Spectroscopic and HPLC methods for the determination of alendronate in tablets and urine

Two methods (spectrophotometric and HPLC) have been developed and validated for the analysis of alendronate sodium in tablet dosage form. Both methods depend on the ability of alendronate sodium to react with o-phthalaldehyde (OPA) at basic pH to produce a light-absorbing derivative. The derivative was found to possess absorption maximum at 330 nm where neither the derivatizing agent nor the analyte had any absorption. Thus, spectroscopic method was based on the derivatization-induced absorption of alendronate sodium at 333 nm. The HPLC method was based on separation of the formed derivative from other ingredients in tablets with detection at 333 nm. Both methods were satisfactory with regard to accuracy, prescion and linearity. Moreover, a HPLC method with fluorescence detection (HPLC-FD) was developed for the quantification of alendronate sodium in urine. The method was also based on the derivatization of alendronate with OPA, but fluorescence detection was employed. Linearity, recovery, selectivity, prescision and sensitivity were satisfactory for the proposed HPLC-FD method. Yet a new quantification limit (0.6 ng ml⁻¹) for alendronate in urine was achieved.     

Derivative and Derivative Ratio Spectrophotometric Analysis of Antihypertensive Ternary Mixture of Amiloride Hydrochloride,Hydrochlorothiazide and Timolol Maleate

Two simple, rapid and reliable spectrophotometric methods are described for the resolution of the three‐component mixture of amiloride hydrochloride (AMD), hydrochlorothiazide (HCT) and timolol maleate (TIM). The first method involves the use of derivative spectrophotometry with the zero‐crossing technique where AMD was easily determined using its ⁰D and ¹D(Δλ = 6) amplitudes at 365 and 385 nm, respectively, while HCT and TIM were determined by measuring the ³D(Δλ = 6) amplitude at 265 nm and the ¹D(Δλ = 8) amplitude at 315.4 nm, respectively. The second method involves the application of the ratio‐spectra zero‐crossing first and second derivative spectrophotometry where two points have been used for the quantification of each compound. For the determination of AMD, HCT was used as divisor and the ¹DD (Δλ = 4) and ²DD (Δλ = 6) values at 299.4 and 311 nm, respectively, were plotted against AMD concentration; while — by using TIM as divisor — the ²DD (Δλ = 6) amplitudes at 264.2 and 290 nm were found to be proportional to HCT concentration. TIM was assayed in the mixture using its ¹DD (Δλ = 6) amplitudes at 289.8 nm (Divisor was AMD) and 314.8 nm (Divisor was HCT). Synthetic mixtures of different proportions and laboratory‐made tablets were assayed by the proposed methods and the results revealed good accuracy and repeatability of the developed methods.     

Comparison of an HPTLC method with the Reflectoquant assay for rapid determination of 5-hydroxymethylfurfural in honey

5-Hydroxymethylfurfural (HMF) was analyzed in 17 botanical varieties of honey from 12 countries. A recently developed high-performance thin-layer chromatographic (HPTLC) method was limited because of increased matrix effects at higher honey sample loading. Therefore, the method was modified to achieve higher sensitivity and eliminate matrix interference by use of rectangular application combined with a focusing step. The HPTLC results were compared with results from the new spectrophotometric Reflectoquant hydroxymethylfurfural assay. Both methods had quantification limits of 4 mg kg^?1 and were suitable for rapid quantification of HMF in honey at the strictest regulated level of 15 mg kg^?1. Comparable results were obtained for the 17 honey samples, with a mean deviation of 2.9 mg kg^?1 (15 %). The optimized HPTLC method was proved to be highly matrix-robust and was validated for the 17 different honey matrices (correlation coefficients ≥0.9994 (n?=?6), mean intra-day precision 3.2 % (n?=?3 within a plate; n?=?2 repeated within a day), mean inter-day precision 3.7 % (n?=?3), mean reproducibility over the whole procedure including sample preparation 4.1 % (n?=?2), and mean recovery 106.9 % (n?=?5 different concentrations; n?=?4 different honey matrices). Recovery for a range of different application volumes, and thus for different honey matrix loading, differed by only ≤4.2 %. HMF results when calculated by use of external calibration and by use of the standard addition method varied by 8.8 %. Both revealed that any matrix effect was minor and that the original matrix interference problem was successfully solved.

Development and Validation of Derivative Spectrophotometric Method for Determination of Rabeprazole Sodium in Pharmaceutical Formulation

Abstract

The aim of this work is to develop and validate the derivative spectrophotometric method for determination of the proton pump inhibitor rabeprazole sodium in pharmaceutical formulations. The technique was applied using water (pH 10.0) as diluent. The first‐order derivative spectra were obtained at N=5, Δλ=4.0 nm, and determinations were made at 304 nm. The method showed high specificity in the presence of formulation excipients and good linearity in the concentration range of 6.0 to 18.0 µg/mL^?1. The intra‐ and interday precision data demonstrated the method has good reproducibility [Relative Standard Deviation ((RSD)=1.0 interdays)]. Accuracy was also evaluated and results were satisfactory (mean recovery of 99.15%). The detection and quantitation limits were 0.055 and 0.17 µg/mL^?1, respectively. The method was demonstrated to be adequate for routine analysis in quality control.     

Simultaneous determination of ofloxacin and flavoxate hydrochloride by first-and ratio first-derivative UV spectrophotometry

Two simple, precise, accurate and sensitive UV spectrophotometric methods were developed and validated for the simultaneous determination of ofloxacin (OFX) and flavoxate HCl (FLX) in bulk and pharmaceutical formulations. In one method, first-derivative absorption at 303.6?nm (for OFX at its zero crossing) and 329.8?nm, (for FLX at its zero crossing) was used for the determination of the drugs and the linearity range was found to be 0.5?C70???g?ml^?1 for FLX and 0.5?C30???g?ml^?1 for OFX. In the second method, the ratio derivative spectrophotometry method was developed making use of amplitude in the first derivative of the corresponding ratio spectra at 290?nm (maxima) and 254?nm (minima) to estimate OFX and FLX, respectively. Further, the linearity range was found to be 0.5?C25???g?ml^?1 for OFX and 0.5?C30???g?ml^?1 for FLX. In both the methods, correlation coefficient was found to be more than 0.999. Both methods were validated according to ICH guidelines by assessing the linearity, accuracy, precision, limit of quantification, limit of detection and selectivity. The results demonstrate that both methods are accurate, precise and reproducible (relative standard deviation <2), while being simple, cheap and less time-consuming, and hence can be suitably applied for the simultaneous estimation of OFX and FLX in pharmaceutical formulation and for dissolution studies.     

Rapid determination of hydrogen peroxide in the wood pulp bleaching streams by a dual-wavelength spectroscopic method

This study has demonstrated a spectrophotometric method for residual hydrogen peroxide analysis in wood pulp bleaching streams. In an acidic medium, hydrogen peroxide can instantly associate with molybdate to form a peroxomolybdic acid complex that has an absorption peak at 330 nm. To avoid the spectral interference from excess molybdate ion, 350 nm is used for spectroscopic quantification. A linear relationship between the absorbance at 350 nm and peroxide concentration was found up to a peroxide concentration of ca. 0.2 mmol l⁻¹. It was discovered that 297 nm was an isosbestic point that could be used to develop a dual-wavelength method to account for the spectral interference from dissolved lignin in pulp bleaching streams, a critical procedure for the success of the present method. This method is simple, rapid, sensitive, accurate, and has the potential for on-line applications.     

Extraction of Ni(II) on micro crystalline naphthalene modified with organic-solution-processable functionalized nano graphene

A novel and selective method for the fast determination of trace amounts of Ni(II) ions in water samples is described. Method has been developed for preconcentration of Ni on organic-solution-processable functionalized-nano graphene (SPFGraphene) adsorbent in the pH range 5.0–10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at λ = 517 nm. This method makes it possible to quantitize Ni in the range of 4.2 × 10^?9 to 2.3 × 10^?5 M, with a detection limit (S/N = 3) of 1.42 × 10^?9 M. This procedure has been successfully applied to determine the ultra trace levels of Ni in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements is better than 3.0%.     

Sensitive and selective spectrophotometric methods for the determination of pheniramine maleate in bulk drug and in its formulations using sodium hypochlorite

Two simple, selective and sensitive spectrophotometric methods are described for the determination of pheniramine maleate (PAM) in pure and dosage forms. The method is based on the reaction of PAM with hypochlorite in the presence of Kolthoff buffer (phosphate-borate) of pH 7.0 to form the chloro derivative of PAM, destruction of the excess hypochlorite by nitrite ion (the chloro derivative of drug is unaffected under the optimized conditions) followed by the oxidation of iodide with the chloro derivative of PAM to iodine (I ₃ ^? which is either measured directly at 355 (method A) or reacted with starch to form a blue chromogen measurable at 590 nm (method B). The optimum conditions that affect the reaction were ascertained, and under these conditions linear relationship was obtained in the concentration ranges of 2–50 and 1–25 μg/mL PAM in methods A and B, respectively. The calculated molar absorptivity values are 7.26 × 10³ and 1.28 × 10⁴ L/(mol cm) for method A and method B, respectively. Sandell’s sensitivity values, limits of detection (LOD) and quantification (LOQ) are calculated as per ICH guidelines. The proposed methods were applied successfully to the determination of PAM in tablets and injection with good accuracy and precision and without interferences from common additives. The results obtained by the proposed methods were compared favourably with those of the reference method. The accuracy and reliability of the proposed methods were further checked by recovery studies via standard addition procedure.     

Spectrophotometric Determination of Esomeprazole Magnesium in Commercial Tablets Using 5‐Sulfosalicylic Acid and N‐Bromosuccinimide

Two simple, sensitive and economical spectrophotometric methods have been developed for the determination of esomeprazole magnesium in commercial dosage forms. Method A is based on the reaction of esomeprazole magnesium with 5‐sulfosalicylic acid in methanol to form a yellow product, which absorbs maximally at 365 nm. Method B utilizes the reaction of esomeprazole magnesium with N‐bromosuccinimide in acetone‐chloroform medium to form α‐bromo derivative of the drug peaking at 380 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration ranges of 2‐48 and 10‐100 μg mL^?1 with molar absorptivity of 2.11 × 10⁴ and 4.57 × 10⁴L mol^?1 cm^?1 for methods A and B, respectively. The limits of detection for methods A and B are 0.35 and 0.46 μg mL^?1, respectively. No interference was observed from excipients commonly present in tablet formulations. Methods A and B are successfully applied to the commercial tablets for the estimation of esomeprazole magnesium with good accuracy and precision. The results compare favorably with the reference spectrophotometric method indicating no significant difference between the methods compared.     

A ratio derivative spectrophotometric method for the simultaneous determination of uranium and plutonium

A ratio derivative spectrophotometric method has been developed for the simultaneous determination of uranium and plutonium at mg levels in 1M HNO₃ medium. In this method the overlapping spectra of uranium and plutonium are well resolved by making use of the first derivative of the ratios of their direct absorption spectra. The derivative ratio absorbances of uranium and plutonium are measured at 411.2 and 473.8 nm, respectively for their quantification. The method is simple, fast and does not require separation of uranium and plutonium. Another salient feature of the method is that it does not lead to generation of analytical waste thereby minimising the efforts required for the recovery of plutonium. Uranium in the conc. range of 10–25 mg/g and plutonium in the conc. range of 0.5 to 2 mg/g (U/Pu ratio varying from about 10 to 25) were determined in the same aliquot with a precision and accuracy of about 0.5% and 1%, respectively.     

Spectrophotometric study of reactions of scandium,ytrium and lanthanum ions with some triphenylmethane dyes in the presence of cationic surfactants

Optimum conditions for the formation of ternary complexes of scandium, ytrium and lanthanum ions with chrome azurol S, eriochrome cyanine R and pyrocatechol violet in the presence of cetyltrimethylammonium, cetypyridinium and tetradecyldimethylbenzyl-ammonium (zephiramine) ions are described. The spectrophotometric determination of scandium with chrome azurol S and zephiramine exhibits the greatest sensitivity (? = 1.50 × 10⁵ l mol^?1 cm^?1 at 610 nm). In the spectrophotometric determination of scandium with eriochrome cyanine R and cetylpyridinium ion (? = 9.2 × 10⁴ at 600 nm), the interference caused by yttrium is the least. In the best method for yttrium (with pyrocatechol violet and zephiramine), the molar absorptivity is 3.3 × 10⁴ at 660 nm. Lanthanum does not form ternary complexes of analytical interest in these systems. Some aspects of the formation of ternary complexes with cationic surfactants are discussed.     

The Use of Internal Standard Method for Dertvative-Spectrophotometric Determination of Chlorpromazine Hydrochloride

ABSTRACT

The use of 1, 10-phenantroline as internal standard (IS) is proposed for spectrophotometric determination of chlorpromazine hydrochloride in pharmaceutical formulations. The spectra of both compounds: analyte and internal standard are partially overlapped, so the Savitzky-Golay alghoritm was used to obtain separated signals of analyte and IS. The best parameters to generate the second-derivative spectra were: ∠λ = 10 nm (5 experimental points) and second polynomial degree. For quantification of chlorpromazine in pharmaceuticals, the zero-crossing technique was used. The values of the second-derivative peaks were measured for chlorpromazine at 256 nm and at 236 nm for IS. Analytical characteristic for proposed method was evaluated (r²=0.9990, detection limit=3.97 ng/ml). The obtained analytical results were in good agreement with results obtained using the UV-spectrophotometric Blazek method.     

Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in oral homeopathic products ("AntimoniumTartaricum") formulated under alcoholic medium

In this work, a flow analysis-hydride generation-gas phase derivative molecular absorption-(UV) spectrophotometric method has been developed for the direct determination of antimony in aqueous and hydro-alcoholic samples. Antimony (III) from undiluted samples is directly transformed into the gaseous stibine (SbH₃) form by on-line reaction with sodium tetrahydroborate (NaBH₄) in acidic medium (HCl). The gaseous phase generated is separated from the liquid phase using a commercial gas-liquid separator, and swept - with the help of a carrier gas (N₂) stream - into a quartz gas cell (10 cm pathlength); where the corresponding absorption spectrum is acquired in a continuous mode over the 190-300 nm wavelength range, using a conventional spectrophotometer. A derivative strategy was selected in order to avoid the strong spectral interference of the ethanol vapor on the gaseous SbH₃ absorption spectrum. In this way, the peak height at 223 nm of the second order derivative spectrum appears as a clear, clean and interference free analytical signal, which allows the direct determination of antimony. The recovery values obtained from homeopathic formulations (prepared in alcoholic medium) spiked with know amounts of antimony ranged between 97.5 and 103%. The method provides a dynamic range from 0.20 to 30 mg Sb l⁻¹. The precision (RDS), evaluated by replicate analysis (n = 5) of samples and standard solution containing between 2.5 and 15 mg Sb l⁻¹ was in all cases lower than 1.2%. The proposed method was applied to the determination of antimony in commercial homeopathic products (“Antimonium Tartaricum”) prepared in hydro-alcoholic medium; and showed to be simple, precise, and accurate.     

A derivative UV spectrophotometric method for the determination of levothyroxine sodium in tablets

A derivative UV (D-UV) spectrophotometric method was developed for the determination of Levothyroxine Sodium (L-T₄) in tablets of different doses. Quantification was performed using the second derivative of the absorption spectrum at 253 nm (²D₂₅₃) in methanol: water (50: 50; v/v) (pH 11.2). The method was validated and compared with an HPLC procedure carried out using a RP-18 column (125 × 4 mm, 5 μm) and methanol: phosphoric acid (0.1%) (70: 30, v/v) (pH 3) as mobile phase. Flow rate was set at 1.5 mL/min, and detection was performed at 225 nm. The proposed D-UV method was linear in the range 3.0–40.0 μg/mL with an appropriate precision and accuracy, and it was selective for the drug under study. On the other hand, results obtained by ²D₂₅₃ analysis were similar to those obtained by HPLC, with no statistically significant differences between them. Therefore, it was concluded that the developed method is suitable for the determination of L-T₄ in tablets at the tested doses.     

Spectrophotometric determination of vanadium in petroleum crudes and derivatives

The spectrophotometric study of the complexation reaction between 5,5′methylenedisalicylhydroxamic acid and V(V) shows that two complexes are formed, the 1:1 (? = 5100 liters mol^?1 cm^?1 at 490 nm, log K_est = 5.8 ± 0.1) and the 1:2 (L:V) (? = 6250 liters mol^?1 cm^?1 at 600 nm, log K_est = 6.1 ± 0.1). A spectrophotometric method is developed for the determination of vanadium (2–9 ppm) at 2 N HCl and 495 nm, which allows its determination in petroleum crude oils with a series of advantages over the ASTM D-1548-63 method.     

Normal spectrophotometric and stopped-flow spectrofluorimetric sequential injection methods for the determination of alendronic acid, an anti-osteoporosis amino-bisphosphonate drug, in pharmaceuticals

A normal spectrophotometric and a stopped-flow (SF) spectrofluorimetric method have been developed and optimized for the determination of alendronic acid (ALD) in its pharmaceutical formulations. Both methods are automated using the sequential injection analysis (SIA) principle. The spectrophotometric assay is based on the reaction of the analyte with Cu(II) ions in acidic medium to form an UV-absorbing derivative (λ_max = 240 nm). The SF spectrofluorimetric method is based on the reaction of ALD with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol at basic medium (λ_ex = 340 nm/λ_em = 455 nm). Linear calibration curves were obtained in the range 1.0-60.0 mg l⁻¹ ALD for the UV method, and in the range 0.13-10.0 mg l⁻¹ ALD for the SF spectrofluorimetric one. The sampling rates were 60 and 30 h⁻¹, respectively. The developed assays are critically compared and their advantages are discussed. Both methods were applied to the analysis of an ALD containing pharmaceutical formulation with satisfactory accuracy and precision.     

A spectrophotometric method for quantitative determination of lactulose in pharmaceutical preparations

A simple spectrophotometric assay for the quantification of lactulose in pharmaceutical preparations was developed. The method is based on hydrolysis of lactulose under acidic conditions. The hydrolyzed product reacts with resorcinol, giving absorption peaks at 398 and 480 nm. Both absorption wavelengths can be used for the determination of lactulose. The limit of detection of lactulose at 398 nm and 480 nm was 0.075 μg mL⁻¹ and 0.65 μg mL⁻¹, respectively. The calibration was linear in the range of 5–25 μg mL⁻¹. Analytical conditions were optimized, and the method was validated for analysis of pharmaceutical preparations. The determined amount of lactulose was found to be in good agreement with labeled claims in commercial products. The proposed method is economical, convenient, and suitable for the quantification of lactulose in pharmaceutical preparations. The text was submitted by the authors in English.     

An application of UV-derivative spectrophotometry and bivariate calibration algorithm for study of photostability of levomepromazine hydrochloride

Derivative spectrophotometry and bivariate calibration algorithm were used for study of run of photooxidation of levomepromazine hydrochloride (LV). The actual concentrations of LV and its main degradation product levomepromazine sulphoxide (LV-SO) were calculated using data provided by applied methods. The direct reading of absorbance values at 302 nm and 334 nm were employed for quantification of LV and LV-SO, respectively, in the case of bivariate method. The derivative spectrophotometric method is based on transformation of zero-order spectra into first derivative. The values of first derivative at 334 nm were used for quantification of LV while at 278 nm for assay of LV-SO. The obtained quantitative data were applied for investigation of kinetics of photodegradation of LV.     

A simple and rapid visual method for the determination of ammonia nitrogen in environmental waters using thymol

Simple visual and spectrophotometric methods for the determination of ammonia nitrogen in water are proposed, based on the color development of indothymol blue formed between ammonia and thymol. The color development was accelerated by nitroprusside to complete in 3 min. This color development is remarkably rapid compared with that of the other conventional methods with indothymol blue and indophenol blue. The concentration range of ammonia nitrogen spectrophotometrically determined was 0.04–1.2 mg/L NH₄-N. The absorbance per 1 μg NH₄-N was 0.0215 (molar absorptivity = 1.51 × 10⁴) at 690 nm. The visual method not using any instrument as an in situ method in field works was developed based on the optimum conditions for the established spectrophotometric method. This visual method was successfully applied to the determination of ammonia nitrogen in environmental waters.     

Direct and Derivative Spectrophotometric Determination of Thorium with 2,4-dihydroxybenzaldehyde Isonicotinoyl Hydrazone

A simple and sensitive spectrophotometric method is developed for the determination of throium in aqueous medium. The metal ion forms yellow coloured complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range 2.0–8.0. The complex shows an absorption maximum at 390 nm. The absorbance of the complex is maximum at pH 5.5 Beer's law is obeyed in the range 0.30–7.00 g/ml of thorium(IV). The molar absorptivity and the Sandell's sensitivity of the method are 2.20· 10⁴ l·mol^–1·cm^–1 and 0.0106 g/cm^–2, respectively. The interference of various ions was studied. The composition of the complex is 1:1 {Th(IV) : 2,4-DHBINH}. The first derivative spectrum of the complex shows a zero cross at 391.2 nm and maximum amplitude at 415 nm. Thus a sensitive derivative spectrophotometric method for the determination of Th(IV) is proposed.