Derivative Spectroscopy Research Articles

Photophysics of a Fluorescent Probe of the Laurdan Molecule in Homogeneous and Binary Solvents

The spectral and luminescent properties of the laurdan molecule (6-dodecanol 2-dimethylamino-naphthalene) are investigated by experimental and theoretical methods of time-dependent density functional theory (TDDFT). The fluorescence spectra of laurdan in homogeneous and binary solvents are analyzed using derivative spectroscopy method. It is shown that the fluorescence band (in hexane, cyclohexane, and triton X-100) is complex: two structures having energy difference 1000–1500 cm–1 are manifested for the molecule. The calculated data show the non-rigidity of its structure. The effect of proton-donor solvents is considered with allowance for not only dipole-dipole interactions, but also formation of the hydrogen bond.

Source indicator of commercial humic products: UV-Vis and fluorescence proxies

Purpose Over the last decades, commercial humic products (HPs) from various resources found multiple applications in agriculture and environmental technologies. The key factor defining chemical properties and biological activity of HPs is their organic matter origin. Thus, there is a need to find diagnostic criteria for differentiating organic sources of HPs. The objective was to determine indicators using absorption and fluorescence spectra in combination with derivative spectroscopy that might serve as tools to compare HPs from various environments, both as bulk materials and their humic acid (HA) fractions.

Characterization and identification of three kinds of wood class medicine by fourier transform infrared spectroscopy

Objective Using infrared spectroscopy to analyze three kinds of lignum Chinese medicine to provide a theoretical basis for the establishment of medicinal overall quality evaluation system. Methods Functional groups identification, Fourier Transform-infrared spectroscopy(FT-IR) and the second derivative infrared spectroscopy (SD-IR) could be applicable to analyze and identify the overall chemical composition of three kinds of lignum Chinese medicine. Results The main chemical components of Aquilariae Lignum Resinatum (ALR), Dalbergiae Odoriferae Lignum (DOL) and Sappan Lignum (SL) were cellulose, lignin and aromatics. The main chemical compositions of Sappan Lignum (SL) were cellulose, lignin and aromatics. The differences in FT-IR and SD-IR of DOL and SL indicated that they had different aromatic compounds. Conclusion Infrared spectroscopy can be used as a simple and accurate quality control method of three kinds of lignum Chinese medicine. Key words: Aquilaria agallocha; Dalbergia odorifera; Lignum sappan; Lignin; Cellulose; Fourier transform infrared spectroscopy; The second derivative infrared spectroscopy

Derivative spectroscopy and the continuous relaxation spectrum

Derivative spectroscopy is conventionally understood to be a collection of techniques for extracting fine structure from spectroscopic data by means of numerical differentiation. In this paper we extend the conventional interpretation of derivative spectroscopy with a view to recovering the continuous relaxation spectrum of a viscoelastic material from oscillatory shear data. To achieve this, the term “spectroscopic data” is allowed to include spectral data which have been severely broadened by the action of a strong low-pass filter. Consequently, a higher order of differentiation than is usually encountered in conventional derivative spectroscopy is required. However, by establishing a link between derivative spectroscopy and wavelet decomposition, high-order differentiation of oscillatory shear data can be achieved using specially constructed wavelet smoothing. This method of recovery is justified when the reciprocal of the Fourier transform of the filter function (convolution kernel) is an entire function, and is particularly powerful when the associated Maclaurin series converges rapidly. All derivatives are expressed algebraically in terms of scaling functions and wavelets of different scales, and the recovered relaxation spectrum is expressible in analytic form. An important feature of the method is that it facilitates local recovery of the spectrum, and is therefore appropriate for real scenarios where the oscillatory shear data is only available for a finite range of frequencies. We validate the method using synthetic data, but also demonstrate its use on real experimental data.

How accurate is Beer's Law in the analysis of NIR Data?

To construct a predictor of the proportional presence of some key component in a material, we assume that the near infrared (NIR) responses of the various component proportions are given by Beer's law. Using a set of NIR spectra of milk powder spiked with different amounts of casein, this assumption is tested by comparing different properties of this set of spectra with the equivalent properties of simulated spectra obtained by combining the spectrum of unspiked milk powder with the spectrum of casein, in the same proportions. The latter set of spectra corresponds to the situation where Beer's law holds exactly with no cross-interaction between the two linearly independent components, and, thereby, described by a rank-two row matrix. The former corresponds to what happens in practice with the possibility of cross-NIR-interaction occurring between the components. The degree to which Beer's law is likely to fail is examined. It is shown how spiking allows the identification of the casein wavelengths that are strongly independent of the NIR spectral responses of the other components in the milk powder. However, there are slight deviations from Beer's law and these are, in part, explained by diffraction effects. References B. Anderssen, F. de Hoog, and M. Hegland. A stable finite difference ansatz for higher order differentiation of non-exact data. Bull. Austral. Math. Soc. 58:223–232, 1998. doi:10.1017/S0004972700032196 R. S. Anderssen and F. R. de Hoog. Finite-difference methods for the numerical differentiation of non-exact data. Computing 33:259–267, 1984. doi:10.1007/BF02242272 R. S. Anderssen, F. R. de Hoog, I. J. Wesley, and A. B. Zwart. How much of a near infrared spectrum is useful? Sparse regularization–-let the data decide! In S. McCue, T. Moroney, D. Mallet, and J. Bunder (Eds), Proceedings of the 16th Biennial Computational Techniques and Applications Conference, CTAC-2012 , ANZIAM J. 54:C788–C808, 2012. http://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/6744 R. S. Anderssen and M Hegland. For numerical differentiation, dimensionality can be a blessing! Math. Comput. 68(227):1121–1141, 1999. doi:10.1090/S0025-5718-99-01033-9 R. S. Anderssen and M. Hegland. Derivative spectroscopy: An enhanced role for numerical differentiation. J. Integral Equat. Appl. 22:355–367, 2010. doi:10.1216/JIE-2010-22-3-355 D. J. Dahm. Explaining some light scattering properties of milk using representative layer theory. J. Near Infrared Spec. 21:323–339, 2013. doi:10.1255/jnirs.1071 T. Naes, T. Isaksson, T. Fearn, and T. Davies. A User-Friendly Guide to Multivariate Calibration and Classification . NIR Publications, Chichester, UK, 2002. doi:10.1002/cem.815

Cation modulation of hemoglobin interaction with sodium n-dodecyl sulphate (SDS) iv: magnesium modulation at pH 7.20

We investigate the interaction of Mg 2+ (0–2.30 mM) and sodium n -dodecyl sulfate (SDS) with hemoglobins (Hbs) A and S at pH 7.20. SDS was used to model both membranes (0.60 mM SDS) and proteases (5.0 mM SDS). Via UV-visible spectroscopy, second derivative and difference second derivative spectroscopy, we interrogated for difference(s) in the interaction of these ligands with the proteins that can account for the HbS resistance to malaria parasite while been prone to sickling. Our results show that Mg 2+ interaction with the proteins lowered the HbS oxygen affinity in comparison with the HbA. Additionally, [SDS]-protein interactions resulted in oxoferryl heme species formation that was prominent for the HbA and highly diminished for the HbS. [Mg 2+ ] introduction to the [SDS]-protein mixture, however decreased the concentration of denatured protein species. The [Mg 2+ ]-[SDS]-protein interactions suggest that while ionic or coulomb interactions for the HbA, in the presence of the surfactants, are [Mg 2+ ] dependent, those of the HbS are not. Furthermore, hydrophobicity is a crucial force for the HbS interaction at neutral pH and is little-masked by ionic, electrostatic or coulombic interactions. In conclusion, at physiological pH, the Mg-SDS interaction decreased the HbS denaturation in comparison to the HbA.

Determination of Insulator-to-Semiconductor Transition in Sol-Gel Oxide Semiconductors Using Derivative Spectroscopy.

We report a derivative spectroscopic method for determining insulator-to-semiconductor transition during sol-gel metal-oxide semiconductor formation. When an as-spun sol-gel precursor film is photochemically activated and changes to semiconducting state, the light absorption characteristics of the metal-oxide film is considerable changed particularly in the ultraviolet region. As a result, a peak is generated in the first-order derivatives of light absorption (A′) vs. wavelength (λ) plots, and by tracing the peak center shift and peak intensity, transition from insulating-to-semiconducting state of the film can be monitored. The peak generation and peak center shift are described based on photon-energy-dependent absorption coefficient of metal-oxide films. We discuss detailed analysis method for metal-oxide semiconductor films and its application in thin-film transistor fabrication. We believe this derivative spectroscopy based determination can be beneficial for a non-destructive and a rapid monitoring of the insulator-to-semiconductor transition in sol-gel oxide semiconductor formation.

Simultaneous Spectrophotometric Estimation of Candesartan Cilexetil and Hydrochlorothiazidein Tablet Dosage Form

A new simple derivative spectrophotometric method has been developed for the simultaneous determination of Candesartan Cilexetil and Hydrochlorothiazide in tablet dosage forms. Candesartan antagonizes the effect of angiotensin II (vasoconstriction and aldosterone secretion) by blocking the angiotensin II receptor in vascular smooth muscle and the adrenal gland and decrease the blood pressure whereas Hydrochlorothiazide increases chloride, sodium and water excretion by interfering with transport of sodium ions across renal tubular epithelium. And there by show the diuretic action. The first derivative method is based on the measurement of absorbance of one drug at the zero crossing point of another drug. Candesartan Cilexetil and Hydrochlorothiazide were determined at two different wavelengths 222.69 (zero crossing point of Hydrochlorothiazide) and 254.63 nm (zero crossing point of Candesartan Cilexetil) from the derivative spectra respectively. The methods hows linearity over the concentration range 0.5-50 and 0.1-50 µg/ml for Candesartan Cilexetil and Hydrochlorothiazide respectively in phosphate buffer. The proposed method was validated and can be used for routine analysis of combined tablet dosage forms containing Candesartan Cilexetil and Hydrochlorothiazide. Key words: Candesartan Cilexetil, Derivative spectroscopy, Hydrochlorothiazide, Simultaneous determination.

New Derivative and Differential Spectrophotometric Methods for the Determination of Pterostilbene-An Antioxidant

Pterostilbene found in blueberries and Pterocarpus marsupium heartwood is structurally similar to resveratrol. It is used for the treatment of cancer, diabetes and fungal infections. Three spectrophotometric methods have been developed for the determination of Pterostilbene. Two first derivative methods and one difference spectrophotometric method were attempted. Two first derivative spectroscopic methods were developed in sodium hydroxide (Method A) and methanol (Method B) and differential spectroscopic method (Method C) was developed using borate buffer and sodium hydroxide. Linearity was observed over the concentration range 0.1-25 and 1-25 μg/ml with linear regression equations y = 0.0043x-0.0003 (R 2 =0.9997) and y=0.0037x - 0.0007 (R 2 =0.9997) for method A and B respectively whereas for method C the linearity was followed over the concentration range 0.1-20 μg/ml with linear regression equation y=0.1124x - 0.0016 (R 2 =0.9999). The three methods were validated and can be applied for the determination of Pterostilbene pharmaceutical formulations. Key words: Derivative spectroscopy, Differential spectroscopy, Pterostilbene, Validation.

Dielectric data analysis: recovering hidden relaxations by fourth-order derivative spectroscopy

Complex materials exhibit dielectric behavior that can shed light on their chemophysical structure through comprehension of the physical mechanisms originating that behavior. For the interpretation of complex dielectric shape, where multiple relaxations are present (and usually described by semi-empirical functions), correct interpretation of each simple relaxation is necessary. The separation of often closely overlapped relaxation curves requires the verification of the meaningfulness of such multiple relaxations and to determine their number and relative magnitudes, in other words to resort to fitting procedure. However, often the physical interpretation of the fitting parameters is not straightforward, and their physical meaning is arguable. The application of even-order derivative spectroscopy is here demonstrated to be able to detect the presence and location of multiple dielectric relaxations, acting on the experimental data without any a priori hypothesis.

Simultaneous Derivative Spectrophotometric Determination of Lornoxicam and Paracetamolin Tablet Dosage Forms

Lornoxicam and Paracetamol in combined dosage forms (Tablets). The zero crossing point of Paracetamol (247.42 nm) has been selected for the quantification of Lornoxicam whereas the zero crossing point of Lornoxicam (233.28 nm) has been selected for the quantification of Paracetamol from the first order derivative spectrum observed in borate buffer. The method obeys Beer-Lambert’s law over the concentration range 5-50 µg/ml for Lornoxicam and 5-60 µg/ml for Paracetamol. The proposed method was validated and can be used for the analysis of tablet dosage forms containing Lornoxicam and Paracetamol. K ey words: Lornoxicam, Paracetamol, Spectrophotometry, Derivative spectroscopy, Validation.

DIFFERENTIATION OF THE WHITE AND PURPLE FLOWER FORMS OF Orthosiphon aristatus (Blume) Miq. BY 1D and 2D CORRELATION IR SPECTROSCOPY

Orthosiphon aristatus (Blume) Mig. is also known as Misai kucing or Kumis kucing. The plant is traditionally used to treat tonsilities, fever, menstrual disorders, gonorrhea, syphilis, gallstones, rheumatism, diabetes, hypertension, epilepsy, edema, hepatitis jaundice and for diuretic activity. The objective of this work was to differentiate the white and purple flower forms of O. aristatus (Blume) by multi-steps infrared (IR) macro-fingerprinting. The analyses included Fourier transform infrared spectroscopy (FT-IR), second derivative IR spectroscopy and two-dimensional correlation infrared (2D IR) spectroscopy with thermal perturbation. A distinctive absorption peak at 1384 cm-1 from the purple flower form clearly differentiated the two forms of O. aristatus. Further differentiation was made by the appearance of a strong auto-peak at 1580 cm-1 for the white flower form and at 1546 cm-1 for the purple flower form. Such results indicate that the multi-steps infrared macro-fingerprinting has the potential for the development of a fast and reliable analytical methodology for distinguishing the white and purple flower forms of O. aristatus (Blume) Miq. effectively.

Rapid determination and chemical change tracking of benzoyl peroxide in wheat flour by multi-step IR macro-fingerprinting

BPO is often added to wheat flour as flour improver, but its excessive use and edibility are receiving increasing concern. A multi-step IR macro-fingerprinting was employed to identify BPO in wheat flour and unveil its changes during storage. BPO contained in wheat flour (<3.0mg/kg) was difficult to be identified by infrared spectra with correlation coefficients between wheat flour and wheat flour samples contained BPO all close to 0.98. By applying second derivative spectroscopy, obvious differences among wheat flour and wheat flour contained BPO before and after storage in the range of 1500–1400cm−1 were disclosed. The peak of 1450cm−1 which belonged to BPO was blue shifted to 1453cm−1 (1455) which belonged to benzoic acid after one week of storage, indicating that BPO changed into benzoic acid after storage. Moreover, when using two-dimensional correlation infrared spectroscopy (2DCOS-IR) to track changes of BPO in wheat flour (0.05mg/g) within one week, intensities of auto-peaks at 1781cm−1 and 669cm−1 which belonged to BPO and benzoic acid, respectively, were changing inversely, indicating that BPO was decomposed into benzoic acid. Moreover, another autopeak at 1767cm−1 which does not belong to benzoic acid was also rising simultaneously. By heating perturbation treatment of BPO in wheat flour based on 2DCOS-IR and spectral subtraction analysis, it was found that BPO in wheat flour not only decomposed into benzoic acid and benzoate, but also produced other deleterious substances, e.g., benzene. This study offers a promising method with minimum pretreatment and time-saving to identify BPO in wheat flour and its chemical products during storage in a holistic manner.

Adulteration screening of botanical materials by a sensitive and model-free approach using infrared spectroscopic imaging and two-dimensional correlation infrared spectroscopy

Infrared (IR) spectroscopy is often used as a simple, fast, and green method for the adulteration screening of botanical materials for foods and herbs. However, the overlapping of absorption signals of various substances significantly decrease the sensitivity and specificity of IR spectroscopy in the detection of adulterated samples. In this research, a model-free approach is proposed for the sensitive and non-targeted screening of botanical materials adulterated by adding other plant materials. First, the spectra of the entities in the test sample are collected by near-infrared spectroscopic imaging and clustered by unsupervised pattern recognition methods. The sample may be adulterated if there are two or more clusters of the entities. Next, the entities of different clusters are characterized by mid-infrared spectroscopy to interpret the chemical compositions to determine the clustering is caused whether by adulteration or other reasons. Second derivative spectroscopy and two-dimensional correlation spectroscopy are often needed to resolve the overlapped bands mathematically or experimentally to find the characteristic signals to identify the authentic and adulterant entities. The feasibility of this approach was proved by the simulated adulterated sample of saffron. In conclusion, botanical materials adulterated by adding other plant materials can be detected by a simple, fast, sensitive, and green screening approach using IR spectroscopic imaging, two-dimensional correlation spectroscopy, and necessary chemometrics techniques.

Trans fatty acids in two classes of reformulated “zero trans” Spanish margarines by use of second derivative ATR-FTIR spectroscopy

This work arouses a criticism about if “no trans fat” really means no trans fat. This issue seems to be interesting because of the direct relationship between trans-fat intake and a pronounced risk of coronary heart disease. Very low amounts of trans-fat (less than 0.5 per cent, as percentage of total fat) have been found in commercial soft and hard reformulated margarine labelled as “zero trans”, by the use of the innovative recently validated second derivative procedure of attenuated total reflection-Fourier transform infrared spectroscopy. In this way the possibility to inform consumers on trans-fat content in 0.1%-trans-fat increments, from 0% to 2%, as percentage of total fat, in the Nutrition Fact label could be feasible.

A computational study on surface-enhanced Raman spectroscopy of para-substituted Benzenethiol derivatives adsorbed on gold nanoclusters

We presented a computational study on para-substituted Benzenethiol (x-BT, x=H, F, Cl, Br, OH, SH, SeH, NH2, CH3) derivatives interacting with gold cluster for chemical effects related to surface-enhanced Raman spectroscopy (SERS). Density functional theory (DFT) calculations were performed on a series of bridge-type and vertex type x-BT/Au13 complexes for geometric, electronic and excitation properties to determine the key factor in spectral enhancement. Results indicated that off-resonance enhancement factors of bridge-type and vertex-type complexes exhibited different dependency on substitutions, which was greatly influenced by molecule–cluster transitions instead of properties such as interaction energy and charge transfer due to same origination for off-resonance and resonance chemical enhancement.

Coencapsulation of Hydrophobic and Hydrophilic Antituberculosis Drugs in Synergistic Brij 96 Microemulsions: A Biophysical Characterization

A microemulsion has been formulated to coencapsulate antituberculosis drugs to solve the issue of stability of rifampicin (RIF) in the presence of isoniazid (INH) and pyrazinamide (PZA). The structural transition, solubilization locus, and quantitative release of drugs without interference have been estimated. Derivative absorbance spectroscopy, especially ratio derivative and double divisor ratio derivative methods, has been employed for estimating the release. The coencapsulation of the anti-tuberculosis drugs were carried out in single, binary, or ternary mixtures and occupy the same solubilization sites in multiple drugs microemulsion systems as in the case of single drug-loaded systems. INH and PZA obey the diffusional (Fickian) release mechanism, whereas RIF shows anomalous release. Resazurin assay and agar well diffusion method were adopted for cytotoxicity analysis and antimicrobial activity, respectively. Cytotoxicity was found to be dependent on concentration and on colloidal structure of microemulsion.

A comparative study of smart spectrophotometric methods for simultaneous determination of sitagliptin phosphate and metformin hydrochloride in their binary mixture

Simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the oral antidiabetic drugs; sitagliptin phosphate (STG) and metformin hydrochloride (MET) in combined pharmaceutical formulations. Three methods were manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and a novel approach of induced amplitude modulation (IAM) methods. The first two methods were used for determination of STG, while MET was directly determined by measuring its absorbance at λmax 232nm. However, (IAM) was used for the simultaneous determination of both drugs. Moreover, another three methods were developed based on derivative spectroscopy followed by mathematical manipulation steps namely; amplitude factor (P-factor), amplitude subtraction (AS) and modified amplitude subtraction (MAS). In addition, in this work the novel sample enrichment technique named spectrum addition was adopted. The proposed spectrophotometric methods did not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined pharmaceutical formulations. Standard deviation values were less than 1.5 in the assay of raw materials and tablets. The obtained results were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there was no significant difference between the proposed methods and the reported one regarding both accuracy and precision.

The interactions of probes based on substituted pyrene derivatives in polymer matrices; spectral study

• Pyrene-cholesterol adducts were synthetized and doped to common polymer matrices. • The behavior of various pyrene derivatives were compared based on spectral data. • Their aggregation was evaluated according to UV–vis and static fluorescence spectra. • Lower aggregation in solid matrices was observed for pyrene-cholesterol adducts. • Spectral data analysis allow us to estimate the interaction in polymer/probe mixture Two substituted pyrene derivatives with cholesterol ((3β)-cholest-5-en-3-ol) moiety as esters were synthetized. The spectral properties of the mono-substituted derivatives of pyrene as esters with different linkages to cholesterol via carboxy unit ( PyCACh1 ) and methylene carboxy unit ( PyMECh2 ) are compared with the mono-substituted pyrene derivatives and the parent pyrene in toluene at low concentration and doped in glassy polymer matrices of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polyvinylchloride (PVC) in the concentration range of 0.002–0.06 mol kg −1 . Fluorescence spectroscopy of the pyrene derivatives in polymer matrices reveals changes in the shape of the fluorescence spectra with increasing concentration. Two limiting cases are observed: (1) a medium or large red shift of the entire fluorescence spectrum or (2) the formation of an emission band in the excimer emission region (approx. 500 nm). These changes are less pronounced in the pyrene-cholesterol esters in the PS matrix due to higher compatibility than in PMMA and PVC matrices. Exploitation of these emissions to estimate the interactions of the components in the polymer matrix is discussed.

Reconstruction of late Quaternary paleohydrologic conditions in southeastern British Columbia using visible derivative spectroscopy of Cleland Lake sediment

Visible derivative spectroscopy (VDS) analysis of sediment from Cleland Lake, Southeastern British Columbia provides a reconstruction of paleolimnological productivity and hydrologic change during the past 14,000 calibrated 14C years before present (calyr BP). The first five principal components (PC) of the VDS data explain 97% of the variance in the VDS data set. Four PCs correlate with standard reflectance derivative spectra for diatom, dinoflagellate algae, and cyanophyte pigments that record ecological change, while two PCs are paleohydrologic indicators. Dinoflagellate algae are predominant from 11,600 to 8600calyr BP then decrease to low levels after ~8500calyr BP. PCs 3–5 represent variations in cyanophyte abundance and exhibit peaks from 14,000 to 11,600, 14,000 to 9500, and 6100 to 5400calyr BP, respectively. Conditions shifted toward favoring diatoms around 9400 and lasted until 170calyr BP. Higher dinoflagellate-related pigment concentrations suggest a lower lake level from 11,600 to 8600calyr BP, followed by higher water levels and wetter conditions after 8500calyr BP. We propose that drier conditions transitioning from the late glacial into the Holocene were caused by summer insolation-driven, non-linear feedbacks between the northern hemisphere subtropical high-pressure systems, vegetation, and soil moisture.