Dual-wavelength Method Research Articles

Simultaneous Determination of Some Antihypertension Drugs in Their Binary Mixtures by Simple Spectrophotometric Methods

Two simple, accurate and cost effective dual wavelength (Method I) and mean centering of ratio spectra MCR (Method II) spectrophotometric methods are developed and validated for determination of two drug combinations. The first comprises Hydrochlorothiazide (HCZ) and Benazepril Hydrochloride (BZ) and the second comprises HCZ and Candesartan Cilexetil (CAN) in their bulk powder and pharmaceutical tablets. In method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. For BZ/HCZ, mixture (I), BZ had equal absorbance values at 224.2 and 252.9 nm, therefore these two wavelengths were used to determine HCZ. Similarly, 243.8 and 293.8 nm were selected to determine BZ, where HCZ had equal absorbance values. For CAN/HCZ, mixture (II), HCZ is determined at 242.2 and 264.4 nm while CAN is determined at 257.8 and 280 nm. In method (II), absorption spectra of each drug were recorded, divided by suitable divisor and the obtained ratio spectra were mean centered. The concentrations of the proposed drugs were then determined from the calibration curves obtained by measuring amplitudes at 274 and 240.2 nm for HCZ and BZ respectively for mixture (I) and 274 and 240.4 nm for HCZ and CAN respectively for mixture (II). The developed methods were validated according to ICH guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by reported methods indicting no significant difference and ability of methods to be used for routine analysis of proposed drugs.

Different Methods for Spectrophotometric Estimation and Validation of Paracetamol and Domperidone in Pure and Tablet Dosage Form

Two simple, accurate and precise spectrophotometric methods were developed for simultaneous determination of Paracetamol and Domperidone in combined pharmaceutical dosage form. The first method is Dual wavelength method principle for which is “the absorbance difference between two points on the mixture spectra is directly proportional to the concentration of the component of interest” and second method is Area under curve. In first method wavelengths selected for determination of paracetamol were 278.0 nm and 287.0 nm, whereas, the wavelengths selected for determination of Domperidone were 236.0 nm and 252.0 nm. In second method wavelength ranges of 237.0-251.0 nm and 275.0-289.0 nm were selected to determine PARA and DOM respectively by AUC. 0.5 M Methanolic HCl was taken as a solvent. Regression analysis of Beer’s plots showed good correlation in concentration range of 5-25 μg/ml for PARA and 5-25 μg/ml for DOM. The precision by repeatability of method was found within limits. The proposed method was successfully applied to determination of these drugs in commercial tablets.

SIMULTANEOUS ESTIMATION AND VALIDATION OF PARACETAMOL AND DOMPERIDONE IN BULK AND TABLET DOSAGE FORM BY USING DIFFERENT SPECTOPHOTOETRIC METHOD

Three simple, accurate and precise spectrophotometric methods have been developed for simultaneous determination of Paracetamol and D omperidone in a binary mixture. In Method I absorbance we re measured at 258 nm and 292 nm corresponding to the absorbance maxima of Paracetamol and Domperidone. Concentration of each drug was obtained by using the absorptive values calculate d for both drugs at wavelengths 258 nm, and 292 nm. Method I I by Dual wa velength method, Paracetamol and Domperidone were quantified using principle that absorbance difference between two points on mixture spectra wa s directly proportional to concentration of component of interest and independent of interfering component. Meth od III describes Area under Curve and involves measurement of area un der curve in the range of 288 - 296 nm (For PARA) and 247 - 269 nm (For DOM) for the analysis in methanol. Linearity range was observed in the concentration range of 5 ‐ 30 μg/ml for Paracetamo l and Domperidone. Developed methods were applied to marketed formulation. The methods were validated statistically and recovery study was performed to confirm the accuracy of both methods. K eywords : Paracetamol, Domperidone, Ultraviolet spectroscopy, Simu ltaneous equation Method , Dual Wavelength Method, Area u nder Curve Method.

Rapid determination of lovastatin in the fermentation broth of Aspergillus terreus using dual-wavelength UV spectrophotometry

Context: Lovastatin, a hypocholesterolemic drug, is produced by submerged fermentation of Aspergillus terreus Thom (Trichocomaceae). High performance liquid chromatography is usually used to determine lovastatin in samples of the fermentation broth. However, this method is inconvenient and costly, especially in the context of high-throughput sample analysis.Objective: A direct and simple dual-wavelength ultraviolet spectrophotometric method for quantifying lovastatin in the fermentation broth of A. terreus was developed.Materials and methods: A. terreus Z15-7 was used for all experiments. The liquid fermentation was conducted at 30 °C in a rotary shaker at 150 rpm for 15 d. Silica gel and neutral alumina column chromatography were used for the separation and purification of lovastatin from the fermentation broth.Results: The limits of detection of lovastatin were 0.320 μg/ml in the lovastatin standard solution and 0.490 μg/ml in the fermentation broth sample and the limits of quantification of lovastatin were 1.265 μg/ml in the lovastatin standard solution and 3.955 μg/ml in the fermentation broth sample. The amounts of lovastatin in the fermentation broth ranged from 876.614 to 911.967 μg/ml, with relative standard deviations from 1.203 to 1.709%. The mean recoveries of lovastatin using silica gel and neutral alumina column chromatography were 84.2 ± 0.82 and 87.2 ± 0.21%, respectively.Discussion and conclusion: Dual-wavelength UV spectrophotometry is a rapid, sensitive, accurate, and convenient method for quantifying lovastatin in fermentation broth. Neutral alumina column chromatography is more efficient than silica gel column chromatography for the purification and determination lovastatin using the developed dual-wavelength UV spectrophotometry method.

Optical fiber sensor for temperature measurement based on Silicon thermo-optics effect

A temperature sensor based on the thermo-optics effect of single crystal silicon diaphragm was proposed and studied. The temperature measurement mechanism by using single crystal silicon diaphragm was theoretically analyzed and found the relation between temperature measurement range and the thickness of single crystal diaphragm. It was found that when the temperature changed from 20°C to 48°C, the reflected resonant peak wavelength was shifted which was detected by using the dual-wavelength signal demodulation method. Experimental results for temperature measurement demonstrated reasonable linearity and repeatability, related linear regression coefficient of the experimental result is 99.94%. The study would be of utility value for the design and fabrication of silicon-based sensors which were used to measure pressure or the other physical quantities.

UV SPECTROPHOTOMETRIC METHOD DEVELOPMENT AND VALIDATION OF SIMULTANEOUS ESTIMATION OF CIPROFLOXACIN AND ORNIDAZOLE IN TABLET DOSAGE FORM

Three simple S pectrophotometric methods have been developed for simultaneous estimation of Ci profloxacin and Ornidazole from tablet dosage form. Method A is Dual wavelength method, involves determination of Ciprofloxacin at the absorbance difference between 261.0 nm and 280.2 nm and ornidazole at the absorbance difference between 302.5 nm and 335 nm. Method B is First order derivative spectroscopy, wavelength selecte d for quantitation were 262 nm for Ciprofloxacin (zero cross for Ornidazole) and 332 nm for Ornidazole (ze ro cross for Ciprofloxacin). Method C is Area under Curve method; AUC in the range of 268.0 - 274.0 nm (for Ciprofloxacin) and 316.0 - 322.0 nm (for Ornidazole) were selected for the analysis. The linearity lies between 2 - 10 μg / ml and 2 – 20 μg / ml for Ciprofloxacin and Ornidazole respectively for Method A, B and C. The accuracy and precision of the methods were determined and validated statically. All the methods showed good reproducibility and recovery with low % RSD. Keywo rds : Ciprofloxacin, Ornidazole, Dual wavelength Method, First order derivative Spectroscopy, Area under curve method.

Application of Chromatographic and Spectrophotometric Methods for The Analysis of Aliskiren and Hydrochlorothiazide Antihypertensive Combination.

High performance liquid chromatographic (HPLC) and spectrophotometric methods developed for the simultaneous determination of Aliskiren (ALK) and Hydrochlorothiazide (HCT) combination in bulk powder and in tablets dosage form. Determination of ALK and HCT was achieved by chromatographic separation on Econosphere C-18 column using a mobile phase consisting of water (pH 7.5): acetonitrile (50:50) at a flow rate of 0.5 mL.min −1 and UV detection at 208 nm. Method validation parameters were found to be acceptable over the concentrations range of 5-150 µg.mL -1 , 1-50 µg.mL -1 for ALK and HCT respectively. Regarding the spectrophotometric methods, two methods were employed. Simultaneous Equation method, absorbance readings are taken at two wavelengths 277.48 nm (for ALK) and 267.48 nm (for HCT) in methanol. Dual Wavelength method, the difference between absorbance readings are taken at two wavelengths 273.3 nm, 260 nm (for Aliskiren) and 270 nm, 280 nm (for HCT) in methanol. The applied spectrophotometric methods were found to be rapid, specific, precise and accurate over the concentration range of 5 - 150 µg.mL -1 and 1 - 41 µg.mL -1 for ALK and HCT respectively and can be applied for the routine analysis of these drugs in bulk, and combined dosage form without any interference by the excipients.

Electrochemiluminescence Ratiometry: A New Approach to DNA Biosensing

Inspired by dual-wavelength fluorescence ratiometric method which could reduce the influence from the environmental change, here, we present a novel dual-potential electrochemiluminescence (ECL) ratiometric sensing approach. CdS nanocrystal (NC) and luminol as two different ECL emitters are employed. ECL from CdS NCs coated on glassy carbon electrode at -1.25 V (vs SCE) could be quenched by closely contacted Pt nanoparticles (NPs) via a biological binding event, while ECL from luminol at +0.45 V (vs SCE) could be enhanced by the same Pt NPs, in the presence of their common coreactant of H₂O₂. Thus, the quenching of ECL from CdS NCs and the enhancement of ECL from luminol could indicate the same biological binding event. With the mp53 oncogene as a model DNA molecule, a molecular beacon (MB) containing a 20-base loop, which is complementary with the mp53 oncogene, is immobilized on CdS NCs/GCE first; Pt NPs are then captured on CdS NCs surface by DNA hybridization between the MB and mp53 oncogene labeled on Pt NPs. By measuring the ratio of ECL intensities at two excitation potentials, this approach could sensitively detect the concentration of target DNA in a wide range from 5.0 fM to 1.0 pM. The sensing scheme is general and can be utilized for many other biological binding events.

Simultaneous determination of Cinnarizine and Domperidone by area under curve and dual wavelength spectrophotometric methods

Accurate, selective and sensitive spectrophotometric methods have been developed and validated for simultaneous determination of Cinnarizine and Domperidone, a binary mixture with overlapping spectra, without preliminary separation. These methods include area under the curve (AUC) and dual wavelength spectrophotometry. For the AUC method, the area under curve of mixture solutions in the wavelength ranges 241–258nm and 280–292nm were selected for determination of Cinnarizine and Domperidone and by applying Cramer’s rule, concentration of each drug was obtained. In dual wavelength method, two wavelengths were selected for each drug in a way so that the difference in absorbance is zero for another drug. Domperidone shows equal absorbance at 240.2nm and 273.2nm, where the differences in absorbance were measured for the determination of Cinnarizine. Similarly, differences in absorbance at 230.8nm and 259.2nm were measured for determination of Domperidone. The proposed methods were applied for determination of Cinnarizine and Domperidone over the concentration ranges of 2–20 and 2–22μgmL−1, respectively. The suggested methods were validated as per USP guidelines and the results revealed that they are reliable, reproducible and precise for routine use with short analysis time. The results obtained by the proposed methods were statistically compared to the reported method, and there was no significant difference between them regarding both accuracy and precision.

Molecular Photoacoustic Imaging of Follicular Thyroid Carcinoma

To evaluate the potential of targeted photoacoustic imaging as a noninvasive method for detection of follicular thyroid carcinoma. We determined the presence and activity of two members of matrix metalloproteinase family (MMP), MMP-2 and MMP-9, suggested as biomarkers for malignant thyroid lesions, in FTC133 thyroid tumors subcutaneously implanted in nude mice. The imaging agent used to visualize tumors was MMP-activatable photoacoustic probe, Alexa750-CXeeeeXPLGLAGrrrrrXK-BHQ3. Cleavage of the MMP-activatable agent was imaged after intratumoral and intravenous injections in living mice optically, observing the increase in Alexa750 fluorescence, and photoacoustically, using a dual-wavelength imaging method. Active forms of both MMP-2 and MMP-9 enzymes were found in FTC133 tumor homogenates, with MMP-9 detected in greater amounts. The molecular imaging agent was determined to be activated by both enzymes in vitro, with MMP-9 being more efficient in this regard. Both optical and photoacoustic imaging showed significantly higher signal in tumors of mice injected with the active agent than in tumors injected with the control, nonactivatable, agent. With the combination of high spatial resolution and signal specificity, targeted photoacoustic imaging holds great promise as a noninvasive method for early diagnosis of follicular thyroid carcinomas.

Dual‐wavelength excitation for fluorescence‐based quantification of zinc protoporphyrin IX and protoporphyrin IX in whole blood

Quantification of erythrocyte zinc protoporphyrin IX (ZnPP) and protoporphyrin IX (PPIX), individually or jointly, is useful for the diagnostic evaluation of iron deficiency, iron-restricted erythropoiesis, lead exposure, and porphyrias. A method for simultaneous quantification of ZnPP and PPIX in unwashed blood samples is described, using dual-wavelength excitation to effectively eliminate background fluorescence from other blood constituents. In blood samples from 35 subjects, the results of the dual-wavelength excitation method and a reference high performance liquid chromatography (HPLC) assay were closely correlated both for ZnPP (rs = 0.943, p < 0.0001; range 37-689 μmol ZnPP/mol heme, 84-1238 nmol/L) and for PPIX (rs = 0.959, p < 0.0001; range 42-4212 μmol PPIX/mol heme, 93-5394 nmol/L). In addition, for ZnPP, the proposed method is compared with conventional single-wavelength excitation and with commercial front-face fluorimetry of washed erythrocytes and whole blood. We hypothesize that dual-wavelength excitation fluorimetry will provide a new approach to the suppression of background fluorescence in blood and tissue measurements of ZnPP and PPIX.

Dual wavelength optical metrology using ptychography

We describe an experimental implementation of ptychography to optical metrology, in particular topography measurement, in combination with the dual wavelength method. This is the first published account of the application of the dual wavelength method to ptychography or any other phase retrieval method in order to obtain surface height information over a wide range of scales, from small fractions of a wavelength up to many tens of wavelengths, in reflection mode. Moreover, the work presented here is the first report on the application of lensless reflection mode ptychography. Advantages of the ptychographic dual wavelength method are compared with other optical topography measurement techniques, especially with respect to the experimental procedures and constraints and the analysis of the data. We show that dual wavelength ptychography can remove material-specific phase changes which adversely affect topography measurements using white light profilometry.

Association of age and macular pigment optical density using dual-wavelength autofluorescence imaging

BackgroundSeveral lines of evidence suggest that macular pigment may play a protective role against age-related macular degeneration, but the influence of age on macular pigment density levels remains unclear. This study was designed to investigate the relationship between age and the normal distribution of macular pigment optical density (MPOD) values surrounding the fovea.MethodsConsecutive healthy subjects with no evidence of ocular disease were enrolled in this study. After inclusion, MPOD values were measured at specific eccentricities (0.5, 1, and 2 degrees) from the foveal center using a dual-wavelength autofluorescence method employing a modified confocal scanning laser ophthalmoscope. Whenever both eyes were eligible, one was randomly selected for analysis. The correlation between age and MPOD values was investigated using regression analysis.ResultsThirty subjects (30 eyes) were included (mean age 48.6 ± 16.4 [range 23–77] years). Significant differences were found between MPOD values measured at 0.5, 1, and 2 degrees from the center of the fovea (0.49 ± 0.12 density units, 0.37 ± 0.11 density units, and 0.13 ± 0.05 density units, respectively, P < 0.05). Significant correlations between age and MPOD values at 0.5 and 1 degree were found (P ≤ 0.02). Values measured at 2 degrees did not correlate significantly with age (P = 0.06).ConclusionIn healthy subjects, MPOD values were highest near the foveal center. These values appeared to increase during adulthood (peak at 45–50 years), followed by a gradual reduction after 60 years of age.

Dual-wavelength fluorescent detection of particles on a novel microfluidic chip

This paper reports a novel lab-on-a-chip device that performs fluorescent particle counting by coupling the electrokinetically-induced pressure-driven flow and a miniaturized dual-wavelength fluorescent detection method. A novel L-shaped PDMS microchannel bonded on a thin glass slide is used to transport the particles. The dual-wavelength fluorescent detection system can count two different fluorescent particles simultaneously. Good agreement is achieved between the results obtained by the microfluidic chip device and the results from a commercial flow cytometer.

A Method for Rapid Determination of Sugars in Lignocellulose Prehydrolyzate

A simple and rapid dual-wavelength spectroscopic method is used for simultaneous determination of pentoses and hexoses in the prehydrolyzate from lignocellulosic biomass. The method is based on the following reaction mechanism: in the solution of hydrochloric acid, phloroglucinol gives color reaction with sugars or their degradation products, showing maximum absorbance at 553 nm and 410 nm. Based on dual-wavelength spectrophotometric measurement, the pentoses and hexoses can separately be quantified. It was found that the derivatives from these two different sugars have an isosbestic point at 425 nm. According to the validation results, high accuracy and reasonable recovery rate is shown with the present method (pentoses recovery 97.1 to 100.0%, hexoses recovery 97.2 to 102.0%). Additionally, the interferences from substances including lignin, furfural, 5-hydroxymethyl furfural (HMF), glucuronic acid, and galacturonic acid are insignificant. All of the above results illustrate the suitability of this method for analyzing sugars in the lignocelluloses prehydrolyzate, especially hardwoods or herbaceous plants, based on forest-related biorefinery research.

A novel fiber Bragg grating sensor for weak pressure measurement based on the Stokes parameter

Unlike usual spectral analysis of the fiber Bragg grating (FBG) sensors, a novel weak pressure sensor based on the Stokes parameter of FBG is proposed in this paper. The evolution of the first normalized Stokes parameter s1 with respect to pressure is studied theoretically and experimentally. A theoretical model for pressure sensing by use of s1 is built and numerically simulation is also carried out. The dual-wavelength analytical method is proposed to reduce the influence of Bragg wavelength drift and improve the measurement accuracy. Under the pressure conditions of 0–5N, the experimental pressure sensitivity is 0.0754/N. Good agreements between experiment results and numerical simulations verify the feasibility of the method.

The Physical and Chemical Analysis of Carbohydrate Content in Acorn Kernel

Carbohydrates are the main source which required to maintain energy equilibrium and normal life activities. In acorn kernel, soluble polysaccharides and starch are the main carbohydrate. In order to accurately measure the carbohydrate content of the acorn kernel in Nanjing Area. Dual-wavelength spectrophotometry and anthrone-sulfuric methods were applied to measure the content of amylose, amylopeetin and soluble polysaccharides,respectively.The other two samples were simultaneously measured for comparative analysis.Testing results show that acorn kernel contain about 79.40% of starch, amylopectin content was up to 59.01%, polysaccharide content is 6.53%.The results indicate that acorn kernel was an important raw material for preparing food, feed and starch-based composites.

Dual-wavelength digital holographic imaging with phase background subtraction

Three-dimensional digital holographic microscopic phase imaging of objects that are thicker than the wavelength of the imaging light is ambiguous and results in phase wrapping. In recent years, several unwrapping methods that employed two or more wavelengths were introduced. These methods compare the phase information obtained from each of the wavelengths and extend the range of unambiguous height measurements. A straightforward dual-wavelength phase imaging method is presented which allows for a flexible tradeoff between the maximum height of the sample and the amount of noise the method can tolerate. For highly accurate phase measurements, phase unwrapping of objects with heights higher than the beat (synthetic) wavelength (i.e. the product of the original two wavelengths divided by their difference), can be achieved. Consequently, three-dimensional measurements of a wide variety of biological systems and microstructures become technically feasible. Additionally, an effective method of removing phase background curvature based on slowly varying polynomial fitting is proposed. This method allows accurate volume measurements of several small objects with the same image frame.

A Modified Dual-Wavelength Matrix Calculation Method for Fiber Bragg Grating (FBG)

Fiber grating is an optical passive device which is developed very fast in recent years. FBG is the most grating which is used as fiber sensor. Cross-sensitivity of fiber grating sensor is an important problem which is restricted the development of the fiber sensor. We do a deep research on the cross-sensitivity problem of the Fiber Bragg grating in this paper. Based on the basic principle of how the cross-sensitivity problem is produced, we suggest a modification in a dual-wavelength matrix calculation method which is used to solve the cross-sensitivity problem in traditional. The modified dual-wavelength matrix calculation method has a higher accuracy than the traditional method.

Fluorescence kinetic parameters and cyclic electron transport in guard cell chloroplasts of chlorophyll-deficient leaf tissues from variegated weeping fig (Ficus benjamina L.)

Residual chlorophyll in chlorophyll-deficient (albino) areas of variegated leaves of Ficus benjamina originates from guard cell chloroplasts. Photosynthetic features of green and albino sectors of F. benjamina were studied by imaging the distribution of the fluorescence decrease ratio Rfd within a leaf calculated from maximum (Fm) and steady-state leaf chlorophyll fluorescence (Fs) at 690 and 740 nm. Local areas of albino sectors demonstrated an abnormally high Rfd(740)/Rfd(690) ratio. Fluorescence transients excited in albino sectors at red (640 and 690 nm) wavelengths showed an abrupt decrease of the Rfd values (0.4 and 0.1, correspondingly) as compared with those excited at blue wavelengths (1.7-2.4). This "Red Drop" was not observed for green sectors. Normal and chlorophyll-deficient leaf sectors of F. benjamina were also tested for linear and cyclic electron transport in thylakoids. The tests have been performed studying fluorescence at a steady-state phase with CO(2)-excess impulse feeding, photoacoustic signal generated by pulse light source at wavelengths selectively exciting PSI, fluorescence kinetics under anaerobiosis and fluorescence changes observed by dual-wavelength excitation method. The data obtained for albino sectors strongly suggest the possibility of a cyclic electron transport simultaneously occurring in guard cell thylakoids around photosystems I and II under blue light, whereas linear electron transport is absent or insufficient.