Absorption Correction Method Research Articles

On the compositional analysis of Coal using calibration free laser induced breakdown spectroscopy

In this contribution, we present analysis of the total carbon contents and the major constituents in the Reference Coal sample of known concentration (SARM 20) and the Pakistani Thar Coal samples using laser induced breakdown spectroscopy (LIBS). A high-power Q-switched Nd:YAG Laser, (532nm, 5ns pulse width and 10 Hz repletion rate) was used to produce the Coal plasma in air and the optical emission spectra were registered using a HR 4000 spectrometer covering the wavelength region from 200 nm to 1100 nm. The emission spectrum of the laser produced plume contains the atomic lines of Ca, Si, Fe, Ti, Mg, Na, K, Li, Al and C along with the traces of Ba, Sr and Mn. The intensities of the observed spectral lines were corrected for self-absorption using the internal reference line self absorption correction method. The excitation temperature was calculated using the Boltzmann plot method and the Stark broadened Hα line profile was used to determine the electron number density. The calibration free LIBS (CF-LIBS) technique with a fixed slope method was utilized for the quantification of the carbon and other elements whereas, a laser-ablation time of flight mass spectrometer (LA-TOF-MS) was used to obtain the mass spectra of the same samples. All the elements identified in the optical emission spectrum have been also observed in the LA-TOF-MS mass spectrum. The results reveal that the Thar Coal samples collected from Sindh, Pakistan are comparable to the Reference Coal samples. It is further demonstrated that CF-LIBS and the LA-TOF-MS are efficient, reliable and complementary techniques for analyzing the Coal samples for the total carbon content, elements forming the ash and even for the detection of the trace elements at the ppm level.

UV-Spectrophotometric Absorbance Correction Methods for the Simultaneous Estimation of Tenofovir Alafenamide and Emtricitabine in Bulk and Tablet Dosage Form

Two UV-spectrophotometric methods have been developed and validated for simultaneous estimation of Tenofovir alafenamide (TAF) and Emtricitabine (EMT) in bulk and tablet dosage form. The Method A employs absorption correction method in zero order, the wavelengths selected were 261.5 nm for TAF (but EMT shows absorbance) and 302 nm for EMT. Method B employs, absorption correction method in first order, the wavelengths selected were 218.5 nm for TAF (but EMT shows absorbance) and 300 nm for EMT. For both the methods drugs were linear between the range of 2-10 µg/ml for TAF and 16-80 µg/ml for EMT using methanol as solvent. The correlation coefficient was found to be 0.9996 for TAF and 0.9997 for EMT for method A and 0.9998 for TAF and 0.9999 for EMT for method B, respectively. The precision (intraday, interday) of methods was found within limits (RSD < 2%). It could be concluded from the results obtained in the present investigation that the two methods for simultaneous estimation of TAF and EMT in bulk and tablet dosage form are simple, rapid, accurate, precise and economical and can be used, successfully, in the quality control of tablet formulations and other routine laboratory analysis.

Development of UV Spectrophotometry Absorption correction method for estimation of Curcumin and Aspirin from Bulk

The present study describes method development and validation of aspirin and curcumin simultaneously by absorption correction method by UV spectroscopy. The maximum wavelength selected for this method were 227nm and 427nm for aspirin and curcumin respectively with ethanol. The described method was linear at 2-12 µg/ml for aspirin 1-6 µg/ml for curcumin. The correlation coefficient was 0.999 for both aspirin and curcumin. The recovery of the drugs was above 95%. The interday and intraday precision were within the limit for both the drug (RSD ?2). The proposed method is simple, accurate and cost effective which can be used for analysis of both drugs from bulk and new formulations.

Earth-friendly spectrophotometric methods for simultaneous determination of ledipasvir and sofosbuvir: Application to average content and uniformity of dosage unit testing

Simple, rapid, sensitive, accurate, precise and earth-friendly spectrophotometric methods were developed for the simultaneous analysis of ledipasvir (LED) and sofosbuvir (SOF) without interference of both sunset yellow dye and copovidone excipients (the most probable interferents) in their combined dosage form.These proposed methods were based on measurement of LED in synthetic mixtures and combined dosage form by first derivative (1D) spectrophotometry at 314 nm over the concentration range of 2–50 μg mL−1 with coefficient of determination (R2) > 0.9999, mean percentage recovery of 99.98 ± 0.62.On the other hand, SOF in synthetic mixtures and combined dosage form was determined by five methods. Method I is based on the use of 1D spectrophotometry at 274.2 nm (zero crossing point of LED). Method II involves the application of conventional dual wavelength method (DW) at the absolute difference between SOF zero order amplitudes at 261 nm (λmax of SOF) and 364.7 nm. At these wavelengths, the absolute difference between LED zero order amplitudes was observed to equal zero. Method III depends on isosbestic point method (ISP) in which the total concentration of both drugs was measured at isosbestic point at 262.7 nm. Concentration of SOF could be obtained by subtraction of LED concentration. While, method IV depends on absorbance correction method (absorption factor method), which is based on determination of SOF concentration at 262.7 nm (λISP) and LED at 333 nm (λmax of LED). Finally, method V depends on absorbance ratio method (Q-analysis) in which 262.7 nm (λISP) and 261 nm (λmax of SOF) were selected to determine SOF concentration. The linearity range for all methods for SOF determination was 2–50 μg mL−1 with coefficient of determination (R2) > 0.9999.Methods I, II & III were also applied for determination of SOF concentration in single dosage form. Their mean percentage recoveries were 100.35 ± 1.85, 99.97 ± 0.54 and 100.03 ± 0.49, for the three methods respectively.The proposed methods were validated according to international conference of harmonization (ICH) requirements and statistically compared to published reference methods. The ANOVA test confirmed that there is no significant differences between the proposed methods, and can be used for routine analysis of LED and SOF in commercial tablets. These developed methods were applied to estimate the average content and uniformity of dosage unit for LED/SOF combined dosage form and SOF single dosage form according to British pharmacopeia (BP) requirements.

Development and Validation of Absorption Correction Method for Simultaneous Estimation of Paracetamol and Nimesulide in Bulk and Combined Tablet Dosage Form

The present paper describes simple, accurate, rapid, precise and sensitive UV spectrophotometric absorption correction method for the simultaneous determination of paracetamol and nimesulide in combined tablet dosage form. This method is more simple than reported methods and is based on use of 0.1 N NaOH as a solvent. The wavelengths selected for the analysis were 257 nm and 393 nm. Beer's law was obeyed in the concentration range of 4–18 μg/ml and 10–30 μg/ml for paracetamol and nimesulide respectively. The mean percentage drug content for paracetamol and nimesilide were found to be 100.03% w/w and 101% w/w respectively. The % RSD value was found to be less than 2 which shows the precision of method. The high recovery and low coefficients of variation conforms it's suitability for the routine quality control analysis of paracetamol and nimesulide in pure and tablet dosage forms.

UV SPECTROPHOTOMETRIC ABSORPTION CORRECTION METHOD FOR SIMULTANEOUS ESTIMATION OF OLMESA RTAN MEDOXOMIL, AMLODIPINE BESYLATE AND HYDROCHLOROTHIAZIDE IN COMBINED TABLET DOSAGE FORM

A simple, accurate, precise, economical and validated uv spectrometric absorption correction method was developed for olmesartan, medoxomil amlodipine besylate and hydrochlorothiazide in bulk and its dosage form. The stock solutions were prepared in methanol followed by further dilutions with double distilled water. The λmax for olmesartan, amlodipine besylate and hydrochlorothiazide were 256.5 nm, 362 nm and 316 nm, respectively. Beer’s law was obeyed in the concentration range of 3-18 μg/mL, 1- 6μg/mL and 2-12 μg/mL, respectively. The method was validated by following the analytical performance parameters suggested by the ICH Guidelines. The percentage assay in commercial formulation was found to be in the range olmesartan 100.06%, amlodipine 99.17% and hydrochlorothiazide 100.14% by the proposed method. The method was validated with respect to linearity, precision and accuracy. recovery was found to be in the range of olmesartan 99.65%,amlodipine 99.97% and hydrochlorothiazide 99.81% by absorbance corrected method. The high recovery and low coefficients of variation conforms the suitability of the method for simultaneous analysis of three drugs in combined tablets.

Determination of efficiency of an aged HPGe detector for gaseous sources by self absorption correction and point source methods

Methods for the determination of efficiency of an aged high purity germanium (HPGe) detector for gaseous sources have been presented in the paper. X-ray radiography of the detector has been performed to get detector dimensions for computational purposes. The dead layer thickness of HPGe detector has been ascertained from experiments and Monte Carlo computations. Experimental work with standard point and liquid sources in several cylindrical geometries has been undertaken for obtaining energy dependant efficiency. Monte Carlo simulations have been performed for computing efficiencies for point, liquid and gaseous sources. Self absorption correction factors have been obtained using mathematical equations for volume sources and MCNP simulations. Self-absorption correction and point source methods have been used to estimate the efficiency for gaseous sources. The efficiencies determined from the present work have been used to estimate activity of cover gas sample of a fast reactor.

Development and validation of UV spectrophotometric method for Simultaneous estimation of Empagliflozin and Metformin hydrochloride in bulk drugs

A new, simple, accurate and sensitive UV-spectrophotometric absorption correction method has been developed for simultaneous determination of Metformin HCl and Empagliflozin in bulk utilizing concept of standard addition. The method is based upon determination of Empagliflozin at 224 nm & Metformin HCl at 230 nm methanol as a solvent. Overlay spectra of both drugs shows absorbance at 227 nm. Linearity was observed in range of 10–50 μg/ml and 1–3 μg/ml for Metformin HCl and Empagliflozin respectively. The correlation coefficient value was found to near to 1. All methods were statistically validated as per ICH guidelines.

Improved determination of particulate absorption from combined filter pad and PSICAM measurements.

Filter pad light absorption measurements are subject to two major sources of experimental uncertainty: the so-called pathlength amplification factor, β, and scattering offsets, o, for which previous null-correction approaches are limited by recent observations of non-zero absorption in the near infrared (NIR). A new filter pad absorption correction method is presented here which uses linear regression against point-source integrating cavity absorption meter (PSICAM) absorption data to simultaneously resolve both β and the scattering offset. The PSICAM has previously been shown to provide accurate absorption data, even in highly scattering waters. Comparisons of PSICAM and filter pad particulate absorption data reveal linear relationships that vary on a sample by sample basis. This regression approach provides significantly improved agreement with PSICAM data (3.2% RMS%E) than previously published filter pad absorption corrections. Results show that direct transmittance (T-method) filter pad absorption measurements perform effectively at the same level as more complex geometrical configurations based on integrating cavity measurements (IS-method and QFT-ICAM) because the linear regression correction compensates for the sensitivity to scattering errors in the T-method. This approach produces accurate filter pad particulate absorption data for wavelengths in the blue/UV and in the NIR where sensitivity issues with PSICAM measurements limit performance. The combination of the filter pad absorption and PSICAM is therefore recommended for generating full spectral, best quality particulate absorption data as it enables correction of multiple errors sources across both measurements.

Comparison of different absorption corrections on the model structure of tetrakis(μ2-acetato)-diaqua-di-copper(II)

Abstract Two different absorption correction methods were compared in order to find out which method is preferable to improve solving and refining a crystal structure. Experiments were performed on the crystal of a tetrakis(μ2-acetato)-diaqua-di-copper(II) complex. The first correction method used was the numerical absorption correction with the aid of a crystal-shape model, and the other was the semi-empirical one, applying scaling routines to the intensity data.

A novel 3D absorption correction method for quantitative EDX-STEM tomography

This paper presents a novel 3D method to correct for absorption in energy dispersive X-ray (EDX) microanalysis of heterogeneous samples of unknown structure and composition. By using STEM-based tomography coupled with EDX, an initial 3D reconstruction is used to extract the location of generated X-rays as well as the X-ray path through the sample to the surface. The absorption correction needed to retrieve the generated X-ray intensity is then calculated voxel-by-voxel estimating the different compositions encountered by the X-ray. The method is applied to a core/shell nanowire containing carbon and oxygen, two elements generating highly absorbed low energy X-rays. Absorption is shown to cause major reconstruction artefacts, in the form of an incomplete recovery of the oxide and an erroneous presence of carbon in the shell. By applying the correction method, these artefacts are greatly reduced. The accuracy of the method is assessed using reference X-ray lines with low absorption.

Self-consistent absorption correction for quantitative energy- dispersive X-ray spectroscopy of InGaN layers in analytical transmission electron microscopy

A new method of absorption correction for energy-dispersive X-ray spectroscopy in a transmission electron microscope is tested on InGaN samples. We simulate the effective k-factor for the In L line with respect to Ga L or Ga K and plot this as a function of the Ga K/L intensity ratio, which can be directly measured from experimental spectra. This basically performs an internal self-consistency check in the quantification using differently absorbed X-ray lines, which is in principle equivalent to an absorption correction as a function of specimen thickness but has the practical advantage that neither specimen thickness nor density or mass-thickness of the specimens need actually be measured.

Conventional univariate versus multivariate spectrophotometric assisted techniques for simultaneous determination of perindopril arginin and amlodipine besylate in presence of their degradation products

The resolving power of spectrophotometric assisted mathematical techniques were demonstrated for the simultaneous determination of perindopril arginin (PER) and amlodipine besylate (AML) in presence of their degradation products. The conventional univariate methods include the absorptivity factor method (AFM) and absorption correction method (ACM), which were able to determine the two drugs, simultaneously, but not in the presence of their degradation products. In both methods, amlodipine was determined directly at 360nm in the concentration range of 8–28μgmL−1, on the other hand perindopril was determined by AFM at 222.2nm and by ACM at 208nm in the concentration range of 10–70μgmL−1. Moreover, the applied multivariate calibration methods were able for the determination of perindopril and amlodipine in presence of their degradation products using concentration residuals augmented classical least squares (CRACLS) and partial least squares (PLS). The proposed multivariate methods were applied to 19 synthetic samples in the concentration ranges of 60–100μgmL−1 perindopril and 20–40μgmL−1 amlodipine. Commercially available tablet formulations were successfully analysed using the developed methods without interference from other dosage form additives except PLS model, which failed to determine both drugs in their pharmaceutical dosage form.

Absorbance Correction Method for Simultaneous Estimation of Nifedipine and Metoprolol Succinate in Their Synthetic Mixture Using From Spectrophotometry

A new simple, economical, precise and accurate method are described for the simultaneous determination of Nifedipine (NIF) and Metoprolol Succinate (MET) in combined tablet dosage form. The proposed method was applied for the determination of Nifedipine and Metoprolol Succinate in synthetic mixture, for determination of sampling wavelength, 10?g/ml of each of NIF and MET were scanned in 200-400 nm range and sampling wavelengths were 313nm for NIF and 275.40nm for MET are selected for development and validation of absorption correction method. For this method linearity observed in the range of 5-25?g/ml for NIF and 25-125?g/ml for MET, and in their pharmaceutical formulation with mean percentage recoveries 100.68 and 100.33, respectively. The method was validated according to ICH guidelines and can be applied for routine quality control testing.

DEVELOPMENT AND VALIDATION OF ABSORBANCE CORRECTION METHOD FOR SIMULTANEOUS DETERMINATION OF LEVOCETIRIZINE AND AMBROXOL IN COMBINED TABLET DOSAGE FORM

A new, s imple, accurate and sensitive U V - Spectrophotometric absorbance correction method has been develop ed and validated for simultaneous estimation of Levocetirizine ( LEV ) and Ambroxol ( AMB ) in a combined tablet dosage form. Distill water was used as solvent. In this method, two wave lengths on Ambroxol curve were selected where it showed same absorbance, w hich were 261 nm and 303 nm. At 303 nm, Levocetirizine showed zero absorbance while at 261 nm it gave considerable absorbance. At 261 nm, both the drugs showed some absorbance . The absorbance of Levocetirizine was corrected at 261 nm. The method was found to be linear between the range of 4 - 28 μg/ml for Levocetirizine and Ambroxol . The mean percentage recovery was found in the range of 99.4 ± 1.11 % and 100 . 2 ± 1 % for Levocetirizine and Ambroxol respectively at three different levels of standard additions . The precision (intra - day, inter day) of method were found within limits (RSD < 2 %). The met h od was validated according to ICH guidelines. Thus the proposed method was simple, precise, economic, rapid and accurate and can be successfully applied for simultaneous determination of Levocetirizin e and Ambroxol in combined tablet dosage form.

Absorbance correction method for simultaneous estimation of Edaravone and Argatroban in synthetic mixture

A simple, accurate and precise spectroscopic method was developed for simultaneous estimation of Edaravone and Argatroban in synthetic mixture using Absorbance correction method. At 333 nm (λmax of Argatroban) Edaravone has zero absorbance so Argatroban is directly estimate at 333 nm. At 242 nm (λmax of Edaravone) both drugs have some absorbance so Edaravone is estimate at 242 nm using absorbance correction method.

Absorbance Correction Method for Simultaneous Estimation of Amlodipine Besylate and Simvastatin in Synthetic Mixture

A simple, accurate and precise spectroscopic method was developed for simultaneous estimation of Amlodipine besylate and Simvastatin in synthetic mixture using Absorbance correction method. At 360.80 nm (λmax of Amlodipine besylate) Simvastatin has zero absorbance so Amlodipine besylate is directly estimate at 360.80 nm. At 237.60 nm (λmax of Simvastatin) both drugs have some absorbance so Simvastatin is estimate at 237.60 nm using absorbance correction method. The method was found to be linear (r2>0.999) in the range of 5–10 μg/ml for Amlodipine besylate at 360.80 nm. The linear correlation was obtained (r2>0.999) in the range of 5–10 μg/ml for Simvastatin at 237.60 nm. The limit of determination was 0.17 μg/ml and 0.10μg/ml for Amlodipine besylate and Simvastatin, respectively. The limit of quantification was 0. 54μg/ml and 0. 32μg/ml for Amlodipine besylate and Simvastatin, respectively. The accuracy of these method were evaluated by recovery studies and good recovery result were obtained greater than 99%. The method was successfully applied for simultaneous determination of Amlodipine besylate and Simvastatin in binary mixture.

Development and Validation of UV Spectroscopic Method for Simultaneous Estimation of Doxofylline and Terbutaline Sulphate in Combined Dosage Form

Two simple spectrophotometric methods have been developed for simultaneous estimation of Doxofylline and Terbutaline sulphate in tablet dosage form. The method is developed using 0.1M NaOH as a solvent. Method (I) is the Q-absorbance ratio method, two wavelengths are selected, one being the isoabsorptive point 294.1 nm and other being the absorption maxima of Doxofylline at 273 nm. Method (II) is the Absorbance correction method, two wavelengths are selected, one being absorption maxima of Doxofylline at 273 nm and other being the corrected absorbance at 302.96 nm. The Linearity was observed in the concentration range of 10–50 μg/ml for Doxofylline and 2–8 μg/ml for Terbutaline sulphate respectively, correlation coefficient (r 2 < 1). The accuracy and precision were determined and found to comply with ICH guidelines. Both the methods showed good reproducibility and recovery with % RSD in the desired range. The proposed methods can be successfully applied for the routine analysis of both the drugs from tablet dosage form.

Simultaneous Equation Method and Absorption Correction Method for the Estimation of Isosorbide Dinitrate and Hydalazine Hydrochloride in Bulk and Their Combined Tablet Dosage Form using UV Spectrophotometry.

In the present work a simple, accurate and precise method has been developed and validated for the simultaneous estimation of isosorbide di nitrate (ISD), hydralazine hydrochloride(HYD)in bulk and their combined dosage form by UV spectrophotometric methods. The method employes estimation of drugs by simultaneous equation method (SEM) using 208.28nm and 232nm i.e λmax values of ISD and HYD respectively. Method B employs the estimation of drugs by absorption correction method (ACM) at 232nm for HYD where absorbance of ISD is very low. Absorbance correction method was based on the property of additively of absorbance. At 232nm, Hydralazine hydrochoride showed absorbance while Isosorbide dinitrate showed very low absorbance. The method involved measurement of absorbance at wavelength 232 nm. For estimation of HYD, corrected absorbance was calculated at 208 nm due to the interference of HYD at this wavelength. Calibration curves were linear with correlation coefficient 0.999 over the concentration range of 2–10μg/mL and 2–10 μg/mL for ISD and HYD respectively. The percent recoveries of the drugs were found nearly 100% representing the accuracy of the both methods. Validation of the proposed methods was carried out for its accuracy, precision, specificity, linearity and limit of detection according to ICH guidelines. The proposed methods can be successfully applied in routine work for the determination of isosorbide dinitrate and hydralazine hydrochloride in combined dosage form.

Absorption Correction Method for Simultaneous Estimation of Nifedipine and Metoprolol Succinate in Their Synthetic Mixture Using From Spectrophotometry

A new simple, economical, precise and accurate method are described for the simultaneous determination of Nifedipine (NIF) and Metoprolol Succinate (MET) in combined tablet dosage form. The proposed method was applied for the determination of Nifedipine and Metoprolol Succinate in synthetic mixture, for determination of sampling wavelength, 10μg/ml of each of NIF and MET were scanned in 200–400 nm range and sampling wavelengths were 313nm for NIF and 275.40nm for MET are selected for development and validation of absorption correction method. For this method linearity observed in the range of 5–25μg/ml for NIF and 25–125μg/ml for MET, and in their pharmaceutical formulation with mean percentage recoveries 100.68 and 100.33, respectively. The method was validated according to ICH guidelines and can be applied for routine quality control testing.