Stability–Indicating Spectrofluorimetric Methods for the Determination of Metolazone and Xipamide in Their Tablets. Application to Content Uniformity Testing

A highly sensitive, simple and rapid stability-indicating spectrofluorimetric method was developed for the determination of metolazone (MET) and xipamide (XPM) in their tablets. The proposed method is based on the measurement of the native fluorescence of MET in methanol at 437 nm after excitation at 238 nm and XPM in alkaline methanolic solution at 400 nm after excitation at 255 nm. The fluorescence–concentration plots were rectilinear over the range of 2.0– 20.0 ng/mL for MET and 0.2– 2.0 μg/mL for XPM, with lower detection limits (LOD) of 0.35 ng/mL and 0.02 μg/mL and a lower quantification limit (LOQ) of 1.05 ng/mL and 0.07 μg/mL for MET and XPM, respectively. The method was successfully applied to the analysis of MET and XPM in their commercial tablets and the results were in good agreement with those obtained using the official and comparison methods, respectively. Furthermore, content uniformity testing of the studied pharmaceutical tablets was also conducted. The application of the proposed method was extended to stability studies of MET and XPM after exposure to different forced degradation conditions, such as acidic, alkaline, oxidative and photolytic degradation conditions, according to ICH Guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and photolytic degradation of MET. The apparent first-order rate constants and half-life times were calculated. Proposals for the degradation pathways for both MET and XPM were postulated.     

Micelle-Enhanced Spectrofluorimetric Method for Determination of Cyproheptadine Hydrochloride in Tablets: Application to In-Vitro Drug Release and Content Uniformity Test

A highly sensitive and simple spectrofluorimetric method was developed for the determination of cyproheptadine hydrochloride (CYP) in its pharmaceutical formulations. The proposed method is based on the investigation of the fluorescence spectral behaviour of CYP in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution, the fluorescence intensity of CYP was greatly enhanced (150 %) in the presence of SDS. The fluorescence intensity was measured at 410 nm after excitation at 280 nm. The fluorescence–concentration plot was rectilinear over the range 0.2–2.0 μg/mL, with lower detection limit of 0.06 μg/mL. The proposed method was successfully applied to the assay of commercial tablets as well as content uniformity testing. The application of the proposed method was extended to test the in-vitro drug release of CYP tablets, according to USP guidelines. The results were statistically compared with those obtained by official USP method and were found to be in good agreement.     

Stability-Indicating Spectrofluorimetric Method for Determination of Itopride Hydrochloride in Raw Material and Pharmaceutical Formulations

A simple, sensitive and rapid spectrofluorimetric method for determination of itopride hydrochloride in raw material and tablets has been developed. The proposed method is based on the measurement of the native fluorescence of the drug in water at 363 nm after excitation at 255 nm. The relative fluorescence intensity-concentration plot was rectilinear over the range of 0.1–2 μg/mL (2.5?×?10^?7–5.06?×?10^?6 mole/L), with good correlation (r?=?0.9999), limit of detection of 0.015 μg/mL and a lower limit of quantification of 0.045 μg/mL. The described method was successfully applied for the determination of itopride hydrochloride in its commercial tablets with average percentage recovery of 100.11?±?0.32 without interference from common excipients. Additionally, the proposed method can be applied for determination of itopride in combined tablets with rabeprazole or pantoprazole without prior separation. The method was extended to stability study of itopride. The drug was exposed to acidic, alkaline, oxidative and photolytic degradation according to ICH guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and oxidative degradation of the drug. A proposal for the degradation pathways was postulated.     

Second-Derivative Synchronous Fluorescence Spectroscopy for the Simultaneous Determination of Fluphenazine Hydrochloride and Nortriptyline Hydrochloride in Pharmaceutical Preparations

A rapid, simple, and highly sensitive second-derivative synchronous fluorimetric (SDSF) method has been developed for the simultaneous analysis of binary mixtures of fluphenazine hydrochloride (FLZ) and nortriptyline hydrochloride (NTP) in their co-formulated tablets. The method is based upon measurement of the native fluorescence of these drugs at constant wavelength difference (Δλ)?=?120 nm in acetic acid. The different experimental parameters affecting the fluorescence intensity of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.25–3.0 and 1–10 μg/ml for FLZ and NTP respectively, with lower detection limits (LOD) of 0.05 and 0.18 μg/ml and quantitation limits of 0.15 and 0.53 μg/ml for FLZ and NTP respectively. The proposed method was successfully applied for the determination of the studied compounds in their synthetic mixtures and in commercial co-formulated tablets. The results obtained were in good agreement with those obtained by the reference methods.     

Spectrofluorometric Determination of Cephalexin in Pharmaceutical Preparations and Spiked Human Urine Using 2‐Cyanoacetamide

A simple, accurate, sensitive, and validated method was developed for the spectrofluorometric determination of cephalexin. The method involves the reaction of cephalexin with 2‐cyanoacetamide in presence of 33% ammonia solution. The formed fluorescent product exhibited maximum fluorescence intensity at λ 439 nm, after excitation at λ 339 nm. Different experimental parameters affecting the derivatization reaction were carefully studied and incorporated in the procedure. Under the described conditions, the proposed method was linear over the concentration range 0.04–0.4 µg/mL. The average percent found was 99.6±0.9%. The LOD was 7.76 ng/mL. The proposed method was applied for determination of cephalexin in pharmaceutical preparations as well as in spiked human urine. A mechanism of the reaction is postulated.     

Liquid Chromatography Coupled with Fluorimetric Detection and Third Derivative Synchronous Fluorescence Spectroscopy as two Analytical Methods for the Simultaneous Determination of Rabeprazole Sodium and Domperidone After Derivatization with 4-Chloro-7-Nitrobenzofurazan

Two simple, sensitive, rapid, economic and validated methods, namely reversed phase liquid chromatography (method Ι) and third derivative synchronous fluorescence spectroscopy (method ΙΙ) have been developed for the simultaneous determination of rabeprazole sodium and domperidone in their laboratory prepared mixture after derivatization with 4-Chloro-7-nitrobenzofurazan. Reversed phase chromatography was conducted using a Zorbax® SB-Phenyl column (250.0 mm × 4.6 mm id) combined with a guard column at ambient temperature with fluorimetric detection at 540 nm after excitation at 483 nm. A mobile phase composed of a mixture of distilled water with methanol and acetonitrile in a ratio of 50:20:30 adjusted pH to 4 has been used at a flow rate of 1 mL/min. Sharp well resolved peaks were obtained for domperidone and rabeprazole sodium with retention times of 5.5 and 6.4 min respectively. While in method ΙΙ, the third-derivative spectra were estimated at 507 and 436 nm for rabeprazole sodium and domperidone respectively. Linearity ranges for rabeprazole sodium and domperidone respectively in both methods were found to be 0.15–2.0 and 0.1–1.5 μg/mL. The proposed methods were successfully applied for the analysis of the two compounds in their binary mixtures, and laboratory prepared tablets. The obtained results were favorably compared with those obtained by the comparison method. Furthermore, detailed validation procedure was also conducted.     

Supramolecular Study on the Interaction Between Ofloxacin and Methyl β-Cyclodextrin by Fluorescence Spectroscopy and its Analytical Application

The supramolecular interaction of ofloxacin (Oflo) and methyl β-cyclodextrin (Mβ-CD) has been examined by UV–vis, IR and fluorescence spectroscopy. The formation of inclusion complex has been confirmed based on the changes of the spectral properties. The results showed that Mβ-CD reacted with Oflo to form an inclusion complex. The Oflo and Mβ-CD complex formed a host-guest complex in 1:1 stoichiometry and inclusion constant (K?=?7.8?×?10^?3 L mol^?1) was ascertained by the typical double reciprocal plots. Furthermore, the thermodynamic parameters (?H°, ?S° and ?G°) associated with the inclusion process were also determined. In addition, solid inclusion complex was synthesized. Based on the significant enhancement of the fluorescence intensity of Oflo produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of Oflo in pharmaceutical formulation was developed. The measurement of relative fluorescence intensity was carried out at 497 nm with excitation at 296 nm. The factors affecting the inclusion complex formation were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9995) were in the concentration range of 50–350 ng/mL for spectrofluorimetry. The limit of detection (LOD) was 11.5 ng/mL. The proposed method was successfully applied to the analysis of Oflo in pharmaceutical preparation.     

Study on the Fluorescence Quenching Reaction of Amitriptyline and Clomipramine Hydrochlorides with Eosin Y and its Analytical Application

Amitriptyline.HCl (AMI) and clomipramine.HCl (CMI) react with eosin Y (EY) in pH 3.8 NaAc-AcH buffer solution to form ion association complex which results in quenching of fluorescence of EY and appearance of a new resonance Rayleigh scattering (RSS) spectrum at 620 nm. The spectral characteristics of absorption, fluorescence and RSS spectra have been investigated. The factors influencing the reaction were studied and optimum conditions for the reaction have been determined. Based on fluorescence quenching, a simple and sensitive spectrofluorimetric method for determination of AMI and CMI has been developed. The fluorescence quenching intensity was measured at 550 nm using an excitation wavelength of 310 nm. The calibration graph was found to be rectilinear in the range 0.08–2.0 μg?mL^?1 with detection limit of 0.017 μg?mL^?1 for AMI and 0.06–2.0 μg?mL^?1 with detection limit of 0.015 μg?mL^?1 for CMI. The method can be satisfactorily applied to the determination of AMI and CMI in tablets without interference from commonly occurring exicipients. The recovery and RSD values obtained indicate good accuracy and precision of the method. The mechanism of the reaction and fluorescence quenching has also been discussed.     

Spectrofluorimetric Determination of Topiramate and Levetiracetam as Single Components in Tablet Formulations and in Human Plasma and Simultaneous Fourth Derivative Synchronous Fluorescence Determination of their Co-Adminstered Mixture in Human Plasma

Two highly sensitive, rapid, simple, economic and validated spectrofluorimetric methods have been developed for determination of Topiramate and Levetiracetam in pharmaceutical tablets and in human plasma. Topiramate and Levetiracetam were determined separately by derivatization using 4-Chloro-7-nitrobenzofuran-2-oxo-1,3-diazole (NBD-Cl) and measured spectrofluorimetrically. The Relative fluorescence intensities were measured at λ_em/_ex of 547/465 nm and 551/465 nm for Topiramate and Levetiracetam, respectively. While a binary mixture of Topiramate and Levetiracetam were determined by the fourth derivative synchronous fluorescence measurement after their reaction with NBD-Cl. In this method, the fourth derivative synchronous spectra were estimated as peak to peak measurement at 493–497 and 490.5–495 nm corresponding with zero-contribution of Levetiracetam and Topiramate, respectively. Linearity ranges for Topiramate and Levetiracetam in both methods were found to be 0.15–1.2 and 0.2–1.5 μg/mL, respectively. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The proposed methods were validated in terms of linearity, accuracy, precision, limits of detection and quantification and other aspects of analytical validation. The proposed methods were successfully applied for the determination of the investigated drugs in human plasma samples obtained from healthy volunteers after single oral administration of the two drugs.     

Spectrofluorometric Determination of Methocarbamol in Pharmaceutical Preparations and Human Plasma

A simple, sensitive and rapid spectrofluorometric method for determination of methocarbamol in pharmaceutical formulations and spiked human plasma has been developed. The proposed method is based on the measurement of the native fluorescence of methocarbamol in methanol at 313 nm after excitation at 277 nm. The relative fluorescence intensity-concentration plot was rectilinear over the range of 0.05–2.0 μg/mL, with good correlation (r = 0.9999), limit of detection of 0.007 μg/ mL and a lower limit of quantification of 0.022 μg/ mL. The described method was successfully applied for the determination of methocarbamol in its tablets without interference from co-formulated drugs, such as aspirin, diclofenac, paracetamol and ibuprofen, The results obtained were in good agreement with those obtained using the official method (USP 30).The high sensitivity of the method allowed the determination of the studied drug in spiked human plasma with average percentage recovery of 99.42 ± 3.84.     

Rapid and Sensitive Online Determination of Some Selective α1-Blockers by Flow Injection Analysis with Micelle-Enhanced Fluorescence Detection

A rapid, sensitive and selective flow injection analysis (FIA) method was developed for the determination of some selective α₁-blockers including; terazosin (TER), doxazosin (DOX), prazosin (PRZ), and alfuzosin (ALF). The method was based on enhancement of the native fluorescence of the studied drugs in the presence of sodium dodecyl sulfate (SDS). The method was optimized for the buffer type, concentration and pH, surfactant type and concentration, flow rate and detection wavelengths in order to achieve the maximum sensitivity. The results showed that the best sensitivity was obtained by using SDS (10 mM) in phosphate buffer (20 mM, pH?=?3), flow rate was 0.5 ml/min and the detector was set at λ_ex?=?250 and λ_em?=?389. Under these optimum conditions there was a linear relationship between the concentration and the fluorescence intensity in the range from 5–400 ng ml^? with correlation coefficient of more than 0.998. The detection and quantitation limits for the studied drugs by the proposed method were 3.2–11.9 ng ml^?1 and 10.8–39.7 ng ml^?1, respectively. The method was validated in accordance with the requirements of ICH guidelines and shown to be suitable for intended applications. Moreover, the binding constants for α₁–blockers –SDS system were determined using the adduct model. The proposed method has been applied successfully for the analysis of the pure forms for studied drugs and also their pharmaceutical formulations and the results were compared with official methods.     

Sensitive Synchronous Spectrofluorimetric Study of Certain Sunscreens Using Fluorescence Enhancers in Cosmeceutical Formulations

Synchronous spectrofluorimetric methods could be successfully adopted for simultaneous determination of Octinoxate (OMC), Avobenzone (AVO), Octyltriazone (OT), and Phenyl benzimidazole sulfonic acid (PBSA) in moisturizing sunscreen lotion, utilizing β-CD as fluorescence enhancer, and determination of Avobenzone (AVO), Homosalate, Tinosorb M and Phenyl benzimidazole sulfonic acid (PBSA) in presence of Octocrylene (OCR) in whitening sunscreen cream, using micellar medium of Sodium Dodecyl Sulfate (SDS) to enhance fluorescence intensity. For first product, zero order synchronous spectrofluorimetric method was used for determination of OMC and AVO, and derivative synchronous spectrofluorimetric technique was utilized for OT and PBSA in quaternary mixture. Linear calibration curves were obtained in a concentration range of 0.5–8 μg mL^??1 for OMC and AVO, and in range of 0.05–3 μg mL^??1 for OT and 0.001–5 μg mL^??1 for PBSA, by measuring the fluorescence at 370, 405, 333.2 and 340.6 nm, respectively. For second product, first derivative synchronous fluorescence method was used for each UV-filter. A linear calibration curves were obtained in a concentration range of 0.5–8 μg mL^??1 for AVO, in range of 0.1–8 μg mL^??1 for Homosalate, 2–10 μg mL^??1 for Tinosorb M and 0.001–5 μg mL^??1 for PBSA, by measuring the fluorescence at 409.8, 373, 307.2 and 316.8 nm, respectively. The detection limits are well below the maximum admissible concentration. The proposed methods were validated according to ICH guidelines and successfully applied to determine sunscreens in pure form and in Cosmeceutical formulations. All the results obtained were compared with those of published methods, where no significant difference was observed.     

Highly Sensitive Synchronous Fluorescence Measurement of Danofloxacin in Pharmaceutical and Milk Samples Using Aluminium (III) Enhanced Fluorescence

A simple, rapid and sensitive constant wavelength synchronous fluorescence method is developed for the determination of danofloxacin (DAN) in pharmaceutical formulations and its residue in milk based on Al(III) enhanced fluorescence. The synchronous fluorescence intensity of the system is measured at 435?nm using ? λ?=?80?nm and an excitation wavelength of 280?nm. A good linear relationship between enhanced fluorescence intensity and DAN concentration is obtained in the range of 3-100?ng?mL(-1)(r (2)?=?0.9991). The limit of detection (LOD, S/N?=?3) of the present method is 0.9?ng?mL(-1). The proposed method can be successfully applied to the determination of DAN in pharmaceutical formulations and in milk without serious interferences from common excipients, metal ions and other co-existing substances. The method can be used as a rapid screening to judge whether the DAN residues in milk exceed Maximum Residue Limits (MRLs) or not.     

A Validated Spectrofluorimetric Method for the Determination of Citalopram in Bulk and Pharmaceutical Preparations Based on the Measurement of the Silver Nanoparticles-Enhanced Fluorescence of Citalopram/Terbium Complexes

A simple, sensitive, and accurate spectrofluorimetric method was developed for the determination of citalopram in bulk and pharmaceutical preparations. The method is based on the enhancement of the weak fluorescence signal (FL) of the Tb (III)-citalopram system in the presence of silver nanoparticles. Fluorescence intensities were measured at 555 nm after excitation at 281 nm. Prepared silver nanoparticles (AgNPs) were characterized by UV-Visible spectra and transmission electron microscopy (TEM). Various factors affecting the formation of citalopram-Tb (III)-AgNPs complexes were studied and optimized. The fluorescence intensity versus concentration plot was linear over the range 0.02–14 μg?mL^?1, with an excellent correlation coefficient of 0.9978. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 7.15?×?10^?6?μg?mL^?1 and 2.38?×?10^?5?μg?mL^?1 respectively. The proposed method was found to have good reproducibility with a relative standard deviation of 3.66 % (n?=?6). The interference effects of common excipients found in pharmaceutical preparations were studied. The developed method was validated statistically by performing recoveries studies and successfully applied for the assay of citalopram in bulk powder and pharmaceutical preparations. Percent recoveries were found to range from 98.98 % to 100.97 % for bulk powder and from 96.57 % to 101.77 % for pharmaceutical preparations.     

Laser-induced fluorescence temperature determination in fuel–air mixtures without additional fluorescence tracers

A concept for temperature determination of fuel–air mixtures using Laser-Induced Fluorescence (LIF) is presented. For this purpose the fluorescence spectra of gasoline were measured after excitation by frequency quadrupled Nd:YAG laser light at 266 nm in a temperature range between 373 K and 448 K. Experiments were performed with colorless near-standard gasoline conforming to the Euro-super specifications. It is shown that the intensities of two fluorescence bands (290–302 nm and 332–344 nm) can be used to determine the temperature.     

Determination of Oxybutynin in Pharmaceuticals <Emphasis Type="Italic">via</Emphasis> Reaction with Mixed Acids Anhydrides: Application to Content Uniformity Testing

Sensitive and simple spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed and validated for the determination of oxybutynin HCl (OXB) in its dosage forms. The method was based on the reaction of OXB with malonic acid anhydride in acetic acid anhydride to form a highly yellow colored product that was measured at 375 nm spectrophotometrically. The same reaction product exihibits strong fluorescence that was measured at 440 nm after excitation at 390 nm. The factors affecting formation and stability of the reaction product were carefully studied and optimized, and the reaction mechanism was postulated. The absorbance-concentration plot is rectilinear over the range 4–40 μg/mL with LOD of 1.12 μg/mL and LOQ of 3.39 μg/mL. The fluorescence-concentration plot is rectilinear over the range 0.5–6 μg/mL with LOD of 0.11 μg/mL and LOQ of 0.33 μg/mL. The method was applied to the analysis of commercial tablets Detronin® and Uripan®. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively. The study was extended to content uniformity testing.     

Determination of Microamounts of Proteins by Resonance Light Scattering with Copper Phthalocyanine Tetrasulfonic Acid

Abstract

Based on the strong enhancement effect of proteins on the resonance light scattering of copper phthalocyanine tetrasulfonic acid, a method for the determination of microamounts of proteins has been developed. Under the experimental conditions (2.0×10^?6 mol/L copper phthalocyanine tetrasulfonic acid, pH 2.60, ionic strength 0.001 mol/L NaCl), the linear range of this assay is 0.06–4.0 µg/mL for bovine serum albumin (BSA), 0.1–2.0 µg/mL for human serum albumin (HSA), 0.0–2.0 µg/mL for human γ‐IgG, and 0.2–6.0 µg/mL for ovalbumin. The detection limits (3δ) are 16.8 ng/mL for BSA, 23.4 ng/mL for HSA, 37.6 ng/mL for human γ‐IgG, and 48.3 ng/mL for ovalbumin, respectively. This method has been applied to the analysis of total proteins in human serum samples collected from the hospital, and the results were in good agreement with those reported by the hospital.     

Determination of Protoporphyrin IX Disodium Salt Based on Fluorescence Quenching of Glutathione-Capped Cadmium/Tellurium Quantum Dots

ABSTRACT

Aqueous glutathione-capped cadmium/tellurium quantum dots with a diameter of about 3 nm were synthesized. The fluorescence was quenched in the presence of protoporphyrin IX disodium salt, with the excitation wavelength at 320 nm. Under the optimal conditions, the quenched fluorescence intensity was linear in the range of 0.096–16 µg · mL^?1 with a concentration of protoporphyrin IX disodium salt, and the detection limit (3σ) was 2.8 × 10^?2 µg · mL^?1. The proposed method has been applied to the determination of protoporphyrin in serum samples with satisfactory results. The interaction mechanism was investigated.