Derivative Synchronous Fluorescence Research Articles

Rapid and simultaneous determination of ultratrace pefloxacin and fleroxacin residues in wastewater by Al3+ sensitized first derivative synchronous fluorescence spectrometry

In this study, a new first derivative synchronous fluorescence spectrometry (SFS) for the accurate and sensitive determination of pefloxacin (PFX) and fleroxacin (FLX) in wastewater was established. PFX and FLX were complexed with Al3+ to significantly enhance their fluorescence intensity. Because the conventional fluorescence spectra of PFX-Al3+ and FLX-Al3+ overlap significantly, the wavelength difference (Δλ = 155 nm) was chosen for SFS scanning to narrow spectral band. And the narrowed synchronous fluorescence spectra was subjected to first derivative processing. Finally, the zero intersections of the first derivative synchronous fluorescence spectra at 281.6 nm and 273.6 nm were chosen for the determination of PFX and FLX, cleverly used of spectral parameters to eliminate the serious interference between PFX-Al3+ and FLX-Al3+ and the interference of wastewater background. The limits of detection of PFX and FLX were 0.0086 ng·mL−1 and 0.0068 ng·mL−1 with linear ranges from 0.1–40 ng·mL−1 and 0.2–80 ng·mL−1, respectively. Recoveries of PFX and FLX in wastewater were 88.60 %-98.60 % and 90.00 %-95.60 %. The first derivative SFS established in this study used spectral separation instead of chromatographic separation, so that sample pretreatment was simple and the detection speed was fast. Compared the conventional method of HPLC, the test results of above two methods were close. And the new method had been successfully used for the determination of PFX and FLX residues in wastewater with good results. Therefore, the new first derivative SFS was expected to become a routine detection technology for PFX and FLX residues in wastewater and widely used.

Eco-friendly second derivative synchronous fluorescence spectroscopic method for simultaneous determination of rosuvastatin and ezetimibe in pharmaceutical capsules

The fixed dose combination of Rosuvastatin and ezetimibe has recently received approval from the FDA for the treatment of elevated levels of low-density lipoprotein cholesterol in adults. Herein, an eco-friendly and highly sensitive spectrofluorimetric method was developed and validated for simultaneous determination of rosuvastatin and ezetimibe in commercial capsules. The developed method involved synchronous fluorescence spectroscopy combined with second derivative spectroscopy to resolve the overlapping fluorescence spectra of rosuvastatin and ezetimibe. The studied drugs were measured in synchronous mode at Δλ of 40 and their recorded synchronous fluorescence spectra were derivatized into second-order spectra, enabling the selective quantification of rosuvastatin and ezetimibe at 370 nm and 312 nm, respectively. Optimization studies regarding to the influence of buffer pH, incorporation of surfactant, choice of diluting solvent, and synchronous Δλ were carried out. The method was validated using the validation characteristics listed in ICH Q2(R1). The calibration curves displayed satisfactory linear relationships across the calibration range of 0.1–2 µg/mL for rosuvastatin and 0.05–3 µg/mL for ezetimibe. The methodology demonstrated robustness to minor modifications in the procedural parameters and selectivity in quantifying the studied drugs in synthetic mixed solutions and commercial capsules without interference. Furthermore, the level of environmental friendliness and sustainability of the suggested spectrofluorimetric approach was assessed in relation to two previously documented methodologies utilizing the AGREE metric. The findings indicated that the suggested method demonstrated a notably superior level of sustainability in comparison to the documented methods.

Eco-friendly simultaneous estimation of atenolol and losartan potassium in spiked human plasma via synchronous fluorescence with sustainability assessment.

A green, sensitive, and fast spectrofluorimetric technique for the simultaneous determination of atenolol (ATN) and losartan potassium (LSR) was developed. The proposed technique relied on the implementation of a first derivative synchronous fluorescence spectroscopy for the determination of the investigated drugs simultaneously without pretreatment procedures. The synchronous fluorescence of both drugs was measured in methanol at Δλ of 100 nm, and the first derivative peak amplitudes (1D) were measured at 321 nm for ATN and 348 nm for LSR, each at the zero-crossing point of the other. The method was rectilinear over the concentration ranges of 100-1000 ng/mL and 50-500 ng/mL for ATN and LSR, respectively. The proposed technique was successfully applied for the determination of the studied drugs in their laboratory-prepared mixture and pharmaceutical formulations, demonstrating high mean recoveries of 100.54% for ATN and 100.62% for LSR, without interference from common excipients. The results were in good agreement with those obtained by the comparison method. Three recent greenness assessment tools, the Eco-Scale tool, the Green Analytical Procedure Index (GAPI) metric, and the Analytical GREEnness metric approach, were employed to affirm the greenness of the proposed method. The developed method was proven to be eco-friendly.

A green micelle-enhanced first derivative synchronous fluorescence approach for determination of donepezil HCl and trazodone HCl in their pure state, pharmaceutical dosage form and spiked human plasma.

The study's objective is to establish an eco-friendly, sensitive and economical quantitative methodology for the concurrent analysis of donepezil HCl (DPZ) and trazodone HCl (TRZ) in raw materials, tablets and human plasma. The first derivative synchronous fluorescence spectroscopic (FDSFS) technique was applied at constant wavelength difference (∆λ = 120) for assessment of DPZ and TRZ at each other's zero-crossing point at 279 nm and 297 nm, respectively. The submitted technique was validated in accordance with ICH Q2 R1 guidelines and the linearity of the standard calibration curve was observed over the concentration range of 10-500 ng/ml for DPZ and 20-1,000 ng/ml for TRZ. The detection limits (LOD) were found to be 2.65 and 5.4ng/ml, and the limits of quantitation (LOQ) were 8.05 and 16.3ng/ml for DPZ and TRZ, respectively. This technique was used further to quantify the studied medications in their laboratory-prepared mixtures, commercial tablets and spiked plasma samples. The results obtained were not significantly different from those acquired from the comparison methods, indicating the high accuracy and precision of the proposed method. Furthermore, the ecological friendliness of the suggested method was evaluated and proven to be excellent using Green Analytical Procedure Index (GAPI) and Analytical GREEnness (AGREE) evaluation tools.

A novel derivative synchronous fluorescence method for the rapid, non-destructive and intuitive differentiation of denitrifying bacteria

It is challenging to differentiate bacteria residing in the same habitat by direct observation. This difficulty impedes the harvest, application and manipulation of functional bacteria in environmental engineering. In this study, we developed a novel method for rapid differentiation of living denitrifying bacteria based on derivative synchronous fluorescence spectroscopy, as exemplified by three heterotrophic nitrification-aerobic denitrification bacteria having the maximum nitrogen removal efficiencies greater than 90%. The intact bacteria and their living surroundings can be analyzed as an integrated target, which eliminates the need for the complex pre-processing of samples. Under the optimal synchronous scanning parameter (Δλ = 40 nm), each bacterium possesses a unique fluorescence spectral structure and the derivative synchronous fluorescence technique can significantly improve the spectral resolution compared to other conventional fluorescence methods, which enables the rapid differentiation of different bacteria through derivative synchronous fluorescence spectra as fast as 2 min per spectrum. Additionally, the derivative synchronous fluorescence technique can extract the spectral signals contributed by bacterial extracellular substances produced in the biological nitrogen removal process. Moreover, the results obtained from our method can reflect the real-time denitrification properties of bacteria in the biological nitrogen removal process of wastewater. All these merits highlight derivative synchronous fluorescence spectroscopy as a promising analytic method in the environmental field.

Applying second derivative synchronous fluorescence spectroscopy combined with Gaussian band fitting to trace variations of DOM fractions along an urban river

Synchronous fluorescence spectroscopy (SFS) combined with Gaussian band fitting, two-dimensional correlation (2D-COS) and perturbation-correlation moving-window two-dimensional (PCMW2D) can provide an excellent mothed to extract fluorescent components of dissolved organic matter (DOM) and reveal its variations in an urban river. Fifteen water samples were collected from the Anyanghe River, which flew across the town, urban, and rural regions. Five peaks (peak1 tyrosine-like, peak2 tyrosine-like, peak3 tryptophan-like, peak4 microbial humic-like, peak5 fulvic-like) were extracted using the Gaussian Amp model from the SFS in the river, while the peak1 only occurred in the rural region. The microbial humic-like in the town region accounting for 50.02 % was the representative substance. The tyrosine-like dominated in the rural regions, for its percentage range was 62.26 %-75.78 %. The average percnetage of tyrosine-like (29.77 %) in the urban region was similar to that of the tryptophan-like (21.86 %), microbial humic-like (25.56 %), and fulvic-like (22.82 %). Based on the two-dimensional correlation, the variation order of DOM fractions in the town and urban regions was tryptophan → tyrosine → microbial humic → fulvic, and the variation order in the rural region was tyrosine → tryptophan → microbial humic → fulvic. This indicated that the changing trend of DOM fractions existed from the labile protein-like to the stable humus in the whole river. According to the perturbation-correlation moving-window two-dimensional correlation spectroscopy, the spectral intensity of tyrosine-like should be linear increase in the town and urban regions, and concave increase in the rural region. The spectral intensity trend of tryptophan-like mainly was linear increase in the whole river. And the intensity of microbial humic-like showed the rough convex increase in the whole river. The trend of the fulvic-like in the town and rural regions was similar to the microbial humic-like. However the fulvic-like intensity in the urban region exhibited a trend from the concave increase to the convex increase, which was obviously different from the tyrosine-like, tryptophan-like and microbial humic-like. This attribute that the untreated domestic sewage in the urban region could discharge into the river. Therefore, for small amounts of samples, the SFS combined with Gaussian band fitting, 2D-COS and PCMW2D can be used as a powerful tool to investigate fluorescent components of DOM, and reveal their variations along the river.

Green approach for tracking the photofate of ciprofloxacin and levofloxacin in different matrices adopting synchronous fluorescence spectroscopy: a kinetic study.

First derivative synchronous fluorescence spectroscopy (FDSFS) was applied to detect and quantify either ciprofloxacin (CIP) or levofloxacin (LEV) simultaneously with their photodegradation products, where the photolytic pathway for each analyte was found to be pH dependent. Under the guidance of early published articles, the structure of the produced photolytic products could be concluded, and further related to their resultant fluorescence spectra. The proposed method was subjected to full validation procedure which enables its application in investigating the photodegradation kinetics for both drugs. The obtained kinetic parameters were in accordance with previous reports and could be linked to predict the antibacterial activity of the resultant photodegradation products. These facts prove the suitability of the suggested FDSFS to serve as a stability-indicating assay method and to trace the photofate of CIP and LEV in the ecosystem as potential contaminants. Furthermore, the greenness of the suggested analytical methodology was evaluated via 'Green Analytical Procedure Index' (GAPI), which classifies it as an eco-friendly assay. Eventually, no extraction, treatment or preparation steps were needed during all analysis steps, which renders the proposed assay an appealing tool in environmental analysis.

Insights into the spectrofluorometric determination of the neuromuscular blocker mivacurium chloride

Fluorescence spectroscopy is gaining interest in the analysis and quantitative determination of different drugs. This study was carried out to investigate the fluorometric properties of the short-acting muscle relaxant mivacurium in its pure form, injection, and human plasma. It is nondepolarizing skeletal muscle relaxant for intravenous (IV) administration. Mivacurium shows a strong native fluorescence in methanol at 317 nm after excitation at 230 nm (Method I). The critical parameters that may influence the fluorescence of this drug were carefully studied. A linear response between concentration and fluorescence was constructed over the concentration range: 20.0 to 400.0 ng/mL with determination coefficient (r2) equal to 0.9998. Additionally, the correlation coefficient of the linear relationship (r) was found to be 0.9999 with a slope = 2.196 and intercept = −16.61. Limits of quantitation and detection were calculated mathematically to be 17.45 and 5.75 ng/mL respectively. Further estimation of mivacurium in spiked human plasma was performed by construction of specific calibration curve and the obtained correlation coefficient was 0.9948. Moreover, the ability to determine mivacurium in the presence of commonly co-administered drugs were investigated including propofol and thiopental. Method II includes the determination of MVC in the presence of propofol utilizing the first derivative synchronous fluorescence spectroscopy. The results of method II indicated acceptable percentage recoveries from 98.88 to 100.75 %. Statistical evaluation of the results revealed satisfactory accuracy and precision.

Derivative Matrix-Isopotential Synchronous Spectrofluorimetry and Hantzsch Reaction: A Direct Route to Simultaneous Determination of Urinary δ-Aminolevulinic Acid and Porphobilinogen.

Early and sensitive detection of δ-aminolevulinic acid (δ-ALA) and porphobilinogen (PBG) is the cornerstone of diagnosis and effective treatment for acute porphyria. However, at present, the quantifying strategies demand multiple solvent extraction steps or chromatographic approaches to separate δ-ALA and PBG prior to quantification. These methods are both time-consuming and laborious. Otherwise, in conventional spectrofluorimetry, the overlapping spectra of the two analytes cause false diagnosis. To overcome this challenge, we present a two-step approach based on derivative matrix-isopotential synchronous fluorescence spectrometry (DMISFS) and the Hantzsch reaction, realizing the simple and simultaneous detection of δ-ALA and PBG in urine samples. The first step is chemical derivatization of the analytes by Hantzsch reaction. The second step is the determination of the target analytes by combining MISFS and the first derivative technique. The proposed approach accomplishes following advantages: 1) The MISFS technique improves the spectral resolution and resolves severe spectral overlap of the analytes, alleviating tedious and complicated pre-separation processes; 2) First derivative technique removes the background interference of δ-ALA on PBG and vice versa, ensuring high sensitivity; 3) Both the analytes can be determined simultaneously via single scanning, enabling rapid detection. The obtained detection limits for δ-ALA and PBG were 0.04 μmol L−1 and 0.3 μmol L−1, respectively. Within-run precisions (intra and inter-day CVs) for both the analytes were <5%. Further, this study would serve to enhance the availability of early and reliable quantitative diagnosis for acute porphyria in both scientific and clinical laboratories.

New possibilities for the glaucoma diagnostics using the synchronous fluorescence spectra of tear fluid

Tear fluid represents a biological material with immense potential in the diagnostics of ocular diseases. Glaucoma is a vision-threatening ocular disease with a great need to speed up and simplify the diagnostic process. For this purpose, tear fluid changes among primary open-angle glaucoma, suspected glaucoma, ocular hypertension, and healthy control subjects were analyzed using the ratio between two peaks in the wavelength range of 210–300 nm at the section of wavelength interval of Δλ = 110 on the synchronous fluorescence spectra and by second derivative synchronous fluorescence spectroscopy. The location of minimum and maximum in the wavelength range 200–260 nm at the section of wavelength interval of Δλ = 110 nm differed between the groups of subjects showing the highest difference in healthy controls (17.5 ± 1.9) followed by ocular hypertension (16.5 ± 1.3), and lowest in suspected glaucoma (14.5 ± 1.7) and primary open-angle glaucoma (14.5 ± 3.9). This factor could serve as a novel discriminative parameter for distinguishing between the groups of subjects. Overall, second derivative synchronous fluorescence spectroscopy might be used for monitoring these patients.

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.

Insight into temporal\u2013spatial variations of DOM fractions and tracing potential factors in a brackish-water lake using second derivative synchronous fluorescence spectroscopy and canonical correlation analysis

BackgroundInsight into temporal–spatial variations of dissolved organic matter (DOM) fractions were undertaken to trace potential factors toward a further understanding aquatic environment in Lake Shahu, a brackish-water lake in northwest China, using synchronous fluorescence spectroscopy (SFS) combined with principal component analysis (PCA), second derivative and canonical correlation analysis (CCA).ResultFive fluorescence peaks were extracted from SFS by PCA, including tyrosine-like fluorescence (TYLF), tryptophan-like fluorescence (TRLF), microbial humic-like fluorescence (MHLF), fulvic-like fluorescence (FLF), and humic-like fluorescence (HLF), whose relative contents were obtained by second derivative synchronous fluorescence spectroscopy. The increasing order of total fluorescence components contents was July (11,789.38 ± 12,752.61) < April (12,667.58 ± 15,246.91) < November (19,748.87 ± 17,192.13), which was attributed to tremendous enhancement in TYLF content from April (1615.56 ± 258.56) to November (5631.96 ± 634.82). The PLF (the sum of TYLF and TRLF) dominated the fluorescence components, whose proportion was 40.55, 37.09, or 46.91% in April, July, or November. DOM fractions in November were distinguished from April and July, which could be attributed to that water of the Yellow River was continuously loaded into the lake as water replenishment from April to September. From the replenishment period to non-replenishment, the contents of the five components gradually changed from low in the middle and high around the lake to high throughout entire lake. Based on the CCA results, the potential factors included TYLF, TRLF, MHLF, SD, and BOD5 in April, which were relative to organic matter pollution. The potential factors contained TYLF, TRLF, FLF, Chl-a, TP, CODCr, and DO in July, indicating the enrichment of TP lead algae and plants growth. The potential factors in November consisted of TYLF, TRLF, CODCr, SD, TN, and FLF, representing residue of the algae and plants have been deeply degraded.ConclusionThe replenishment of water led to enrichment of TP, resulting in growth of algae and plants, and was the key factor of water quality fluctuations. This work provided a workflow from perspective of DOM to reveal causes of water quality fluctuations in a brackish-water lake and may be applied to other types of waterbodies.

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.

Prediction of protein and oil contents in soybeans using fluorescence excitation emission matrix

To investigate the potential of fluorescence spectroscopy in evaluating soybean protein and oil content, excitation emission matrix (EEM) was measured on 34 samples of soybean flours using a front-face measurement, and the accuracy of the protein and oil content prediction was evaluated. The EEM showed four main peaks at excitation/emission (Ex/Em) wavelengths of 230/335, 285/335, 365/475, and 435/495 nm. Furthermore, second derivative synchronous fluorescence (SDSF) spectra were extracted from the EEMs, and partial least square regression and support vector machine models were developed on each of the EEMs and SDSF spectra. The R2 values reached 0.86 and 0.74 for protein and oil, respectively. From the loading spectra, fluorescence at Ex/Em of 230–285/335 nm and 350/500 nm mainly contribute to the protein and oil content prediction, respectively. Those results revealed the potential of fluorescence spectroscopy as a tool for a rapid prediction of soybean protein and oil content.

Second derivative synchronous fluorescence determination of avanafil in the presence of its acid-induced degradation product aided by powerful Lean Six Sigma tools augmented with D-optimal design.

In this work, the quantitative determination of an erectile dysfunctional drug avanafil in the presence of its acid-induced degradation product was achieved via the application of a pre-optimized novel spectrofluorimetric method. The fluorescence emission wavelength was recorded at 370 and 407 nm, after being excited at 268 and 271 nm for avanafil and its acid-induced degradation product, respectively. Direct determination of avanafil based on its native fluorescence is restricted because the emission spectra of both components are heavily overlapped. Therefore, to overcome this constraint, a novel second derivative synchronous fluorescence method was evolved to eliminate this overlapping. The ideal determination wavelength was found to be 377 nm. Augmentation of lean six sigma (LSS) with response surface methodology (RSM) play a significant role in the development of robust specifications to ensure quality at the six sigma level with a high level of statistical confidence and targeted performance. All of the experimental conditions were optimized using D-optimal design as a RSM to select the optimal parameters. In addition, this work includes a graphical representation of the relationships between various variables that can greatly affect the results and the intensity of the synchronous fluorescence.

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.

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.

Validated Chromatographic and Spectrofluorimetric Methods for Analysis of Silodosin: A Comparative Study with Application of RP-HPLC in the Kinetic Investigation of Silodosin Degradation.

Stability indicating determination of pharmaceuticals is crucial, especially for drugs which have few published official analytical methods. Silodosin (SLD) is an FDA approved α1A-adrenoceptor blocker. Efficient analytical methods were suggested, based on different instrumental techniques for quantification of SLD, besides conducting kinetic investigation of its degradation. The first method is based on Reversed Phase High Performance Liquid Chromatography with Photodiode Array Detector (RP-HPLC-PDAD). Detection is done at wavelength 225 nm. The second method is focused on using High Performance Thin Layer Chromatography (HPTLC) and eluting the drug by solvent mixture followed by scanning at wavelength 270 nm. The third method depends on the First Derivative Synchronous Fluorescence Spectroscopy (1DSFS) for analysis of solutions of SLD and its acid and oxidative induced degradation products at Δλ = 90 nm, then determining the first derivative of the spectra and measuring peak amplitudes at 360 nm. Acceptable linearities were found in the concentration range of 0.50-90 μg/mL, 0.10-3.0 μg/band, and 0.05-0.50 µg/mL, for RP-HPLC-PDAD, HPTLC, and spectrofluorimetric methods, respectively. Statistical analysis showed no significant difference between the suggested and the reported method. In monitoring the kinetics of SLD degradation, the order of reactions was determined and effects of degrading agent concentration and temperature on reaction rate were studied. Three analytical methods were developed for the determination of SLD based on RP-HPLC-PDAD, HPTLC, and 1DSFS in bulk and capsule dosage form. In addition, kinetic investigation of SLD degradation was performed using the developed RP-HPLC-PDAD method.

Development and validation of a highly sensitive second derivative synchronous fluorescence spectroscopic method for the simultaneous determination of elbasvir and grazoprevir in pharmaceutical preparation and human plasma

Elbasvir and grazoprevir combination has been newly approved for the treatment of patients infected with hepatitis C virus.

Derivative constant wavelength synchronous fluorescence spectrometry for the simultaneous detection of cefadrine and cefadroxil in water samples.

A sensitive accurate spectrofluorimetric technique was developed to detect cefadroxil and cefradine traces in water samples simultaneously, by applying a procedure based on the formation of hydrolysis products corresponding to these compounds by sodium hydroxide (1N NaOH) treatment. The conventional and the synchronous fluorescence spectra of these hydrolyzed products were totally overlapped making resolving of this mixture impossible. The second-derivative constant-wavelength synchronous fluorescence spectra allowed their detection simultaneously in a single scan after experimental conditions optimization, which was measured at 390nm and 379nm for cefadroxil and cefradine, respectively at Δλ=30.0. The calibration curves between derivative synchronous fluorescence intensity and drugs concentration showed suitable linear correlation in the range of 0.1 to 5μg.mL-1 for cefadroxil and 0.5-10μg.mL-1 for cefradine. The proposed fluorimetric method is superior in being simple, environmental friendly and cost effective in comparison to the previously published reported methods.