Vibrational Spectroscopy最新文献

The polymorphism of drugs exists widely in solid chemical drugs. It will affect the physical and chemical properties of drugs, as well as bioavailability. So it is very necessary to establish an quantitative method to improve the quality control level of polymorphic drugs. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and Raman spectra have been included in many countries’ pharmacopoeia as the drug polymorph analytical technique, and they have many unique advantages. However, for multiple mixed systems, due to the complexity of optical signals, it is difficult to obtain an ideal content prediction model by classical linear regression, so the application of chemometric methods shows advantages. Pyrazinamide is a typical polymorphism drug, three polymorphic forms (α, δ, γ) were obtained. The model prediction ability of two kinds of spectroscopy combined with three kinds of stoichiometric methods was investigated by orthogonal experiment. On this basis, the influence of different combinations of five data preprocessing methods on improving modeling quality was investigated. In this research, Raman spectra combined with partial least squares (PLS), multiplicative scatter correction (MSC), denoise, median and first derivative at the whole spectral range resulted in a better calibration model. It had a RMSEP of 5.3%, 21.6%, and 20.8% for polymorphs α, δ, and γ, respectively. Several methods were used for preprocessing the spectral data could remove unimportant baseline (offset) interference from samples or to correct scattering effects and emphasize spectral the interesting signals. PLS can derive a few components from the independent variable system. Therefore, it may be an effective method to establish a quantitative model for a multi-polymorphism component mixed system.

Explanation and prediction for the product of trehalose dihydrate dehydration process was realized in this work. β form is the thermodynamic dehydration product of trehalose dihydrate. And α form is the kinetic dehydration product of trehalose dihydrate, which was analyzed by low-frequency Raman spectra, mid-frequency Raman difference spectra and IR difference spectra, and the analysis results confirmed that the crystal structure of trehalose dihydrate and α form are similar. The selective dehydration process from trehalose dihydrate to α form is due to their similar short-range orders. Amorphous trehalose is the uncontrollable dehydration product of trehalose dihydrate due to the collapse of water channels. The dehydration product of trehalose dihydrate by freeze-drying was a mixture of α form and amorphous phase, and the content of amorphous trehalose in the freeze-drying product increases with the decrease of the particle size of dihydrate. Study on the dehydration principle of organic hydrates will guide the preparation, storage and desolvation of drugs and foods.

Stratum corneum, and epidermis, regions of human skin were analyzed in vivo using confocal Raman spectroscopy to evaluate age-related biochemical and spectral changes. The data consisted of two defined age groups comprising 71 volunteers (27 ± 3 and 55 ± 4 years old). Multivariate statistical analyses were used to interpret and classify the average spectral data for each skin layer. The analyses demonstrated the measurement of two different groups of skin with different ages and revealed the most representative peaks for both the stratum corneum and epidermis. The Amide III and Amide I, both in α-helix conformation, exhibited increased signals in the spectra of the epidermis and stratum corneum of the younger group, and it was observed that an increased crosslinking of keratin filaments with age is a potential contributor to the stiffness increment, which consequently leads to a decrease in the Raman signal in the older group. The opposite occurred for the lipids signal, as changes in the lateral packing of lipids indicate skin ageing and an increase in the Raman signal. The disparity in the means of total natural moisturizing factor, was statistically significant between the two age groups. The statistical results demonstrated the emergence of distinct groups pertaining to the epidermis and stratum corneum, as well as pertaining to group I or II.

As a dihydrochalcone natural sweetener extracted from Lithocarpus litseifolius, trilobatin is an emerging functional sweetener in the international arena in recent years and is gaining attention in the food industry. The detection of trilobatin has also gradually received the attention of researchers, however, the detection means for trilobatin still remain in the traditional high performance liquid chromatography (HPLC) and other traditional methods, which are costly and have a large detection range. In this work, a method based on the principle of surface-enhanced Raman (SERS) using a composite substrate of silver nanoparticles (Ag NPs) and covalent organic frameworks (COFs) materials is proposed for the detection of trilobatin in tea beverages. After Gaussian simulation and a series of spectral analysis methods for validation, the functionalized SERS substrates contain abundant hydroxyl groups on the surface, which can be combined with trilobatin through hydrogen bonding and greatly enhance the Raman signal of trilobatin. The specific detection of trilobatin in tea beverages has been realized and the problem of weak SERS signal of trilobatin in liquid environment has been solved. The limit of detection (LOD) of trilobatin in tea beverage was 2.8 nM, and the correlation coefficient (R²) was 0.995. The recoveries were in the range of 100.6∼106.0% with the RSD of 1.756∼4.921%. In conclusion, the experimental method is highly sensitive and specific, and can realize the nondestructive detection of trilobatin in samples with high practical value.

We report results from a study of the local structure of hydrated nanocrystalline 2 $\mu$m films of the well known proton conductor BaZr_1-xSc_xO_3-x/2 with x = 0.45, 0.54 and 0.64, using infrared (IR) spectroscopy. The films were prepared by magnetron sputtering. Analysis of the IR spectra focused on the O–H stretching region (2000—3700 cm^-1), which reveals the presence of several distinct O–H stretching bands for which the intensity and frequency of each band vary in an unsystematic manner with Sc concentration. The spectra for the two higher Sc concentrations, x = 0.54 and 0.64, exhibit a distinct, highly intense O–H stretching band centered at around 3400–3500 cm^-1, which is assigned to relatively symmetric, weakly hydrogen-bonding, proton configurations. The spectrum for the lower Sc concentration, x = 0.45, does not feature such a band but a broader, weaker, O–H stretching band between approximately 2500 and 3700 cm^-1, suggesting that the protons are more homogeneously distributed over a range of different local proton coordinations in this relatively weakly doped material. A comparison to the IR spectra of powder samples of similar compositions suggests that for x = 0.45, the spectra and proton coordination of films and powder samples are similar, whereas for x = 0.54 and 0.64, a larger fraction of protons seems to be located in weakly hydrogen-bonding proton configurations in the films compared to the respective powder samples.

As a traditional Chinese medicine, Panax notoginseng (Burk.) F.H.Chen (P. notoginseng) is abundant in chemical compounds, particularly the high content of saponin compounds, which have been extensively implemented in clinical treatment. The traditional chemical methods have drawbacks of destroying samples and taking a long time to analyze the saponin compounds content. In this study, we investigated the viability of employing Fourier transform near infrared spectroscopy (FT-NIR) to assess the saponin compounds content of P. notoginseng rapidly. The partial least squares regression (PLSR) prediction model was established based on spectral information from 252 samples. The effects of various variable selection methods, including variable importance in projection (VIP), competitive adaptive reweighted sampling (CARS), uninformative variables elimination (UVE), and correlation coefficients (Correlation) on the model performance, were compared. One examined variable selection algorithm that stood out was the correlation coefficient method. The Correlation-PLSR model’ calibration and prediction sets had a high coefficient of determination (Rc²: 0.966-0.989; Rp²: 0.968-0.999) and low root mean square error (RMSEC: 1.293-5.984; RMSEP: 0.291-1.810). It was indicated it can rapidly predict saponin compounds in P. notoginseng. This study offers a rapid and reliable quantitative method for P. notoginseng quality control.

We used Raman spectroscopy to analyze amorphous polyetherketoneketone (PEKK) and identified the conditions to obtain this material’s exploitable Raman spectrum. Our study assigns the vibrational modes observed from 100 spectra recorded on the amorphous PEKK’s surface, obtained by injection moulding. The peaks recorded on this polymer are specific to its amorphous microstructure. The vibration modes are similar to PEK and PEEK since they belong to the same family of materials, the polyaryletherketones. However, PEKK has a unique molecular structure with a ketone content of 67 % and an ether content of 33 %, resulting in an amplification or appearance of vibration modes associated with the ketone group’s vibrations and a decrease in the modes related to the ether group. This work provides a valuable database for those studying the microstructure of PEKK and its evolution with processing conditions and ageing.

This work reports the potential use of surface-enhanced Raman spectroscopy (SERS) in rapid, label-free assaying of testosterone (TE) and growth hormone (GH) in whole blood. Biomarker SERS spectral bands from the two hormones (TE and GH) in intentionally spiked water for injection and in male Sprague-Dawley (SD) rat’s blood are reported. These concentration-sensitive Raman bands as deduced through Principal Component Analysis (PCA) and Analysis of Variance (ANOVA), were centered around 1490 and 1510 cm⁻¹ for GH, 1614 and 1636 cm⁻¹ for TE; and 684 cm⁻¹ for the hormone mixture (GH+TE) in blood. These bands exhibited significant intensity changes with the concentration of GH and TE hormones in blood. They were tentatively assigned to C-C stretching (684, 786, 856, 1614 and 1636 cm⁻¹), CH₂ bending (1490 cm⁻¹) and CH₂ stretching (1510 cm⁻¹). These bands may be used in SERS assaying of the respective hormones in blood using a customized and calibrated Raman system thus utilizing the strengths of the SERS method that include, being label-free, rapid (<1 min), chemically specific, minimal sample preparation among others. Besides, the method may potentially be used in detecting abuse of TE and GH in sports where they are often abused concurrently.