Spectra - Science topic

Dear Juan

I don't know why you want to add PRINT. Because as I remembered, it is used to control how much to print in the output file. But you have already p at the beginning. This may arouse the conflicts between two same commands. That may be why Guassian gives you an error in ntran and fopen, the part for write the file.

Most likely CO2 fluctuations since background was recorded.

Possibility of hydrogen as CH bonds?

Chehat Nour El Houda

The effect of UV radiation on polymers depends on their structure. You haven't written anything about the structure. There are polymers where UV radiation doesn't break chains.

What also has to be taken into account is that the peaks in ATR spectra are redshifted, the more the stronger the corresponding oscillator is. For oxy-anions you can easily get shifts of 20 cm^-1 or more if you use a ZnSe crystal and 45° angle of incidence.

I would say it is common to show processed spectra in the publication. For reproducibility reasons you should describe accurately in the methods section what you did.

If the processing involves large changes to the spectrum, you could place the unprocessed spectrum in the supplement; I once did that for the case that a Raman spectrum was dominated by a glass background while the actual material only gave rise to a set of wiggles on said background. Alternatively, nowadays putting research data in a repository is also an option, that would ensure maximum tranparency.

Electronic, rotational, and vibrational spectra are different types of spectroscopic techniques used to study the energy levels and transitions of molecules. Here are the key differences between them:

1. Electronic Spectra:

- Electronic spectra involve transitions between different electronic energy levels of a molecule.

- These transitions typically occur in the ultraviolet (UV) or visible regions of the electromagnetic spectrum.

- Electronic spectra provide information about the electronic structure of a molecule, such as the arrangement of electrons in different orbitals.

2. Rotational Spectra:

- Rotational spectra involve transitions between different rotational energy levels of a molecule.

- These transitions occur in the microwave region of the electromagnetic spectrum.

- Rotational spectra provide information about the rotational motion of molecules and can be used to determine molecular structure and bond lengths.

3. Vibrational Spectra:

- Vibrational spectra involve transitions between different vibrational energy levels of a molecule.

- These transitions occur in the infrared (IR) region of the electromagnetic spectrum.

- Vibrational spectra provide information about the vibrational motion of molecules, such as bond stretching, bending, and twisting motions.

In summary, electronic spectra deal with electronic transitions, rotational spectra deal with rotational transitions, and vibrational spectra deal with vibrational transitions in molecules. Each type of spectra provides unique information about the molecular properties and behavior.

You may find these previous RG threads helpful:

Have you found the raw data of the absorption spectra of phytochrome? Could you please share it with me? Thank you!

Dear all, yes and various parameters may contribute to that, such as chains orientation, crystallinity, thermal phase heterogeneity (due to nonuniform cooling down), air bubbles, stress history, and possibly others. My Regards

Thanks for your suggestions. I will conduct the trial experiments as soon as possible.

Solved the issue.

Determining the exact phyto-constituents in a plant extract using LC-MS (Liquid Chromatography-Mass Spectrometry) involves several key steps:

1. Sample Preparation

2. LC-MS Setup

3. Mass Spectrometry Parameters

4. Method Development

5. Data Acquisition

6. Data Analysis

7. Validation

8. Interpretation

Additional Considerations

By carefully optimizing each of these steps, you can accurately determine the phyto-constituents present in your plant extract.

The increased strength of hydroxyl (OH) stretching and bending vibrations observed in FTIR spectra is often correlated with enhanced photocatalytic efficiency. This correlation arises due to several key factors:

Thus, the stronger OH stretching and bending vibrations in FTIR spectra are indicators of more reactive and effective photocatalytic processes.

Veeresh Verma

Now you can simply find links by keywords.

The expected intensities can be estimated from the excitation-dependent cross section tables (see my answer to your other question). In a real measurement, you would also have to account for the electron escape path (see e.g. the Seah/Dench tables), an angular correction (except when you're scanning in magic angle geometry) and the detector transmission function which the manufacturer should have provided.

For your reference, this supplement contains a substituted Imidazolium chloride's spectrum:

In ESI, you can tune settings, which includes varying the pH of the sprayed solution so that you can favor the formation of aggregated or isolated species in the gas phase. Therefore, species with or without counterions may be created.

Colleagues

A reminder about this effort! We are moving forward with a first manuscript covering the database but we have plans for follow-on studies and are looking for a broader group of collaborators!

Take a look and let us know if you want to get involved!

If the existing methods don't suffice, you could simulate Raman spectra by DFT and compare with and without stress:

Chris Taylor, the InVia system avoids a certain amount of light from hitting the detector by cutting the signal if the signal is higher than a certain threshold. So, you can try to decrease the exposure time and lower the laser power.

I hope this helps.

What are the specifications of your spectrometer's notch filter? If it cuts off the first 100 cm^-1 which would be a normal order of magnitude, that would be an easy explanation for the intensity increase at 100 cm^-1 and also typically a first pseudopeak right after the cutoff due to the software subtraction is also common.

Here are some sources for public datasets containing FTIR spectra of blood samples:

NIST Chemistry WebBook

UCI Machine Learning Repository

MetaboLights

BioSpec-NIR

PRIDE Archive

European Bioinformatics Institute (EBI)

PubChem

General-purpose repositories (Zenodo, Figshare, Dryad)

Kaggle

You can also search for relevant studies in scientific literature and contact researchers for data.

I haven't done this in a while, but I believe to recall the analysis procedure was as follows:

Plot the spectrum as a function of the absolute frequency instead of the relative Raman shift. Determine the frequency periodicity of what you have there. Recalculate this frequency to the associated wavelength and divide the result by the material's refractive index. That should yield a quantity equal to one of the material's spatial dimensions, so a film thickness or maybe a fiber diameter.

Hopefully I haven't messed up the order of steps here, but that's how I recall it.

if powder was dispersed not dissolved in the carrier medium, the bond structures by FTIR should be the same, but with some extra peaks of the dispersed sample, i.e. from the carrier molecules.

Dear Francesco Gagliani,

you can see

Fitting of Electrochemical Impedance Spectroscopy data with Zview 3 2b!! #electrochemistry

Dear Abdelhak,

thank you very much for your kind and detailed reply!

Best Regards

Marcella

(Supplementary, page S25, DMSO-d6, 400 MHz)

I would fit the CD spectra instead. Take a look into or in this book (chapter 16):

Hello Santoshkumar Kaushik ,

Please find if the method for calculating the raman spectra as described in https://github.com/raman-sc/VASP is what you are looking for. It nicely gives the basic theory and procedures.

Here are some free databases where you can find UV/Vis spectra:

You can find NIR spectra on SpectraBase (https://spectrabase.com/). You need to create a free account to see the full spectra. The free account is limited though to about 10 searches/month.

A FTIR spectrometer might work. There are some 'low cost', modest resolution FTIR systems that might do the job.

Spectral Products supplies a 1.5 - 5.0µm spectrometer (10-30 nm resolution). Alternatively, there are more pricy spectrum analyzers from e.g. Bristol Instruments (1-12 μm), NLIR (7.6-12 μm), or A.P.E. (0.2 - 6.3 μm).

Hello Jaime,

The asymmetry in the M(0) originates from the possibility of a additional energy loss due to inelastic scattering. As metallic samples have no bandgap the shake-up process manifests as a continuous asymmetric shoulder rather than a defined shake-up peak seen in i.e. oxides.

The degree of this varies and depend on the details of a materials band structure. Particularly for small clusters they can change significantly, typically acting less metallic with hence less asymmetry.

Regarding 1) low resolution spectra taken at larger pass energies will show less of an asymmetry as the instrumental broadening, which is Gaussian will dominate (all sources of broadening add up in square sums).

Regarding 2) Reliable prediction would require detailed band structure calculations and are not easily done. For example see:

Regarding 3) Just from very generic size confinement rules I'd suspect the smaller the cluster the less asymmetry. from my own experience even in thin metal films this can be seen with thin films showing less than i.e. single crystal bulk metals.

Hope that helps

Karsten

or some of their older stuff.

You can try Standard Normal Variate (SNV) normalisation. You should subtract the mean of each spectral feature (in this case intensity for each wavelength) and then divide it with standard deviation. In other words, you find the mean and std of all intensities for each wavelength, and then do the aforementioned subtraction and division.

This should bring each spectrum to the mean of zero and std close to one. It should look better.

Averaging is advisable to reduce LIBS reproducibility error. Every LIBS spectrum is actually average over 10 or 20 successive laser shots. Very often authors do 10 shots on one place, then repeat it for lets say 20 other places on the target. Then the final spectrum is the average of all 200 spectra. On these spectra, calibration models are often constructed.

I do not know what your nanoparticles are but the main bands look like a polyamide with some OH. Are they coated ? the main difference between EO and E6 is a loss of OH at 3200 and 1970 cm-1 plus loss of aliphatic CH3, CH2 in the 2900 and 1400cm-1 regions. There is no evidence of the bands from the drug even if it becomes less crystalline.

Try to melt and quench the sample to get the amorphous form.

Thank you very much. Pierre Caulet

Dear Akansha,

You can use both the quasi-static approximation and Mie theory depend on the radii of the nanospheres. You can also refer one of our article ( ).

I have obtained the Supplemental Material for the contribution “Pressure-Induced Sublattic Disordering in SnO2: Invasive Selective Percolation” from the corresponding author, Prof. Denis Machon. Many thanks!

In order to support your claim of a satellite, you could try a fit with two satellite lines with the same binding energy difference and intensity ratio as the "regular" Sr 3d lines. An additional satellite line to the one at 133.6 eV would explain the somewhat high intensity of the 132.3 eV line compared to the 133.6 eV line. The width of the 133.6 eV line is large in line with a bad representation of the small dip at 133. This indicates that there is something else, which is large enough to "disturb" the fit, but too small to fit with something reasonable. The small feature at 135.5 eV also increases the width of the 133.6 line. This might be a hint to a similar, but weaker feature on the Pb lines. The shape of the Pb lines also looks quite "triangular" and not like Gaussian, which hints to more features, although not obvious enough to be determined in detail. I am also wondering a bit about the inelastic background. Has it been subtracted, like with a Shirley-type background? In order to nail down the general and the inelastic background better, a wider range of the spectrum would help. Admittedly, it wouldn't answer your primary question about the satellite.

Four novel spectrophotometric methods, induced dual wavelength method (IDW), dual wavelength resolution technique (DWRT), advanced amplitude modulation method (AAM), and induced amplitude modulation method (IAM), are reliable for determining overlapping spectral components in binary mixtures.

It is not possible to have of a p orbital only one spin orbit emission. The distance between Co2p3/2 and 1/2 is about 15 eV with 3/2 at around 780 and 1/2 at 795. Make sure your window is large enough.

It's possible, sometimes when the sample is subjected to the laser for too long it might "burn" it, I lost some good tests this way with fossils.

IR Spectroscopy in Qualitative and Quantitative Analysis

Written By

Nabeel Othman

Submitted: 03 June 2022 Reviewed: 18 July 2022 Published: 07 September 2022

DOI: 10.5772/intechopen.106625

📷

IntechOpen

Infrared Spectroscopy Perspectives and Applications Edited by Marwa El-Azazy

From the Edited Volume

Infrared Spectroscopy - Perspectives and Applications

Edited by Marwa El-Azazy, Khalid Al-Saad and Ahmed S. El-Shafie

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Abstract

The infrared technique is one of the oldest techniques; it deals with the frequencies of bond vibration in a molecule. The main uses of this technique are to identify and determine components in various organic or inorganic compounds. In this technique, a part of the incident infrared radiation is absorbed by the molecules of the sample and the other is transmitted. The favorite method of infrared spectroscopy is FTIR (Fourier transform infrared). There have been many developments in using IR technique in qualitative and quantitative analyses, including the first and second derivatives of the infrared spectrum. IR rays do not damage the exposed skin like other rays such as ultraviolet light. It must be mentioned that the IR technique was used in hyphenated techniques (instead of the detector in chromatographic device), for example, after separation by gas chromatography detected by IR. Also, this chapter contains essential information about Raman spectroscopy. Infrared spectroscopy is a technique that has acceptable accuracy and sensitivity to be one of the most important analytical techniques used in the qualitative analysis, and also, it is used in the quantitative estimation of compounds through measuring the transmitted or absorption intensity of the active groups.

Keywords

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1. Introduction

The introduction included the followings below:

1.1 Infrared spectroscopy

Spectroscopy is the branch of science contracts with learning about the interaction of the radiation of electromagnetic rays with substances.

Electromagnetic Radiation (EMR) is a type of energy that is around us and taking various forms, these types included radio waves, microwaves, infrared, visible light, ultraviolet X-rays, and gamma-rays. Sunlight is also considered a form of EMR, with Vis light only a minor share of the EM spectrum, which covers a wide range of wavelengths. Visible light has high energy compared with IR light [1, 2].

Infrared Spectroscopy (IRS) deals with the frequencies of bond vibration in a molecule. The main use is to identify the functional groups in many samples. The most covalently bonded compounds, whether organic or inorganic compounds, absorb electromagnetic radiation in the region of infrared. This IR region lies between the visible light and the microwaves region. IR radiation mainly considers thermal energy, in covalent bonds it gives stronger vibrations to molecules. Near-IR can be used in direct determination (nondestructively) of protein present in feeds, and this type of IR region is increasingly used in analytical chemistry for quantitative analysis of various compounds [1].

IR can be divided into main three different bands:

In UV and Vis. of the spectrum, the unite of wavelength is nanometer (nm), while in the infrared region wavenumbers are used, and cm−1 is the unit [2, 4]. The IR spectrum is drawn via a plot of absorbed or transmittance% (T%) against the wavenumber (Figures 1 and 2).

📷Figure 1. The spectrum of an absorption mode.

📷Figure 2. The spectrum of T% mode.

1.2 Fourier transform infrared spectroscopy (FTIR)

The favorite method of IRS is FTIR (Fourier Transform infrared), in IRS the infrared radiation is passed through the investigated sample. A part of the incident infrared radiation is absorbed by the sample and the other is transmitted. The resulting spectrum represents the absorption molecules. FTIR spectrophotometers have many advantages when compared with the older techniques IR, the FTIR instruments are more accurate, and more sensitive, all frequencies of functional groups are estimated simultaneously compared with an individual estimation of functional groups in IR, and they are fast in performance as was in the case of older IR instruments.

1.3 Classification of IR bands

Figure 3 shows the main three types of IR bands they classified according to their relative intensities in the IR spectrum.

📷Figure 3. The types of IR bands according to their relative intensities.

An increase in the dipole moment according to the increase in the distance between atoms caused an increase in the intensity of the absorption peak [5].

1.4 IR peaks shapes

Two main types of IR band shapes are narrow (thin and pointed) and broad (wide and smoother). An example for broad is the O-H peak in alcohols and carboxylic acids, as shown below in Figure 4 [5].

📷Figure 4. The broad peak of the hydroxyl group.

1.5 Range of IR absorption

The typical IR absorption range to covalent bonds in molecules is from 600 to 4000 cm−1. The graph shows the regions of the spectrum where the following types of bonds normally absorb. For example, the sharp band around 2200–2400 cm−1 would designate the possibility of the presence of a C-N or a C-C triple bond, and other ranges in IR-absorption for other types of bounds.

1.6 Overtones and combination bands

When a molecule absorbed electromagnetic radiation in the IR region, then the molecule is promoted from the ground state to the second, third, or even fourth vibrational excited state. These bands are known as Overtones. The intensity of these bands is very weak. It is helpful in the characterization of aromatic compounds.

When two fundamental vibrational frequencies (ν1 + ν2) in a molecule couple give rise to a new vibrational frequency within the molecule, it is known as a combination band.

1.7 Coupled vibrations

The coupled vibrations are observed in groups such as –CH2, NH2, etc. In these groups, the same atoms are attached to the central atom. When –CH2 undergoes vibration, vibrational frequencies for the –CH2 group are observed at 2950 cm−1 (asymmetric stretching) and 2860 cm−1 (symmetric stretching). A number of molecules contain the same functional group and show a similar peak above 1500 cm−1, but they show a different peak in the fingerprint region. Therefore, we can say that each and every molecule has a unique peak or band, which is observed in the fingerprint region; it is just like the fingerprint of a human.

1.8 The functional groups and fingerprint regions

IR spectrum can be separated mainly into two regions. Most of the functional groups show absorption bands at the wavelength (4000–1200 cm−1) region, which is called the functional group region. Will the second region from 1200 to 400 cm−1 is called the fingerprint region. Fingerprint region is characteristic of the compound as a whole. An example is 2-pentanol and 3-pentanol, the two compounds with similar absorption in the functional group region. However, their fingerprint regions are different, because the two compounds differ, and to accurately identify the compound by comparing the fingerprint area with the fingerprint area of a standard or known sample of this compound [6].

1.9 Factors affecting the vibrational frequency

The main factors affecting the vibrational frequency are listed below:

CyclohexanoneCyclopentanoneCyclobutanone1710 cm−11745 cm−11780 cm−1

Empty heading

An increase in wavenumber of the carbonyl group

1.10 General uses of IR

A molecule to absorb IR, the vibrations or rotations within a molecule must cause a net change in the dipole moment of the molecule. The principle of action is to shine infrared light so that it passes through the organic compound to be identified; absorption occurs for some of the frequencies by the model. The different precise frequencies of absorption can be used to identify the different groups in the unknown compound, which represent specific groups of atoms within the molecules over a period of time. We can identify the compound because each group has an absorption frequency that differs from the other. Using a detector to determine the different absorbance, which records the amount of infrared light that passes through the compound. Some frequencies pass without being fully absorbed, while others will be greatly absorbed due to the special chemical bonds in the molecules. This leads to obtaining a spectrum containing different selves expressing the totals in the model [7].

It is now approved that the PBM therapy is an extra accurate and exact term for the therapeutic application of low-level light compared with “LLLT.” A basic principle called the biphasic dose-response included that the large doses of light were found to be less actual than smaller doses. The human skin is reliably exposed to environmental IR radiation, which indirectly or directly stimulates the manufacture of free radicals or reactive oxygen species( ROS). 8~12 μm IR radiation is almost used on full-thickness skin wound therapeutic in rats.

IR light crosses the outer layers of the skin and reaches the tissues of the body. The good thing about using infrared light in therapy is that IR rays do not damage the exposed skin like other rays such as ultraviolet light. An advantage of exposure to IR ray that it improves the circulation of blood and promotes cell regeneration [8, 9, 10, 11].

1.11 Raman spectroscopy

Raman scattering firstly was observed by Raman and Krishnan (Indian physicists) in 1928. It is an analytical technique where the scattered light is used to measure the vibrational energy styles of molecules. Raman spectroscopy can offer chemical structural information, as well as identify the substances to be studied through their characteristic Raman “fingerprint.” Raman spectroscopy extracts the information over the detection of Raman scattering from the investigated sample. After the light is scattered via molecule, the oscillating electromagnetic field of the photon persuades a polarization of the molecular electrons cloud. The photon is transported to the molecule, due to the formation of a very short-lived complex (photon-molecule), and it is called commonly the virtual state. It is not stable and the photon can be re-emitted immediately as scattered light. Approximately 1/10 million photons Raman scattering occurs. The transfer of energy between the scattered photon and molecule and if the molecules gain energy from the photon according to the scattering (an excitation to a higher vibration level) and after that, the scattered photon loses energy, and this phenomena is called Stokes Raman, included an increase in wavelength. If the molecule loses energy by transferring to a lower vibrational level the scattered photon gains energy, inversely, the wavelength decreases, which is called Anti-Stokes Raman. Finally, if most of the molecules are in the ground vibrational level (Boltzmann distribution) and as a result, the Stokes Raman scatter is a continuously more probable process and intense than the anti-Stokes; for this reason, it is approximately always the Stokes Raman scatter used in Raman spectroscopy.

The main differences between IR and Raman scattering are listed in Table 1.

No.IRRaman1.The principle based on the light absorption.The principle based on scattering of light.2.To appear the spectrum the variation in the polar moment of the molecule to be study must not be equal to zero.To achieve the Raman spectrum it is not important to have dipole moment or the change of polarity, the bonds of molecular have specific transition energy in which cause a change of polarizability to give a rise to Raman active.3.The source of light used depend on the region of electromagnetic spectrum, tungsten filament lamp in Near-infrared, coil of Nichrom wire in Mid- infrared and high pressure mercury-arc lamp in Far infrared.laser was the excitation source. Almost , solid state lasers types are used in Raman tools with general wavelengths of 532, 785, 830 and 1064 nm.

Table 1.

The main differences between IR and Raman spectroscopy.

As a common rule included that everything that does not seem in the IRS is taken in Raman (bond of molecule either be with Raman active or be IR active but it not with be both). H2 or CCL4 doesn’t have spectrum in IR; but they give spectra in Raman. Also nitrogen-nitrogen, carbon-carbon, and sulfur-sulfur bonds have a change in polarizability, the incident photons interact with these models, these are examples of bonds that give rise to Raman active spectrum bands, but it is difficult to get spectrum in FTIR [12, 13].

Raman spectroscopy has several applications, such as the identification of materials and identification of different minerals ranging from iron oxy (hydroxides) to rare minerals. Study of the crystallinity, the composition, and uniformity, and also measurement of local temperature and stress. Raman spectroscopy is nondestructive, and the technique has a good resolution [14].

Recently, Raman spectroscopy has been used in blood identification and distinguishing between human and nonhuman blood using a portable Raman spectrometer, which can be used at a crime division, and the bloodstain of human could be distinguished from the non-human ones via using a principal component analysis, and also this analysis is useful for forensic [15].

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2. Application

2.1 Qualitative analysis

FTIR spectroscopy is the most reliable tool for identifying bone types and can also be widely used in forensic medicine. Identification of human and non-human skeletal remains unknown to investigators and is of great interest in forensic and anthropological procedures. Especially when the traditional morphological methods for diagnosing and differentiating between these types of bones took a long time. Therefore, the use of infrared spectroscopy and chemical measurement methods to determine the spectral differences between these two types of bones, human, and non-human bones (such as pigs, goats, and cows). The results showed that pig bone is not suspicious of human bone in the study of changes after death because it is more sensitive to environmental conditions than human bone [16].

The micro-FTIR technique was used to characterize the components of a dye painted on the walls of a church in Cyprus. The product was copper-based and the dye contained hydrated copper oxalate. Reflective imaging of the localization sites for the presence of copper and calcium oxalate within the layers of the plate. We conclude from this study that imaging calcium oxalate within different layers of paint samples is very important for studying copper-based pigments in general, and in particular for analyzing pigments used in coatings on different external surfaces [17].

Different heterocyclic compound derivatives have been synthesized via the reaction of ortho-Carboxybenzaldehyde with various aromatic amines (using six amino compounds) to produce Schiff bases (Figure 5).

📷Figure 5. The reaction of Schiff base preparation.

The Schiff bases compounds gave FTIR spectra with an absorption appeared at wavenumber between 1602 and 1614 cm−1 this peak belongs to the new C=N group, and also carbonyl of carboxyl group gave absorption appeared at (1741–1766) cm−1, and the absorption at (3306–3462) cm−1 for OH group of carboxylic acid. The authors noticed that the carbonyl of aldehyde disappeared, therefore our conclusion that FTIR proves the suggested mechanism and helps to suggest the structure of the product using the absorption of selective functional groups (Table 2, Figure 6) [18].

📷

Table 2.

The aromatic part of amine.

📷Figure 6. FTIR spectrum of the product resulted from the reaction of p- toluidine with ortho-carboxybenzaldehyde [from reference 18].

2.2 Quantitative analysis

Fourier transform infrared (FTIR) is used in numerous areas of industrial pharmacy with satisfactory results. The technique’s characteristic and nature tolerate unequivocally bright forecasts for quantitative analysis. FTIR is considered a green analytical chemistry technique. It is very easy, fast to work by a temperately knowledgeable technician, covers a large range of spectra to analyze the pharmaceutical formulations, the main advantages are that it has a good resolution and is considered nondestructive device, and it is also friendly to the environment because in procedure no use of a dangerous organic solvent or any harmful reagents is required for the analysis. Many attempts were suggested for using derivative IR in determination diclofenac sodium in its formulations, but the results indicated that the first derivative spectra are the best technique for determination of diclofenac sodium. The first derivative spectra deleted IR band overlapping with the band understudies and increased sensitivity without any interference of the other band’s [19].

Abdulhameed and Nabil (2022) developed a simple and rapid method for the determination of ketoprofen. The method is based on normal and infrared derivative (first derivative) spectroscopy. The results of the study found that the method is accurate and there is the possibility of its application in quality control to determine ketoprofen in pharmaceutical formulations. Ketoprofen was quantified in a range of estimation from 1000 to 4000 μg/ml. This range was based on measuring the T% of the normal spectrum and its first derivative spectrum versus the concentration of ketoprofen in the solution (Figure 7). The results prove the validity of the method, as the relative errors were +4.33% and 4.78% and the RSD% values were 1.15% and 1.37%, respectively, and since the values ​​are less than ±5%, the method is considered accurate and precise. The research also included the application of the two methods to estimate the compound under study in its different pharmaceutical preparations with a comparison of the results obtained with the results obtained via using high-performance liquid chromatography technique and calculating the t-student and F tests at P = 0.05.

📷Figure 7. The first derivative and the normal spectra of two standard ketoprofen from two companies Erbil and Turkey [from reference 20].

Figure 7 shows the derivative spectra of Standard, Erbil, and Turkey ketoprofen solutions, CCl4 was the solvent used. The two individual peaks of carbonyl groups at 1718 cm−1 as a positive peak and at 1705 cm−1 as a negative peak, and these peaks gave two calibration curves as various concentrations analyses, there is a reverse proportional relationship between the concentration and the percentage of transmittance(T%) (Figure 8) and the other indirect proportion. The reverse proportional relationship is according to decreases in the transmittance% of the solution with an increase in concentration (as shown in Figure 8), will in Figure 9there is a direct proportion or positive relationship for the first derivative IR according to the peak chosen (peaks of carbonyl groups at 1718 cm−1 as a positive peak) [20].

📷Figure 8. Calibration curve via normal IR method via first derivative IR.

📷Figure 9. Calibration curve [from reference 20]. method [from reference 20].

Michael et al (1995) used second derivative IR spectroscopy as a non-destructive tool to assess the purity and structural integrity of various samples such as proteins. Spectroscopy using second derivative infrared is a fast, easy, reproducible, cost-effective, and nondestructive method for assessing the purity of samples of some proteins (water-soluble) extracted from a diversity of sources. The 2ed IR spectra were calm under the lab-proven conditions of aqueous (D2O) solutions of seven different commercial samples for the same enzyme, porcine pancreatic elastase (2.0–3.8 mg protein/100 μl D2O, pD = 5.4–9.1). , the amide at the region defined by I (1700–1620 cm−1) from the IR spectra using the 2ed derivative for each of the seven elastase samples displays a characteristic pair of bands: one of them is very weak showing intensities near to 1684 cm−1; the other is close to 1633 cm−1 is moderate to strong. While one of the 7 samples under study shows a striking decrease in the noted density of amide I bands relative to the 1516 cm absorbance, along with the appearance of a new strong band at 1614 cm−1. That the seventh sample is of much lower quality than the other samples and sure contains a quintile of the protein present in the non-native state. In addition, the apparent slight changes in the relative location, and intensity of a section of the separate amide I band among the seven spectra indicate slight differences in the formation of the amount of the peptide support of the samples under study. From the results of two samples, it seems that these few changes, sample purity, and identification of non-protein contaminants [21].

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3. Hyphenated techniques

During the past five decades, hyphenated techniques developed rapidly and seemed to dominate many analyzes by introducing them to solve many problems related to complex analyzes, as they were widely used in the pharmaceutical industries from the stage of discovery to human use and the study of its concentration in living body fluids. Accuracy and high sensitivity, and one of the most important disadvantages are the high costs of the devices, and they need maintenance and accurate knowledge while working on the device. Liquid chromatography-mass spectroscopy (HPLC -MS) is one of the most widely applied hyphenated techniques because MS is more compatible with high performance-liquid chromatography (HPLC), and has good sensitivity compared with nuclear magmatic resonance (NMR) or IR. It is also possible to connect infrared spectrometers with thermal analyzers, the methods used by thermal analysis give information about the important temperature to study the physical properties of different materials. However, it is not always possible to obtain information about the chemical changes that occur as a result of changes in temperature through the literature. We note that it is possible to link the thermal analyzer with an infrared spectrometer in order to obtain information about the chemical and physical changes that occur at different and more appropriate temperatures. More suitable is the connection between thermogravimetric analysis (TGA) and FTIR spectroscopy However, there are limitations in its analytical use. The more advantages of the hyphenated technique include sensitivity, accuracy, speed, and applicability [7, 22].

3.1 Gas chromatography–infrared (GC-IR)

3.1.1 Difficulties in the combination of GC-IR

In the development of joining the IR technique with GC, the speed of the IR must be changed to a high speed so that the unknown components can enter at the same speed from the GC column, in this case, there is a loss of efficacy and the results are not complete. The best way to solve the connecting problem is that the condensation of the gas that comes out from the column and the process is not easy, it must collect all gas eluted because it contains the component and the gas is collected in a cooled part that converts the gas into a liquid because the infrared technique deals with the liquid solutions. Reentry GC technique combined with Fourier transform infrared to give faster and more accurate technique.

3.1.2 Application

Salerno, et al (2020) suggest an accurate method for determination of illicit drugs via gas chromatography–Fourier transform infrared spectroscopy. According to the increasing number of synthetic molecules that can be used in the illicit drug market, correspondingly they require strong separation and sophisticated analytical techniques. It can be achieved by spectroscopic measurements, using firstly a gas chromatography (GC) technique as the separation device. Then the GC is coupled with FTIR to give a powerful tool. In the current study, the efficacy of GC-FTIR, in achieving elucidation of the structure of 1-pentyl-3(1-naphthyl) indole, known as JWH-018, a synthetic cannabinoid whose components have been identified as being a component of non-incense “incense blends” have been demonstrated in the current study. Moreover, it was quantified with an estimation range on the nano-gram scale. It was obtained in the range of 20–1000 ng, the detection limit and the quantification limit were evaluated to be 4.3 and 14.3 ng, respectively. Finally, the new technique was applied to quantify the activity in the “ST” sample." A real drug seized by law enforcement officers, consisted of a herbal collection containing four types of industrial cannabis belonging to the JWH class. Correct estimation of this type of compound showed that they are chemically similar to each other. The usefulness of the proposed method of analysis using related techniques. It obtains reliable results for complex mixtures of illegal drugs and is a widely applicable alternative to measurement using mass spectrometry [23].

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4. Conclusions

Infrared is an important technique and its main application at the beginning to identify polar organic compounds that have a dipole moment. The infrared device has been developed, and we have obtained Fourier transform infrared (FTIR) technique, which is characterized by high accuracy, high sensitivity, and speed of analysis of the compound as a whole. The uses of the technique in the qualitative analysis are identifying the effective groups and the type of bonds between the different atoms constituting the molecule. The technique is used in the quantitative analysis through measurement of absorption or percentage of transmittance (proportional with co

Hi Tuhin,

I was just checking on the internet how to normalize PL emission spectra based on different abs. of samples. I found your answer to some questions. This seems correct to me. But in the past to match the concentration between different samples, I always divide the emission intensity with absorbance at the excitation wavelength. You have mentioned dividing the emission spectra by {1-10^(-Absorbance)} as compared to absorbance only. Which one is correct and can we have a citation for this in any reference or book?

Thanks and regards,

Manoj

Hi, Sudipta, have you did that Elliott fitting successful? I recently also wanted to do an Elliott fitting, but i do not know how to conduct it. Can you give me some advice or comments?

Fairly common effect. Often due to resonance issues. Take a look at graphene Raman spectra - well documented changes with excitation frequency. However, it doesn't look like you have much change in the figures that couldn't just be sample prep issues.

When you change the excitation wavelength, you change the cross sections and thus sensitivity for the corresponding photoelectron emission energies.

So if you're thinking about e.g. switching between Mg and Al excitation which would be the most common in XPS, you can check cross section tables, e.g. the classical Scofield or Yeh/Lindau tables, whether the line you're interested in would loose sensitivity in a substantial manner.

If these do not indicate that you would run into difficulties, switching the emitter metalfor better separation between your desired emission bands and the Auger bands definitely makes sense.

Well, atomic (at) and weight (wt) percentages are different numbers and it makes a difference whether you are providing a stoichiometry or mass ratio.

Since these can be calculated from each other, providing one usually is sufficient, but it has to be provided what it is.

For general advice on handling multiple OPUS files and performing PCA analysis in FTIR spectra, you might want to check the user manual or documentation provided by the software. However, if you're unable to find specific guidance for your software, here are some general suggestions:

Why don't you try correcting the original light intensity (Rsc) and sample (Ssc) spectra rather than their ratio (ATR)?

For hydrogen bonding you need OH or NH groups. The bands are more likely due to structural symmetry or asymmetry. Looking at ref spectra of Acetone (1) the higher band is seen as a shoulder, not easily explained other than small methyl molecules do have prominent normally weak bands (Fermi resonance ?) There is a danger in looking at expanded short areas of spectra without seeing the full spectrum. I would have guessed that the doublet in the diones was due to symmetric and asymmetric stretching of he carbonyls. However a Aldrich reference spectrum of 2,4-pentadione shows a small doublet at 1700cm-1 but the strongest broad band is at 1630 cm-1 and other bands in the 3200- 2000 cm-1 also indicate OH. Other diketones are similar. This implies that the diketones actually have an enol structure. You need to see the full spectra to try to make sense of the published short spectra.

Thomas is correct. However 150% transmittinace is the equivalent of negative absorbance,. What it means in practice is that the ATR element was not clean when you recorded the background. There is/was something on the crystal nt present in your sample. Unless the peaks is CO2 which again is the difference between background and sample spectra.

Thank you Milena Nakagawa de Arruda Ma'am, Thank you Muhammad Shoaib sir.

sir, but I have a powder sample. Is the above equation is applicable in my case?

Actually, my recommendation would be not to use Peakfit or something like that except if you are sure that you have only weak oscillators in your material. In particular when you are dealing with inorganic materials, you should use something like RefFIT (https://reffit.ch/) to determine the damping constant instead (which is identical with FWHM for weak oscillators). It is free of charge and a manual is available.

It is possible to fully correct ATR spectra, see, e.g.,

However, you have to keep in mind that there is, strictly speaking, no such thing as IR-absorbance (FT is just a recording technique). What you probably mean are transmittance-absorbance spectra (-log₁₀T), but those do also not reflect (no pun intended... ;-) IR-absorbance. Instead you have to determine the absorption index function (the imaginary part of the complex refractive index function) to obtain the true absorbance, see, e.g., or

Are the signals from the protein itself or from something else?

The subtraction doesn't always remove the protein signals completely, and in that case you can use one of the pulse sequences that uses a spin lock to destroy the protein signals. On Bruker systems these are the std pulse sequences ending in .3

If the signals are from something else, you could try to run a cpmg experiment or similar to see what they might be.

silver nitrate are 99.8% pure and its SPR spectra appear at 300nm and teir nps appear at 210nm.

Anisotropic g tensor maybe? g(X) different g(y) different g(z), try orienting the crystal in different directions.

Dear Abhishek Srivastava,

What do you mean by a blocking electrolyte and a line at 45°C?

Why would you add a baseline to the absorbance? Maybe I lack imagination, but I cannot see under which circumstances this could make sense in case of real samples/materials...

Dear Dr. Usha Pandey ,

as you surely known, the EIS technique is a very useful method used for monitor coated systems during accelerated tests involving, for example, the increase of temperature of the electrolyte or scribing the surface of the coating, exposing a portion of the metal surface to an aggressive environment or environmental cycle.

For more details, please see the source:

Evaluating organic coating performance by EIS: Correlation between long-term EIS measurements and corrosion of the metal substrate

Vincenzo Bongiorno, Emmanouela Michailidou, Michele Curioni

Materials and Corrosion, 1–18 (2023)

Available at: https://onlinelibrary.wiley.com/doi/full/10.1002/maco.202313863

My best regards, Pierluigi Traverso.

Dear all, first be sure that the substance has an absorption within UV-Vis domain. If the maximum absorption is known from literature for example, then the corresponding concentration is deducible from Beer-Lambert law. My Regards

For beta carotene

Food Sci. Biotechnol. 24(1): 117-124 (2015) DOI 10.1007/s10068-015-0017-z

Characterization and Antioxidant Potential of a Carotenoid from a Newly Isolated Yeast

For Betanin

Betanin: A Red-Violet Pigment - Chemistry and Applications Deepak Devadiga and T.N. Ahipa

For anthocyanin

Optimization of enzyme aided extraction of anthocyanins from Prunus nepalensis L.