KBr Pellet Technique Research Articles

Novel Strategy of Treating 2-Nitrobenzoic Acid Crystals with Energetic N2 Neutrals Using Cold Plasma

The organic adduct compounds of 2-nitrobenzoic acid crystals were grown as optically transparent crystals using the conventional slow evaporation solution technique. The crystals were powdered and irradiated with cold plasma. Cell parameter analysis confirmed the formation of a new crystalline material that resides in the triclinic P crystal system with space group P1. Fourier transform infrared spectra were recorded using the KBr pellet technique to determine the vibrational functional groups in the compound. Powder X-ray diffraction analysis was used to reveal the crystalline orientation of the powdered samples of the grown crystals. The obtained full width at half maximum for the (001) plane in the XRD spectrum indicates the excellent crystalline quality of the 2-nitrobenzoic acid crystals. The recorded UV–Vis absorption spectra reveal that the grown powdered crystal samples possess cut-off edges wavelengths at 428 and 428 nm and 353 and 354 nm for pure and plasma-treated samples, respectively. The optical energy bandgaps were found to be 2.0, 2.25, 4.06, and 4.02 eV for the pure and plasma-treated samples, respectively. The photoluminescence spectra show the blue emissions of the crystal. The FE-SEM images show the morphological modifications in which rounded platelets appear on the surfaces of the treated crystals.

Method to derive the infrared complex refractive indices n(λ) and k(λ) for organic solids from KBr pellet absorption measurements.

Obtaining the complex refractive index vectors n(ν~) and k(ν~) allows calculation of the (infrared) reflectance spectrum that is obtained from a solid in any of its many morphological forms. We report an adaptation to the KBr pellet technique using two gravimetric dilutions to derive quantitative n(ν~)/k(ν~) for dozens of powders with greater repeatability. The optical constants of bisphenol A and sucrose are compared to those derived by other methods, particularly for powdered materials. The variability of the k values for bisphenol A was examined by 10 individual measurements, showing an average coefficient of variation for k peak heights of 5.6%. Though no established standards exist, the pellet-derived k peak values of bisphenol A differ by 11% and 31% from their single-angle- and ellipsometry-derived values, respectively. These values provide an initial estimate of the precision and accuracy of complex refractive indices that can be derived using this method. Limitations and advantages of the method are discussed, the salient advantage being a more rapid method to derive n/k for those species that do not readily form crystals or specular pellets.

Phytochemical characterisation and toxicity effect of Tithonia diversifolia (Hemls.) A. Gray leaf extract on fall army worm Spodoptera frugiperda (JE Smith) larvae.

To mitigate the losses due to fall armyworm (FAW) infestation in maize, chemical pesticides had been the first choice and widely used as an emergency response. However, it comes with attendant health effect. This necessitates the development of plant based effective and safer pesticides. This research investigate response of fall armyworm larvae when they are exposed to crude and partially purified Tithonia diversifolia leaf extract. Chemical constituent of the extract was identified using NIST08.LIB library spectra provided by the software on a GC-MS system and FTIR analysis was done using KBr pellet technique with a resolution and scanning speed of 4 cm-1 and 2 mm/s. Dose dependent toxicity assay of T.diversifolia extracts on FAW at different growth stages under controlled environment in laboratory, followed by its effect under phytotron were examined against control and azadirachtin from neem. The GC-MS of the butanol eluent revealed 20 compounds out of which the major ones being beta-d-glucopyranoside, methyl (15.225 %) palmitic acid, TMS derivative (10.98 %) and hexadecanoic acid, 2-[(trimethylsily)oxy]-, methyl ester (8.75 %). The FT-IR spectroscopic analysis of the butanol eluent of T.diversifolia leaf extract revealed the presence of alcohols, phenols, aldehydes, ketones, alkanes and primary amines. The butanol eluent and crude extract caused 96 % mortality at neonate and first instar FAW larvae. The toxic and repellant effects revealed by diet bioassay and phytotron experiment respectively suggest that butanol eluent of T.diversifolia leaf extract could be a good and effective target for biopesticide production against FAW.

Identification of Biochemical Composition and Pesticides Residue in Ten Rose Cultivars Leaves Using FT-IR Spectroscopy

In order to optimize the application of nutritive solutions and the phytosanitary treatments with direct influence on the quality of cut roses from hydroponic culture (soilless culture), it is necessary to study the biochemical composition of the different organs of the plant (leaves). By FT-IR spectroscopy using the standard KBr pellet technique; it was possible to differentiate between 10 Rosa cultivars based on the chemical composition of the leaves and also to identify the pesticide residue within the leaf tissues and some of its effects. Thus, it was observed that the intensity of the bands corresponding to amide I (proteins) and aromatic compounds were weaker in leaf sheath and petiole compared with the leaf lamina. Aldehydes were present only in leaf sheath and petiole and not in the leaf lamina. As for the six pesticides tested, simple bond vibration C–H corresponding to aromatic compounds has been detected at 817 cm-1 and 805 cm-1 in the samples treated with penconazole based pesticide (Topas) and a triadimenol with folpet pesticide (Shavit). Also, application of penconazole increases the concentration of polisaccharides in the treated leaves, while a strong intensity band that could be attributed to the presence of halogenated compounds (chlorinated) C-Cl can be observed at 715 cm-1 for the samples treated with the triadimenol and folpet pesticide. The overall results of the present study could provide helpful information for the development of pesticides that have a shorter persistence and a lower biochemical influence on the plant tissues.

Analytical methods for meldonium determination in urine samples

Here is reported a rapid analytical method for meldonium and other beta blockers (metoprolol, amlodipine, bisoprolol, nebivolol, betaxolol, and carvediol) in urine samples using Fourier transform infrared spectroscopy (FTIR) for the detection of these forbidden compounds in athletes. A thin layer chromatography (TLC) plate coated with SiO2 was employed. Simple analytical methods for screening meldonium and the aforementioned beta blockers in urine samples were developed using the TLC plates, FTIR spectroscopy with the aid of KBr pellet technique, and mass spectrometry. The surface hydroxyl groups were employed for the indirect detection of meldonium in the urine samples. The detection and quantification of meldonium were also confirmed by mass spectrometry by the use of both electron impact (EI) and electrospray (ESP) ionization systems.

Recycling Control of Histological Xylol: A Chemometric Approach

AbstractFractional distillation was applied to recycle and reuse histological xylol waste. A new sample preparation technique for analyzing liquid samples by transmission FTIR spectroscopy was developed and validated. Pressing time, sample volume, and xylol volatility were the optimized variables to acquire good quality spectra by using the KBr pellet technique. The suitability of this technique for analyzing a volatile sample, xylol, was contrasted against a non‐volatile coal sample. Semi‐quantitative IR‐derived ratios were calculated and used as input variables in principal components analysis (PCA). One‐way analysis of variance (ANOVA) test was applied to determine whether the samples of distillate, xylol waste, and commercial xylol showed significant differences among them. Unlike currently used analytical methodologies based on GC, the proposed methodology based on FTIR‐PCA‐ANOVA provided a simple way to monitor the samples (including xylol waste containing water traces and paraffin) throughout xylol recycling process. The results indicated there were no significant differences (p>0.05) between commercial and recycled xylol, being comparable.

XRD, LPF and FTIR investigation of Mn-Bi alloy

High purity MnBi low temperature phase has been prepared and analyzed using X- ray diffraction, Lorentz-Polarization Factor and Fourier transforms infrared measurement. After synthesis of samples structural characterization has done on samples by X-ray diffraction, which shows that after making the bulk sample is in no single phase MnBi has been prepared by sintering Mn and Bi powder. The X-ray diffraction measurements were carried out using Bruker D8 Advance X-ray diffractometer. The X-rays were produced using a sealed tube and the wavelength of x-ray was 0.154nm (Cu K-alpha).and x-rays were detected using a fast counting detector based on Silicon strip technology (Bruker LynxEye detector). By Lorentz- Polarization Factor is affecting the relative intensity of diffraction lines on a powder form. The infrared absorption spectra of the alloys and intermetallic compound were measured at room temperature, in the wave number range 4000 to 400 cm−1 by a computerized spectrometer type Jasco FTIR-300 (JAPAN) using the KBr pellet technique. And by FTIR which shows absorption peaks of MnBi alloys.

EVALUATION OF PHARMACOLOGICAL ACTIVITIES OF PECTIN EXTRACTED FROM APPLE AND CITRUS POMACE

In the present study, the pectin, a natural gelling plant polysaccharide was extracted from pomace portion of apples and oranges. Further the antimicrobial, antioxidant and anti-inflammatory activities of pectin extracts were investigated. It was found that the yield of pectin content extracted was predominant in apples (20.60 %) in comparison to that of oranges (10.56%). The pectin samples extracted from apples and oranges were qualitatively evaluated for characteristic properties. Further the phytochemical constituents were qualitatively determined by conventional procedures. The results confirmed the presence of alkaloids, flavanoids, reducing sugars, steroids and cardiac glycosides in orange pectin while alkaloids, reducing sugars, steroids, cardiac glycosides and anthraquinones were present in apple pectin. Tannins, saponin and anthraquinones were absent in orange pectin while tannins, flavanoids and saponin were absent in apple pectin. In separation of pectin extracts by TLC, the Rf values of the pectin samples were found to be similar viz. Apple pectin (0.62), Orange pectin (0.62) to that of standard pectin (procured from Ranchem), 0.63. The apple pectin and orange pectin showed almost similar retention time viz. 1.821 minutes and 1.757 minutes specifically on HPLC chromatogram. The FT-IR spectra of extracted pectin samples were determined using a computerized FTIR spectrometer in the range of 4400–400 cm 1 by the KBr pellet technique. Two outstanding features of the infrared spectra of pectinate are bands at 1745-1743 and at 1607-1604 cm -1 . One other feature which should be mentioned is a band, beyond the afore mentioned range, appearing at 1418-1417 cm -l

Experimental investigation of rates and mechanisms of isotope exchange (O, H) between volcanic ash and isotopically-labeled water

The hydrogen and oxygen isotope ratios in hydrous minerals and volcanic glass are routinely used as paleo-proxies to infer the isotopic values of meteoric waters and thus paleo-climatic conditions. We report a series of long-term exposure experiments of distal 7700BP Mt. Mazama ash (−149‰ δ2H, +7‰ δ18O, 3.8 wt.% H2O) with isotopically-labeled water (+650‰ δ2H, +56‰ δ18O). Experiments were done at 70, 40 and 20°C, and ranged in duration from 1 to 14454h (∼20months), to evaluate the rates of deuterium and 18O exchange, and investigate the relative role of exchange and diffusion. We also investigate the effect of drying on H2Otot and δ2H in native and reacted ash that can be used in defining the protocols for natural sample preparation. We employ Thermal Conversion Elemental Analyzer (TCEA) mass spectrometry, thermogravimetric analysis and a KBr pellet technique with infrared spectroscopy to measure the evolution of δ2H, total water, and OH water peaks in the course of exposure experiments, and in varying lengths of vacuum drying.Time series experiments aided by infrared measurements demonstrate the following new results: (i) It wasobserved that from 5 to >100‰ δ2H increases with time, with faster deuterium exchange at higher temperatures. Times at 15% of theoretical “full δ2H exchange” are: 15.8years at 20°C, 5.2years at 40°C, and 0.4years at 70°C. (ii) Even at extended exposure durations experiments show no net increase in water weight percent nor in δ18O in ash; water released from ash rapidly by thermal decomposition is not enriched in δ18O. This observation clearly suggests that it is hydrogen exchange, and not water addition or oxygen exchange that characterizes the process. (iii) Our time series drying, Fourier transform infrared (FTIR)-KBr and Thermogravimetric Analyzer (TGA) analyses collectively suggest a simple mechanistic view that there are three kinds of “water” in ash: water (mostly H2O) that is less strongly bonded on the surface of ash particles that are getting lost with 24–48h of drying to up to 200–300°C, bound water in glass in a range of combining proportions of SiOH to H2O, and a small reservoir of residual, tightly held water.Experimentation with vacuum drying at 130–220°C, and with TGA up to 1000°C provides a set of simple relationships and recommendations for users. Ash loses 1–1.2wt.% water with weight loss stabilizing after 48h of vacuum drying at 130°C. This ash drying removes molecular water over the hydroxyl group in a proportion of ∼80:20% resulting in relatively constant δ2H values of the remaining total water in native ash.This study demonstrates that δ2H in ash can be rapidly changed by minor diagenesis even at relatively low temperatures of 20°C. A diagenetic history of ash is needed to interpret the D/H ratio, but the δ18O values of water in ash are more robust.

Characterization of chemical functional groups in macerals across different coal ranks via micro-FTIR spectroscopy

Fourier transform infrared spectra of a suite of coals of varying rank from peat to anthracite were obtained via reflectance micro-FTIR and traditional KBr pellet techniques. With increasing rank of coal samples, KBr-FTIR spectra exhibit rising aromaticity (ratio of CH ar at 3000–3100 or 700–900 cm − 1 versus CH al at 2800–3000 cm − 1 ) and enhanced condensation of aromatic rings (ratio of CH ar versus C=C at ~ 1600 cm − 1 ), whereas the aliphatic chain length (ratio of CH 2 /CH 3 at 2800–3000 cm − 1 ) and the ‘C’ factor (ratio of C=O at ~ 1710 cm − 1 versus (C=O + C=C)) decrease. The ratio of CH al /(CH al + C=C) (i.e., the ‘A’ factor), which reflects the hydrocarbon-generating potential, initially rises at low rank and later decreases in higher-rank coal= ( R o > 0.98%). However, the trends of these semi-quantitative FTIR ratios are difficult to trace in high-rank coals ( R o > 1.50%), probably attributable to limited peak areas and enhanced uncertainties in ratio calculations. The overall evolutionary trends of functional group abundances in bulk coals and their individual macerals are similar; distinct differences in chemical properties, however, exist among maceral groups, and these variations depend on rank. Within the three maceral groups, liptinite generally exhibits the lowest aromaticity, the longest aliphatic chains having the least amount of branching, and the highest ‘A’ factor testifying to the highest hydrocarbon-generating potential. In contrast, inertinite shows the highest aromaticity and degree of condensation of aromatic domains and the lowest hydrocarbon-generating potential. Vitrinite generally exhibits intermediate characteristics between liptinite and inertinite. Compared to KBr spectra, micro-FTIR spectra present better detection capability and stronger signals in the 700–900 cm − 1 region, which allows for close investigation of aromatic CH x out-of-plane deformation modes. The rapid decrease in the peak area ratio at ~ 870 cm − 1 /~ 750 cm − 1 in vitrinite from peat to low-volatile bituminous coal is followed by a significant increase after R o > 1.50%, which indicates the dominance of highly substituted aromatic rings in immature coal's structure, while condensed aromatic domains become prevalent in higher-rank coals (semi-anthracite and anthracite). The increase in coal aromaticity during coalification is attributed largely to the accumulation of condensed aromatic structures in more mature coals. Novel reflectance micro-FTIR mapping is a promising and powerful tool providing high-resolution information on chemical properties of coal macerals relating to parent material and coalification. ► We demonstrate the applicability of micro-FTIR mapping to the study of coal macerals. ► Aromaticity increases and aliphatic chain length decreases with coal rank. ► Highly substituted aromatic rings dominate in immature coal’s structure. ► Condensed aromatic domains are prevalent in higher-rank coals.

Comparison of fluorescence spectroscopy and FTIR in differentiation of plant pollens

Spectroscopic techniques are under investigation on possibility of differentiation of airborne particles. This paper describes pollen discrimination among others bio-particles in laboratory conditions. Pollen samples were characterized with UV–Vis fluorescence, drift and KBr pellet techniques of infrared spectroscopy. Principal Component Analysis of UV–Vis fluorescence and FTIR spectra revealed that pollens can be distinguished from other bio-materials with use of these methods. Both methods resulted in similar classification capability. Combined FTIR and fluorescence data analysis did not improve the discrimination between pollen allergens and other airborne biological materials.

Growth and characterization of pure and doped btzs single crystals

The growth and characterization of pure and doped BTZS single crystals are discussed. In the present study powder X-Ray diffraction data of the grown crystal were recorded using BRUKER D8 Advance powder crystal X-ray diffractometer with 2.2 KW Cu anode ceramic X-ray tube. The various functional groups present in the grown crystals were identified and confirmed by recording the FTIR spectrum using BRUKER IFS-66V spectrophotometer by KBr Pellet Technique in the region 4000 - 400 cm 1 . The UV - Vis - NIR optical spectra of the crystals were recorded using the VARIAN CARY 5E model spectrophotometer. The degree of dopant inclusion was estimated by using Atomic Absorption Spectroscopy. The SHG efficiencies of the crystals were studied using Nd:YAG Q - switched laser.

Spectroscopic studies on the influence of 10 mol% of glycine on nonlinear optical crystal l-valinium picrate

Nonlinear optics is a fascinating field, which plays a vital role in the emerging field of photonics and optoelectronics. A new nonlinear optical crystal of glycine mixed l-valine picrate (GVP) have been grown from saturated aqueous solution by slow evaporation method at a temperature of 36 °C using a constant temperature bath of accuracy of ±0.01 °C. The synthesized organic optical material has been purified by repeated recrystallization. Single crystal X-ray diffraction analysis has been made to determine the cell parameters and it confirms the crystal lattice to be orthorhombic. UV–vis-NIR spectrum have recorded for GVP crystals in the range from 190 nm to 1100 nm and it is found that the crystal has cut-off at 450 nm. Fourier transform infrared transmission has confirmed the presence of the functional group present in the title compound. The spectrum has been recorded by KBr pellet technique. The 1H and 13C NMR spectra have been recorded to elucidate the molecular structure of GVP crystals. The second harmonic generation (SHG) of the grown crystal have been confirmed by Kurtz–Perry method using Nd:YAG laser as source.

Analysis on air suspended particles of Coimbatore — a FTIR study

An infrared absorption method has been used to identify the minerals in dust collected from some parts of Coimbatore, Coimbatore district, Tamil Nadu without grinding. The KBr pellet technique was employed. The results obtained from the IR spectra show the presence of quartz, asbestos, kaolinite, calcite, haematite, montmorllonite, nacrite and coal. The hazardous effect of inhalation of these minerals are explained. The results show Pollachi main road is more contaminated with hazardous minerals.

Fourier transform infrared spectroscopy of dental unit water line biofilm bacteria

Fourier transform-infrared (FT-IR) spectroscopy has become an important tool for rapid analysis of complex bi- ological samples. The infrared absorbance spectrum could be regarded as a which is a feature of biochemical substances. The FT-IR spectra of fresh and stored dried samples of six bacterial isolates (Klebsiella sp., Bacillus cereus, Bacil- lus subtilis, Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobacter sp.) were observed by variation in sample preparation. The results indicated that variation in sample preparation did not affect the spectra of isolates. However, less promiment/absence of a small shoulder peak at 1738 cm −1 was evident in fresh dried samples of Achromobacter sp. and A. xylosoxidans compared to prominent and broad shoulder band at 1724 cm −1 in stored dried samples of these two isolates. In addition to the established KBr pellet technique, attenuated total reflectance (ATR) spectroscopy was used to analyse the spectra of planktonic growth (−80 ◦ C liquid cultures) and biofilm growth of six isolates. ATR spectroscopy of −80 ◦ C plank- tonic and biofilm growth showed variation in absorption spectra in fingerprint (1200-900 cm −1 ) region. Two clear absorption bands were prominent in biofilm at 1175 and 1143 cm −1 whereas, one prominent broad band at 1075 cm −1 resulting from the overlapping of two band was noted in planktonic cultures. Biofilm forming capability of the six isolates was also determined by acridine orange staining method. The microscopic analysis of biofilms formed on glass slides revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Maximum biofilm formation was observed after 175 h in P. aeruginosa and Klebsiella sp.

Fourier transform infrared spectroscopy of dental unit water line biofilm bacteria

Fourier transform-infrared (FT-IR) spectroscopy has become an important tool for rapid analysis of complex biological samples. The infrared absorbance spectrum could be regarded as a “fingerprint” which is a feature of biochemical substances. The FT-IR spectra of fresh and stored dried samples of six bacterial isolates (Klebsiellasp.,Bacillus cereus, Bacillus subtilis, Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobactersp.) were observed by variation in sample preparation. The results indicated that variation in sample preparation did not affect the spectra of isolates. However, less promiment/absence of a small shoulder peak at 1738 cm−1was evident in fresh dried samples ofAchromobactersp. and A.xylosoxidanscompared to prominent and broad shoulder band at 1724 cm−1in stored dried samples of these two isolates. In addition to the established KBr pellet technique, attenuated total reflectance (ATR) spectroscopy was used to analyse the spectra of planktonic growth (−80°C liquid cultures) and biofilm growth of six isolates. ATR spectroscopy of −80°C planktonic and biofilm growth showed variation in absorption spectra in fingerprint (1200−900 cm−1) region. Two clear absorption bands were prominent in biofilm at 1175 and 1143 cm−1whereas, one prominent broad band at 1075 cm−1resulting from the overlapping of two band was noted in planktonic cultures. Biofilm forming capability of the six isolates was also determined by acridine orange staining method. The microscopic analysis of biofilms formed on glass slides revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Maximum biofilm formation was observed after 175 h inP. aeruginosaandKlebsiellasp.

Degree of conversion and temperature increase of a composite resin light cured with an argon laser and blue LED

Different light sources and power densities used on the photoactivation process may provide changes in the degree of conversion (DC%) and temperature (T) of the composite resins. Thus, the purpose of this study was to evaluate the DC (%) and T (°C) of the microhybrid composite resin (Filtek™ Z-250, 3M/ESPE) photoactivated with one argon laser and one LED (light-emitting diode) with different power densities. For the KBr pellet technique, the composite resin was placed into a metallic mould (2-mm thickness, 4-mm diameter) and photoactivated as follows: a continuous argon laser (CW) and LED LCUs with power density values of 100, 400, 700, and 1000 mW/cm2 for 20 s. The measurements for DC (%) were made in a FTIR spectrometer Bomen (model MB 102, Quebec, Canada). Spectroscopy (FTIR) spectra for both uncured and cured samples were analyzed using an accessory of the reflectance diffusion. The measurements were recorded in absorbance operating under the following conditions: 32 scans, 4 cm−1 resolution, 300 to 4000-cm−1 wavelength. The percentage of unreacted carbon double bonds (% C=C) was determined from the ratio of absorbance intensities of aliphatic C=C (peak at 1638 cm−1) against an internal standard before and after the curing of the specimen: aromatic C-C (peak at 1608 cm−1). For T (°C), the samples were created in a metallic mould (2-mm thickness, 4-mm diameter) and photoactivated for 20 s. The thermocouple was attached to the multimeter allowing temperature readings. The DC (%) and T (°C) were submitted to ANOVA and Tukey’s test (p < 0.05). The degree of conversion values varied from 35.0 to 50.0% (100 to 1000 mW/cm2) for an argon laser and from 41.0 to 49% (100 to 1000 mW/cm2) for an LED. The temperature change values varied from 1.1 to 13.1 °C (100 to 1000 mW/cm2) for an argon laser and from 1.9 to 15.0 °C (100 to 1000 mW/cm2) for an LED. The power densities showed a significant effect on the degree of conversion and changes the temperature for both lightcuring units.

Effect of power densities and irradiation times on the degree of conversion and temperature increase of a microhybrid dental composite resin

The different parameters used for the photoactivation process provide changes in the degree of conversion (DC%) and temperature rise (TR) of the composite resins. Thus, the purpose of this study was to evaluate the DC (%) and TR of the microhybrid composite resin photoactivated by a new generation LED. For the KBr pellet technique, the composite resin was placed into a metallic mould (1-mm thickness and 4-mm diameter) and photoactivated as follows: continuous LED LCU with different power density values (50–1000 mW/cm2). The measurements for the DC (%) were made in a FTIR Spectrometer Bomen (model MB-102, Quebec-Canada). The spectroscopy (FTIR) spectra for both uncured and cured samples were analyzed using an accessory for the diffuse reflectance. The measurements were recorded in the absorbance operating under the following conditions: 32 scans, 4-cm−1 resolution, and a 300 to 4000-cm−1 wavelength. The percentage of unreacted carbon-carbon double bonds (% C=C) was determined from the ratio of the absorbance intensities of aliphatic C=C (peak at 1638 cm−1) against an internal standard before and after the curing of the specimen: aromatic C-C (peak at 1608 cm−1). For the TR, the samples were made in a metallic mould (2-mm thickness and 4-mm diameter) and photoactivated during 5, 10, and 20 s. The thermocouple was attached to the multimeter to allow the temperature readings. The DC (%) and TR were calculated by the standard technique and submitted to ANOVA and Tukey’s test (p < 0.05). The degree of conversion values varied from 35.0 (±1.3) to 45.0 (±2.4) for 5 s, 45.0 (±1.3) to 55.0 (±2.4) for 10 s, and 47.0 (±1.3) to 52.0 (±2.4) for 20 s. For the TR, the values ranged from 0.3 (±0.01) to 5.4 (±0.11)°C for 5 s, from 0.5 (±0.02) to 9.3 (±0.28)°C for 10 s, and from 1.0 (±0.06) to 15.0 (±0.95)°C for 20 s. The power densities and irradiation times showed a significant effect on the degree of conversion and temperature rise.

Determination of Humic Acids Content in Composts by Means of Near- and Mid-Infrared Spectroscopy and Partial Least Squares Regression Models

Humic acids are part of the stable organic matter fraction in soils and composts. Due to their favorable properties for soils and plants, and their role in carbon sequestration, they are considered a quality criterion of composts. Time-consuming chemical extraction of humic acids and the inherent source of errors require alternative approaches for humic acids quantification. Different measurement techniques in the mid-infrared (MIR: KBr pellet technique) and near-infrared (NIR: fiber probe as well as an integrating sphere with a sample rotator) regions were applied. Partial least squares regression (PLSR) models based on infrared spectra were developed to determine humic acids contents in composts. As the wavenumber regions used (NIR: 6105-5380 cm(-1) and 4360-4220 cm(-1), MIR: 1745-1685 cm(-1) and 1610-1567 cm(-1)) represent different molecular vibrations, the importance of the methylene-group-derived vibrations for the NIR models is discussed. The correlation coefficients obtained for the KBr pellet technique, the NIR fiber probe technique, and the NIR integrating sphere (r = 0.94, 0.93, and 0.94) and the root mean square errors of cross-validation (RMSECV = 2.2% organic dry matter (ODM), 2.5% ODM, and 2.2% ODM) make the models appropriate for application in composting practice.

Calcium Carbodiimide Compounds Revisited – Syntheses, Single Crystal Structure Determination and Vibrational Spectra of Ca11N6[CN2]2, Ca4N2[CN2] and Ca[CN2

Single crystals of Ca11N6[CN2]2 (dark red needles, tetragonal, P42/mnm (no. 136), a = 1456.22(5), and c = 361.86(2) pm, Z = 2), Ca4N2[CN2] (transparent yellow needles, orthorhombic, Pnma (no. 62), a = 1146.51(11), b = 358.33(4), and c = 1385.77(13) pm, Z = 4) and Ca[CN2] (transparent, colorless, triangular plates, rhombohedral, R3̅m (no. 166), a = 369.00(3), and c = 1477.5(3) pm, Z = 3) were obtained by the reaction of Na2[CN2], CaCl2 and Ca3N2 (if demanded by stoichiometry) in arc-welded Ta ampoules at temperatures between 1200 - 1400 K. Their crystal structures were re-determined by means of single crystal X-ray structure analyses. Additionally, the Raman spectra were recorded on these same single crystals, whereas the IR spectra were obtained with the KBr pellet technique. The title compounds exhibit characteristic features for carbodiimide units with D∞h symmetry (d(C-N) = 121.7 - 123.8 pm and ∡ (N-C-N) = 180°). The vibrational frequencies of these units are in the expected range (Ca11N6[CN2]2: νs = 1230, νs = 2008; δ = 673/645/624 cm−1; Ca4N2[CN2]: νs = 1230, νs = 1986; δ = 672/647 cm−1; Ca[CN2]: νs = 1274, νs = 2031, δ = 668 cm−1). The structural results are more precise than the previously reported data, and with the newly attained Raman spectrum of Ca11N6[CN2]2 we correct data reported earlier.