Data Preprocessing Method for the Analysis of Spectral Components in the Spectra of Mixtures

This paper describes a data preprocessing algorithm that can be used to mitigate the effects of interfering spectral components when the goal is to detect the spectrum of unknown components in a mixture of known components or to verify the presence of suspected components in the spectrum of a mixture of known components. The algorithm is both relatively simple and applicable to a wide range of problems in spectroscopy. The range of applicability can be increased by combining the method with other data preprocessing methods, for example derivative spectra, and can also accommodate variability in the spectra of one or more of the known components. Examples of the application of the algorithm to real problems are given for near-infrared analysis of antibiotic drug formulations inside gelatin capsules and mid-infrared analysis of atmospheric pollutants.

DIFFERENT ULTRAVIOLET SPECTROSCOPIC METHODS: A RETROSPECTIVE STUDY ON ITS APPLICATION FROM THE VIEWPOINT OF ANALYTICAL CHEMISTRY

In routine practice, some simple and rapid analytical methods are needed for the assessment of formulations containing multiple elements, complex matrix system and for biotherapeutic products. There are several methods available for ultraviolet (UV) spectrophotometry that rely on the concept of absorbance difference, absorbance spectra, and additivity, also included in the list are simultaneous equation method, Q-absorbance ratio method, derivative spectrophotometry, ratio derivative spectra, successive ratio-derivative spectra, absorption and absorptivity factor method, and difference spectrophotometry along with multivariate chemometric methods. In this review, emphasis has been given to the theories, mathematical context, advantages, and disadvantages along with the vast applications of UV spectrophotometry. The findings further highlighted that for the analysis of drugs, UV spectrophotometry remains as one of the most simple, cheap, and promising option for routine practice in the field of pharmaceuticals.

On the determination of the dissipation rate of turbulence kinetic energy

The paper presents a comparison of the dissipation rate obtained from numerical differentiation of the time-resolved velocity, analog differentiation of the hot-wire signal, integration of the velocity derivative spectra obtained from the velocity spectra, and the application of a power decay law. Hot-wire measurements downstream of an active-grid provide the time-resolved velocity with a Taylor Reynolds number in the range of 200–470, turbulence intensities in the range of 5.8–11%, and nominal mean velocities of 4, 6, and 8 m s$$^{-1}$$ - 1 . The dissipation rate calculated using a ninth-order central-difference scheme differs at most by $${\pm }$$ ± 4% from the value obtained by analog differentiation. For comparison, a 23rd-order central-difference scheme offers negligible (0.02%) difference relative to the ninth-order scheme. Correction for an apparent uncertainty in the calibration of the analog differentiator reduces the difference to $${\pm }$$ ± 2.5%. In contrast, integration of the velocity derivative spectra obtained from the velocity spectra leads to a dissipation rate 14–45% larger than the corresponding values obtained using analog differentiation. Results obtained from the application of a power decay law of turbulence kinetic energy with a nonzero virtual origin to determine the dissipation rate deviate by 1.7%, 1.6%, and 3.6% relative to the corresponding values obtained from the analog differentiator based on the ensemble average of downstream locations with a $${\pm }$$ ± 5.6% scatter about the ensemble average. Graphic abstract

Development of derivative spectrophotometric method for simultaneous determination of pyrazinamide and rifampicin in cubosome formulation

The ultraviolet spectrophotometry analysis for quantitative assay of drugs is a method accurate, sensitive, selective and reproductive with the advantage of being a simple and less expensive method. In this study, a derivative ultraviolet spectrophotometric method was developed for simultaneous determination of pyrazinamide (PYZ) and rifampicin (RIF). The spectrophotometric method was evaluated according to validation guidelines for specificity, linearity, limits of detection and quantification, precision, accuracy and robustness. The first-derivative spectra were obtained and by the zerocrossing point, the wavelength 247 nm and 365 nm were selected for PYZ and RIF quantification, respectively. No interference from cubosome excipients was detected in the proposed method. The results demonstrated linearity in a range of 4.0 – 12.0 µg/mL with an adequate correlation coefficient for both drugs. The intra and inter-day precision results (RSD < 5%) indicated the reproducibility of the method. The accuracy data showed satisfactory results (RSD < 5%) from recovery test. In addition, the robustness results showed that the PYZ and RIF content were unaffected by the solvent alteration of methanol to methanol:water (99:1, v/v). The derivative ultraviolet spectrophotometric method proved to be an excellent strategy for simultaneous determination of PYZ and RIF.

Adulteration of Gabus (Channa striata) fish oil with corn oil and palm oil: the use of FTIR spectra and chemometrics

The adulteration practice in fats and oils industry can be in the form of addition or substitution high quality oils such as Gabus Fish oil (GFO) with lower price oils. This research highlighted the application of FTIR spectroscopy combined with multivariate calibrations and discriminant analysis (DA) for quantitative analysis and classification of oil adulterants of palm oil (PO) and corn oil (CO) in GFO. The methods involved preparation of training/calibration and validation samples, scanning of samples using FTIR spectrophotometer using attenuated total reflectance, development of calibration and validation models for quantitative analysis of oil adulterants assisted with multivariate calibrations and classification between genuine GFO and GFO adulterated with PO and CO using discriminant analysis. The quantitative analysis of PO in ternary mixtures with CO as an adulterant in GFO was carried out using first derivative spectra at wavenumbers of 3200-600 cm-1 assisted with partial least square (PLS), while quantitative analysis of CO in ternary mixture with PO and GFO was performed using first derivative spectra at wavenumbers region of 3200-2700 cm-1 assisted with principle component regression (PCR). The R2 values for the correlation between actual and predicted values of PO and CO in ternary mixtures either in calibration or prediction samples were of > 0.97 with low errors. In addition, DA using the same wavenumbers region as used in the quantitative analysis could classify or discriminate genuine GFO and GFO mixed/adulterated with PO and CO with an accuracy level of 100%. FTIR spectroscopy using suitable wavenumbers region combined with PLS, PCR and DA could be proposed as analytical tools for quantification and classification of oil adulterants in GFO.

Alternative Methods for Measuring the Susceptibility of White Wines to Pinking Alteration: Derivative Spectroscopy and CIEL*a*b* Colour Analysis

Pinking is the term used for describing the pink colouration that appears in white wines produced under reducing conditions when oxidised. The ability to predict the susceptibility of white wines for pinking is of utmost importance for wine producers. In this work, we critically compare the two most currently used methods for measuring pinking susceptibility and the use of the first derivative spectra and the CIEL*a*b* colour space method. The amplitude of the first derivative spectra in the 450–550 nm range has a good correlation with the values obtained by subtracting the extrapolate background at 500 nm (R2 = 0.927); therefore, first derivative spectroscopy seems to be a more straightforward approach for eliminating the background problem that occurs in this method. The CIEL*a*b* method using the a* value after oxidation seems to be the most appropriate method to measure the pinking susceptibility of white wines, showing a very good correlation with the amplitude of the first derivative spectra. The pink colouration visualisation is linearly related to the b* value of the white wine, showing that no universal cut-off value for predicting the pink visualisation should be used. Second derivative spectra allow the observation of the formation of different chromophores in wines after induced oxidation.

Spectrophotometric Determination of Carbimazole and Its Major Impurity, Degradation Product and Metabolite: Methimazole -=SUP=-*-=/SUP=-

The present research work was carried out in order to develop simple, accurate and precise UV sprctrophotometric methods having comparable sensitivity as that of sophisticated chromatographic techniques. Two methods were developed namely first derivative spectrophotometry and ratio spectra derivative spectrophotometry for accurate determination of specified impurity methimazole (imp A) in presence of drug carbimazole. First derivative spectrophotometric method involves recording of zero order spectra of both the drugs carbimazole and methimazole and its mixture in the range of 200-400 nm and subsequent conversion of these spectra into first derivative spectra. The drugs carbimazole and methimazole were determined by using zero crossing wavelengths of 227 and 260 nm respectively. In the second approach, ratio spectra were recorded for carbimazole and methimazole by selecting appropriate divisor concentration and converted into first derivative spectra. The determination of carbimazole and methimazole were carried out at wavelength 226.2 and 257 nm, respectively. Both the methods were validated as per ICH guideline. The drugs carbimazole and methimazole showed linear response with good correlation coefficient and exhibited specificity, accuracy and precision within acceptable range. The second method of ratio spectra derivative spectrophotometry was found more sensitive as compare to first derivative spectrophotometry in detecting level of impurity methimazole up to 0.5&#37; as per official specification. Hence, these developed methods can be used as alternative to sophisticated chromatographic technique for determination of assay and related impurity in bulk drug and formulation. Keywords: carbimazole, methimazole, first derivative spectrophotometry, ratio spectra derivative spectrophotometry.

Impact Study of Mathematical Manipulation on the Resolution Efficiency of the Spectrophotometric Technique—An Application on Veterinary Binary Mixture with Overlapping Absorption Bands

Background The impact of mathematical manipulation on the efficiency of smart spectrophotometric approaches was considered for analyzing a veterinary binary mixture of tylosin tartrate (TYT) and doxycycline hydrochloride (DOX). Objective Based on subtraction which can be response subtraction via numerical factor calculation between two wavelengths. Method Absorbance subtraction (AS) and amplitude summation (A-Sum), or subtraction of constant value or spectrum, was used to eliminate the contribution of the interfering component, as is done in spectrum subtraction (SS), extended ratio subtraction (EXRS), ratio subtraction (RS), and derivative subtraction (DS), or multiplication of a constant value by the divisor to get the spectrum of one component, or division by the normalized spectrum to modulate the original absorption spectrum to concentration as in concentration value and also detected in amplitude modulation (AM). The derivative transformation method (DT) is a form of mathematical manipulation that transforms a derivative to its original absorption form. Results The consumption of these methods will become more significant in quality control departments for the repetitive quantitative analysis of different veterinary products in both research and industry laboratories. Some manipulations may be used for simultaneous analysis of DOX and TYT, such as absorbance subtraction, amplitude modulation, ratio subtraction and derivative subtraction coupled with spectrum subtraction, concentration value, and amplitude summation, while others may be used for DOX only, such as derivative transformation and constant value. Conclusions The recovery percentages confirmed that the accuracy and the reproducibility were approved by the following ICH guidelines. Highlights 1. Partitioning methods: which perfectly divide the drugs response at the iso-point such as amplitude modulation, absorbance subtraction and amplitude summation. 2. Extracting methods: which easily calculate zero-order of the two cited drugs in such as ratio subtraction were coupled with extended ratio subtraction method (RS-EXRS), spectrum subtraction (SS), constant multiplication method (CM) or extract their derivative spectra such as derivative subtraction. 3. Transforming methods: which able to change the derivatized spectrum to its original zero spectra such as derivative transformation. 4. Graphical methods: which directly measure the concentration of the drugs from the chart.