Development and validation of a sensitive spectrofluorimetric method for the determination of amoxapine in human plasma and urine

A selective and sensitive spectrofluorimetric method was developed and validated for the determination of amoxapine in human plasma and urine. The developed method is based on labeling with 5‐dimethylaminonaphthalene‐1‐sulfonyl chloride (dansyl chloride) and monitoring at 397 nm (excitation)/514 nm (emission). The method was validated for linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, recovery and robustness. The calibration curves were linear over a concentration range of 250–2500 and 50–1250 ng/mL for plasma and urine, respectively. The LOD values were calculated to be 13.31 and 13.17 ng/mL for plasma and urine, respectively. The proposed method was applied to study of amoxapine in human plasma and urine. Copyright © 2013 John Wiley & Sons, Ltd.     

Sensitive spectrofluorimetric determination of tizanidine in pharmaceutical preparations,human plasma and urine through derivatization with dansyl chloride

A sensitive spectrofluorimetric method was developed for the determination of tizanidine in human plasma, urine and pharmaceutical preparations. The method is based on reaction of tizanidine with 1‐dimethylaminonaphthalene‐5‐sulphonyl chloride (dansyl chloride) in an alkaline medium to form a highly fluorescent derivative that was measured at 511 nm after excitation at 383 nm. The different experimental parameters affecting the fluorescence intensity of tizanidine was carefully studied and optimized. The fluorescence–concentration plots were rectilinear over the ranges 50–500 and 20–300 ng/mL for plasma and urine, respectively, detection limits of 1.81 and 0.54 ng/mL and quantification limits of 5.43 and 1.62 ng/mL for plasma and urine, respectively. The method presents good performance in terms of linearity, detection and quantification limits, precision, accuracy and specificity. The proposed method was successfully applied for the determination of tizanidine in pharmaceutical preparations. The results obtained were compared with a reference method, using t‐ and F‐tests. Copyright © 2011 John Wiley & Sons, Ltd.     

Highly sensitive HPLC method for the determination of galantamine in human plasma and urine through derivatization with dansyl chloride using fluorescence detector

A new method based on fluorescence derivatization with 5‐(dimethylamino) naphthalene‐1‐sulfonyl chloride (dansyl chloride) was developed for the quantitative determination of galantamine in human plasma and urine using high‐performance liquid chromatography. The reaction between galantamine and dansyl chloride was optimally realized in 30 min at room temperature and pH 10.5, with a reagent to galantamine molar ratio of 2.13. The derivative was extracted with dichloromethane, and the extract was dried under a nitrogen stream and dissolved in the mobile phase. Chromatographic analysis was performed with an Inertsil C₁₈ column and a mobile phase comprising 40% acetonitrile and 60% 10 mM o‐phosphoric acid, 1.2 ml/min. The injection volume was 20 μl. The derivatives were detected with a fluorescence detector (excitation 375 nm/emission 537 nm). The retention time for the dansyl derivative of galantamine was 16.8 min. Linearity was observed between 125 and 2000 ng/ml in water, urine and plasma. The limit of detection and limit of quantification for the developed method were 6.27–70.99 and 18.81–212.97 ng/ml, respectively. Per cent recovery was calculated as 95.15 for urine and 95.78 for plasma. Interday repeatability values for urine and plasma samples (n = 6) at three different concentrations were calculated as a per cent relative standard deviation of 0.24–0.59 and 0.35–0.56. The corresponding per cent relative standard deviation values for intraday repeatability were 0.13–0.51 and 0.04–0.15, respectively.     

Validated spectrofluorimetric method for determination of two phosphodiesterase inhibitors tadalafil and vardenafil in pharmaceutical preparations and spiked human plasma

A valid, sensitive and rapid spectrofluorimetric method has been developed and validated for determination of both tadalafil (TAD) and vardenafil (VAR) either in their pure form, in their tablet dosage forms or spiked in human plasma. This method is based on measurement of the native fluorescence of both drugs in acetonitrile at λ_em 330 and 470 nm after excitation at 280 and 275 nm for tadalafil and vardenafil, respectively. Linear relationships were obtained over the concentration range 4–40 and 10–250 ng/mL with a minimum detection of 1 and 3 ng/mL for tadalafil and vardenafil, respectively. Various experimental parameters affecting the fluorescence intensity were carefully studied and optimized. The developed method was applied successfully for the determination of tadalafil and vardenafil in bulk drugs and tablet dosage forms. Moreover, the high sensitivity of the proposed method permitted their determination in spiked human plasma. The developed method was validated in terms of specificity, linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), precision and accuracy. The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from the comparison methods, as revealed by statistical analysis of the obtained results using Student's t‐test and the variance ratio F‐test. Copyright © 2015 John Wiley & Sons, Ltd.     

Validated spectrofluorimetric method for the determination of clonazepam in pharmaceutical preparations

A simple, highly sensitive and validated spectrofluorimetric method was applied in the determination of clonazepam (CLZ). The method is based on reduction of the nitro group of clonazepam with zinc/CaCl₂, and the product is then reacted with 2‐cyanoacetamide (2‐CNA) in the presence of ammonia (25%) yielding a highly fluorescent product. The produced fluorophore exhibits strong fluorescence intensity at ?_em = 383 nm after excitation at ?_ex = 333 nm. The method was rectilinear over a concentration range of 0.1–0.5 ng/mL with a limit of detection (LOD) of 0.0057 ng/mL and a limit of quantification (LOQ) of 0.017 ng/mL. The method was fully validated and successfully applied to the determination of CLZ in its tablets with a mean percentage recovery of 100.10 ± 0.75%. Method validation according to ICH Guidelines was evaluated. Statistical analysis of the results obtained using the proposed method was successfully compared with those obtained using a reference method, and there was no significance difference between the two methods in terms of accuracy and precision. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel spectrofluorimetric method for determination of imatinib in pure,pharmaceutical preparation,human plasma,and human urine

The following paper represents a simple, highly sensitive, responsive validated and developed spectrofluorimetric method for estimation of imatinib (IMB) in its pure, commercial preparation, human urine and human blood plasma. The calibration curve was in the range 4–900 ng ml^?1 for pure form and urine and 8–900 ng ml^?1 for plasma in a medium contains carboxymethyl cellulose (CMC) and acetate buffer (pH 5) with excitation wavelength (λ_ex) 230 nm and emission wavelength (λ_em) 307 nm. The limit of detection (LOD) was 0.37 ng ml^?1 for the pure form, 0.64 ng ml^?1 for human urine, and 0.70 ng ml^?1 for human plasma, while the limit of quantitation (LOQ) was 1.2 for pure form, 1.91 for urine and 2.1 for plasma. The suggested method was successfully applied for evaluation of IMB in tablets within 99% mean percentage recovery. The excipients that are usually used as additives in pharmaceutical dosage form did not interfere with the suggested method. The method was efficiently used for estimation of IMB in human urine and human plasma. The effect of some cations that might be present in urine and plasma was also studied. The method was also focused on human volunteers and in vitro drug release.     

Development of sensitive spectrofluorimetric and spectrophotometric methods for the determination of duloxetine in capsule and spiked human plasma

A new, sensitive and selective spectrofluorimetric method has been developed for the determination of duloxetine (DLX) in capsule and spiked human plasma. DLX, as a secondary amine compound, reacts with 7‐chloro‐4‐nitrobenzofurazon (NBD‐Cl), a highly sensitive fluorogenic and chromogenic reagent used in many investigations. The method is based on the reaction between the drug and NBD‐Cl in borate buffer at pH 8.5 to yield a highly fluorescent derivative that is measured at 523 nm after excitation at 478 nm. The fluorescence intensity was directly proportional to the concentration over the range 50–250 ng/mL. The reaction product was also measured spectrophotometrically. The relation between the absorbance at 478 nm and the concentration is rectilinear over the range 1.0–12.0 µg/mL. The methods were successfully applied for the determination of this drug in pharmaceutical dosage form. The spectrofluorimetric method was also successfully applied to the determination of duloxetine in spiked human plasma. The suggested procedures could be used for the determination of DLX in pure form, capsules and human plasma being sensitive, simple and selective. Copyright © 2014 John Wiley & Sons, Ltd.     

Utility of green chemistry for sustainable fluorescence derivatization approach for spectrofluorimetric quantification of Darolutamide as antineoplastic drug in pharmaceutical formulation and spiked human plasma

Darolutamide is an oral nonsteroidal androgen receptor antagonist used to delay the process of prostate cancer to metastatic disease and to increase the quality of life for people with advanced prostate cancer. Here, a second spectrofluorimetric method was advanced for quantifying Darolutamide in pharmaceutical formulation and spiked human plasma. This method depends on the fluorescence derivatization of Darolutamide with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) at 75°C in a (pH 9) of borate buffer to produce a fluorescent derivative that can be detected at 520 nm after excitation at 460 nm. The method has been validated using ICH criteria, and it demonstrated linearity in the range 5–200 ng ml⁻¹_. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.15 and 3.84 nm, respectively. The proposed method was applied precisely and accurately for quantifying Darolutamide within the pharmaceutical formulation and spiking human plasma without any interferences. Moreover, the method's sustainability was evaluated and compared with the published method using two greenness assessment tools termed analytical eco-scale and Analytical GREEnness (AGREE). These findings suggest that the method is more sustainable than the published method.     

Condensation of heptaminol hydrochloride for its spectrofluorimetric determination in pure form and tablets: application in human plasma

A sensitive, simple, accurate and less expensive fluorimetric method was designed and validated for analysis of heptaminol HCl in both its pure and dosage forms, as well as in human plasma. The main principle used in the proposed approach was the condensation reaction between heptaminol's primary amino moiety and ethyl acetoacetate/formaldehyde reagents, giving a derivative that was highly fluorescent at 416 nm after excitation at 350 nm. Various experimental parameters that affected either the product's development or its stability were evaluated and optimized. The constructed calibration curve was linear over the range 0.2–2 μg/ml, with a good correlation coefficient (0.9996). Both the calculated limit of detection and limit of quantitation were 0.06 and 0.18 μg/ml, respectively. The presented approach was a success when used to determine Corasore® tablets and was validated according to International Council for Harmonisation guidelines.     

Spectrofluorimetric method for the determination of sulpiride in pharmaceutical preparations and human plasma through derivatization with 2‐cyanoacetamide

A sensitive and accurate spectrofluorimetric method has been developed for the determination of sulpiride in pharmaceutical preparations and human plasma. The developed method is based on the derivatization reaction of 2‐cyanoacetamide with sulpiride in 30% ammonical solution. The fluorescent derivatized reaction product exhibited maximum fluorescence intensity at 379 nm after excitation at 330 nm. The optimum conditions for derivatization reactions were studied and the fluorescence intensity versus concentration plot was found to be linear over the concentration range 0.2–20.0 µg/mL with a correlation coefficient of 0.9985. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.82 and 2.73 ng/mL, respectively. The proposed method was validated according to ICH guidelines. The effects of common excipients and co‐administered drugs were also studied. The accuracy of the method was checked using the standard addition method and percent recoveries were found to be in the range of 99.00–101.25% for pharmaceutical preparations and 97.00–97.80% for spiked human plasma. The method was successfully applied to commercial formulations and the results obtained for the proposed method were compared with a high‐performance liquid chromatography reference method and statistically evaluated using the Student's t‐test for accuracy and the variance ratio F‐test for precision. A reaction pathway was also proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

A novel green spectrofluorimetric method for simultaneous determination of antazoline and tetryzoline in their ophthalmic formulation

A novel spectrofluorimetric method has been developed for determination of antazoline (ANT) and tetryzoline (TET) in their pharmaceutical formulation. A combined application of synchronous spectrofluorimetry and second derivative mathematical treatment was developed. The proposed method depends on reacting the cited drugs with dansyl chloride (DNS-Cl) being a suitable derivatizing agent generating highly fluorescent derivatives measured at emission wavelengths of 703.0 and 642.0 nm after excitation wavelengths of 350.0 and 320.0 nm for ANT and TET, respectively. The joint use of synchronous spectrofluorimetry with second derivative mathematical treatment is for the first time to be developed and optimized in aid of using fluorescence data manager software generating second derivative peak amplitudes at 556.5 nm for ANT and 516.7 nm for TET. Linear responses have been represented over a wide range of concentration (0.5–12.0 μg/mL for ANT and 0.5–10.0 μg/mL for TET). Additionally, statistical comparison of the developed method with the official ones has been carried out where no significant difference was found. Additionally, greenness profile assessment was accomplished by means of four metric tools. Indeed, the method developed is found to be precise, sensitive, and discriminating to assess the cited drugs for regular analysis.     

Green sensitive spectrofluorimetric determination of pemetrexed as antineoplastic drug: Application in pharmaceutical dosage forms and spiked human plasma

A recent antineoplastic medication is pemetrexed, this medicine is now being developed and produced on a large scale, thus approaches for quality control are urgently needed. Spectrofluorimetric guidelines for the simple estimation of pemetrexed were validated. Pemetrexed's assay depends on observations of its native fluorescence at wavelengths 275/450 nm and pH 4. The proposed approach was also used to identify the examined drug in both its formulation and in human plasma that had been spiked.     

Highly sensitive spectrofluorimetric method for rapid determination of orciprenaline in biological fluids and pharmaceuticals

Orciprenaline sulphate (ORP) is a direct‐acting sympathomimetic with mainly beta‐adrenoceptor stimulant activity. It is used as a bronchodilator in the management of reversible airway obstruction. For the first time, a rapid highly sensitive spectrofluorimetric method is described that is relied on measuring the fluorescence spectra of ORP at acidic pH and without addition of any chemical reagents. The relative fluorescence intensity was measured at 310 nm and after excitation at 224 nm. ORP native fluorescence was calibrated in both water and acetonitrile as diluting solvents. The method was designed to estimate the drug in miscellaneous matrices with high accuracy and precision. Linear ranges of calibration curves were 30.0–400.0 ng/ml and 10.0–240.0 ng/ml in water and acetonitrile, respectively. The detection limits were calculated and reached as low as 3.3 and 3.1 ng/ml, respectively, representing the ultra‐sensitivity of the proposed method. This result permitted application of this method for spiked human plasma and urine and was used as a preliminary investigation with good percentage recovery (89.4–106.8%). The application was further extended to analyse ORP in its pharmaceutical formulations. The method was validated in compliance with International Council of Harmonization (ICH) Guidelines.     

A novel solid‐phase extraction–spectrofluorimetric method for the direct determination of atenolol in human urine

A novel, simple, sensitive and selective solid‐phase extraction (SPE)–spectrofluorimetric method has been developed for the determination of atenolol (ATE) in human urine. Because an extraction procedure is required to isolate ATE or eliminate the interfering molecules present in complex human urine for the direct spectrofluorimetric determination, a pH‐sensitive poly(acrylic acid‐ethylene glycol dimethacrylate) [poly(AA‐EGDMA)] hydrogel was developed and used as a SPE adsorbent. Some factors affecting the ATE extraction efficiency, such as washing solvent type and volume, and the volume of elution solvent were optimized. Eluates from SPE cartridges were analyzed using a spectrofluorimeter (λ_ex = 277 nm and λ_em = 300 nm). The calibration graph was linear over the concentration range 0.15–4.0 µg/mL. Limit of detection (LOD) and limit of quantification (LOQ) values were found to be 0.03 and 0.10 µg/mL, respectively. Relatively high intraday [2.06%, mean relative standard deviation (RSD)] and interday (2.6%, mean RSD) precisions were achieved. High mean recovery (95.4%) and low RSD values (3.8%) were obtained for spiked ATE in human urine. The spectrofluorimetric method presented here can be easily applied to assay trace amounts of ATE in pharmaceuticals and biological samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Spectrofluorimetric determination of nomifensine in human plasma and urine by derivatization with fluorescamine

A sensitive, simple and rapid spectrofluorimetric method was developed for the determination of nomifensine in human plasma and urine. The present method was based on the derivatization by fluorescamine in phosphate buffer at pH 4.0 to produce a highly fluorescent product which was measured at 488 nm (excitation at 339 nm). The method was validated according to the ICH guidelines with respect to linearity, limit of detection, limit of quantification, accuracy, precision, recovery and robustness. The assay was linear over the concentration ranges 100–2,000 and 50–2,000 ng/mL for plasma and urine, respectively. The limits of detection were calculated to be 13.9 and 7.5 ng/mL for plasma and urine, respectively. The method was successfully applied to the analysis of the drug in human plasma and urine. Copyright © 2011 John Wiley & Sons, Ltd.     

Validated sensitive spectrofluorimetric method for determination of antihistaminic drug azelastine HCl in pure form and in pharmaceutical dosage forms: application to stability study

A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of azelastine HCl (AZL) in either its pure state or pharmaceutical dosage form. The proposed method was based on measuring the native fluorescence of the studied drug in 0.2 M H₂SO₄ at λ_em = 364 nm after excitation at λ_ex = 275 nm. Different experimental parameters were studied and optimized carefully to obtain the highest fluorescence intensity. The proposed method showed a linear dependence of the fluorescence intensity on drug concentration over a concentration range of 10–250 ng/mL, with a limit of detection of 1.52 ng/mL and limit of quantitation of 4.61 ng/mL. Moreover, the method was successfully applied to pharmaceutical preparations, with percent recovery values (± SD) of 99.96 (± 0.4) and 100.1 (± 0.52) for nasal spray and eye drops, respectively. The results were in good agreement with those obtained by the comparison method, as revealed by Student's t‐test and the variance ratio F‐test. The method was extended to study the stability of AZL under stress conditions, where the drug was exposed to neutral, acidic, alkaline, oxidative and photolytic degradation according to International Conference on Harmonization (ICH) guidelines. Copyright © 2016 John Wiley & Sons, Ltd.     

Sensitive method for determination of DON in cocoa by means of HPLC-techniques

The mycotoxin deoxynivalenol (DON) is one of a group of mycotoxins known as type B trichothecenes and is particularly formed by the mould speciesFusarium graminearum andFusarium culmorum. The frequency of the occurrence of DON in certain raw materials and the concentrations found make it one of the world’s most significant mycotoxin contaminants. Positive findings of the toxin especially have been established in cereal-based foods, as well as in oilseeds. The main objective of this study was to set up a current situation assessment of the possible occurrence of deoxynivalenol in cocoa and cocoa products. As there was no analytical method for determining DON in cocoa and cocoa products, a special method was developed. The applicability and consistency of the method was confirmed by performing recovery assays on various cocoa products. A special post-column derivatisation procedure was developed to increase selectivity and raise sensitivity by a factor of 80. The method was used to test 230 samples for possible DON content, ranging from cocoa beans to cocoa bean shells, nibs, cocoa liquor and cocoa powders through to finished cocoa-based products. The results suggest that DON may occasionally occur in cocoa beans in very low concentrations. Presented at the 29^th Mykotoxin-Workshop, Fellbach, Germany, May 14–16, 2007     

Spectrophotometric and spectrofluorimetric determination of indacaterol maleate in pure form and pharmaceutical preparations: application to content uniformity

Two simple, rapid, sensitive and precise spectrophotometric and spectrofluorimetric methods were developed for the determination of indacaterol maleate in bulk powder and capsules. Both methods were based on the direct measurement of the drug in methanol. In the spectrophotometric merthod (Method I) the absorbance was measured at 259 nm. The absorbance‐concentration plot was rectilinear over the range 1.0–10.0 µg mL^?1 with a lower detection limit (LOD) of 0.078 µg mL^?1 and lower quantification limit (LOQ) of 0.238 µg mL^?1. Meanwhile in the spectrofluorimetric method (Method II) the native fluorescence was measured at 358 nm after excitation at 258 nm. The fluorescence‐concentration plot was rectilinear over the range of 1.0–40.0 ng mL^?1 with an LOD of 0.075 ng mL^?1and an LOQ of 0.226 ng mL^?1. The proposed methods were successfully applied to the determination of indacaterol maleate in capsules with average percent recoveries ± RSD% of 99.94 ± 0.96 for Method I and 99.97 ± 0.81 for Method II. In addition, the proposed methods were extended to a content uniformity test according to the United States Pharmacopoeia (USP) guidelines and were accurate, precise for the capsules studied with acceptance value 3.98 for Method I and 2.616 for Method II. Copyright © 2015 John Wiley & Sons, Ltd.     

Kinetic spectrophotometric method for the determination of ramipril in pharmaceutical formulations

The objective of this research was to develop a kinetic spectrophotometric method for determination of ramipril in pure form and pharmaceutical formulations. The method was based on the reaction of carboxylic acid group of the drug with a mixture of potassium iodate (KIO₃) and potassium iodide (KI) in aqueous medium at room temperature. The reaction is followed spectrophotometrically by measuring the increase in absorbance at 352 nm as a function of time. The initial-rate and fixed-time methods were adopted for constructing the calibration curves. Both the calibration curves were linear in the concentration range of 10.0–70.0 μg mL⁻¹. The detection limits were 0.02μg mL⁻¹ and 0.15-μg mL⁻¹ for initial rate and fixed time methods, respectively. The proposed methods are validated statistically and through recovery studies. The point and interval hypothesis tests have been performed confirming that there is no significant difference between the proposed methods and the reference method. The experimental true bias of all samples is less than ±2%. The methods have been successfully applied to the determination of ramipril in tablets and capsules. Published: October 27, 2005     

Enhanced spectrofluorimetric determination of esomeprazole and pantoprazole in dosage forms and spiked human plasma using organized media

A simple, sensitive and rapid spectrofluorimetric method was developed for the determination of esomeprazole (EMZ) and pantoprazole (PRZ) in their pharmaceutical formulations and human plasma. The proposed method is based on the fluorescence spectral behavior of EMZ in methanol in the presence of 0.1 m NaOH containing 0.5% methyl cellulose (MC) at 306/345 nm. The fluorescence intensity of EMZ was enhanced about 1.3‐fold and good linearity in the range 0.4–4.0 µg/mL with a lower detection limit of 0.04 µg/mL and lower quantification limit of 0.14 µg/mL. For PRZ, its methanolic solution exhibited marked native fluorescence at 290/325 nm after enhancement (about 2.1‐ or 1.4‐fold) using either 0.025% sodium dodecyl sulfate (SDS) or 0.05% MC in the presence of 0.2 m borate buffer of pH 9.5. The fluorescence–concentration plots of PRZ were rectilinear over the ranges 0.2–2.0 and 0.3–3.0 µg/mL with lower detection limits of 0.02 and 0.03 µg/mL and lower quantification limits of 0.07 and 0.09 µg/mL using sodium dodecyl sulfate and MC, respectively. The method was successfully applied to the analysis of EMZ and PRZ in their commercial dosage forms and the results were in good agreement with those obtained with the comparison method. Furthermore, in a preliminary investigation, the proposed method was extended to the in vitro determination of the two drugs in spiked human plasma and the results were satisfactory. Copyright © 2014 John Wiley & Sons, Ltd.