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 the determination of tamsulosin in spiked human urine,pure and pharmaceutical preparations

A novel, sensitive and selective spectrofluorimetric method was developed for the determination of tamsulosin in spiked human urine and pharmaceutical preparations. The proposed method is based on the reaction of tamsulosin with 1‐dimethylaminonaphthalene‐5‐sulfonyl chloride in carbonate buffer pH 10.5 to yield a highly fluorescent derivative. The described method was validated and the analytical parameters of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, recovery and robustness were evaluated. The proposed method showed a linear dependence of the fluorescence intensity on drug concentration over the range 1.22 × 10^‐7 to 7.35 × 10^‐6 M. LOD and LOQ were calculated as 1.07 × 10^‐7 and 3.23 × 10^‐7 M, respectively. The proposed method was successfully applied for the determination of tamsulosin in pharmaceutical preparations and the obtained results were in good agreement with those obtained using the reference method. 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.     

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.     

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.     

Development and validation of a spectrofluorimetric method for the quantification of ceftriaxone in pharmaceutical formulations and plasma

We describe the development and validation of a new, simple, sensitive and cost‐effective method for the determination of ceftriaxone in commercial formulations and spiked human plasma. The method proposes the conversion of ceftriaxone into a fluorescent product by reacting with ortho‐phthalaldehyde (OPA) in the presence of sulfite at room temperature. The reaction medium is buffered to pH 10 using borate buffer. The derivatized reaction product is highly fluorescent and exhibits maximum fluorescence intensity at λ_em = 386 nm after excitation at λ_ex = 324 nm. The experimental parameters affecting progress of the derivatization reaction were carefully studied and optimized. Under optimum experimental conditions, the method has an excellent correlation coefficient of 0.9984 with a broad linear range of 0.4?20 µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 1.30 × 10^?3 and 3.90 × 10^?3 µg/mL, respectively. The interference effects of common excipients on the quantification of drug were investigated and no interference effect was observed. The proposed method has been successfully applied to the determination of ceftriaxone in pharmaceutical formulations and spiked human plasma samples. The method has been validated statistically through percent recovery studies using standard addition and by comparison with a reference HPLC method. The developed method exhibits excellent inter‐ and intraday precision. 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.     

A novel spectrofluorimetric method for the determination of calcitonin in ampules through derivatization with fluorescamine

In this study, a simple, sensitive and selective spectroflourimetric method has been developed for the determination of salmon calcitonin (sCT) in ampules. The method is based on the reaction between sCT and fluorescamine at pH 8.5 in borate buffer, resulting in a highly fluorescent derivative. Fluorescence of derivatized sCT solutions was measured by setting the excitation and emission monochromators and slit widths to 390, 484 and 10 nm, respectively. Sevaral derivatization parameters were optimized. A calibration graph was constructed using standard solutions of the derivatized calcitonin in the range 0.5–6.0 µg/mL. Limit of detection and limit of quantification values were determined to be 0.124 and 0.372 µg/mL, respectively. The proposed method was successfully applied for the determination of sCT in commercially available ampules. High recovery values (101.0–102.0 %), and a low relative standard deviation (RSD %) value (5.3–5.4) proved the accuracy and precision of the proposed method. An isocratic reversed‐phase high‐performance liquid chromatographic (HPLC) method, as a reference, was also developed for the determination of sCT. A reversed‐phase Nucleosil® C₁₈ column (250 mm × 4.6 mm i.d., 10 µm particle size, 120 Å pore size) was used and the detector was set at 210 nm. Statistical comparison of the results of the two methods showed clearly that there was no significant difference between them. Copyright © 2012 John Wiley & Sons, Ltd.     

Utility of Hantzsch reaction for development of highly sensitive spectrofluorimetric method for determination of alfuzosin and terazosin in bulk,dosage forms and human plasma

A highly sensitive, cheap, simple and accurate spectrofluorimetric method has been developed and validated for the determination of alfuzosin hydrochloride and terazosin hydrochloride in their pharmaceutical dosage forms and in human plasma. The developed method is based on the reaction of the primary amine moiety in the studied drugs with acetylacetone and formaldehyde according to the Hantzsch reaction, producing yellow fluorescent products that can be measured spectrofluorimetrically at 480 nm after excitation at 415 nm. Different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The fluorescence–concentration plots of alfuzosin and terazosin were rectilinear over a concentration range of 70–900 ng ml^?1, with quantitation limits 27.1 and 32.2 ng ml^?1 for alfuzosin and terazosin, respectively. The proposed method was validated according to ICH guidelines and successfully applied to the analysis of the investigated drugs in dosage forms, content uniformity test and spiked human plasma with high accuracy.     

A new spectrofluorimetric method for determination of trace amounts histamine in human urine and serum

A new spectrofluorimetric method was developed for the determination of trace amounts of histamine in human urine and serum samples. In NaAc–HAc buffer solution of pH 4.0, histamine can react with the acetylacetone–formaldehyde system to produce a fluorescent derivative which emits yellow‐green fluorescence at 476 nm, according to the Hantzsch reaction, and the enhanced fluorescence intensity is in proportion to the concentration of histamine. Optimum conditions for the determination of histamine were also investigated. The dynamic range and detection limit for the determination of histamine is 5.96 × 10^–8–1.50 × 10^–5 mol/L and 4.35 × 10^–8mol/L, respectively. This method is practical and can be successfully applied to determination of histamine in human urine and serum samples. A proposal of the reaction pathway is suggested. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Microenvironment improvement protocol for the sensitive spectrofluorimetric determination of an hepatitis C virus antiviral (Simeprevir): application to human plasma

Simeprevir (SPV) is a powerful antihepatitis C virus agent that was newly introduced into the pharmaceutical market. We here established and validated an easy, simple, and sensitive spectrofluorimetric method for its estimation at λ_em 427 nm (λ_ex 337 nm). The suggested procedure was based on two times enhancement in the original emission of SPV through modifying its microenvironment in buffered aqueous solution by adding Triton X‐100. The relationship between the concentration of SPV and the observed fluorescence intensity was linear in the range 0.06–1.0 μg ml^?1 with a correlation coefficient of 0.9997. The limits of detection and quantitation were 21 and 64 ng ml^?1, respectively. The present method was effectively applied to quantify SPV content in pharmaceutical tablets and human plasma spiked with the drug with no interference from tablet excipients or plasma components.     

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.     

First derivative synchronous spectrofluorimetric method for the simultaneous determination of tramadol and celecoxib in their dosage forms and human plasma

One of the most common features of many different clinical conditions is pain; hence, there is a crucial need for eliminating or reducing it to a tolerable level to retrieve physical, psychological and social functioning. A first derivative synchronous spectrofluorimetry technique is proposed for the simultaneous determination of celecoxib and tramadol HCl, a recent coformulation authorized for treating acute pain in adults. The method includes using synchronous spectrofluorimetry at ∆λ = 80 nm where tramadol HCl was determined using first derivative technique at λ = 230.2 nm, while celecoxib was determined at λ = 288.24 nm. The proposed method was successfully applied to their co-formulated dosage forms in addition to spiked human plasma and validated in agreement with the guidelines of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH). The linear ranges were found to be 0.50–5.0 and 0.15–0.50, the limits of detection to be 0.088 and 0.011 and the limits of quantification to be 0.266 and 0.032 μg/ml for celecoxib and tramadol, respectively. Statistical analysis revealed no significant difference when compared with previously reported methods as evidenced by the values of the variance ratio F-test and Student t-test. The proposed method was successfully applied to commercial dosage forms and spiked human samples. Moreover, the greenness of the proposed method was investigated based on the analytical eco-scale approach, with the results showing an excellent green scale with a score of 95.     

A new spectrofluorimetric method for determination of losartan potassium in rabbit plasma and its application to pharmacokinetic study

A new spectrofluorimetric method to determine losartan potassium (LP) in rabbit plasma is described. The method was based on measuring the native fluorescence of LP in acidic medium. Optimum excitation and emission wavelengths were found to be 248 nm and 410 nm, respectively, in methanol that was diluted with a sulfurous acid solution LP was extracted from rabbit plasma by methyl‐tertiary‐butyl‐ether in acidic media and then back extracted with NaOH. The calibration curves were linear between 0.025 and 0.5 µg/mL with a lower limit of detection 0.004 µg/mL. Precision and accuracy values of the method were calculated as lower than 4.97% and ± 5.68, respectively and the recovery of LP from rabbit plasma was higher than 91.1%. In addition, stability studies of LP in rabbit plasma were carried out and demonstrated its good stability at − 20 °C and at room temperature. The developed and validated method was successfully applied for estimating the pharmacokinetic parameters of LP following oral administrations of a single 10 mg LP/kg to rabbits and it could be concluded that the method can be applied to clinical trials. Copyright © 2014 John Wiley & Sons, Ltd.     

A highly sensitive micelle-enhanced synchronous spectrofluorimetric determination of the recently approved co-formulated drugs,bilastine and montelukast in pharmaceuticals and human plasma at nanogram levels

In this study, the simultaneous determination of bilastine and montelukast, two recently approved co-formulated antihistaminic medications, was accomplished using a quick, sensitive, environmentally friendly, and reasonably priced synchronous fluorescence spectroscopic approach for the first time. Enhancement of the method's sensitivity down to nanogram levels was achieved by the addition of sodium dodecyl sulfate (1.0% w/v) as a micellar system. According to the results, bilastine and montelukast's fluorescence was measured at 255.3 and 355.3 nm, respectively, using Δλ of 40.0 nm and distilled water as a green diluting solvent. With respect to the concentration ranges of bilastine (5.0–300.0 ng/ml) and montelukast (50.0–1000.0 ng/ml), the method showed excellent linearity (r ≥ 0.9998). The results showed that the suggested method is highly sensitive, with detection limits of 1.42 and 13.74 ng/ml for bilastine and montelukast, respectively. Within-run precisions (intra- and interday) per cent relative standard deviations (RSD) for both analytes were <0.59%. With high percentage recoveries and low percentage RSD values, the designed approach was successfully applied for the simultaneous estimation of the cited medications in their dosage form and human plasma samples. To evaluate the green profile of the suggested method, an analytical GREENNESS metric approach (AGREE) and green analytical procedure index (GAPI) metric tools were used. These two methods for evaluating greenness confirmed that the developed method met the highest number of green requirements, recommending its use as a green substitute for the routine analysis of the studied drugs. The proposed approach was validated according to ICHQ2 (R1) guidelines.     

Simple and sensitive spectrofluorimetric method for the determination of pregabalin in capsules through derivatization with fluorescamine

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of pregabalin (PG) in capsules. The method is based on the reaction between pregabalin and fluorescamine in borate buffer solution of pH 10 to give a highly fluorescent derivative that is measured at 487 nm after excitation at 390 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence intensity concentration plot was rectilinear over the range of 0.01–0.3 µg mL^?1 with a lower detection limit of 0.0017 µg mL^?1 and limit of quantitation of 0.005 µg mL^?1. The developed method was successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recovery of PG in its capsule was 99.93±1.24 (n = 3). Statistical comparison of the results with those of the comparison method revealed good agreement and proved that there was no significant difference in the accuracy and precision of the two methods. A proposed reaction pathway was postulated. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

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.     

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.