Infrared Spectroscopy Methods Research Articles

A micro-reflectance IR spectroscopy method for analyzing volatile species in basaltic, andesitic, phonolitic, and rhyolitic glasses

Volatile contents of geologic glasses are used to model magma chamber and degassing processes, thus, there is considerable interest in small-scale analytical techniques for analyzing volatiles in glasses. Infrared (IR) spectroscopy has the advantage of determining volatile speciation in glasses (e.g., OH − , molecular H 2 O, molecular CO 2 , and CO 3 2− ). However, sample preparation for the most common IR method used, micro-transmission IR spectroscopy, is complicated because glasses must be prepared as thin, parallel-sided wafers. Raman analysis, while valuable for Fe-poor samples, can be difficult to use for Fe-rich glasses. We have calibrated a micro-reflectance infrared method for determining volatile species using calculated Kramers-Kronig absorbance (KK-Abs.) spectra that requires that only one side of a glass be polished. The method is easier to use than other reflectance methods where it is difficult to determine the baseline for the IR bands. Total H 2 O wt% = m ·(3600 cm −1 KK-Abs.), where m , is the slope of the calibration line that is obtained from a fit to the data. The m value is related to the calculated refractive index, n , for a range of aluminosilicate glass compositions allowing the technique to be applied to samples with unknown calibration slopes. For calc-alkaline andesite glasses we determined calibration slopes for micro-reflectance IR measurements of molecular H 2 O, molecular CO 2 , and CO 3 2− . The method has been calibrated for glasses with up to 6.76 wt% total H 2 O (but is useful for glasses with more than 20 wt% total H 2 O) and has been calibrated for glasses with up to 0.575 wt% total CO 2 . This technique provides a means to analyze volatile abundances in samples that are not possible to analyze or prepare for analysis with transmission micro-IR techniques. We have determined volatile contents in fragile samples such as cracked, vesicular, or crystal-bearing glasses formed by volcanic or impact processes or in high-pressure bubble nucleation experiments and H diffusion experiments. We have monitored H uptake during weathering of basaltic glasses that cannot be polished and determined volatiles in melt inclusions and pumice.

Ion Beam Induced Modifications in Conducting Polymers

High energy ion beam induced modifications in polymeric materials is of great interest from the point of view of characterization and development of various structures and filters. Due to potential use of conducting polymers in light weight rechargeable batteries, magnetic storage media, optical computers, molecular electronics, biological and thermal sensors, the impact of swift heavy ions for the changes in electrical, structural and optical properties of polymers is desirable. The high energy ion beam irradiation of polymer is a sensitive technique to enhance its electrical conductivity, structural, mechanical and optical properties. Recent progress in the radiation effects of ion beams on conducting polymers are reviewed briefly. Our recent work on the radiation effects of ion beams on conductive polymers is described. The electrical, structural and optical properties of irradiated films were analyzed using V-I, X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible spectroscopy and Fourier transform infrared spectroscopy methods.

Exploring Sampling for near Infrared Spectroscopy

S ampling and sample preparation are two aspects of analytical work by near infrared (NIR) spectroscopy or reference methods in which, regrettably, research has usually lagged behind other developments in the technology. There are a number of things that the average NIR user needs to know about samples, sampling, sample preparation and sample presentation to the instrument. These include: 1) What is a sample? 2) What is the significance of a “truly representative” sample? 3) How should a sample be taken? 4) What affects the accuracy of sampling? An in-depth article on sampling that appeared in the Mythbuster column of the previous issue of NIR news comprehensively dealt with items 2 and 3. This article will discuss items 1 and 4, together with some other aspects of this all-important aspect of NIR technology. But first a note on the “Truly Representative Sample”. The truly representative sample should provide the material for the most accurate method of determination of the composition and functionality of the entire population. To save expense and time in testing, fully representative samples are usually thoroughly-blended composites of sub-samples that have been taken during operations such as storage of grain in elevators or silos, and other operations where the populations are too big, and the number of sub-samples too numerous to test individually. The danger with truly representative composite samples of large bulks is that they mask the variance that occurs within the sample. For example, if a composite sample is taken during storage of farmers’ deliveries of freshly-harvested grain into a 3000-tonne silo, the composite may show that the moisture content is 12.9%, a safe value for storage. But the individual deliveries may have ranged from 11% to 16% in moisture content. The delivery of, for example, 12 tonnes of grain at 16% moisture into a silo could cause spoilage within the silo that would not become apparent until the grain was later moved out of the silo for marketing. The heated grain would become dispersed throughout the grain as it moved out of the silo (Figure 1). When a composite sample is going to be prepared from a series of deliveries or sub-samples of cargo loading, the variance or the standard deviation (SD) among the samples and the range in analytical data should be determined. To obtain this important information, each individual sub-sample that goes to make up the composite should be tested before compositing. This used to be impracticable with reference testing, but it can be easily and cheaply achieved using NIR spectroscopy by scanning every subsample as it is taken.

Thermal stabilization of poly(hexamethylene adipamide) fibers in the presence of ferric chloride prior to carbonization

Thermal stabilization of poly(hexamethylene adipamide) (polyamide 66, PA66) fibers in the presence of ferric chloride was performed in air at 215 °C for stabilization times ranging from 15 min to 6 h. The presence of ferric ions in the PA66 structure enhanced thermal stabilization reactions. Optical microscopy, density, elemental analysis, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and infrared (IR) spectroscopy measurements were used to examine and characterize the structural transformations occurring during the thermal stabilization. Ferric chloride (FeCl3) pretreatment followed by thermal stabilization in an air atmosphere resulted in major physical and structural transformations. Physical transformations were revealed as a reduction in fiber diameter and an increase in density values together with major color changes. Ferric chloride pretreated and thermally stabilized PA66 fibers were found to be fully stabilized after 6 h of stabilization and acquired infusible and nonburning characteristics prior to the carbonization stage. Elemental analysis showed a reduction in carbon, nitrogen and hydrogen contents. The DSC and TGA measurements demonstrated that there was an improvement in the thermal stability. The TGA thermograms showed a relative improvement in thermal stability as indicated by increasing char yield with progressing time. The char yield reached a maximum value of 40% at 1000 °C for the ferric chloride pretreated PA66 fibers stabilized for 6 h at 215 °C. Experimental results obtained from the DSC, X-ray diffraction and infrared spectroscopy methods indicated gradual and continuous disordering reactions as a result of the scission of the hydrogen bonds with progressing time. The IR measurements also indicated the formation of the carbonyl (CO) group as a result of oxidative crosslinking reactions and the occurrence of dehydrogenation reactions caused by the loss of hydrogens from the methylene (CH2) groups in agreement with the elemental analysis. Sample preparation appeared to play an important role in the formation of ferric ion coordination bonds with the carbonyl oxygen atoms. The unconstrained stabilization method caused an enhancement of the complexation of ferric ions with the amide groups. A new method of evaluating the X-ray stabilization index was devised specifically for the thermally stabilized PA66 fiber.

A Fourier Transform Infrared Spectroscopy Method for Analysis of Palm Oil Adulterated with Lard in Pre-Fried French fries

Fourier transform infrared spectroscopy with attenuated total reflectance accessory was used to detect the presence of lard in French fries pre-fried in palm oil adulterated with lard. A Fourier transform infrared calibration model was obtained using partial least squares for prediction of lard in a blend mixture of lard and palm oil. The coefficient of determination (R2) of 0.9791 was obtained with 0.5% of detection limit. The error in calibration expressed with root mean square error of calibration was 0.979%. In addition, the error obtained during cross validation was 2.45%. A discriminant analysis test was able to distinguish between fries samples adulterated with lard and samples, which were pre-fried with palm oils. Fourier transform infrared spectroscopy is a fast and powerful technique for quantification of lard present in French fries.

Productividad y calidad nutricional de genotipos de sorgo para doble propósito.

The objective of this study was to evaluate a set of dual purpose sorghum genotypes for their grain and fodder productivity, as well as for nutritional quality of leaves and stems for livestock. From 2003 through 2005, 26, 15 and 8 genotypes were evaluated respectively, in comparison with the control variety INTA CNIA during the postrera season (August to November) in the experimental fields of the National Agricultural Research Centre (INTA CNIA), Nicaragua. Agronomic traits were measured as well as nutritional quality of leaves and stems using the Near Infrared Spectrometry method. For all agronomic and nutritional quality traits were found significant differences among genotypes, except for grain yield in 2004, and the neutral and acid detergent fiber contents in stems. The heritability of agronomic and quality traits in leaves was high (≥ 0.50), with values between 0.96 and 0.51 but lower for most of quality parameters in stems, with values between 0.47 and 0.20. The only significant positive correlation was among crude protein (MAT) and leave – stem ratio in fresh stems (H/RF). The genotypes BF 95-11/195, Sureño, SH 688, V142 and V 144, achieved the best results for grain and fodder yield and fodder quality (regarding both leaves and stems). Sureño out-yielded the control variety for crude protein content per hectare (MPB/ha) in 50 and 33 % for leaves and stems respectively.

Synthesis and Molecular Crystal Structure of 4-(4,5-Dimethoxy-2-nitrophenyl)-2,6-dimethyl-3,5-dicarbmethoxy-1,4-dihydropyridine (C19H22N2O8)

A novel three-component one-pot synthesis of 4-(4,5-dimethoxy-2-nitrophenyl)-2,6-dimethyl-3,5-dicarbmethoxy-1,4-dihydropyridine from methyl 3-oxobutanoate, ammonium carbonate, and 4,5-dimethoxy-2-nitrobenzaldehyde has been carried out by typical Hantzsch synthesis. The single crystal was obtained by crystallization from methanol in 0.30 × 0.20 × 0.20 mm dimensional of 4-(4,5-dimethoxy-2-nitrophenyl)-2,6-dimethyl-3,5-dicarbmethoxy-1,4-dihydropyridine (C19H22N2O8), which was investigated by X-ray diffraction. The compound crystallizes in the monoclinic P21/c space group with unit cell dimensions a = 14.4830(3) Å, b = 8.66000(10) Å, c = 15.1036(3) Å, α = 90°, β = 90.0870(10)°, γ = 90°. 1H NMR (hydrogen-1 nuclear magnetic resonance), mass, and IR (infrared) spectroscopic methods of the compound are also described.

Mechanical Properties of Chitosan Modified Montmorillonite Filled Tapioca Starch Nanocomposite Films

This study was carried out to develop renewable and degradable plastics film with good mechanical properties. The mechanical properties between compatibilized montmorillonite (MMT)/chitosan filled tapioca starch (TPS), uncompatibilized MMT/TPS, and chitosan/TPS nanocomposite films were investigated. Experimental works were started with the extraction of local chitosan from chitin derived from prawn shells which involving deprotenization, demineralization and deacetylation treatments. Degree of deacetylation of chitosan was determined using infrared spectroscopy method. Chitosan was acted as compatibilizer between MMT and starch in order to improve the dispersion of MMT in nanocomposite systems. Nanocomposite films were prepared using a solution casting method with addition of glycerol as the plasticizer. The starch solution was cast onto PTFE mold with cavity thickness of 0.5mm. Characterizations of the nanocomposite films were done using Fourier Transform Infrared Analysis (FTIR). Tensile properties of nanocomposites were investigated. The compatibilized nanocomposite films, chitosan/MMT/TPS give significant effects to tensile properties. Chitosan has played its role as the compatibilizer and also as flexibility improvers to nanocomposite films because elongation at break improved after addition of chitosan.

FT-IR Method Development and Validation for Quantitative Estimation of Zidovudine in Bulk and Tablet Dosage Form

New, simple and cost effective infrared spectroscopic method has been developed for the estimation of zidovudine (CAS 30516-87-1) in bulk and tablet dosage form. The quantitative analysis of zidovudine was carried out in solid form using KBr pellet method and in liquid form using quartz cuvette. These methods were developed and validated for various parameters according to ICH guidelines. Linearity range was found to be 0.8-1.6% w/w in KBr pellet method and 250-1 500 μg ml-1 in solution. The proposed methods were successfully applied for the determination of zidovudine in pharmaceutical formulation (tablets). The results demonstrated that the proposed methods are accurate, precise and reproducible (relative standard deviation<2%), while being simple, economical and less time consuming than other available methods and can be used for estimation of zidovudine in different dosage forms.

Near infrared spectroscopy (NIT) analysis of maize hybrids starch content

The purpose of my research is to find the most favourable maize hybrids for bioethanol-production feedstock, using the so called „NIT”, near infrared spectroscopy method in the analysis of the inner contents especially of starch content. The other goal of my analysis is to reflect on how the effects of the most important growing factors – such as irrigation and the use of different dose fertilizers – contribute to the maize hybrids starch content.

Influence of proteins content in the feed on the course of membrane distillation

The formation of deposit on the membrane surface (fouling) is one of the major operating problems of membrane processes. The influence of proteins on the course of membrane fouling was investigated during the whey concentration process. The Fourier transform infrared spectroscopy method was applied in order to determine the composition of the deposit precipitated from the feed as well as accumulated on the membrane surface on the feed side. The intensity of fouling can be limited by the pretreatment of feed and the selection of operating parameters of membrane distillation. The thermal and chemical pretreatment methods were used for whey deproteinization. The whey was subsequently concentrated by direct contact membrane distillation using polypropylene membranes at 323, 333, and 343 K. The concentrated whey contained all components of the feed.

近红外光谱法快速测定干粉灭火剂含水率的可行性研究

Usual analytical methods are complex and require rigorous experimental condition.In order to meet the demand of fire product supervisory department in rapidly detecting the quality of dry chemical,a rapid and non-destructive method was proposed to determine the moisture content in ABC dry chemical using near infrared spectroscopy of fiber diffuse reflection.The calibration models were established for determination of moisture content of ABC dry chemical by partial least squares and 47ABC dry chemical sample spectra.Spectral data preprocessing and Spectral region selection were discussed.Correlation Coefficient of Calibration Set of the model was 0.976,root mean square of error cross validation was 0.037 1,correlation coefficient of prediction set was 0.952,and root mean square error of prediction was 0.021 6in the predicted rang of 0.075%～0.334%for moisture content of ABC dry chemical.Using the Chi-square test method,repeatability standard deviation measurements all belonged to the same overall at a 95% confidence level.All the relative standard deviations were less than 7.0%.The near infrared spectroscopy method is used to test the moisture content of ABC dry chemical is feasible.

Respirable Crystalline Silica (RCS) emissions from industrial plants – Results from measurement programmes in Germany

Numerous research articles dealing with Respirable Crystalline Silica (RCS) in occupational health because epidemiological studies reveal an association between RCS-dust and the development of silicosis as well as an increased probability of developing lung cancer. Research activities about RCS in ambient air are known from US-measurements. However there is a lack of knowledge regarding RCS-emissions in several industrial sectors. Industrial sources of crystalline silica include construction, foundries, glass manufacturing, abrasive blasting or any industrial or commercial use of silica sand, and mining and rock crushing operations. This paper describes a RCS-emission measurement method for stack gases and report results from the German RCS-emission measurement programmes which were used to identify installations and types of industries with the highest concentration levels of RCS in stack gases. A two-stage cascade impactor was used for the measurements which separate particles into the following size fractions: >10 μm, 10–4 μm und <4 μm of aerodynamic diameter. The measurements were carried out according to international sampling standards. The size of crystalline silica particles of most concern are those respirable particles that are smaller than four microns (millionths of a metre), also called particulate matter 4 (PM4). The analytical procedure of determining crystalline silica in emission samples (in the fraction below 4 μm) consists of using x-ray diffraction and infrared spectroscopy methods which are the same methods as used in the field of occupational health. A total of 37 emission measurement campaigns were assessed (112 RCS-samples in nine industrial sectors). The investigated plants are located in different German states such as Bavaria, North Rhine Westphalia, Baden-Wuerttemberg, Rhineland-Palatinate and Saxony-Anhalt. The results of the measurements show that most of the investigated plants can achieve compliance with the newly developed German emission limit value (ELV) of 1 mg m−3. The ELV is expressed as the concentration of RCS in stack emissions. According to the German emission minimising principle and the precautionary principle it is assumed that by complying with the RCS-ELV there is no ambient air health risk for people living these plants. In the case of increased total dust concentration in the stack gas (more than 20 mg m−3) combined with increased percentage of crystalline silica in PM4 dust, a violation of the above mentioned ELV is more likely. This applies mostly to installations in the silica sand processing industry. To comply with the ELV of 1 mg m−3, efficient emission control technology should be implemented and should be well maintained.

Characterization of the structure and optical properties of micron porous layers on antimony-doped silicon substrates

A real structure and optical properties of micron porous silicon layers on Si(111) (Sb) substrates were studied by the two-crystal X-ray diffractometry and reflectometry, scanning electron microscopy, and infrared spectroscopy methods in a 4000- to 12000-cm−1 frequency range. The porous silicon layers were formed by the electrochemical etching method at a 50-mA/cm2 current in a hydrofluoric acid/ethanol mixture in a ratio of 1: 1. The structural parameters of the layers are determined, namely, the thickness is 6–66 μm, the average deformation is ≈4.5 × 10−4, and the density is ≈0.72. It is shown that the studied porous layers can be considered uniform only to some extent. The optical transmission spectra were analyzed within the frameworks of the effective medium model and the refractive index n of the substrate was estimated. It is determined that the Si(111) (Sb) substrates have a pronounced transmission band in the spectral range of 1.05–1.5 μm. To restore the dispersion of optical constants from transmission spectra, the procedure, based on the mathematical treatment with regard to real geometric and physical parameters of several transmission spectra by minimizing functional χ 2, was proposed. Possibilities of applying the proposed procedure for determinations of optical characteristics of thin layers and heterostructures are discussed.

Stability of iron (Fe) nanowires

The iron nanowires were obtained by DC electrochemical method in nanoporous anodic alumina templates (AAO). For stability tests these materials were placed in different solutions: white wine, citric acid, 0.9% NaCl, distilled water and ethanol for a 1–3week time period. The results of such treatment (solubility or possible changes on the surface) of the Fe nanowires were measured by IR (infrared spectroscopy), ASA (atomic absorption spectroscopy), TEM (transmission electron microscopy), XRD (X-ray diffraction) and DSC (differential scanning calorimetry) methods.

Study on Camellia Sect. Chrysantha Chang species identification by FTIR technology

FTIR spectra from 16 kinds of Camellia Sect. Chrysantha by Fourier transform infrared spectroscopy (FTIR) method combined with the system clustering and correlation coefficient method were used to analyze and compare these spectral data. The results, show that: Camellia Sect. Chrysantha of 16 kinds were divided into three groups, the first kind was: C. longzhouensis etc, in all eleven kinds; The second kind was: C. achrysantha, C. limonia, C. pingguoensis and C. chuongtsoensis; The third kind was C. microcarpa, which for a class alone. According to the difference in related anatomy and morphology, this study supported that C. longgangensis and C. ptilosperma should be incorporated into one kind; C. multipetala, C. longgangensis, C. parvipetala, C. tunghinensis and C. limonia, C. achrysantha, C. microcarpa, C. nitidissima, C. terminali and C. pingguoensis should be divided into separate species. FTIR-cluster analysis can be used as a possible means for the identification of Camellia Sect. Chrysantha.

A study on the use of near-infrared spectroscopy for the rapid quantification of major compounds in Tanreqing injection

In this paper we describe the strategy used in the development and validation of a near infrared spectroscopy method for the rapid determination of baicalin, chlorogenic acid, ursodeoxycholic acid (UDCA), chenodeoxycholic acid (CDCA), and the total solid contents (TSCs) in the Tanreqing injection. To increase the representativeness of calibration sample set, a concentrating–diluting method was adopted to artificially prepare samples. Partial least square regression (PLSR) was used to establish calibration models, with which the five quality indicators can be determined with satisfied accuracy and repeatability. In addition, the slope/bias (S/B) method was used for the models transfer between two different types of NIR instruments from the same manufacturer, which is contributing to enlarge the application range of the established models. With the presented method, a great deal of time, effort and money can be saved when large amounts of Tanreqing injection samples need to be analyzed in a relatively short period of time, which is of great significance to the traditional Chinese medicine (TCM) industries.

Analysis of Relationship Between Basic Composition, pH, and Physical Properties of Selected Bovine Muscles

Abstract The aim of this study was to analyse the correlation between basic meat composition (water, protein, fat, and connective tissue contents), pH value, and physical parameters (texture and colour, drip loss) of selected beef muscles. Five different muscles (LTH, SEM, SET, PSM, TRI) from 20 carcasses were examined. Measurements of the basic meat composition were conducted using a near infrared spectrometry method, colour parameters in L*a*b system, and texture parameters. Drip loss correlated strongly negatively with the pH value. Depending on the muscle type, the correlation ranged -0.601≤r≤-0.282, whereas drip loss correlated moderately positively with connective tissue content. The most significant positive correlation (r≈0.67) between hardness, tenderness, and fat content was noted in the SEM. Colour parameters strongly depended on pH values (-0.831≤rL*≤-0.338; - 0.828≤ra*≤-0.542; -0.912≤rb*≤-0.719) and to a lesser extent on the content of connective tissue.

Enzymatic transesterification monitored by an easy‐to‐use Fourier transform infrared spectroscopy method

Transesterification of triglycerides with short chain alcohols is the key reaction in biodiesel production, in addition to other applications in chemical synthesis. However, it is crucial to optimize reaction conditions to make enzymatic transesterification a cost-effective and competitive process. In this work, a new, easy Fourier transform infrared (FTIR) spectroscopic approach for monitoring the transesterification reaction is reported and compared with a gas-chromatographic method. The concentration of the total methyl esters in the reaction mixture is determined from the peak intensity at ∼1435 cm(-1) in the second derivatives of the FTIR absorption spectra using a linear regression calibration. Interestingly, we found that the use of second derivatives allows an accurate determination of the methyl esters without the interference of free fatty acids. Moreover, information on substrate hydrolysis can be obtained within the same measurement by the infrared absorption at ∼1709 cm(-1) . We applied this approach to monitor methanolysis and hydrolysis reactions catalyzed by different commercial lipases, which displayed different sensitivities to methanol inhibition. Therefore, the FTIR approach reported in this work represents a rapid, inexpensive, and accurate method to monitor enzymatic transesterification, requiring very limited sample preparation and a simple statistical analysis of the spectroscopic data.

Use of near infrared spectroscopy to predict microbial numbers on Atlantic salmon

The potential of a near infrared spectroscopy (NIR) method to detect as well as predict microbial spoilage on Atlantic salmon (Salmo salar) was investigated. Principal component analysis (PCA) of the NIR spectra showed clear separation between the fresh salmon fillets and those stored for nine days at 4°C indicating that NIR could detect spoilage. A partial least squares regression (PLS) prediction model for total aerobic plate counts after nine days was established using the NIR spectra collected when the fish was fresh to predict the number of bacteria that would be present nine days later. The calibration equation was good (R2 = 0.95 and RMSE = 0.12 log cfu/g) although the error of the validation curve was larger (R2 = 0.64 and RMSE = 0.32 log cfu/g). These results indicate that with further model development, it may be possible to use NIR to predict bacterial numbers, and hence shelf-life, in Atlantic salmon and other seafood.