Temperature Dependence of the Mid-Infrared OH Spectral Band in Liquid Water

1997 ◽  
Vol 51 (9) ◽  
pp. 1269-1275 ◽  
Author(s):  
Tetsuo Iwata ◽  
Jun Koshoubu ◽  
Chihiro Jin ◽  
Yusei Okubo
Keyword(s):  
Temperature Dependence ◽  
Liquid Water ◽  
Spectral Band ◽  
Principal Component ◽  
Attenuated Total Reflection ◽  
Vibration Band ◽  
Mid Infrared ◽  
Spectral Components ◽  
Stretching Vibration ◽  
Ft Ir

We have studied the temperature dependence (14–57 °C) of the OH-stretching vibration band in liquid water by the use of a microscope Fourier transform infrared (FT-IR) instrument with an attenuated total reflection (ATR) cell. In order to eliminate spectral distortions, we performed Kramers–Kronig transform of the ATR spectra and derived absorption- and refractive-index spectra. The numerical values are shown in detail. Application of principal component analysis (PCA) and partial least-squares 1 (PLS 1) modeling methods to the absorption-index spectra shows that the OH band consists of two abstract spectral components. The intensity of the first component changes linearly with temperature, whereas the second component changes nonlinearly, with a turning temperature around 30 °C. Each abstract spectrum has a pair of peaks, the intensities of which vary in an inverse manner with respect to each other for the temperature change.

scholarly journals Spectroscopy as a useful tool for the identification of changes with time in post-mortem vitreous humor for forensic toxicology purposes

2021 ◽  
Author(s):  
Anna Wójtowicz ◽  
Agata Mitura ◽  
Renata Wietecha-Posłuszny ◽  
Rafał Kurczab ◽  
Marcin Zawadzki
Keyword(s):  
Ir Spectra ◽  
Forensic Toxicology ◽  
Principal Component ◽  
Hierarchical Cluster ◽  
Vitreous Humor ◽  
Attenuated Total Reflection ◽  
Glass Slides ◽  
Added Benefit ◽  
Ft Ir ◽  
Non Destructive

AbstractVitreous humor (VH) is an alternative biological matrix with a great advantage of longer availability for analysis due to the lack of many enzymes. The use of VH in forensic toxicology may have an added benefit, however, this application requires rapid, simple, non-destructive, and relatively portable analytical analysis methods. These requirements may be met by Fourier transform infrared spectroscopy technique (FT-IR) equipped with attenuated total reflection accessory (ATR). FT-IR spectra of vitreous humor samples, deposited on glass slides, were collected and subsequent chemometric data analysis by means of Hierarchical Cluster Analysis and Principal Component Analysis was conducted. Differences between animal and human VH samples and human VH samples stored for diverse periods of time were detected. A kinetic study of changes in the VH composition up to 2 weeks showed the distinction of FT-IR spectra collected on the 1st and 14th day of storage. In addition, data obtained for the most recent human vitreous humor samples—collected 3 and 2 years before the study, presented successful discrimination of all time points studied. The method introduced was unable to detect mephedrone addition to VH in the concentration of 10 µg/cm3. Graphic abstract

Chemometric Approach to a Rapid Attenuated Total Reflection Fourier Transform Infrared Analysis of Complex Heroin-Based Mixtures

2020 ◽  
pp. 000370282096971
Author(s):  
Nataša Radosavljević Stevanović ◽  
Milena Jovanović ◽  
Federico Marini ◽  
Slavica Ražić
Keyword(s):  
Principal Component Analysis ◽  
Fourier Transform ◽  
Principal Component ◽  
Fourier Transform Infrared ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Illegal Market ◽  
Ft Ir

Heroin is one of the most frequently seized drugs in Southeastern Europe. Due to the position in the Balkan route, the Republic of Serbia keeps important role in suppression of the trafficking of heroin for domestic and foreign illegal market. This research is aimed to provide a good scientific approach in the field of seized heroin analysis. Two different forms of heroin are present in the illegal market, mostly in mixtures with typical “cutting” agents: caffeine, paracetamol, and sugars. It was observed that the quantity of pure heroin in seized samples slightly increases from year to year. The aim of this study was to produce a reliable and fast procedure for classification of illicit heroin samples and determination of the concentration range of heroin in the samples. For that purpose, the attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) technique was used and combined with such chemometric methods as principal component analysis, cluster analysis, and partial least squares. Principal component analysis (PCA) as an unsupervised model was used for exploratory purposes to identify trends, similarities, and differences between samples by reducing the dimensionality of the data. The cluster classification of examined samples turned out to be extremely useful to evaluate the possibilities of the ATR FT-IR technique to classify the samples appropriately into the patterns, the constituted clusters. Additionally, partial least square was the suitable method for the purpose of determination of the heroin hydrochloride concentration range in examined samples. It is proved that the joined application of spectroscopy and chemometrics can be extremely convenient and useful for forensic and drugs control laboratories.

IN SITU HIGH TEMPERATURE FT-IR STUDY OF THE INTERLAYER NAPHTHALENE-2,6-DISULFONATE IN Mg AND Al LAYERED DOUBLE HYDROXIDE

2011 ◽  
Vol 25 (31) ◽  
pp. 4185-4189
Author(s):  
EIJI KANEZAKI ◽  
MASAHIRO KATOH
Keyword(s):  
High Temperature ◽  
Layered Double Hydroxide ◽  
Basal Spacing ◽  
Vibration Band ◽  
Stretching Vibration ◽  
Ft Ir ◽  
Ir Study ◽  
Double Hydroxide ◽  
Heating Up

In high temperature in situ FT-IR (HTFTIR) spectra of Mg and Al layered double hydroxide with interlayer naphthalene-2,6-disulfonate ( Mg / Al / N 26 DS - LDH ), one S - O stretching vibration band of the non-coordinating - SO 3 group in the interlayer N 26 DS dianion is observed below 400 °C at 1035 cm-1 with keeping intensity. High temperature in situ X-ray diffraction (HTXRD) indicates that the basal spacing remains also constant up to 400 °C, MgSO 4 appears after the LDH collapses at 500 °C and some metal oxides are formed at higher temperature. Both results in HTXRD and HTFTIR indicate that the layered structure in this LDH is stable against heating up to 400 °C.

Application of Chemometrics Approaches to Analysis of Mid-Infrared Spectra of Ibuprofen Diluted in Supercritical Carbon Dioxide

2018 ◽  
Vol 72 (10) ◽  
pp. 1548-1560
Author(s):  
Roman D. Oparin ◽  
Michael G. Kiselev
Keyword(s):  
Correlation Analysis ◽  
Cross Correlation ◽  
Spectral Band ◽  
Principal Component ◽  
Matrix Analysis ◽  
Data Matrix ◽  
Two Dimensional ◽  
Mid Infrared ◽  
Temperature Range ◽  
Cross Correlation Analysis

This work represents a comprehensive analysis of mid-infrared (mid-IR) spectra of ibuprofen diluted in supercritical CO2 (in the temperature range of 40–90 ℃ and at the CO2 density corresponding to 1.3 of its critical value). The study employed mathematical approaches based on data matrix analysis such as two-dimensional cross-correlation analysis (2D-COS) and principal component analysis (PCA). Two-dimensional cross-correlation analysis allowed us to reveal correlations between the spectral contributions constituting the analytical spectral band and assigned to certain ibuprofen conformers, as well as the significance of these correlations. It has been shown that the considerable increase in the total intensity of the analytical spectral band, proportional to the equilibrium ibuprofen concentration in the supercritical CO2 phase, is accompanied by certain redistribution of intensities of the spectral components related to the corresponding conformers. The PCA allowed us to determine the changes of intensities of individual spectral contributions for each thermodynamic point in the considered temperature range. It has been shown that these two complementary methods provide more precise information that may be used as the initial data in the classical analysis of spectral data based on spectral curve deconvolution into individual spectral contributions.

scholarly journals Potential Recognition Layer in Electrochemical Sensor: A Comparative Characterization of p-Cyano Schiff Base Compounds

2021 ◽  
Vol 12 (2) ◽  
pp. 1803-1813
Keyword(s):  
Schiff Base ◽  
Electrochemical Sensor ◽  
Schiff Bases ◽  
Spectroscopic Techniques ◽  
Vibration Band ◽  
Dna Sensor ◽  
Stretching Vibration ◽  
Sensitivity And Selectivity ◽  
Ft Ir

The effective conjugation of electrons in aromatic Schiff bases has been utilized as an electrochemical sensor in forensic, pharmaceutical and environmental applications. The use of the Schiff base enhances the sensitivity and selectivity of the sensor. In this study, p-cyano Schiff base derived from 4-(4-aminostyryl)benzonitrile and three different aldehydes were synthesized. The spectroscopic techniques via Fourier transform-infrared spectroscopy (FT-IR), Uv-Vis spectrophotometry and Nuclear Magnetic Resonance (NMR) of 1H and 13C were used for structural elucidation resulted compounds. The targeted p-cyano Schiff base showed a clear imine (C=N) stretching vibration band at 1681-1708 cm-1, n→π* electronic transition at 355-360 nm in UV-Vis and a singlet: 8.34-8.39 ppm and 118.07-119.09 ppm for 1H and 13C NMR, respectively, supporting the formation of Schiff bases. The application of Schiff base as spacer in electrochemical DNA (E-DNA) sensor has not been much research done on it so far. The obtained compounds are potentially valuable for electrochemical-DNA sensor study in the future.

Synthesis and Thermal Properties of Etherified Konjac Glucomannan

2009 ◽  
Vol 620-622 ◽  
pp. 197-200 ◽  
Author(s):  
Qiang Wu ◽  
Xiao Yan Lin ◽  
Xue Gang Luo ◽  
Yan Chen
Keyword(s):  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Decomposition Temperature ◽  
Konjac Glucomannan ◽  
Vibration Band ◽  
Hydrophobic Polymer ◽  
Stretching Vibration ◽  
Ft Ir ◽  
Dsc Thermograms

A novel etherified KGM (EKGM) was synthesized with Konjac glucomannan (KGM) and 1-bromopropane in Lithium chloride/dimethyl sulfoxide (LiCl/DMSO). The EKGM was characterized by FT-IR, DSC and TG. The IR of EKGM showed that –OH stretching vibration band decreased and the C–H and C–O–C stretching vibration bands increased comparing with the unmodified KGM, which was indicating that KGM had been etherified. The DSC thermograms showed that an obvious glass transition of EKGM appeared and its glass transition temperature (Tg) decreased with the increasing of Pr/OH ratio. And it was also found that the EKGM had a higher decomposition temperature than unmodified. Meanwhile, it was proved that the EKGM was a good hydrophobic polymer and dissolved in some organic solvent easily.

Transmittance Fourier Transform Infrared Spectra of Liquid Water in the Whole Mid-Infrared Region: Temperature Dependence and Structural Analysis

2005 ◽  
Vol 59 (9) ◽  
pp. 1155-1159 ◽  
Author(s):  
M. Freda ◽  
A. Piluso ◽  
A. Santucci ◽  
P. Sassi
Keyword(s):  
Fourier Transform ◽  
Liquid Water ◽  
Fourier Transform Infrared ◽  
Infrared Region ◽  
Deformation Bands ◽  
Mid Infrared ◽  
Region Temperature ◽  
Sample Chamber ◽  
Ft Ir ◽  
Two State Model

Transmittance Fourier transform infrared (FT-IR) spectra of liquid water in the 4–80 °C temperature range are reported in the whole mid-infrared (MIR) region (4000–360 cm−1). The spectra were recorded by using a newly developed, home-made transmittance cell, working in light vacuum conditions (pressures of the order of 3–4 millibar). This permits the elimination of the aqueous vapor bands from the liquid spectra, particularly in the bending region, and the rapid collection of data without fluxing large amounts of nitrogen through the interferometer sample chamber. The temperature evolution of the OH stretching and HOH deformation bands is discussed in terms of Gaussian components analysis and a two-state model describing the equilibrium between different H-bond structures of liquid water. From this picture, structural and thermodynamic information about the hydrogen-bonding network of water is obtained.

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