Second-derivative IR Research Articles

One-dimensional convolutional neural networks with infrared spectroscopy for classifying the origin of printing paper

Herein, the challenge of accurately classifying the manufacturing origin of printing paper, including continent, country, and specific product, was addressed. One-dimensional convolutional neural network (1D CNN) models trained on infrared (IR) spectrum data acquired from printing paper samples were used for the task. The preprocessing of the IR spectra through a second-derivative transformation and the restriction of the spectral range to 1800 to 1200 cm-1 improved the classification performance of the model. The outcomes were highly promising. Models trained on second-derivative IR spectra in the 1800 to 1200-cm-1 range exhibited perfect classification for the manufacturing continent and country, with an impressive F1 score of 0.980 for product classification. Notably, the developed 1D CNN model outperformed traditional machine learning classifiers, such as support vector machines and feed-forward neural networks. In addition, the application of data point attribution enhanced the transparency of the decision-making process of the model, offering insights into the spectral patterns that affect classification. This study makes a considerable contribution to printing paper classification, with potential implications for accurate origin identification in various fields.

Simultaneous Identification and Species Differentiation of Major Allergen Tropomyosin in Crustacean and Shellfish by Infrared Spectroscopic Chemometrics

To solve the lack of rapid and accurate methods for allergen identification and traceability, an infrared spectroscopic chemometric analytical model (IR-CAM) was established by combining infrared spectroscopy with principal component and cluster analysis. By comparing the second derivative infrared (SD-IR) spectra of 5 proteins and 14 crustaceans and shellfish tropomyosin (TM), 8 shared peaks and unique fingerprint peaks in the amide III region were found for crabs, shrimps, and shellfish. Based on the unique fingerprint peaks coexisting with shared peaks, allergen TM in crustaceans and shellfish could be identified within 10 min (cf. ELISA ∼ 4 h). Concurrently, the species differentiation of TM at the Class/Family level was achieved based on IR-CAM. Validation by fermented aquatic products TM (n = 60) demonstrated that the developed IR-CAM could simultaneously identify and differentiate TM in crustaceans and shellfish accurately. It could be applied for allergen detection and traceability of aquatic products on an antibody-free basis.

Application of FT-IR spectroscopy and chemometric technique for the identification of three different parts of Camellia nitidissima and discrimination of its authenticated product.

Camellia nitidissima C.W. Chi is a golden camellia recognized in Chinese herbology and widely used as tea and essential oil in Chinese communities. Due to its diverse pharmacological properties, it can be used to treat various diseases. However, unethical sellers adulterated the flower with other parts of Camellia nitidissima in their product. This study used an integrated tri-step infrared spectroscopy method and a chemometric approach to distinguish C. nitidissima’s flowers, leaves, and seeds. The three different parts of C. nitidissima were well distinguished using Fourier transform infrared spectroscopy (FT-IR), second-derivative infrared (SD-IR) spectra, and two-dimensional correlation infrared (2D-IR) spectra. The FT-IR and SD-IR spectra of the samples were subjected to principal component analysis (PCA), PCA-class, and orthogonal partial least square discriminant analysis (OPLS-DA) for classification and discrimination studies. The three parts of C. nitidissima were well separated and discriminated by PCA and OPLS-DA. The PCA-class model’s sensitivity, accuracy, and specificity were all >94%, indicating that PCA-class is the good model. In addition, the RMSEE, RMSEP, and RMSECV values for the OPLS-DA model were low, and the model’s sensitivity, accuracy, and specificity were all 100%, showing that it is the excellent one. In addition, PCA-class and OPLS-DA obtained scores of 27/32 and 26/32, respectively, for detecting adulterated and other TCM reference flower samples from C. nitidissima. Combining an infrared spectroscopic method with a chemometric approach proved that it is possible to differentiate distinct sections of C. nitidissima and discriminate adulterated samples of C.nitidissima flower.

Fourier-Transform Infrared Spectroscopy for Discrimination of Cynomorium songaricum Inflorescence Samples from Different Origins

Cynomorium songaricum Rupr. has been used as a medicinal tonic in China for thousands of years. The Fourier-transform infrared (FT-IR) spectroscopy and second-derivative infrared (SD-IR) spectroscopy were used to study 200 samples of C. songaricum inflorescence collected at 20 sites in four different regions. A resemblance was found among the FT-IR spectra of samples from different origins and developed an IR fingerprint spectrum. The main absorption peaks in the range 1800-1200 cm-1 suggests that C. songaricum inflorescences may be rich in phenolic compounds, proteins and flavonoids. The SD-IR spectra of samples from different origins revealed an obvious intensity differences for peaks in the range 1800-1200 cm-1, especially for samples from Gansu province of China. An origin discrimination model based on principal component analysis is established. The prediction accuracy of the model is 87.25%. The results indicated that our origin discrimination model can differentiate production areas for C. songaricum.

Curing mechanism of triglycidylamine crosslinked soybean protein adhesive analyzed by Fourier transform infrared, second derivative infrared and two-dimensional correlation spectroscopy

Triglycidylamine (TGA) modified soybean protein isolate (SPI) adhesive can increase the bonding strength of soy protein and improve its utilization. In order to study the chemical changes of TGA modified SPI adhesives during the heating process, the curing mechanism of soybean protein adhesives was studied by Fourier transform infrared (FTIR), second derivative infrared (SDIR) and two-dimensional correlation spectroscopy (2D-COS). With the increase of temperature, there were significant differences in the absorption peaks at 1075 cm−1, 1169 cm−1, 1390 cm−1, 1735 cm−1 indicating the active functional groups bared and reacted in the modified SPI, which formed hydrophobic ester, amide groups. Besides, some functional groups were dismissed or weakened such as N–H and –CH2- at 3440 cm−1 and 2847 cm−1 respectively. The epoxy ring of TGA opened to cross-link with the amino and hydroxyl groups within the molecular structure of SPI. The addition of TGA can effectively improve the molecular weight of soybean protein and form a network structure, which provides a method for improving the performance of a soybean protein adhesive.

RAPID INVESTIGATION OF THE METABOLITE CONTENT IN HIBISCUS SABDARIFFA var. UKMR-2 CULTIVATED UNDER THE INFLUENCE OF ELEVATED CO2 USING TRI-STEP FT-IR SPECTROSCOPY

Rapid methods based on untargeted analysis technique such as Fourier Transform Infrared (FT-IR) spectroscopy can provide much faster and easier solution for food authentication. However, studies on the metabolite content in UKMR-2 calyces using FT-IR spectroscopy has not been reported yet in any previous studies. Thus, the present study was performed to analyze the differences in metabolite content in UKMR-2 calyces under the influences of different [CO2] treatment by applying tri-step infrared based fingerprinting. The UKMR-2 plant cultivation was exposed to ambient [CO2] (400 µmol/mol) and elevated [CO2] (800 µmol/mol) treatment. The UKMR-2 calyx extracts were analysed by conventional infrared (1D-IR), second derivative infrared (SD-IR) and two-dimensional correlation infrared (2D-IR) spectroscopy. The 1D-IR spectrum results revealed a similar absorption spectrum in the range of 1900 - 650 cm-1, which suggest similar major metabolites content present in both extracts. For SD-IR spectrum, both treatments clearly showed have more peaks with different shape, position and intensity in the range of 1650 - 1450 cm-1 and 1200 - 950 cm-1, which is likely to have different flavonoid and carbohydrate content in UKMR-2 calyces. The 2D-IR synchronous correlation spectrum in the range of 1000 – 650 cm-1 clearly distinguished the metabolite content in the UKMR-2 calyx extract from different [CO2] treatment. Therefore, this tri-step infrared based fingerprinting has the potential as one of the effective methods to discriminate extract samples with similar infrared fingerprint features and indicate that the metabolite content in UKMR-2 calyces were influenced by different [CO2] treatments.

Insights into antibacterial mechanism of Apocynum Venetum L. fiber: Evolution of bioactive natural substances in bast during chemical degumming process

There is an increasing interest in the study of biomass-derived cellulosic fiber. Apocynum venetum L. (A. venetum) is considered as a promising source for functional fiber. The antibacterial activity of textiles made from A. venetum fibers has been validated by fabrics testing, but the underlying antibacterial mechanism is still obscure. Here, a hypothesis of transformation and deposition was presented to explain the mechanism of antibacterial activity of A. venetum technical fiber. An in vitro experiment was designed and performed to simulate the chemical reaction pathway of antibacterial substances in the bast of A. venetum undergoing chemical degumming process. Chemical compositions and antibacterial properties of polyphenols and A. venetum bast, before and after the process were measured and analyzed. Results showed that water-soluble polyphenols became insoluble after alkaline degumming treatment at high temperature. MALDI-TOF spectrometry analysis also revealed the formation of oligomers from quercetin. Structural consistency between the insoluble product and A. venetum fiber was confirmed by second derivative infrared (SD-IR) and Raman spectroscopy. While, the resulting derivatives had significant antibacterial activity toward the assayed microorganisms in broth dilution tests. This investigation of transformation behavior of polyphenols provided new insights into material basis of A. venetum fiber for antibacterial property.

Fast Screening and Primary Diagnosis of COVID-19 by ATR FT-IR

Background: The outbreak of coronavirus disease 2019 (COVID-19) has led to substantial infections and mortality around the world. Fast screening and diagnosis are thus crucial to quick isolation and clinical intervention. Methods: Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A/B, and respiratory syncytial virus (RSV), as well as healthy controls, were included in this study. All viral infections were confirmed by reverse transcriptase PCR (RT-PCR). The serum samples were measured by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR). Multivariate and statistical analysis was performed to differentiate between or among groups. Findings: We found that the most discriminatory bands for COVID-19 vs. control classification were amide I, amide II, and νs(PO2−) in original spectra and centered at 1632, 1545, 1400, 1079, and 1037 cm-1 in the second derivative infrared (SD-IR) spectra. Normal controls, non-severe, and severe COVID-19 patients were well separated by unsupervised methods. ATR FT-IR coupled with partial least square discriminant analysis (PLS-DA) was effective to differentiate COVID-19 from normal controls and other respiratory viral infections with the area under the receiver operating characteristic curve (AUROC) of 0·9866 (95%CI 0·9721-0·9939). Interpretation: The band centered at 1633 cm-1 in the SD-IR spectra is mainly attributed to the β-pleated sheet structure from immunoglobulins. Increases in antibody levels and dysregulation of phospholipids can be derived from the measured spectra. The serum FT-IR spectra exhibited “chemical fingerprints” towards different viral infections.Funding Statement: This work was funded by the National Natural Science Foundation of China (52041701).Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: This study was approved by the Ethics Committees from TsinghuaUniversity and Peking Union Medical College Hospital.

Combined Application of Fourier-transform Infrared, Second Derivative Infrared, and Two-dimensional Correlation Infrared Spectroscopy to Monitor the Quality of Dendrobium Huoshanense During Processing

The objective of this study was to develop a multi-steps infrared macro-fingerprint method to discriminate Dendrobium huoshanense “Fengdou” (DHS FD) produced under different toasting and soaking conditions as well as to examine the effect of production conditions on the total polyphenol content, total water soluble polysaccharide content, and antioxidant activities. The results showed that though the Fourier transform infrared and second derivative infrared (SD-IR) spectra of the DHS FD processed under different conditions were similar visually, the DHS FDs could be discriminated by their characteristic peaks in the range of 1800–600 cm–1 from their IR and SD-IR files and the cross-peaks in the region of 1280–950 cm–1 in their two-dimensional correlation spectroscopy IR spectra. The total polyphenol content increased and the total water soluble polysaccharide content decreased in the DHS FDs toasted at temperatures from 110°C to 190°C for 30 min. Soaking process showed variable effects on the total polyphenol content and total water soluble polysaccharide content. The total polyphenol content of the DHS FDs toasted below 150°C increased as the soaking temperatures increased while the total water soluble polysaccharide content showed an opposite trend. Both the total polyphenol content and total water soluble polysaccharide content of the DHS FDs toasted at 170°C and 190°C showed little difference when soaking temperatures varied from 4°C to 100°C. The investigation of the 2,2-Diphenyl-1-picrylhydrazyl cleaving activity revealed that toasting and soaking process might increase the antioxidant activity of the DHS while too high toasting temperatures would decrease their activity. The multi-steps infrared macro-fingerprint analysis with high resolution and excellent macroscopic fingerprint features could effectively discriminate the DHS produced under different conditions without involving any separation and extraction. Consequently, the use of this method is recommended for quality control of the DHS FD.

Multilevel profiling and identification of Dalbergia odorifera and Dalbergia stevensonii by FTIR, NMR and GC/MS

As a rare and valuable wood and herbal material, Dalbergia odorifera is often counterfeited by Dalbergia stevensonii in the market. For the confident chemical identification of D. odorifera and D. stevensonii, the ethanol-benzene extractives are characterized by multiple metabolomics tools, including Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometry (GC/MS). Conventional FTIR spectroscopy, second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared (2D-IR) spectroscopy are combined to interpret the functional groups of the ethanol-benzene extractives. Fingerprint-like characteristics make FTIR a rapid and accurate method to distinguish D. odorifera from D. stevensonii. Chemical differences of the extractives revealed by FTIR methods can be further confirmed by 1H NMR and 13C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS. The combination of FTIR, NMR and GC/MS makes it possible to obtain the multiple profiles of the ethanol-benzene extractives, which is essential for the confident chemical identification of D. odorifera and D. stevensonii.

Vasorelaxation Study and Tri-Step Infrared Spectroscopy Analysis of Malaysian Local Herbs.

Objectives:The aim of this paper is to investigate the activities of Malaysian local herbs (Clinacanthus nutans Lindau, Strobilanthes crispus, Murdannia bracteata, Elephantopus scaber Linn., Pereskia bleo, Pereskia grandifolia Haw., Vernonia amygdalina, and Swietenia macrophylla King) for anti-hypertensive and vasorelaxant activity. An infrared (IR) macro-fingerprinting technique consisting of conventional fourier transform IR (FTIR), second-derivative IR (SD-IR), and two-dimensional correlation IR (2D-correlation IR) analyses were used to determine the main constituents and the fingerprints of the Malaysian local herbs.Methods:The herbs were collected, ground into powder form, and then macerated by using three different solvents: distilled water, 50% ethanol, and 95% ethanol, respectively. The potentials of the extracts produced from these herbs for use as vasorelaxants were determined. Additionally, the fingerprints of these herbs were analyzed by using FTIR spectra, SD-IR spectra, and 2D-correlation IR spectra in order to identify their main constituents and to provide useful information for future pharmacodynamics studies.Results:Swietenia macrophylla King has the highest potential in terms of vasorelaxant activity, followed by Vernonia amygdalina, Pereskia bleo, Strobilanthes crispus, Elephantopus scaber Linn., Pereskia grandifolia Haw., Clinacanthus nutans Lindau, and Murdannia bracteata. The tri-step IR macro-fingerprint of the herbs revealed that most of them contained proteins. Pereskia bleo and Pereskia grandifolia Haw. were found to contain calcium oxalate while Swietenia macrophylla King was found to contain large amounts of flavonoids.Conclusion:The flavonoid content of the herbs affects their vasorelaxant activity, and the tri-step IR macro- fingerprint method can be used as an analytical tool to determine the activity of a herbal medicine in terms of its vasorelaxant effect.

Identification of the traditional Tibetan medicine “Shaji” and their different extracts through tri-step infrared spectroscopy

Hippophae rhamnoides subsp. sinensis Rousi, Hippophae gyantsensis (Rousi) Y. S. Lian, Hippophae neurocarpa S. W. Liu & T. N. He and Hippophae tibetana Schlechtendal are typically used under one name “Shaji”, to treat cardiovascular diseases and lung disorders in Tibetan medicine (TM). A complete set of infrared (IR) macro-fingerprints of these four Hippophae species should be characterized and compared simply, accurately, and in detail for identification. In the present study, tri-step IR spectroscopy, which included Fourier transform IR (FT-IR) spectroscopy, second derivative IR (SD-IR) spectroscopy and two-dimensional correlation IR (2D-IR) spectroscopy, was employed to discriminate the four Hippophae species and their corresponding extracts using different solvents. The relevant spectra exhibited the holistic chemical compositions and variations. Flavonoids, fatty acids and sugars were found to be the main chemical components. Characteristic peak positions, intensities and shapes derived from FT-IR, SD-IR and 2D-IR spectra provided valuable information for sample discrimination. Principal component analysis (PCA) of spectral differences was performed to illustrate the objective identification. Results showed that the species and their extracts can be clearly distinguished. Thus, a quick, precise and effective tri-step IR spectroscopy combined with PCA can be applied to identify and discriminate medicinal materials and their extracts in TM research.

Rapid Discrimination of Different Grades of White Croaker Surimi by Tri-Step Infrared Spectroscopy Combined with Soft Independent Modeling of Class Analogy (SIMCA)

White croaker surimi, an important raw material of traditional kamaboko industry, commonly has four grades, A, AA, FA, and SA which have distinct quality but are tough to be identified and discriminated rapidly and holistically by conventional methods. A Tri-step infrared spectroscopy, Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared (SD-IR) spectroscopy, and two-dimensional correlation infrared spectroscopy (2DCOS-IR), combined with statistical pattern recognition, was employed to rapidly characterize and discriminate four grades of white croaker surimi (A, AA, FA, and SA). The four surimis had similar IR, and SD-IR macro-fingerprints (similarity >0.9) especially for the absorption bands of amide groups due to proteins were the main compositions. However, relative contents of lipids in all surimis could be directly observed. Compared to the other three surimis, SA had a middle strong characteristic peak of lipids at 1745 cm−1, indicating that SA had the highest content of lipids. The sequence of lipid contents in the four surimis was SA > FA > AA > A, which was further verified by SD-IR spectra. Moreover, evident differences were disclosed visually in 2DCOS-IR spectra of 1680–1610 cm−1, indicating that the four surimis have fine differences in protein secondary structures. Furthermore, 76 parallel samples (18 A, 19 AA, 19 FA, and 20 SA) were objectively classified by soft independent modeling of class analogy (SIMCA) based on principal component regression (PCR). It has been demonstrated that the Tri-step infrared spectroscopy combined with cluster analysis could be a scientific and powerful tool for rapid discrimination and identification of different grades of surimi in a holistic manner.

Rapid discrimination of three marine fish surimi by Tri-step infrared spectroscopy combined with Principle Component Regression

A Tri-step infrared spectroscopy (Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared spectroscopy (2DCOS-IR)) combined with Principal Component Regression (PCR) were employed to characterize and discriminate three marine fish surimi (white croaker surimi (WCS), hairtail surimi (HS) and red coat surimi (RCS)). The three surimi had similar IR macro-fingerprints (similarity>0.7) especially for the absorption bands of amide groups. Compared to the other two surimi, however, RCS had a middle strong characteristic peak of lipids at 1745cm−1, indicating that RCS had the highest content of lipids. SD-IR spectra of the three surimi enhanced the spectral resolution and amplified the small differences, especially at about 1682cm−1, 1679cm−1, 1656cm−1 and 1631cm−1, suggesting that the three had different profiles of proteins. Moreover, evident differences were observed in 2DCOS-IR spectra of 1500–1800cm−1. WCS had one strong (1620cm−1) and three weak auto-peaks (1520cm−1, 1552cm−1, 1706cm−1). HS had three strong (1621cm−1, 1648cm−1, 1708cm−1) and two weak auto-peaks (1523cm−1, 1553cm−1), whereas RCS had one strong (1623cm−1) and three weak auto-peaks (1525cm−1, 1709cm−1, 1738cm−1). Furthermore, sixty batches of surimi (twenty for each surimi) were objectively classified by PCR. It was demonstrated that the Tri-step infrared spectroscopy combined with PCR could be applicable for discrimination of precious marine fish surimi in a direct, rapid and holistic manner.

Identification of some Piper crude drugs based on Fourier transform infrared spectrometry

The common peak ratio and variant peak ratio were calculated by FTIR spectroscopy of seven medicinal plants of Piper. The dual index sequence of common peak ratio and variant peak ratio was established, which showed the sibship of the medicinal plants. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper wallichii (Miq.) Hand.-Mazz. Piper laetispicum (C. DC.) was greater than 77%, and the variant peak ratio was less than 30%. The results showed the near sibship between the three drugs. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper nigrum L. and Piper boehmeriae folium Wall (Miq.) C. DC. Var. tonkinense (C. DC.) was about 61% which showed the farther sibship. The common peak ratio of Piper kadsura (Choisy) Ohwi and Piper betle (Linn.) was only 44%, which showed the farthest sibship. Piper kadsura (choisy) Ohwi and its adulterants, such as Piper wallichii (Miq.) Hand. -Mazz., Piper boehmeriaefolium Wall (Miq.) C. DC. Var. tonkinense C. DC. , Piper laetispicum C. DC., Piper nigrum L., could be identified by comparing their second order derivative IR spectrum of the samples. FTIR technique is a non-destructive analysis method which provides information of functional group, type and hydrogen bond without complex pretreatment procedures such as extraction and separatioin. FTIR method has some characteristics such as rapid and simple analysis procedure, good reproducibility, non-destructive testing, few amount of required sample and low cost and is environment-friendly. The method solved the problems of limit in resource of Piper kadsura (Choisy) Ohwi, many fakes and difficulties in identification, and brought the security for the clinical medication. FTIR provides a new method for identification of Piper kadsura (choisy) Ohwi and its fakes and meets the requirement for comprehensive analy sis and global analysis of traditional Chinese medicine.

Macro-fingerprint analysis-through-separation of licorice based on FT-IR and 2DCOS-IR

In this paper, a step-by-step analysis-through-separation method under the navigation of multi-step IR macro-fingerprint (FT-IR integrated with second derivative IR (SD-IR) and 2DCOS-IR) was developed for comprehensively characterizing the hierarchical chemical fingerprints of licorice from entirety to single active components. Subsequently, the chemical profile variation rules of three parts (flavonoids, saponins and saccharides) in the separation process were holistically revealed and the number of matching peaks and correlation coefficients with standards of pure compounds was increasing along the extracting directions. The findings were supported by UPLC results and a verification experiment of aqueous separation process. It has been demonstrated that the developed multi-step IR macro-fingerprint analysis-through-separation approach could be a rapid, effective and integrated method not only for objectively providing comprehensive chemical characterization of licorice and all its separated parts, but also for rapidly revealing the global enrichment trend of the active components in licorice separation process.

Rapid identification of Pterocarpus santalinus and Dalbergia louvelii by FTIR and 2D correlation IR spectroscopy

Since Pterocarpus santalinus and Dalbergia louvelii, which are of precious Rosewood, are very similar in their appearance and anatomy characteristics, cheaper Hongmu D. louvelii is often illegally used to impersonate valuable P. santalinus, especially in Chinese furniture manufacture. In order to develop a rapid and effective method for easy confused wood furniture differentiation, we applied tri-step identification method, i.e., conventional infrared spectroscopy (FT-IR), second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared (2DCOS-IR) spectroscopy to investigate P. santalinus and D. louvelii furniture. According to FT-IR and SD-IR spectra, it has been found two unconditional stable difference at 848cm−1 and 700cm−1 and relative stable differences at 1735cm−1, 1623cm−1, 1614cm−1, 1602cm−1, 1509cm−1, 1456cm−1, 1200cm−1, 1158cm−1, 1055cm−1, 1034cm−1 and 895cm−1 between D. louvelii and P. santalinus IR spectra. The stable discrepancy indicates that the category of extractives is different between the two species. Besides, the relative stable differences imply that the content of holocellulose in P. santalinus is more than that of D. louvelii, whereas the quantity of extractives in D. louvelii is higher. Furthermore, evident differences have been observed in their 2DCOS-IR spectra of 1550–1415cm−1 and 1325–1030cm−1. P. santalinus has two strong auto-peaks at 1459cm−1 and 1467cm−1, three mid-strong auto-peaks at 1518cm−1, 1089cm−1 and 1100cm−1 and five weak auto-peaks at 1432cm−1, 1437cm−1, 1046cm−1, 1056cm−1 and 1307cm−1 while D. louvelii has four strong auto-peaks at 1465cm−1, 1523cm−1, 1084cm−1 and 1100cm−1, four mid-strong auto-peaks at 1430cm−1, 1499cm−1, 1505cm−1 and 1056cm−1 and two auto-peaks at 1540cm−1 and 1284cm−1. This study has proved that FT-IR integrated with 2DCOS-IR could be applicable for precious wood furniture authentication in a direct, rapid and holistic manner.

Differentiation of Rhizoma Curcumas Longae and Radix Curcumae by a Multistep Infrared Macro-Fingerprint Method

A multistep infrared macro-fingerprint method was applied to identify two Chinese herbal drugs, Rhizoma Curcumas Longae (RCL) and Radix Curcumae (RC). Fourier transform infrared (FT-IR) spectra of the two were similar to each other and consistent with the 11 peaks of the spectrum of starch. RCL had a characteristic absorption peak at approximately 1514 cm−1 that correlated to the strong peak near 1509 cm−1 of curcumin. Between 900 cm−1–1700 cm−1 of the second derivative infrared (SD-IR) spectra, with higher resolution, RCL, and curcumin had 10 common peaks. In the FT-IR and SD-IR spectra of the ethanol extract, the spectra of the RCL extract and curcumin were similar, but RC was different. According to the fingerprint characteristics of the infrared spectra for RC and its extracts, the strongest peak at 1055 cm−1; the C-O absorption peaks at 1124 cm−1, 1106 cm−1, and 996 cm−1; and the strong methylene peaks at 2925 cm−1 and 2853 cm−1 suggest that RC contains more saccharides. In the range of 1350 cm−1–1700 cm−1, RCL and RC had similar two-dimensional infrared (2D-IR) correlation spectra. Both of them had three autopeaks, but the autopeaks were located at 1458 cm−1, 1560 cm−1, and 1641 cm−1 for RCL and 1458 cm−1, 1560 cm−1, and 1669 cm−1 for RC, suggested that the aromatic components of the two were not identical. The average correlation for the 18 RCL and 18 RC samples were 0.9906 and 0.9878, respectively, and this method achieves a good classification of the sample type.

Study on Light Aging of Silk Fabric by Fourier Transform Infrared Spectroscopy and Principal Component Analysis

To investigate environmental effect on cultural materials, Fourier transform infrared technique (FTIR/ATR) was applied to analyze the silk aging process. Changes in chemical and conformational structures of silk fabric undergoing ultraviolet induced degradation were investigated. The IR spectra provided strong bands of photosensitive amide I, II, and III. For overlapping amide III region, both of the original and second-derivative IR spectra revealed that UV irradiation induced the structural transformation from β-sheet domain to β-turn conformation, which was supported by the increase of β-turn marker band at 1015 cm−1 associated with polyglycine. Additionally the reduced bands associated with (GlyAla)n segment at 1000 and 976 cm−1, and the decreased band at 1070 cm−1 related to β-sheet structure also illustrated the conformational transition. Furthermore, we applied a chemometric method of principal component analysis for the evaluation of silk degradation based on variations in amide I spectral region. The score plot using the first two principal components effectively summarized the general trend of silk-aging and revealed the quick degradation appeared in the initial stages (12 h and 24 h) and the 108-hr stage. This work provides a potential novel application of the infrared spectroscopy in noninvasive qualitative and quantitative investigation of silk degradation.

Structure of 4-(trimethylammonium)benzoate hydrate studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra

► X-ray, DFT, FTIR, NMR of 4-(trimethylammonium)benzoate hydrate. ► Water molecule interacts with two 4-(trimethylammonium)benzoate molecules. ► The molecular structure is stabilized by hydrogen bonds and electrostatic interactions. The structure of 4-(trimethylammonium)benzoate hydrate ( 1 ) has been studied by X-ray diffraction, B3LYP/6-311++G(d,p) calculations, FTIR and NMR spectroscopic techniques. The crystals are monoclinic, space group P 2 1 /c. Water molecule interacts with two 4-(trimethylammonium)benzoate molecules via two O(1w)–H⋯O hydrogen bonds of the lengths 2.781(2) and 2.774(2) Å. The FTIR spectrum of the solid compound is consistent with the X-ray results. The second-derivative IR spectrum of 1 and calculated frequencies for the optimized structure 2 are used to explain frequencies in the experimental FTIR spectrum. The interpretation of 1 H and 13 C NMR spectra have been based on 2D experiments and calculated GIAO/B3LYP/6-311++G(d,p) magnetic isotropic shielding constants. Interesting are dimer structures ( 6 and 7 ) estimated by B3LYP/6-311++G(d,p) calculations, which are stabilized by N + ⋯O–C electrostatic interactions.