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.     

Conventional and First Derivative Synchronous Fluorometric Determination of Ethamsylate in Pharmaceutical Preparations and Biological Fluids. Application to Stability Studies

Two simple, accurate and highly sensitive spectrofluorometric methods were developed for the determination of ethamsylate (ETM). Method I is based on measuring the native fluorescence of ethamsylate in water at 354 nm after excitation at 302 nm. The calibration plot was rectilinear over the range of 0.05–1 μg/mL for ETM with limits of detection and quantitation of 7.9 and 26 ng/mL, respectively. Method II involved synchronous and first derivative synchronous fluorometric methods for the simultaneous determination of ethamsylate (ETM) and hydroquinone (HQ) which is considered as an impurity and/or acidic degradation product. The synchronous fluorescence of both the drug and its impurity were measured in methanol at Δ λ of 40 nm. The peak amplitudes (¹D) were estimated at 293.85 or 334.17 nm for ETM and at 309.05 nm for HQ. Good linearity was obtained for ETM over the ranges 0.1–1.4 μg/mL and 0.1–1.0 μg/mL at 293.85 and 334.17 nm, respectively. For HQ, the calibration plot was rectilinear over the range of 0.01–0.14 μg/mL at 309.05 nm. Limits of detection were 20, 2.01 ng/mL and limits of quantitation were 60, 6.7 ng/mL for ETM and HQ by method II, respectively. Both methods were successfully applied to commercial ampoules and tablets. The results were in good agreement with those obtained by the reference method. Method I was utilized to study the stability of ETM and its degradation kinetics using peroxide. The apparent first-order rate constant, half-life times and activation energy of the degradation process were calculated. Method I was further extended to the in-vitro and in-vivo determination of ETM in spiked and real plasma samples. The mean% recoveries were 99.57 ± 3.85 and 89.39 ± 5.93 for spiked and real human plasma, respectively.     

Spectrofluorimetric Determination of Oxamniquine in Dosage Forms and Spiked Human Plasma through Derivatization with 1-dimethylaminonaphthalene-5-sulphonyl chloride

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of oxamniquine (OXM) in pharmaceutical formulations and biological fluids. The method is based on the reaction between the drug and 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) in presence of 0.5 M sodium carbonate (pH 10) to yield a highly fluorescent derivative that is measured at 445 nm after excitation at 335 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence concentration plot was rectilinear over the range of 0.02–0.2 μg ml⁻¹ with a lower detection limit (LOD) of 0.007 μg ml⁻¹ and limit of quantitation (LOQ) of 0.02 μg ml⁻¹. The proposed method was successfully applied to the analysis of commercial capsules. The results obtained were in good agreement with those obtained using the official spectrophotometric method. Furthermore, the method was applied for the determination of oxamniquine in spiked human plasma, the mean % recovery (n = 4) is 97.77 ± 1.19. A proposal of the reaction pathway was presented.     

Spectrofluorimetric Determination of Famotidine in Pharmaceutical Preparations and Biological Fluids. Application to Stability Studies

A simple, economic, selective, and stability indicating spectrofluorimetric method was developed for the determination of famotidine (FMT); is based on its reaction with 9, 10-phenanthraquinone in alkaline medium to give a highly fluorescent derivative measured at 560 nm after excitation at 283 nm. The fluorescence intensity - concentration plot was rectilinear over the concentration range of 50–600 ng/ml with minimum quantification limit (LOQ) of 13.0 ng/ml and minimum detection limit (LOD) of 4.3 ng/ml. The factors affecting the development of the fluorescence intensity of the reaction product were carefully studied and optimized. The method was applied for the determination of FMT in its dosage forms. The stability of the compound was studied, and the proposed method was found to be stability indicating one. The results obtained were in good agreement with those obtained by the official method. Furthermore, the method was applied for the determination of FMT in spiked and real human plasma. The mean % recovery (n = 4) was found to be 99.94 ± 0.24, and 105.13 ± 0.64 for spiked and real human plasma, respectively. The composition of the reaction product as well as its stability constant was also investigated. Moreover, the method was utilized to investigate the kinetics of both alkaline and oxidative induced degradation of the drug. The apparent first order rate constant and half life time of the degradation product was calculated. A proposal of the reaction pathway was postulated.     

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.     

Spectrofluorimetric Method for Determination and Validation of Cefixime in Pharmaceutical Preparations Through Derivatization with 2-Cyanoacetamide

A simple, sensitive and accurate method has been developed for spectrofluorimetric determination of cefixime in pure form and pharmaceutical preparations. The method is based on the reaction of cefixime with 2-cyanoacetamide in the presence of 21% ammonia at 100 °C. The fluorescent reaction product showed maximum fluorescence intensity at λ 378 nm after excitation at λ 330 nm. The factors affecting the derivatization reaction were carefully studied and optimized. The fluorescence intensity versus concentration plot was rectilinear over the range of 0.02 to 4 μg mL⁻¹ with correlation coefficient of 0.99036. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 2.95 ng mL⁻¹ and 9.84 ng mL⁻¹, respectively. The proposed method was validated statistically and through recovery studies. The method was successfully applied for the determination of cefixime in pure and dosage form with percent recoveries from 98.117% to 100.38%. The results obtained from the proposed method have been compared with the official HPLC method and good agreement was found between them.     

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.     

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.     

Simple and Sensitive Spectrofluorimetric Method for the Determination of Oseltamivir Phosphate in Capsules Through Derivatization with Fluorescamine

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of oseltamivir phosphate (OSP) in capsules. The method is based on the reaction between oseltamivir and fluorescamine in borate buffer solution of pH 8.50 to give highly fluorescent derivatives that are measured at 483 nm using an excitation wavelength of 381. The different experimental parameters effecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence intensity concentration plot is rectilinear over the range 50–450 ng mL⁻¹ with a lower detection limit (LOD) of 1.219 ng mL⁻¹ and limit of quantitation (LOQ) of 4.064 ng mL⁻¹. Selectivity was validated by subjecting stock solution of OSP to acidic, basic, oxidative, and thermal degradation. No interference was observed from excipients present in formulations. The developed method was successfully applied to determination of the drug in capsules. The mean % recovery (n = 6) was 100.08. The results obtained were in good agreement with those obtained using a reported spectrophotometric method.     

First Derivative Synchronous Fluorescence Spectroscopy for the Simultaneous Determination of Sulpiride and Mebeverine Hydrochloride in Their Combined Tablets and Application to Real Human Plasma

A rapid, simple and highly sensitive first derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of sulpiride (SUL) and mebeverine hydrochloride (MEB). The method is based upon measurement of the synchronous fluorescence intensity of these drugs at ∆λ = 100 nm in water. The different experimental parameters affecting the fluorescence of the two drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.05–1 μg/mL and 0.2–3.2 μg/mL for SUL and MEB respectively with lower detection limits (LOD) of 0.006 and 0.01 μg/mL and quantification limits (LOQ) of 0.0.02 and 0.05 μg/mL for SUL and MEB, respectively. The proposed method was successfully applied for the determination of the two compounds in synthetic mixtures and in commercial tablets. The high sensitivity attained by the proposed method allowed the determination of both of SUL and MEB metabolite (veratic acid) in real human plasma samples applying second derivative synchronous fluorometric technique. The mean% recoveries (n = 3) for both MEB metabolite (veratic acid) and SUL were 99.82 ± 2.53 and 98.84 ± 6.20 for spiked human plasma respectively, while for real human plasma, the mean% recoveries (n = 3) were 91.49 ± 4.25 and 91.36 ± 8.46 respectively.     

Selective Spectrofluorimetric Method with Enhanced Sensitivity for Determination of Silodosine in Dosage Form and Human Plasma. Application to Stability Studies and Content Uniformity Testing

A novel, sensitive and selective spectrofluorimetric method has been developed and validated for determination of silodosine (SLD) in its dosage form and human plasma. The method is based on nucleophilic substitution reaction of SLD with 5-(dimethylamino) naphthalene-1-sulfonyl chloride (dansyl chloride) in presence of 5.0 × 10^?4 M sodium carbonate (pH 10.50) to yield a highly fluorescent derivative that was measured at 435 nm after excitation at 347 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence-concentration plot was rectilinear over the range 30.0–200.0 ng ml^?1, with a correlation coefficient of 0.9979. The limits of detection (LOD) and quantification (LOQ) were found to be 5.44 and 16.47 ng ml^?1, respectively. The proposed method was validated according to ICH guidelines, and successfully applied to the assay of commercial capsules as well as content uniformity testing. The high sensitivity of the proposed method allowed its successful application to the analysis of SLD in spiked human plasma with % recovery of 92.88 ± 1.05–100.73 ± 0.75%, (n = 6). The application of the proposed method was further extended to stability studies of SLD after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines, where this work describe the first attempt for selective spectrofluorimetric determination of silodosine in plasma and in the presence of its oxidative degradation.     

Validated Spectrofluorimetric Method for the Determination of Lamotrigine in Tablets and Human Plasma Through Derivatization with <Emphasis Type="BoldItalic">o</Emphasis>-phthalaldehyde

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of Lamotrigine (LMT) in pharmaceutical formulations and biological fluids. The method is based on reaction of LMT with o-phthalaldehyde in presence of 2-mercaptoethanol in borate buffer of pH 9.8 to yield a highly fluorescent derivative that is measured at 448 nm after excitation at 337 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence-concentration plot was rectilinear over the range of 0.1–1.0 μg ml⁻¹ with lower limit of detection (LOD) 0.02 μg ml⁻¹ and limit of quantification (LOQ) 0.06 μg ml⁻¹ respectively. The proposed method was successfully applied to the the analysis of commercial tablets. Statistical comparison of the results obtained by the proposed and reference method revealed no significant difference in the performance of the two methods regarding the accuracy and precision respectively. The proposed method was further extended to the in-vitro and in-vivo determination of the drug in spiked and real human plasma. The mean percentage recoveries in spiked and real human plasma (n = 3) were 95.78 ± 1.37 and 90.93 ± 2.34 respectively. Interference arising from co-administered drugs was also studied. A proposal for the reaction pathway with o-phthalaldehyde was postulated.     

甜茶叶中甜茶苷的UPLC-MS/MS分析

采用超高效液相色谱-质谱联用法测定广西特产甜茶叶中的主要甜味成分甜茶苷的含量.样品经前处理后以Acquity UPLC BEH C18柱为色谱柱,流动相为乙腈(含体积分数为0.1％甲酸)-蒸馏水(含体积分数0.1％甲酸),梯度条件为10min乙腈相体积由20％变化到65％,柱温35℃,进样量5μL,流速为0.15mL/...     

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.     

Selectivity Improvement for Spectrofluorimetric Determination of Oseltamivir Phosphate in Human Plasma and in the Presence of Its Degradation Product

A simple and sensitive spectrofluorimetric method has been developed and validated for determination of oseltamivir phosphate (OSP). The proposed method is based on condensation reaction of the primary amino group of OSP with ninhydrin and phenylacetaldehyde in buffered medium (pH 6.5). The formed yellow fluorescent product exhibits excitation and emission maxima at 390 and 460 nm, respectively. The selectivity improvement of our proposed method is based on the water insolubility of the oseltamivir carboxylic acid (OSC) the active metabolite of OSP, which contains the same primary amino group as OSP but cannot, condensed with ninhydrin and phenylacetaldehyde reagents. The different experimental parameters affecting the formation and stability of the reaction product were carefully studied and optimized. The fluorescence intensity concentration plot is rectilinear in the range of 2–15 μg ml^?1 with detection and quantitation limits of 0.32 and 0.98 μg ml^?1, respectively. The proposed method was successfully applied for determination of OSP in commercial capsules, suspension and spiked human plasma with good percentage recovery. In addition, the developed procedure was extended to study the stability of OSP under different stress conditions; including acid and alkali hydrolysis, oxidation, photolysis, and thermal degradation. Furthermore, the kinetic of alkaline and acidic degradation of the cited drug were investigated. The apparent first order degradation rate constants were 0.258 and 0.318 K h^?1 with half times of 2.68 and 2.17 h, for acidic and alkaline degradation, respectively.     

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.     

Spectrofluorimetric Determination of Terbinafine Hydrochloride and Linezolid in their Dosage Forms and Human Plasma

A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of Terbinafine HCl (TRH) and linezolid (LNZ) in their pharmaceutical formulations. The proposed method is based on measuring the native fluorescence of the studied drugs in water at 336 nm after excitation at 275 nm for TRH and 375 nm after excitation at 254 nm for LNZ. The fluorescence–concentration plots were rectilinear over the range of 0.02–0.15 μg/mL for TRH and 0.5–5.0 μg/mL for LNZ. With lower detection limits of 3.0 and 110.0 ng/mL and a lower quantification limit of 9.0 and 320.0 ng/mL for TRH and LNZ, respectively. The method was successfully applied to the analysis of TRH in its commercial tablets, cream, gel and spray formulations and the results were in good agreement with those obtained with the official method. In addition the method was also applied to the analysis of LNZ in its capsule and I.V solution and the results were in good agreement with those obtained with the comparison method. The effect of sensitizers was studied. The method was extended to the determination of the studied drugs in spiked human plasma and the results were satisfactory.     

Stability-Indicating Spectrofluorimetric Method for the Assay of Ziprasidone in Capsules

A simple, rapid and highly sensitive spectrofluorimetric method was developed for determination of ziprasidone hydrochloride (ZPS) in capsules. The method is based on measuring the native fluorescence of ZPS in acetate buffer of pH 4.5 at 398 nm after excitation at 315 nm. The fluorescence-concentration plot was rectilinear over the range of 0.05–0.80 μg mL⁻¹ with a lower detection limit (LOD) of 6.0 ng mL⁻¹ and quantification limit (LOQ) of 20.0 ng mL⁻¹. The method was fully validated and successfully applied to the determination of ZPS in its capsules with average percentage recovery of 99.7 ± 1.4. The method was extended to stability study of ZPS. 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.     

Micelle-Enhanced Spectrofluorimetric Method for Determination of Cholesterol-Reducing Drug Ezetimibe in Dosage Forms

A simple and sensitive spectrofluorimetric method was developed for the determination of ezetimibe in its pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behavior of ezetimibe in sodium dodecyl sulfate (SDS) micellar system. In aqueous solution of acetate buffer pH 5.0, the fluorescence intensity of ezetimibe was greatly enhanced, 200% enhancement, in the presence of SDS. The fluorescence intensity of ezetimibe was measured at 380 nm after excitation at 268 nm. The fluorescence-concentration plot was rectilinear over the range of 0.03–3.0 μg/mL with lower detection limit of 3.08 × 10⁻³ μg/mL. The method was successfully applied to the analysis of ezetimibe in its commercial tablets; the results were in good agreement with those obtained with the reported method. The application of the proposed method was extended to the stability studies of ezetimibe after exposure to different forced degradation conditions, such as acidic, alkaline, photo and oxidative conditions, according to ICH guidelines.     

荜茇宁与邻硝基苯基荧光酮的荷移反应及其测定

建立了一种测定荜茇宁的方便快捷的荷移分光光度法。荜茇宁和邻硝基苯基荧光酮在中性三酸缓冲液中发生电荷转移反应,荷移络合物在515 nm处有最大吸收,表观摩尔吸光系数为6.571×10⁴ L·mol^-1·cm^-1。该络合物的组成是1:1,药物质量浓度在0.054 6~10.92 μg/mL范围内服从比尔定律,检出限为0.015 3 μg/mL。对反应机理进行了初步探索,并利用本方法对生物样品中的荜茇宁进行了加标回收,回收率为99.8%~100.9%,相对标准偏差(RSD)为0.90%。