Derivative Subtraction Research Articles

Novel spectrophotometric determination of chloramphenicol and dexamethasone in the presence of non labeled interfering substances using univariate methods and multivariate regression model updating

Smart and novel spectrophotometric and chemometric methods have been developed and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and dexamethasone sodium phosphate (DSP) in presence of interfering substances without prior separation. The first method depends upon derivative subtraction coupled with constant multiplication. The second one is ratio difference method at optimum wavelengths which were selected after applying derivative transformation method via multiplying by a decoding spectrum in order to cancel the contribution of non labeled interfering substances. The third method relies on partial least squares with regression model updating. They are so simple that they do not require any preliminary separation steps. Accuracy, precision and linearity ranges of these methods were determined. Moreover, specificity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied for analysis of both drugs in their pharmaceutical formulation. The obtained results have been statistically compared to that of an official spectrophotometric method to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

Novel spectrophotometric methods for simultaneous determination of Amlodipine, Valsartan and Hydrochlorothiazide in their ternary mixture

This work represents a comparative study of two smart spectrophotometric techniques namely; successive resolution and progressive resolution for the simultaneous determination of ternary mixtures of Amlodipine (AML), Hydrochlorothiazide (HCT) and Valsartan (VAL) without prior separation steps. These techniques consist of several consecutive steps utilizing zero and/or ratio and/or derivative spectra. By applying successive spectrum subtraction coupled with constant multiplication method, the proposed drugs were obtained in their zero order absorption spectra and determined at their maxima 237.6nm, 270.5nm and 250nm for AML, HCT and VAL, respectively; while by applying successive derivative subtraction they were obtained in their first derivative spectra and determined at P230.8–246, P261.4–278.2, P233.7–246.8 for AML, HCT and VAL respectively. While in the progressive resolution, the concentrations of the components were determined progressively from the same zero order absorption spectrum using absorbance subtraction coupled with absorptivity factor methods or from the same ratio spectrum using only one divisor via amplitude modulation method can be used for the determination of ternary mixtures using only one divisor where the concentrations of the components are determined progressively. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. Moreover comparative study between spectrum addition technique as a novel enrichment technique and a well established one namely spiking technique was adopted for the analysis of pharmaceutical formulations containing low concentration of AML. The methods were validated as per ICH guidelines where accuracy, precision and specificity were found to be within their acceptable limits. The results obtained from the proposed methods were statistically compared with the reported one where no significant difference was observed.

A comparative study of novel spectrophotometric resolution techniques applied for pharmaceutical mixtures with partially or severely overlapped spectra

Simultaneous determination of mixtures of lidocaine hydrochloride (LH), flucortolone pivalate (FCP), in presence of chlorquinaldol (CQ) without prior separation steps was applied using either successive or progressive resolution techniques. According to the concentration of CQ the extent of overlapping changed so it can be eliminated from the mixture to get the binary mixture of LH and FCP using ratio subtraction method for partially overlapped spectra or constant value via amplitude difference followed by ratio subtraction or constant center followed by spectrum subtraction spectrum subtraction for severely overlapped spectra. Successive ratio subtraction was coupled with extended ratio subtraction, constant multiplication, derivative subtraction coupled constant multiplication, and spectrum subtraction can be applied for the analysis of partially overlapped spectra. On the other hand severely overlapped spectra can be analyzed by constant center and the novel methods namely differential dual wavelength (D1 DWL) for CQ, ratio difference and differential derivative ratio (D1 DR) for FCP, while LH was determined by applying constant value via amplitude difference followed by successive ratio subtraction, and successive derivative subtraction. The spectra of the cited drugs can be resolved and their concentrations are determined progressively from the same ratio spectrum using amplitude modulation method. The specificity of the developed methods was investigated by analyzing laboratory prepared mixtures and were successfully applied for the analysis of pharmaceutical formulations containing the cited drugs with no interference from additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the official or reported methods; using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

A comparative study of progressive versus successive spectrophotometric resolution techniques applied for pharmaceutical ternary mixtures

This work represents a comparative study of a novel progressive spectrophotometric resolution technique namely, amplitude center method (ACM), versus the well-established successive spectrophotometric resolution techniques namely; successive derivative subtraction (SDS); successive derivative of ratio spectra (SDR) and mean centering of ratio spectra (MCR). All the proposed spectrophotometric techniques consist of several consecutive steps utilizing ratio and/or derivative spectra. The novel amplitude center method (ACM) can be used for the determination of ternary mixtures using single divisor where the concentrations of the components are determined through progressive manipulation performed on the same ratio spectrum. Those methods were applied for the analysis of the ternary mixture of chloramphenicol (CHL), dexamethasone sodium phosphate (DXM) and tetryzoline hydrochloride (TZH) in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the official BP methods, showing no significant difference with respect to accuracy and precision.

Successive spectrophotometric resolution as a novel technique for the analysis of ternary mixtures of pharmaceuticals

A novel spectrophotometric technique was developed for the simultaneous determination of ternary mixtures, without prior separation steps. This technique was called successive spectrophotometric resolution technique. The technique was based on either the successive ratio subtraction or successive derivative subtraction. The mathematical explanation of the procedure was illustrated. In order to evaluate the applicability of the methods a model data as well as an experimental data were tested. The results from experimental data related to the simultaneous spectrophotometric determination of lidocaine hydrochloride (LH), calcium dobesilate (CD) and dexamethasone acetate (DA); in the presence of hydroquinone (HQ), the degradation product of calcium dobesilate were discussed. The proposed drugs were determined at their maxima 202nm, 305nm, 239nm and 225nm for LH, CD, DA and HQ respectively; by successive ratio subtraction coupled with constant multiplication method to obtain the zero order absorption spectra, while by applying successive derivative subtraction they were determined at their first derivative spectra at 210nm for LH, 320nm or P292–320 for CD, 256nm or P225–252 for DA and P220–233 for HQ respectively. The calibration curves were linear over the concentration range of 2–20μg/mL for both LH and DA, 6–50μg/mL for CD, and 3–40μg/mL for HQ. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs with no interference from other dosage form additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the official BP methods for LH, DA, and CD, and with the official USP method for HQ; using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

Application of near Infrared Spectroscopy to Control the Protective Reaction in the Synthesis of Emamectin Benzoate

A near infrared (NIR) method was developed for the control of the protective reaction in the synthesis of emamectin benzoate. A NIR spectrometer with a fibre-optic probe was used to analyse the residual content of avermectin and the by-product content of the shield. Partial least squares regression was used to develop the calibration models, which for the residual content were preprocessed by second derivative and for the by-product content by first derivative and straight-line subtraction preprocessing methods. After optimising the spectral pre-treatment, the coefficient of determination ( R2) of the residual content and by-product content were 0.92 and 0.99 and the root mean square errors of calibration were 0.18% and 0.46%, respectively. When the models were used to determine the residual content and by-product content, the root mean square errors of prediction were 0.20% and 0.48%, respectively. These preliminary findings suggest that the NIR method could be used to predict the residual content and by-product content simultaneously and the process could be completed within 2 min without sample destruction. The control of the protective reaction could be adjusted according to the results obtained using the NIR method. The results indicated that information contained in NIR spectra may be useful to control the protective reaction in the synthesis of the emamectin benzoate.

Specular reflectance and derivative spectrometric studies on lac‐epoxy resin blends

PurposeThis paper aims to gain a greater insight into the molecular level changes occurring in lac‐epoxy blends, at elevated temperatures for different intervals of time. It is also to determine the changes in key physico‐chemical parameters of these blends, before and after applying thermal stress on these blends.Design/methodology/approachFilms of lac‐epoxy blends, applied on tin panels, were baked at 200°C for different time intervals. The baked films were examined by specular reflectance spectroscopy, as these were otherwise difficult to examine through conventional IR techniques, using KBr pellet method. The results obtained were compared and reported. The blends were also tested for different physico‐chemical parameters like scratch hardness, flexibility, adhesion, acid resistance, etc.FindingsOn baking the blends of lac‐epoxy resin at 200°C for different time intervals, the strained three membered epoxy ring apparently break open, releasing some free hydroxyl groups, which react with carboxylic groups in lac resin to form ester linkages, resulting in condensation. In terms of different physico‐chemical parameters, blends of 70 per cent lac:30 per cent epoxy were found to be better in performance than blends of 50 per cent lac:50 per cent epoxy and blends of 30 per cent lac:70 per cent epoxy resins, baked at 200°C for different time intervals. Adhesion and acid resistance of lac‐epoxy blends were very good compared with the parent resins.Research limitations/implicationsThe spectral studies on lac‐epoxy blends were done qualitatively. Although desirable, quantitative studies could not be carried out, due to the inherent difficulties in handling the resins.Practical implicationsLac‐epoxy blends may find an important role in printing inks, varnishes and finishing industries owing to their very good adhesion, gloss, scratch hardness and resistance to the action of acids.Originality/valueAs of now, there is no record of specular‐reflectance and derivative spectrometric studies on lac‐synthetic resin blends. This paper represents the first attempt to obtain and correlate reflectance data with physico‐chemical changes. It also highlights the convenience of the method and the scope of sophisticated data analysis, including derivative spectrometry and spectral subtraction techniques.

Skin diseases in war

A novel spectrophotometric technique was developed for the simultaneous determination of ternary mixtures, without prior separation steps. This technique was called successive spectrophotometric resolution technique. The technique was based on either the successive ratio subtraction or successive derivative subtraction. The mathematical explanation of the procedure was illustrated. In order to evaluate the applicability of the methods a model data as well as an experimental data were tested. The results from experimental data related to the simultaneous spectrophotometric determination of lidocaine hydrochloride (LH), calcium dobesilate (CD) and dexamethasone acetate (DA); in the presence of hydroquinone (HQ), the degradation product of calcium dobesilate were discussed. The proposed drugs were determined at their maxima 202 nm, 305 nm, 239 nm and 225 nm for LH, CD, DA and HQ respectively; by successive ratio subtraction coupled with constant multiplication method to obtain the zero order absorption spectra, while by applying successive derivative subtraction they were determined at their first derivative spectra at 210 nm for LH, 320 nm or P292–320 for CD, 256 nm or P225–252 for DA and P220–233 for HQ respectively. The calibration curves were linear over the concentration range of 2–20 μg/mL for both LH and DA, 6–50 μg/mL for CD, and 3–40 μg/mL for HQ. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs with no interference from other dosage form additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the official BP methods for LH, DA, and CD, and with the official USP method for HQ; using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

Saturn's E Ring Revisited

Saturn's E ring is revealed by image processing of direct photographs of the 1966 edge-on presentation of the planet's ring plane. Two different techniques were used: scanning with an image quantizer operated in the derivative mode and computer-enhanced background subtraction from digitized images.