rubezhnoe, Ukraine) it was developed and validated a prompt, specific and quite simple method for quantitative determination of sildenafil and its active metabolite - N-desmethyl sildenafil concentrations in the human blood using deuterium labeled internal standards. Direct liquid-liquid extraction procedure was utilized to extract the analytes from the blood plasma.Methods. Contents of sildenafil and its metabolite in supernatant were determined by means of the high performance liquid chromatography / tandem mass spectrometric detection technique. Ionization of sildenafil, N-desmethyl sildenafil, sildenafil-d8 and N-desmethyl sildenafil-d8 was performed in the positive electrospray mode (ESI, Positive). Detection of the analytes was carried out in the multi reactions monitoring (MRM) regimen with the following m/z values for selected parent ions: 475,30; 483,20; 461,20 and 469,20, respectively. The daughter ion m/z value was selected to be 283,10 for all analytes.Results. Analytical method proposed proved to demonstrate reliable accuracy and reproducibility for both analytes and has been validated within linear range 5,05-1009,92 ng/ml for sildenafil and 2,24-400,84 ng/mL for N-desmethyl sildenafil with correlation coefficient (r2) equaled to 0.9975 and 0.9973, respectively.Conclusions. It was developed and validated a simple, specific and sensitive HPLC-MS/MS method for quantitative determination of sildenafil and its active metabolite N-desmethyl sildenafil concentrations in human blood plasma utilizing stable isotope labeled internal standards – deuterated sildenafil-d8 and N-desmethyl sildenafil- d8. Important feature of the method was a modified preanalytical procedures of biological samples preparation – direct liquid-liquid extraction that allowed to avoid laborious and time-consuming procedures such as evaporation to concentrate the samples with consequent recovery of dry residue, as well as to refuse from expensive solid-phase extraction. Application of the deuterium labeled internal standards allowed to suppress a biological matrix effect drastically, as well as to reach target LLOQ level. Experimental data obtained in the course of full validation of the method proposed that was performed in accordance with approved national and international technical and regulatory requirements, allowed to affirm high specificity, sensitivity, accuracy, reproducibility and efficiency of the method.

Simple and Sensitive Spectrophotometric Determination of Sildenafil Citrate in Pharmaceutical Formulations

Two simple, rapid and sensitive spectrophotometric methods have been developed for the determination of Sildenafil Citrate (SIL) in pure form and pharmaceutical formulations. The spectrophotometric methods are based on the formation of binary complexes (ion-pair complexes)in dichloromethane (DCM) medium between the drug and tow acidic sulfonephthalein dyes, bromocresol purple (BCP)(method A) and bromophenol blue (BPB) (method B) with absorption maxima at 404 and 410 nm, respectively. The effects of analytical parameters on the reported systems were investigated. The complexation reactions were extremely rapid at room temperature and t¬he absorption values remain unchanged up to 24h. Beer’s law was obeyed in the concentration ranges of 0.6 - 20 and 0.8 -48 µg/ml, detection limits were 0.097 and 0.105µg/ml and the molar absorptivity coefficients were 2.77×104 and 2.60 ×104 L .moL-1.cm-1for BCP and BPB respectively. The proposed methods were successfully applied to the analysis of commercial tablets containing the drugs. Two methods were free-extractive, rapid, and have high sensitivity compared with other previous direct spectrophotometric methods. Interferences of the other ingredients and excipients were not observed.

Reversed Phase High Performance Liquid Chromatographic Method for Determination of Sildenafil in Human Plasma and its Application to a Bioequivalence Study

Reversed Phase High Performance Liquid Chromatographic Method for Determination of Sildenafil in Human Plasma and its Application to a Bioequivalence Study

THe quantitative determination of sildenafil in human plasma by high performance liquid chromatography - mass spectrometry (lc-ms/ms)

Purpose. For the study of pharmacokinetics of sildenafil oral spray “Tegrum”, developed by pharmaceutical company “Microkhim” (Rubezhnoe, Ukraine) with the aim to improve the pharmacokinetic characteristics of existing solid formulations for oral use it was worked out and validated a rapid, simple and specific method of quantitative determination of sildenafil concentration in human plasma using internal standard labeled with 8 deuterium atoms - sildenafil-d8.Methods. Sildenafil was extracted from plasma by the liquid-liquid extraction, and quantitatively determined in supernatant by means of а high performance liquid chromatography - tandem mass spectrometry method (HPLC-MS/MS). Separation of components was performed using the chromatographic column Kinetex 2.6u C18, 50 x 4.6 mm, 2.6 μm (Phenomenex) at 45˚C at isocratic elution mode and mobile phase, that consisted of 2 mM aqueous ammonium acetate solution (pH 5,45 ± 0,05) and acetonitrile (10/90, vol./vol.); flow rate equaled to 0.4 ml/min. Ionization of sildenafil and sildenafil-d8 was performed in the positive electrospray mode (ESI, Positive). Multi reactions monitoring (MRM) mode was used for selected daughter and parent ions detection with the following settings of the mass spectrometer: m/z 475,20/283,20 and 483.20/283.20 for sildenafil and sildenafil-d8 respectively.Results. The method described above was validated in the linear range 10,00-400,00 ng/mL of sildenafil with a correlation coefficient (r2) 0,99764 and demonstrated reliable accuracy and reproducibility of results.Conclusions. Utilization of elaborated method of fast direct liquid - liquid sildenafil extraction from the blood plasma with simultaneous proteins precipitation, avoiding commonly used supernatant evaporation and subsequent restoration of dry residue at preanalytical stage allowed to achieve target sensitivity of determination and reduced the analysis runtime. Usage of the deuterated internal standard (sildenafil-d8) at analytical stage gave an opportunity to reduce the limit of quantification, to achieve high sensitivity and specificity, as well as suppress matrix effect. Rather high analytical characteristics of the method proposed allow its application in routine bioanalysis during pharmacokinetic studies.

High Performance Liquid Chromatographic Method for Determination of Sildenafil Citrate (Viagra) in Pharmaceutical Formulation and Industrial Effluent Sample

A simple, precise, rapid and accurate reversed–phase high performance liquid chromatographic method has been developed for the determination of sildenafil citrate in a pure form, pharmaceutical formulations and industrial effluent samples. Chromatography was carried out on supelco L7 reversed- phase column (25cm × 4.6mm), 5 microns, using a mixture of methanol: water: triethylamine (630: 370 :2 v/v/v) and adjusted to pH 4.0 with dilute phosphoric acid as a mobile phase at a flow rate of 1.0 ml.min -1 .Uv detection was performed at 220 nm at ambient temperature (25 °C). The retention time for sildenafil citrate found to be 4.6 minutes. The calibration curve was linear (r= 0.9998) over a concentration range from 10 to 70 µg/ml. Limit of detection (LOD) and limit of quantification (LOQ) were 60 ng/ml and 180 ng/ml respectively. The method was validated for its linearity, precision and accuracy. The proposed method was successfully applied to the determination of sildenafil citrate in tablets and industrial effluent samples. Keyword: HPLC, Sildenafil citrate, Viagra, Pharmaceutical preparations, Industrial effluent. ــــــــــــــــ ـــــــــــــ ــــــــــــــــ ـــــــــ

Chromatographic determination of sildenafil in blood plasma using spectrophotometric and mass-spectrometric detection

Methods for the determination of sildenafil in human blood plasma by reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) and mass-spectrometric (MS) detection have been developed. Sildenafil was isolated from blood plasma by solid-phase extraction on Sep-Pak Vac tC18 cartridges with the recovery 95 ± 4%. The limits of quantification of sildenafil were 20 and 5 ng/mL using HPLC-UV and HPLC-MS methods, respectively.