Nuclear Magnetic Resonance Spectroscopy Spectra Research Articles

Chemical Composition of Organic Carbon in Tropical Soils Under Agricultural Cultivation and Peat-Swamp Forest

ABSTRACT Soil organic carbon (SOC) is important for agricultural production and from an environmental perspective. This research determined the chemical composition of SOC and studied factors related to its distribution for various crops and peat-swamp forests in the tropical region. In total, 21 topsoil samples were collected from areas of paddy rice, sugarcane, cassava, pineapple, oil palm, para rubber, and peat-swamp forest in Thailand. Four groups of SOC chemical composition were investigated (carbonyl C, aromatic C, O-alkyl C, and alkyl C) using solid-state 13C nuclear magnetic resonance spectroscopy (NMR). The dominant peak of the NMR spectra indicated that SOC originated from a variety of lignin compound units. The results revealed the dominant SOC chemical component was O-alkyl C (36.57–50.90%), followed by alkyl C (22.32–32.60%), aromatic C (16.65–23.41%), and carbonyl C (7.99–10.95%), respectively. Most of the SOC chemical components were derived from plant debris, particularly biodegraded lignin compounds. There were slightly differences between the distributions of the SOC functional groups in each vegetation type, perhaps partially as a result of the specific management activities for each crop, including tillage. Furthermore, alkyl C was related to some soil properties (silt and clay fractions), while O-alkyl C was related to available P in the soil. The hydrophobicity index, aromaticity index, and degree of humification were in the ranges 0.69–1.12, 0.17–0.23, and 0.46–0.92, respectively. These findings provided SOC chemical composition data of several economic crops to further support soil management for crop production and carbon stock preservation in tropical soils.

SPA-STOCSY: an automated tool for identifying annotated and non-annotated metabolites in high-throughput NMR spectra.

Nuclear magnetic resonance spectroscopy (NMR) is widely used to analyze metabolites in biological samples, but the analysis requires specific expertise, it is time-consuming, and can be inaccurate. Here, we present a powerful automate tool, SPatial clustering Algorithm-Statistical TOtal Correlation SpectroscopY (SPA-STOCSY), which overcomes challenges faced when analyzing NMR data and identifies metabolites in a sample with high accuracy. As a data-driven method, SPA-STOCSY estimates all parameters from the input dataset. It first investigates the covariance pattern among datapoints and then calculates the optimal threshold with which to cluster datapoints belonging to the same structural unit, i.e. the metabolite. Generated clusters are then automatically linked to a metabolite library to identify candidates. To assess SPA-STOCSY's efficiency and accuracy, we applied it to synthesized spectra and spectra acquired on Drosophila melanogaster tissue and human embryonic stem cells. In the synthesized spectra, SPA outperformed Statistical Recoupling of Variables (SRV), an existing method for clustering spectral peaks, by capturing a higher percentage of the signal regions and the close-to-zero noise regions. In the biological data, SPA-STOCSY performed comparably to the operator-based Chenomx analysis while avoiding operator bias, and it required <7min of total computation time. Overall, SPA-STOCSY is a fast, accurate, and unbiased tool for untargeted analysis of metabolites in the NMR spectra. It may thus accelerate the use of NMR for scientific discoveries, medical diagnostics, and patient-specific decision making. The codes of SPA-STOCSY are available at https://github.com/LiuzLab/SPA-STOCSY.

Development of Mucoadhesive Chitosan-Iodoacetamide Buccal Tablets for Local Delivery of Dextromethorphan

Abstract This study aimed to synthesize a chitosan (CHI) derivative, chitosan-iodoacetamide (CHI-IA), with enhanced mucoadhesive properties and develop buccal mucoadhesive tablets of CHI-IA for local delivery of dextromethorphan (DXT). Mucoadhesive CHI-IA was synthesized by a chemical reaction between CHI and iodoacetic acid (IA) in different weight ratios. The synthesized CHI-IA was characterized by Fourier-transformed infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR) to confirm the chemical structure and assure successful synthesis. DXT was selected as the model drug to be incorporated into the matrix tablet to develop mucoadhesive buccal cough relief tablets. The mucoadhesive strength of the CHI-IA tablets was determined by a texture analyzer. Moreover, the drug content and the release characteristics of DXT from the mucoadhesive tablets were evaluated. The FT-IR and NMR spectra of CHI-IA indicated the conjugation of IA on the structure of CHI. The CHI-IA tablets exhibited a 4-time increase in mucoadhesion force compared with that of unmodified CHI. Moreover, a gradual release of DXT from the tablets was observed, and the release kinetics best fit with the Higuchi model (R2 = 0.9912). Therefore, the CHI-IA could be applied as the mucoadhesive carrier system for drug delivery. Keywords: Chitosan, Iodoacetic acid, Mucoadhesive, Buccal tablets, Dextromethorphan

Synthesis, characterization, antibacterial and emulsifying properties of agar benzoate

Agar benzoate (AB) with different degrees of substitution (DS) was synthesized by the esterification of agar and benzoic anhydride in aqueous solution. The DS could be regulated by adjusting composition ratio, pH, and temperature. Its chemical structure was determined by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). 13C NMR spectrum of the AB suggested the main substitution occurred at the C-6 in the d-galactopyranose. Cryo-scanning electron microscopy (Cryo-SEM) showed that the aperture of AB was larger than that of agar. The thermal performance of AB decreased slightly, but this did not affect its performance. AB showed the highest relative antibacterial activity against Escherichia coli, S. aureus and Alternaria alternata, reaching 100 % (AB 20 g/L), 100 % (AB 40 g/L) and 19.35 % (7 d incubation), respectively. Moreover, the obtained AB possessed good emulsion stability. These antibacterial AB have broad application prospects in the field of fruit and vegetable preservation.

Evaluation of natural ageing responses on Burmese amber durability by FTIR spectroscopy with PLSR and ANN models

Amber ageing is an inevitable process, which is very important in precious organic gemstone relics protection. In order to explore the mechanism of amber ageing and estimate the durability of Burmese amber, this research investigates the changing spectral features of Burmese ageing amber via Fourier Transform Infrared Spectroscopy (FTIR) and solid 13C Nuclear Magnetic Resonance spectroscopy (NMR) and develops the regression models for its micro-hardness by micro-FTIR spectra. The Partial Least Squares Regression (PLSR) and Artificial Neural Networks (ANN) methods as well as Competitive Adaptive Reweighted Sampling (CARS) algorithm for wavelength variables selection have been applied to predict and assess the Vickers hardness of amber samples with different ageing degrees. As a result, the FTIR and the solid 13C NMR spectra reveal that the contents of CO groups (of esters) increase substantially, and which of the other oxygenic groups (CO (of acids), COC, COCC) increase modestly in amber ageing. When comparing with the results of four different models (PLSR, ANN, CARS-PLSR and CARS-ANN), the CARS-PLSR model obtained the optimal results as follows: the squared correlation coefficient of calibration(R2cal) is 0.9230 and the root mean square error of calibration (RMSEC) is 1.2977 HV; the squared correlation coefficient of prediction (R2pre) is 0.7762 and the root mean square error of prediction (RMSEP) is 2.2208 HV. The overall results sufficiently demonstrate that FTIR spectroscopy technique coupled with appropriate chemometrics methods are very promising tools to estimate and predict the hardness property of Burmese ageing amber.

HPTLC determination of ergosterol in wheat and structure elucidation by NMR: Toward confirming method selectivity

Ergosterol (ERG) is considered as an excellent fungal biomarker, therefore it was utilized for the determination of the degree of fungi infection in wheat grains. A novel, fast, cost-effective and selective high performance thin layer chromatography (HPTLC) with reflectance/absorbance densitometry method was developed and validated for ERG determination. Separation was attained on pre-coated silica gel HPTLC plate with ethyl acetate: petroleum ether (6: 4 v/v) as a mobile phase. This system gave compact bands at retardation factor (Rf) of 0.45 ± 0.002 and quantification was performed at 282 nm over concentration range of 40–600 ng/band. The lower detectable limit was 10.79 ng per band which is three times more sensitive than the previously reported TLC method. The developed method could be utilized efficiently for the detection of ERG in pure powders and in fungi infected wheat samples. Resolution of ERG from other compounds in wheat grain extract allowed utilizing preparative TLC for separating and purifying ERG in a sufficient quantity for structure elucidation by nuclear magnetic resonance spectroscopy (NMR) for the first time. H1 and C13 NMR spectra indicated the purity of ERG extracted from the scrapped silica of preparative TLC plate at the Rf of the standard ERG verifying the method selectivity.

Intrinsic anisotropy parameters of a series of lanthanoid complexes deliver new insights into the structure-magnetism relationship

Intrinsic anisotropy parameters of a series of lanthanoid complexes deliver new insights into the structure-magnetism relationship

Lorentzian peak sharpening and sparse blind source separation for NMR spectroscopy

In this paper, we introduce a preprocessing technique for blind source separation of nonnegative and overlapped data. For nuclear magnetic resonance spectroscopy (NMR), the classical method of Naanaa and Nuzillard (NN) requires the condition that source signals to be non-overlapping at certain locations, while they are allowed to overlap with each other elsewhere. NN’s method works well with data signals that possess stand-alone peaks (SAPs). The SAP does not hold completely for realistic NMR spectra, however. Violation of SAP often introduces errors or artifacts in the NN’s separation results. To address this issue, a preprocessing technique is developed here based on Lorentzian peak shapes and weighted peak sharpening. The idea is to superimpose the original peak signal with its weighted negative second-order derivative. The resulting sharpened (narrower and taller) peaks enable NN’s method to work with a more relaxed SAP condition, the so-called dominant peaks condition, and deliver improved results. To achieve an optimal sharpening while preserving the data nonnegativity, we prove the existence of an upper bound of the weight parameter and propose a selection criterion. Numerical experiments on NMR spectroscopy data show satisfactory performance of our proposed method.

Development of Pelubiprofen Tromethamine with Improved Gastrointestinal Safety and Absorption.

Pelubiprofen (PEL), which is a commercialized non-steroidal anti-inflammatory drug (NSAID), is associated with the risk of gastrointestinal (GI) adverse events following long-term exposure and has poor water-soluble properties. Here, a new pelubiprofen tromethamine (PEL-T) with improved solubility, permeability, GI safety, and absorption, compared to PEL, has been developed. The nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR) results confirmed that the PEL-T was well formed. The powder of PEL-T showed the presence of additional 6H protons at δ 3.66–3.61 in the 1H NMR spectrum, and shifted the sharp endothermic peaks at 129 °C in DSC, and the spectrum of distinct absorption peaks in FT-IR. In addition, compared with PEL, PEL-T showed a significantly improved solubility in various media and an increased permeability coefficient (Kp) in Caco-2 cells. Furthermore, compared to PEL oral administration, PEL-T was found to significantly reduce the damaged area in an acute gastric damage rat model. The pharmacokinetic study of the PEL-T powder showed higher maximum plasma concentration (Cmax) and area under the plasma concentration–time curve from 0 h to the last time point (AUCt) than those of the PEL powder. Taken together, our data suggest that PEL-T is a recommendable candidate with enhanced gastrointestinal safety and better absorption compared with commercial PEL.

Variable-temperature &amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt;H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism

Rotational isomerism has been observed on some C-glycosyl flavonoids with special chemical strutures. It may bring rotamers arising from restricted rotation about one single bond. C-glycosyl flavonoids showed a wide range of biological activities. This emphasizes the significance to understand the conformational stability of C-glycosyl flavonoids in drug development. Three C-glycosyl flavonoids, vaccarin (1), isovitexin-2”-O-arabinoside (2) and spinosin (3), were found to exist as rotamers in the light of their featured behavior in nuclear magnetic resonance spectroscopy (NMR). Some separated signals were observed in their ¹H-NMR and ¹³C NMR spectra. Variable-temperature (VT) ¹H-NMR experiments were then conducted to study the observation and to determine their rotational energy barriers and then evaluate their conformational stability. The temperature varied from 298K to 363K and separated signals merged at high temperature. With the help of Eyring equation, the rotational energy barriers of compounds 1-3 were calculated and found much lower than 24 kcal/mol. When the energy barrier is high enough (> 24 kcal/mol) and the time scale for interconversion (halflife > 1000 s) is long enough for isolation of individual rotamers, the isomers are termed atropisomers, which thus will display axial charity. According to this standard, the compounds 1-3 may not exhibit atropisomerism and isolation of rotamers should be difficult. Their relatively low energy barriers indicate they can be developed as rapidly equilibrating mixture.

Fractionation platform for target identification using off-line directed two-dimensional chromatography, mass spectrometry and nuclear magnetic resonance

The unambiguous identification of unknown compounds is of utmost importance in the field of metabolomics. However, current identification workflows often suffer from error-sensitive methodologies, which may lead to incorrect structure annotations of small molecules. Therefore, we have developed a comprehensive identification workflow including two highly complementary techniques, i.e. liquid chromatography (LC) combined with mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR), and used it to identify five taste-related retention time and m/z features in soy sauce. An off-line directed two-dimensional separation was performed in order to purify the features prior to the identification. Fractions collected during the first dimension separation (reversed phase low pH) were evaluated for the presence of remaining impurities next to the features of interest. Based on the separation between the feature and impurities, the most orthogonal second dimension chromatography (hydrophilic interaction chromatography or reversed phase high pH) was selected for further purification. Unknown compounds down to tens of micromolar concentrations were tentatively annotated by MS and structurally confirmed by MS and NMR. The mass (0.4–4.2 μg) and purity of the isolated compounds were sufficient for the acquisition of one and two-dimensional NMR spectra. The use of a directed two-dimensional chromatography allowed for a fractionation that was tailored to each feature and remaining impurities. This makes the fractionation more widely applicable to different sample matrices than one-dimensional or fixed two-dimensional chromatography. Five proline-based 2,5-diketopiperazines were successfully identified in soy sauce. These cyclic dipeptides might contribute to taste by giving a bitter flavour or indirectly enhancing umami flavour.

1H NMR chemometric models for classification of Czech wine type and variety

A set of 917 wines of Czech origin were analysed using nuclear magnetic resonance spectroscopy (NMR) with the aim of building and evaluating multivariate statistical models and machine learning methods for the classification of 6 types based on colour and residual sugar content, 13 wine grape varieties and 4 locations based on 1H NMR spectra. The predictive models afforded greater than 93% correctness for classifying dry and medium dry, medium, and sweet white wines and dry red wines. The trained Random Forest (RF) model classified Pinot noir with 96% correctness, Blaufränkisch 96%, Riesling 92%, Cabernet Sauvignon 77%, Chardonnay 76%, Gewürtztraminer 60%, Hibernal 60%, Grüner Veltliner 52%, Pinot gris 48%, Sauvignon Blanc 45%, and Pálava 40%. Pinot blanc and Chardonnay, varieties that are often mistakenly interchanged, were discriminated with 71% correctness. The findings support chemometrics as a tool for predicting important features in wine, particularly for quality assessment and fraud detection.

Insights into the behavior of ethylene oxide-1,2-epoxybutane diblock copolymers in water as a function of temperature and the presence of colloidal silica

HypothesisNonionic surfactants have been widely used for many consumer products and industrial processes, and their applications often involve temperature-cycling across cloud point temperature (Tcloud). To explore the behavior of nonionic surfactants across Tcloud and when mixed with colloidal silica at a very dilute concentration around 0.1 wt%, a series of 1,2-epoxybutane-capped alcohol ethoxylates (BAEs) with various cloud points is used as a model system. ExperimentsBAEs with cloud points from 15 to 64 °C were successfully prepared by varying the lengths of 1,2-epoxybutane (BO) and ethylene oxide (EO) blocks and their phase behavior across Tcloud was studied using nuclear magnetic resonance spectroscopy (NMR), dynamic light scattering (DLS) and differential scanning calorimetry (DSC). FindingsIn the absence of silica, the NMR signals are not greatly affected by the cloud point transition, but both the water and surfactant exhibit a decrease in spin-spin relaxation time once the temperature reaches the Tcloud. In the presence of silica, the NMR spectra indicate significantly reduced mobility of the EO portion relative to the alkyl and BO segments. Furthermore, our results suggest that the BAE surfactants are not fractionally clouding out or precipitating with a portion of the compositional distribution during the cloud point transition.

Determining the Regiochemistry and Relative Stereochemistry of Small and Druglike Molecules Using an Alignment Algorithm for Infrared Spectra.

The relative stereochemistry and isomeric substitution pattern of organic molecules is typically determined using nuclear magnetic resonance spectroscopy (NMR). However, NMR spectra are sometimes nonconclusive, e.g., if spectra are extremely crowded, coupling patterns are not resolved, or if symmetry reasons preclude interpretation. Infrared spectroscopy (IR) can provide additional information in such cases, because IR represents a molecule comprehensively by depiction of the complete set of its normal vibrations. The challenge is thereby that diastereomers and substitution isomers often give rise to highly similar IR spectra, and visual distinction is insufficient and may be biased. Here we show the adaptation of an alignment algorithm, originally developed for vibrational circular dichroism (VCD) spectroscopy, to automatically match IR spectra and provide a quantitative measure of the goodness of fit, which can be used to distinguish isomers. The performance of the approach is demonstrated for different use cases: diastereomers of flexible druglike molecules, E/Z-isomers, and substitution isomers of pyrazine and naphthalene. It can be applied to IR spectra measured both in the gas phase (gas chromatography IR) and in solution.

Oxidative conversion of lignin isolated from wheat straw into aromatic compound catalyzed by NaOH/NaAlO2.

Lignin was isolated from wheat straw via organosolv process and further transferred to monophenolic compounds via oxidative conversion. Wheat straw lignin (WSL) with purity at 91.4 wt% was acquired in the presence of heterogeneous and recyclable catalyst of Amberlyst‐45. WSL was characterized by infrared spectrometer (IR), nuclear magnetic resonance spectroscopy (NMR) including 1H NMR and 13C NMR spectra. The results showed that WSL possesses typical syringyl (S), guaiacyl (G), and p‐hydroxyphenyl (H) units, and it is mainly composed of S and G units. The product distribution was dependent on the composition of WSL. Derivatives from S and G units were found to be the main products. The oxidative conversion of WSL was performed by varying oxidant and catalyst. Both the formation of monophenolic compounds and aromatic aldehydes were enhanced by combining oxidants and catalysts. The composite catalyst composed of NaOH/NaAlO2 was effective for the oxidation of WSL in the presence of nitrobenzene and atmospheric pressure air. The total yield of monophenolic compounds reached up 18.1%, and yields at 6.3 and 5.7% for syringaldehyde and vanillin were achieved, respectively.

Water structure of poly(2-methoxyethyl acrylate) observed by nuclear magnetic resonance spectroscopy

Poly(2-methoxyethyl acrylate) (PMEA) is known to show excellent blood compatibility. The performance of PMEA has been attributed to the existence of cold-crystallizable water in it, as observed using differential scanning calorimetry (DSC). However, little is known on the property of the water in PMEA above 0 °C, especially at ambient temperature including the body temperature, because blood compatibility is observed at 37 °C. The present study was performed to clarify the state of water in PMEA in the temperature range 15–45 °C using solution nuclear magnetic resonance spectroscopy (NMR). In addition, water in poly(butyl acrylate) (PBA), which exhibited poor blood compatibility, was used as a control. In the NMR spectra of water in PMEA, two peaks appeared at 4.87 ppm and 3.71 ppm at 30 °C, showing the existence of two types of water structures. The peak intensity of the upfield water was considerably higher than that of the downfield water. On the other hand, the hydrated PBA showed only one peak at 4.98 ppm at 30 °C. The dynamic property of water in these polymers was estimated from the deuterium solution NMR spin-lattice relaxation time, T12H. The T12H values of peaks observed at 4–5 ppm were relatively high, denoting rapid motion, while those of water at 3.7 ppm in PMEA were small, denoting slow mobility. Thus, the states of water molecules in PMEA in terms of chemical shift and mobility were considered different from those in PBA at ambient temperature.

P052 Nuclear magnetic resonance metabolomic profiling of IBD patients under anti-TNF treatment. Are the pathways network deregulated?

Abstract Background The deregulation of immune system cell response implies loss of T-cell apoptosis, high rate of proinflammatory cytokines production and subsequent exacerbate activation of TNF-α pathway. The use of biologic antibody decrease inflammation rate and symptoms, but it remains unclear if it has a direct effect on the pathways activation/inactivation on peripheral blood mononuclear cells (PBMCs). The aim of this study is evaluate the role of nuclear magnetic resonance spectroscopy (NMR) applied to the metabolomic study of serum samples isolated from fresh blood from inflammatory bowel disease (IBD) patients under IFX treatment to understand the activated/inactivated pathways of PBMCs. Methods A case–control study was performed. Inclusion criteria were IBD patients under IFX treatment. Blood samples were obtained in Crohn’s disease (CD) and ulcerative colitis (UC) patients before IFX and in healthy controls (CTRL). CD patients were divided into subgroups according to the gut affected, in Ileocolic (IC), ileum and colon. NMR samples of the serum were collected and measured according to Standard Operation Procedures. Three types of NMR spectra were measured for each serum sample (1Hnoepresat, 1Hcpmgpresat and 1HDfilterpresat). The signal in each NMR spectrum was integrated in a series of equidistant little portion of the spectrum called buckets of a constant width of 0.04 ppm, covering the complete 1H NMR spectral window from −5 to 14 ppm. Buckets in regions depleted from signal at the two extremes of the spectrum were discarded as well as those in the proximity of the water peak at ca. 4.7 ppm which was affected by the presaturation. The vectors corresponding to a number of samples of two or more groups can be rapidly analysed using Multivariant Statistical Analysis methods. Results Twenty-two IBD patients (12 CD and nine UC) were included, 10 CTRL were also included. The metabolomic analyses of the NMR spectra of the serum of the different patients and control groups by the fingerprinting and targeting profiling strategies provided OPLS-DA statistical models (Figure 1) that permitted the successful classification of certain groups of samples which are summarised in Table 1. Conclusion The results of this pilot NMR metabolomic study of serum samples of IBD found a series of spectral fingerprints that are able to discriminate between groups of patients CTRL and CD, which underlines its potential use for the diagnosis of the disease.

Solid-state and time domain NMR to elucidate degradation behavior of thermally aged poly (urea-urethane)

We have demonstrated that solid-state and time-domain Nuclear Magnetic Resonance spectroscopy (NMR) techniques are effective in monitoring the degradation site of poly (urea-urethane). We prepared two types of commercial poly (urea-urethane), Urethane-A and Urethane-B, and aged them at 100 °C for up to 10000 h. We performed tensile strength tests and solid-state NMR experiments, in which 13C and 15N NMR spectra and T2 were collected. The tensile strength of Urethane-A decreased, increased and decreased again, whereas that of Urethane-B decreased at a lower rate with aging. Solid-state NMR experiments clearly showed that the degradation of Urethane-A was caused by molecular chain scission and cross-linking in its urea bonds, and that of Urethane-B occurred owing to molecular chain scission in its urethane bonds. T2 had three components, short T2 (T2S), intermediate T2 (T2I) and long T2 (T2L), whose fractions were xS, xI and xL, respectively. We have demonstrated that molecular chain scission in urea bonds decreases xS and increases xL, and that in urethane bonds increases T2I and T2L without changing all the T2 fractions.

Madhuca indica flower extract as cheaper carbon source for production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) using Ralstonia eutropha

Abstract In this study, the poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was synthesized using Madhuca indica flower extract as cheaper carbon source by Ralstonia eutropha. The Influence of fermentation parameters such as incubation time, temperature, pH and inoculum size were studied on production of PHBV. The maximum production of PHBV (1.44 ± 0.016 g/l with yield of 49.4%) was obtained at a temperature, pH, inoculum size and incubation time of 35 °C, 6, 5% v/v and 48 h, respectively. The PHBV was characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric/differential scanning calorimetric (TGA/DSC) and scanning electron microscopic (SEM) analysis. The biodegradation and corrosion resistance of the polymer were also studied. The functional group C O was observed in the FTIR spectrum indicated the presence of PHA. Moreover, the NMR spectrum showed the formation of hydroxyvalerate copolymer. Hence, it can be confirmed that the synthesized polymer was PHBV. TGA analysis showed that the maximum decomposition occurred at a temperature of 474 °C. The DSC showed the dual melting point (136 °C and 140.69 °C), which inferred the re-crystallization behavior of synthesized PHBV. In addition, the PHBV showed good biodegradation and corrosion resistance. Henceforth, the Madhuca indica flower extract is suggested as cheaper carbon source for production of PHBV.

Characterization of single chain length chlorinated paraffin mixtures with nuclear magnetic resonance spectroscopy (NMR)

Chlorinated paraffins (CPs) are complex mixtures of polychlorinated n-alkanes of different chain length. Despite their environmental relevance, quantification is still a challenge. Moreover, the individual structures of the molecules in technical CP mixtures are largely unknown. Here, we synthesized 21 and studied 29 single chain length CP mixtures ranging from C10- to C17-CPs with different chlorine contents between 41.8% and 62.6% Cl and analyzed them by means of nuclear magnetic resonance spectroscopy (NMR). Discrete ranges of chemical shifts were observed in one-dimensional 1H and 13C NMR spectra. Two dimensional heteronuclear single quantum coherence spectroscopy (HSQC) enabled to assign nine substructures. These measurements also verified the presence of [-CCl2-] groups and chlorine atoms on terminal carbons in highly chlorinated (>59% Cl) mixtures. 1H NMR spectra of different chain length and the same degree of chlorination looked virtually the same. However, with increasing degree of chlorination the observed patterns in the spectra were slightly shifted downfield. Based on these findings, a calculation mode was developed to estimate the chlorine content (%) of the single chain length CP mixtures. The results agreed well (<0.9% mean deviation) with parallel measurements by elemental analysis.