Synchronous Fluorescence Intensity Research Articles

Simultaneous and rapid determination of lomefloxacin and chlortetracycline hydrochloride residues in meat foods by Al3+ sensitized synchronous fluorescence spectrometry

The fluorescence intensity of lomefloxacin and chlortetracycline hydrochloride were significantly enhanced after the complexation of the two antibiotics with Al3+ and the synchronous fluorescence spectra of the two complexes could be well separated when Δλ = 70 nm. Based on the above facts, a new method combining Al3+ sensitization with synchronous fluorescence spectrometry was developed to determine lomefloxacin and chlortetracycline hydrochloride residues in meat foods in this study. This study showed that the concentration of the two antibiotics had an excellent linear relationship with the synchronous fluorescence intensity in the range of 1–550 ng mL−1 and 5–1800 ng mL−1. Detection limits of the two antibiotics were 0.0378 μg kg−1 and 0.3530 μg kg−1, respectively. Recovery rates for lomefloxacin and chlortetracycline hydrochloride were 86.1 - 90.2% and 85.3 - 96.5% in meat samples, respectively. The novel synchronous fluorescence spectrometry established in the experiment had the advantages of high sensitivity, good selectivity, low detection limit, fast detection speed and high accuracy. It had been applied to the detection of lomefloxacin and chlortetracycline hydrochloride residues in meat with satisfactory results.

Eco‐friendly synchronous fluorescence spectrofluorimetric method for simultaneous determination of montelukast sodium and fexofenadine hydrochloride in their antiallergic rhinitis fixed‐dose combination tablets

AbstractAn innovative, simple, accurate, sensitive, and eco‐friendly synchronous fluorescence spectrofluorimetric method has been developed for the simultaneous analysis of montelukast sodium (MON) and fexofenadine hydrochloride (FEX). The method relies on measuring the relative synchronous fluorescence intensity of both drugs using Δλ of 60 nm in methanol at 405 nm for MON and 288 nm for FEX. The experimental parameters influencing the developed method were investigated and optimized. The method was linear over the ranges 0.1–2.0 and 2.0–20.0 μg/ml for MON and FEX, respectively. The limits of detection were 0.018 and 0.441 μg/ml, and the limits of quantitation were 0.055 and 1.336 μg/ml for MON and FEX, respectively. The developed method was applied successfully for the determination of the two drugs in their newly released fixed‐dose combination prescribed for the treatment of allergic rhinitis. The mean per cent recoveries were found to be 100.680 ± 0.890 and 100.110 ± 0.940 for MON and FEX, respectively. Furthermore, the method was found to be eco‐friendly green as was evaluated according to the Green Analytical Procedure Index tool guidelines and analytical eco‐scale.

Development and validation of synchronous spectrofluorimetric method for the simultaneous determination of duvelisib and moxifloxacin: greenness metric assessment and application to a pharmacokinetic study in rats

Duvelisib (DUV) is a potent anticancer drug whereas Moxifloxacin (MOX) is an antimicrobial drug with anti-proliferative potency against cancerous cells, which is empirically administered in cancer treatment. DUV and MOX combination is commonly prescribed to combat infections in patients while they are under chemotherapy treatment. This study describes, for the first time, the development of a simple and green synchronous spectrofluorimetric (SSF) method for the simultaneous estimation of DUV and MOX in plasma. DUV and MOX were quantified at 273 and 362 nm, respectively without interference between each other at Δλ of 120 nm. The experimental variables influencing fluorescence intensities were thoroughly investigated and the optimum conditions were established. At pH 3.5, the optimum synchronous fluorescence intensity (SFI) was achieved in water solvent by using sodium acetate buffer solution. Calibration curves for DUV and MOX, correlating the SFI with the corresponding drug concentration, were linear in the range of 50–1000 ng mL−1 for both drugs, with good correlation coefficients. The method was extremely sensitive, with limits of detection of 24 and 22 ng mL−1, and limits of quantitation of 40 and 45 ngmL−1 for DUV and MOX, respectively. The SSF method was validated according to the Food and Drug Administration (FDA) guidelines for validation of analytical procedures, and the validation parameters were acceptable. The proposed SSF method was applied to the pharmacokinetic and bioavailability studies in rats’ plasma after single concurrent oral administration of both drugs. The results of the study revealed that caution should be taken with DUV dose when concurrently administered with MOX. The greenness of SSF method was assessed by three different metric tools namely Analytical Eco-scale, Green Analytical Procedure Index, and Analytical Greenness Calculator. The results confirmed that SSF method is an eco-friendly and green analytical approach. In conclusion, the proposed SSF method is a valuable tool for pharmacokinetic/bioavailability studies and therapeutic drug monitoring of simultaneously administered DUV and MOX.

A novel sustainable second‐derivative synchronous spectrofluorimetric method for the simultaneous determination of olmesartan medoxomil and rosuvastatin calcium in bulk and formulations: Integrated greenness and whiteness evaluation

AbstractThe present research has established a quick and highly sensitive second‐derivative synchronous fluorometric technique for the simultaneous quantification of a binary mixture of olmesartan medoxomil and rosuvastatin calcium. Simultaneously, the suggested approach was used to detect the synchronous fluorescence intensity of the cited drugs at Δ λ = 80 nm in ethanol to determine the concentrations of olmesartan medoxomil and rosuvastatin calcium at 265 and 240 nm, respectively. Various experimental conditions were tested, and each variable was analyzed and optimized. The calibration graphs were shown to be linear within ranges of 0.1–2.0 and 0.5–6.0 μg ml−1 for each drug concentration, respectively. The newly developed Green Solvents Selecting Tool (GSST) was utilized to assess the solvent's sustainability. Furthermore, the proposed method was found to be environmentally friendly after being evaluated with three different tools [the Green Analytical Procedure Index (GAPI), the Analytical Greenness Metric (AGREE), and the Analytical Eco‐Scale with Eco‐score equal to 95]. The whiteness qualities were also studied using the Red–Green–Blue (RGB12) model, which was recently designed and showed a high score equal to 92.9. The proposed method’s good findings, as well as its ongoing sustainability, simplicity, and economy, stimulate its application in QC laboratories.

Coupling of synchronous fluorescence spectroscopy with derivative amplitude outcomes for simultaneous determination of metoprolol succinate and olmesartan medoxomil in combined pharmaceutical preparation: Application in spiked human plasma.

For the first time a spectrofluorimetric method had been achieved for the concurrent analysis of metoprolol succinate (MET) and olmesartan medoxomil (OLM). The approach depended on assessing the first order derivative (1D) of the synchronous fluorescence intensity of the two drugs in aqueous solution at Δλ of 100nm. The amplitudes of 1D at 300nm and 347nm were measured for MET and OLM, respectively. The linearity ranges were 100-1000ng/mL and 100-5000ng/mL for OLM and MET, respectively. This approach is uncomplicated, repetitive, quick, and affordable. The results of analysis had been statistically verified. The validation assessments were carried out following the recommendations of The International Council for Harmonization (ICH). This technique could be employed to assess marketed formulation. The method was sensitive with limits of detection (LOD) of 32ng/ml and 14ng/mL for MET and OLM, respectively. Limits of quantitation (LOQ) were 99ng/ml for MET and 44ng/mL for OLM. So it can be applied to determine both drugs in spiked human plasma within the linearity ranges of 100-1000ng/mL for OLM and 100-1500ng/mL for MET.

Green fluorometric strategy for simultaneous determination of the antihypertensive drug telmisartan (A tentative therapeutic for COVID-19) with Nebivolol in human plasma

Telmisartan (TEL) and Nebivolol (NEB) are frequently co-formulated in a single dosage form that is frequently prescribed for the treatment of hypertension, moreover, telmisartan is currently proposed to be used to treat COVID19-induced lung inflammation. Green rapid, simple, and sensitive synchronous spectrofluorimetric techniques for simultaneous estimation of TEL and NEB in their co-formulated pharmaceutical preparations and human plasma were developed and validated. Synchronous fluorescence intensity at 335 nm was used for TEL determination (Method I). For the mixture, the first derivative synchronous peak amplitudes (D1) at 296.3 and 320.5 nm were used for simultaneous estimation of NEB and TEL, respectively (Method II). The calibration plots were rectilinear over the concentration ranges of 30–550 ng/mL, and 50–800 ng/mL for NEB and TEL, respectively. The high sensitivity of the developed methods allowed for their analysis in human plasma samples. NEB`s Quantum yield was estimated by applying the single-point method. The greenness of the proposed approaches was evaluated using the Eco-scale, National Environmental Method Index (NEMI), and Green Analytical Procedure Index (GAPI) methods.

Green synchronous spectrofluorimetric method for the simultaneous determination of agomelatine and venlafaxine in human plasma at part per billion levels

A novel sustainable, simple, sensitive, and green spectrofluorimetric method was developed for the concurrent estimation of venlafaxine and agomelatine in pharmaceuticals and biological fluids. The method relies on synchronous fluorescence spectroscopy, where venlafaxine and agomelatine were measured at 276 and 328 nm, respectively, using Δλ of 20 nm. The potential factors affecting the fluorescence intensity were optimized by the one-factor-at-a-time (OFAT) strategy, where synchronous fluorescence intensity was significantly enhanced using a 1% w/v sodium dodecyl sulfate micellar system. The method was fully validated and exhibited excellent linearity (r2 > 0.999 for both drugs) with very low limits of detection (LODs) in the range of 0.14–0.84 ng/mL. Consequently, the proposed approach was efficiently adopted to analyze the co-administered drugs in their pharmaceuticals and in spiked human plasma with excellent % recovery between 97.4 and 102.2%. Finally, the method's greenness was evaluated using different metric tools, including Green Analytical Procedure Index (GAPI) and Analytical GREEnness (AGREE), which proved its excellent greenness.

Synchronous Fluorescence Method for Determination of Bevacizumab and Fluorouracil in Laboratory Prepared Mixture, Pharmaceutical Dosage Forms and Spiked Plasma

Bevacizumab (BVC) is commonly co-administered with 5-fluorouracil (FLO) as a highly successful treatment for colon cancer. In this study, two spectrofluorimetric techniques were combined to provide an approach for concurrent quantification of BVC and FLO that is very sensitive, quick, easy and accurate. The inclusion of Tween-80 micellar system increased the native fluorescence intensity values of BVC and FLO, while the second derivative of the synchronous fluorescence intensity of the cited drugs at Δλ=100 nm allowed the concurrent estimation of cited drugs. The effect of various experimental conditions on the synchronous fluorescence of cited drugs were extensively examined to optimize them. The second derivative synchronous fluorimetry peak amplitudes for BVC and FLO were recorded at 450 nm and 440 nm, respectively. At a range of 100–1100 and 100–600 ng mL−1, the fluorescence-concentration graphs were built, with smaller quantification limits of 60.0 and 70.0 ng mL−1 and detection limits of 20.0 and 23.0 ng mL−1 for BVC and FLO, respectively. Without any major interference, the technique was effectively used to determine the cited drugs in raw material along with pharmaceutical formulations. The proposed technique was shown to be extremely precise and accurate when related to the reported techniques statistically.

Quantitative analysis of favipiravir and hydroxychloroquine as FDA-approved drugs for treatment of COVID-19 using synchronous spectrofluorimetry: application to pharmaceutical formulations and biological fluids.

Coronavirus disease 2019 (COVID‐19) is a contagious viral infection caused by coronavirus 2 (SARS‐CoV‐2) that causes severe acute respiratory syndrome. It has ravaged several countries and burdened many healthcare systems. As the process of authorizing a novel treatment for human use is extensive and involves multiple phases to obtain safety information and identify potential concerns. Therefore, the fastest and easiest choice was to use United States Food and Drug Administration (US FDA)‐approved drugs such as favipiravir and hydroxychloroquine. For the simultaneous estimation of both medications, a simple synchronous spectrofluorimetric approach was established in which both drugs were measured at 372 and 323 nm, respectively in the presence of each other without interference at Δλ 60 nm. The effect of various experimental conditions on synchronous fluorescence intensities were thoroughly investigated and optimized. The maximum synchronous fluorescence intensities were obtained at pH 5.4 using acetate buffer (0.2 M, 0.5 ml) and ethanol as a diluent. Excellent linearity ranges were obtained using 1.0–18.0 ng/ml and 10.0–120.0 ng/ml for favipiravir and hydroxychloroquine, respectively. The approach exhibited high sensitivity with detection limits down to 0.25 ng/ml and 1.52 ng/ml and quantitation limits down to 0.77 ng/ml and 4.62 ng/ml, respectively. Spiking human plasma samples with the studied drugs yielded high % recoveries, allowing a significant bioanalytical application. Moreover, the method was validated according to International Conference on Harmonization guidelines and further applied to commercial pharmaceutical preparations with good results.

N-doped carbon hollow spheres for the simultaneous determination of atorvastatin and amlodipine by synchronous fluorescence spectroscopy

A green and sensitive analytical procedure by dispersive solid-phase nanoextraction (DSPNE) strategy based on mesoporous nitrogen-doped hollow carbon sphere as adsorbent is developed for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in spiked human plasma. The determination method was based on measuring the synchronous fluorescence intensity of the drugs at a constant wavelength difference (Δλ = 40 nm). The different experimental parameters influencing the extraction efficiency of the two drugs were studied and optimized. The limits of detection were 3.24 and 0.406 ng. ml−1 and quantification limits were 10.8 and 1.36 ng. ml−1 for AT and AM, respectively. Validation assays indicated that the concentration ranges were linear in 11–120 for AT and 2–90 ng ml−1 for AM, with R2 > 0.993 for both drugs. Under optimum conditions, extraction recovery was 94% and 89% with RSD% 3.9 and 4.7 (n = 4) for AT and AM, respectively. The developed method has been found to be simple, economical, and reproducible for the routine analysis of both drugs in biological fluids.

First-order derivative synchronous spectrofluorimetric determination of two antihypertensive drugs, metolazone and valsartan, in pharmaceutical and biological matrices

In this study, a facile, rapid, and sensitive spectrofluorimetric method was evolved to analyse two antihypertensive drugs, namely, metolazone (MTZ) and valsartan (VST), in pharmaceutical and biological matrices. Both analytes exhibited intrinsic fluorescence activities which were significantly affected by environmental factors such as pH and solvent systems. However, simultaneous determination of MTZ and VST by conventional spectrofluorometry cannot be achieved simply because of the strong overlap between their fluorescence spectra. Thus, a combination of derivative and synchronous spectrofluorometry was conducted to overcome this dilemma. The proposed method relies on measurement of the first-order derivative of synchronous fluorescence intensity of the studied drugs at Δλ = 160 nm using 0.1 M acetic acid as the optimum solvent. The amplitudes of the first derivative synchronous fluorescence spectra of MTZ and VST were recorded at 236.0 nm (zero-crossing point of VST) and at 262.8 nm (zero-crossing point of MTZ) for simultaneous analysis of MTZ and VST, respectively. The fluorescent method was optimized efficiently to get the maximum selectivity and sensitivity by investigating different solvents, different buffer pHs, and different surfactants. The highest sensitivity and selectivity were achieved when 0.1 M acetic acid was used as a solvent. The method showed a linear concentration range of 10.0–100.0 ng mL−1 and a limit of detection of <3.0 ng mL−1 for each analyte. Statistical data analysis confirmed that no significant difference between the proposed spectrofluorometric method and the reference methods. The validity of the proposed spectrofluorometric method approved its suitability for quality control work. The proposed spectrofluorometric method was applied to assay the studied drugs in pharmaceutical dosage and in biological matrices with acceptable %recoveries and small RSD values.

Concurrent estimation of some co-administered antimicrobial drugs applying conventional and first derivative synchronous fluorescence spectroscopy techniques

For the estimation of some co-administered antimicrobials, two highly accurate and precise spectrofluorimetric methods were developed. Fluconazole (FLZ) is co-administered with either ciprofloxacin (CPR) or ofloxacin (OFX) for the treatment of certain microbial infections. On the other hand, another antimicrobial drug, vancomycin (VNC) is co-administered with ciprofloxacin (CPR) for peritonitis treatment. In method I, conventional spectrofluorimetry has been introduced for the concurrent quantitative estimation of FLZ in presence of OFX or CPR. While in method II, a first derivative synchronous spectrofluorimetric technique was adapted for quantitation of VNC and CPR co-administered combination. Both of them were utilized for estimation of the considered drugs in raw materials, laboratory prepared mixtures, dosage forms, and biological fluids. Method I was relied on simultaneous measuring of the native fluorescence of FLZ and OFX or CPR without any overlapping between the emission spectra of each binary mixture (FLZ / OFX) and (FLZ / CPR). Fluorescence intensities were measured at 283.0, 483.0 and 436.0 nm after excitation at 262.0, 292.0 and 275.0 nm for FLZ, OFX and CPR, respectively. Method II was utilized the synchronous fluorescence intensity of VNC and CPR in methanol at Δλ = 40 nm. The first derivative synchronous spectra were calibrated at 297.0 nm for VNC and at 379.5 nm for CPR. Different variables influencing conventional and synchronous fluorescence intensities of the four antimicrobials under investigation were precisely optimized. Both methods were successfully investigated for the determination of the studied drugs in plasma. The linear data analysis for the calibration curves reveals a good relationship in the ranges of 1.0–10.0, 0.25–2.5 and 0.06–0.6 μg/mL for FLZ, OFX and CPR for method I with limits of detection 0.144, 0.038 and 0.007 μg/mL and limits of quantitation of 0.437, 0.114 and 0.021 μg/mL for FLZ, OFX and CPR, respectively. Linearity range for method II was 0.5 –10.0 μg/mL for VNC and CPR with detection limits of 0.127 and 0.110 μg/mL and quantitation limits of 0.380 and 0.334 μg/mL for VNC and CPR, respectively. International Council on Harmonization ICH Q2 (R1) Guidelines were followed in the developed methods validation. The achieved outcomes were statistically compared with those found by the reported ones, and no significant difference was observed.

Quality control of dietary supplements: An economic green spectrofluorimetric assay of Raspberry ketone and its application to weight variation testing

Although Dietary supplements are readily accessible and extensively used worldwide, they are inadequately regulated and consumers are victims of manufacturers' fraud. Thus, quality regulations are required to ensure safety of products available to the public. We propose the first native spectrofluorimetric quality control assay of raspberry ketone, a popular dietary supplement ingredient for weight loss. This work relies on the constant wavelength synchronous scan of the Raspberry Ketone native fluorescence, overcoming the demerits of conventional excitation/ emission spectra. For the best measurement conditions, several parameters were optimized including Δλ value, diluting solvent, medium pH and the effect of surfactants/ macromolecules. In aqueous medium (Δλ = 110 nm), a linear relationship exists between synchronous fluorescence intensity at peak maximum 405.6 nm and solution concentration in the range 300–1500 ng/mL. Method sensitivity was recorded with LOD and LOQ values 60.63 and 183.72 ng/mL; respectively. Validation was done in accordance to International Conference on Harmonization (ICH) guidelines. This simple procedure was successfully applied to the analysis of Raspberry Ketone in commercially available dietary supplement capsules with average recovery 98.67% ± 1.74 and further extended to weight variation testing following the official United States Pharmacopeial (USP) guidelines. Finally, green assessment was done using the ''Analytical Eco-scale'' tool. The total score was 89/100 points revealing excellent greenness of our proposal. Our proposal is simple, eco-friendly and cheap. It can be conveniently adopted for routine quality control practices especially in developing countries.

N-Doped Carbon Hollow Spheres for the Simultaneous Determination of Atorvastatin and Amlodipine by Synchronous Fluorescence Spectrofluorimetry

A green and sensitive analytical procedure by dispersive solid-phase nanoextraction (DSPNE) strategy based on mesoporous nitrogen-doped hollow carbon sphere as adsorbent is developed for the simultaneous determination of atorvastatin (AT) and amlodipine (AM) in spiked human plasma. The determination method was based on measuring the synchronous fluorescence intensity of the drugs at a constant wavelength difference (Δλ=40 nm). The different experimental parameters influencing the extraction efficiency of the two drugs were studied and optimized. The limits of detection were 3.24 and 0.406 ng. ml -1 and quantification limits were 10.8 and 1.36 ng. ml -1 for AT and AM, respectively. Validation assays indicated that the concentration ranges were linear in 11-120 for AT and 2-90 ng ml -1 for AM, with R 2 >0.993 for both drugs. Under optimum conditions, extraction recovery was 94% and 89% with RSD% 3.9 and 4.7 (n=4) for AT and AM, respectively. The developed method has been found to be simple, economical, and reproducible for the routine analysis of both drugs in biological fluids.

Micelle-Enhanced conventional and synchronous spectrofluorimetric methods for the simultaneous determination of lesinurad and febuxostat: Application to human plasma

A simple synchronous spectrofluorimetric method was developed for simultaneous determination of lesinurad and febuxostat. The investigated drugs were measured at 294 and 329 nm, respectively in the presence of each other without interference at Δλ of 50 nm (Method I). The different experimental parameters affecting the fluorescence intensities were carefully studied and optimized. The maximum synchronous fluorescence intensities were obtained at pH 6.5 using borate buffer and distilled water was used as a diluting solvent. Excellent linearity ranges were obtained using 20.0–500.0 ng mL−1 and 1.0–80.0 ng mL−1 for lesinurad and febuxostat, respectively. The method exhibited high sensitivity with detection limits down to 4.0 ng mL−1 and 0.01 ng mL−1 and quantitation limits down to 12.12 ng mL−1 and 0.02 ng mL−1, respectively. Recovery percentages ranged from 97.68 to 103.37% were obtained upon spiking of human plasma samples, indicating high bioanalytical applicability. Concerning Method II, methanolic solution of lesinurad was measured spectroflourimetrically with λexcitation at 290 nm and λemission at 341 nm with high sensitivity using borate buffer of pH 6.5 and methanol as a diluting solvent. A considerable enhancement of the fluorescence intensity was achieved by using 1.0% w/v cetremide as a micellar system. The method was rectilinear over the concentration range of 3.0–80.0 ng mL−1 with detection and quantitation limits down to 0.47 and 1.42 ng mL−1, respectively. The developed method was efficiently applied for the estimation of the cited drug in spiked human plasma with high recovery percentages (98.58–101.64%). The methods were validated according to the ICH guidelines and further applied to commercial tablets with good results.

Simultaneous determination of elbasvir and grazoprevir in their pharmaceutical formulation by synchronous fluorescence spectroscopy coupled to dual wavelength method

In the present study, a sensitive, selective and accurate synchronous fluorescence spectroscopic method was utilized for simultaneous estimation of elbasvir and grazoprevir in their pharmaceutical formulation. The developed method based on measurement of the synchronous fluorescence intensity of the studied drugs at constant wavelength difference (Δλ) = 50 nm. Elbasvir can be determined directly at 312 nm without interference from grazoprevir. Grazoprevir can be determined by application of dual wavelength method by taking the difference in synchronous fluorescence intensity at 390 & 372 nm to remove interference from elbasvir. Calibration graphs were found to be linear over the concentration range of 50–700 ng/mL for elbasvir and 100–900 ng/mL for grazoprevir. The developed method was successfully applied to the quantitative analysis of the two drugs in Zepatier® tablets.

Simultaneous determination of citalopram and tadalafil by the second derivative synchronous fluorescence method in biological fluids; application of Box-Behnken optimization design.

This is the first study focusing solely on that determination of tadalafil in the presence of citalopram as an antidepressant drug. The determination in biological fluids of a co-administered antidepressant drug and a sexual stimulation drug is a very critical and important step for psychotic and ischaemic heart disease patients, especially in cases of emergency and this requires therapeutic drug monitoring. A sensitive, efficient and rapid assay was selected satisfactorily and applied for simultaneous determination of citalopram and tadalafil either in their pure forms, in tablet dosage forms or in spiked human plasma. There was a large overlap for both drugs, forming the broad band found in conventional fluorescence spectra and their related synchronous fluorescence intensity. Therefore, the development of a highly sensitive second derivative synchronous fluorescence method was demonstrated that removed this overlap. The proposed method depended on measuring the amplitudes of the second derivative of synchronous fluorescence intensity at suitable wavelengths of 301 nm and 367 nm for citalopram and tadalafil at Δλ = 60 nm, respectively. Box-Behnken design as a response surface methodology was used to fit models and create an optimization process encompassing a set of factors and resulting in an optimum response value specifically designed for this method. Under optimum conditions, the linear dynamic ranges for citalopram and tadalafil estimation were 20-900 and 5-400 ng ml-1 with detection limits of 5.40 and 1.43 ng ml-1 , respectively.

Micelle sensitized synchronous spectrofluorimetric approaches for the simultaneous determination of simeprevir and ledipasvir: Application to pharmaceutical formulations and human plasma.

Simeprevir (SMV) is commonly co-administered with ledipasvir (LDS) and sofosbuvir (SOF) as an effective combination regimen for treatment naive hepatitis C virus infected patients. In the present study, two spectrofluorimetric approaches were combined together for the development of highly sensitive, rapid, simple and accurate method for simultaneous quantification of SMV and LDS. The native fluorescence intensity values of SMV and LDS were enhanced by the addition of Tween-80 micellar system, while second derivative of the synchronous fluorescence intensity of the drugs at Δλ=120nm enabled the determination of both drug concomitantly. Different experimental parameters affecting the synchronous fluorescence of the cited drugs were carefully evaluated for their optimization. The peak amplitudes of the second derivative synchronous fluorimetry were measured at 429nm for SMV and at 417nm for LDS. The fluorescence-concentration plots were rectilinear over the range of 60-1500 and 36-540ngmL-1 with lower detection limits of 9.0 and 6.0ngmL-1 and quantification limits of 27.0 and 17.0ngmL-1 for SMV and LDS respectively. The method was successfully applied for the determination of both drugs in their pure forms as well as their pharmaceutical products and human plasma without any significant interference. Statistical comparison with the reported method revealed excellent accuracy and precision of the proposed method.

D-optimal design as a useful tool response surface methodology for the optimization of signals from synchronous fluorescence prior to simultaneous determination of avanafil and tadalafil.

A rapid, smart and sensitive first derivative spectrofluorimetric method has been carried out for the simultaneous estimation of avanafil and tadalafil either in their pure form, tablet dosage form or spiked human plasma. The measurements of normal emission spectra or synchronous fluorescence intensity of both drugs show severe overlap which hindered their determination using normal fluorescence or synchronous intensity. Therefore, a highly sensitive first derivative synchronous fluorescence procedure was used to resolve this overlap. The method is based upon measurement of the amplitude of the first derivative of synchronous fluorescence intensity of both drugs at Δλ=70nm and at suitable wavelength of 396nm and 364nm for avanafil and tadalafil, respectively. Under the optimum conditions, the linear determination ranges are 50-1800 and 5-400ngmL-1 with a detection limit of 12.93 and 1.46ngmL-1 for avanafil and tadalafil, respectively. A response surface methodology was used for optimization using D-optimal design which can be used for determination of the exact optimum parameters specifically designed for this method. In addition; it is a good way to graphically clarify the relationship between various experimental variables and the synchronous fluorescence intensity.

Synchronous spectrofluorometric methods for simultaneous determination of diphenhydramine and ibuprofen or phenylephrine in combined pharmaceutical preparations.

Simple and rapid synchronous fluorometric methods were adopted and validated for the simultaneous analysis of a binary mixture of diphenhydramine (DIP) and ibuprofen (IBU) (Mix I) or DIP and phenylephrine (PHE) (Mix II) in their co-formulated pharmaceuticals without prior separation. Analysis of Mix I is based on the measurement of the peak amplitudes (D1 ) of synchronous fluorescence intensities at 265.1 nm for DIP and 260 nm for IBU. The relationship between the concentration and the amplitude of the first-derivative synchronous fluorescence spectra showed good linearity over the concentration ranges 0.50-10.00 μg ml-1 and 0.50-7.90 μg ml-1 for DIP and IBU, respectively. Analysis of Mix II was based on measurement of the peak amplitude (D1 ) synchronous fluorescence intensities at 230 nm for DIP and at 253.9 nm for PHE. Moreover, for Mix II, the peak amplitude (D2 ) synchronous fluorescence intensities were measured at 227.9 nm for DIP and at 264.9 nm for PHE. Calibration plots were rectilinear over the concentration range 0.30-3.50 μg ml-1 and 0.03-0.75 μg ml-1 for DIP and PHE, respectively. The proposed methods were successfully applied to determine the studied compounds in pure form and in pharmaceutical preparations.