Diffuse Reflectance Infrared Fourier Transform Spectroscopy Drift

Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS)[1] is an infrared spectroscopy sampling technique used on powder samples without prior preparation. The sample is added to a sample cup and the data is collected on the bulk sample. The infrared light on a sample is reflected and transmitted at different amounts depending on the bulk properties of the material. Diffuse reflection of the incident light produced by the sample's rough surface reflection in all directions is collected by use of an ellipsoid or paraboloid mirror. Shape, compactness, refractive index, reflectivity and absorption of the particles are all characteristic of the material being analyzed. If the sample is too absorbent, then it can be diluted with a nonabsorbent material such as potassium bromide, potassium chloride, etc. The particle size should be smaller than the wavelength of the incident light in order to minimize Mie scattering, so this would infer that it should be less than 5 Âµm for mid-infrared spectroscopy. The spectra are plotted in units of log inverse reflectance (log 1/R) versus wavenumber. Alternative plots of Kubelka-Munk units can be used, which relate reflectance to concentration using a scaling factor. A reflectance standard is needed in order to quantify the reflectance of the sample because it cannot be determined directly.[2][3]

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to analyze four types of forensically relevant fabrics coated with varying dilutions of blood. The blood was applied in two manners, dip coating with a smooth and uniform layer and drip coating with droplets from pipettes. Spectra of neat and dip coated fabrics were acquired using controlled orientations, and these were compared to spectra collected on samples with random orientations. The improved reproducibility seen in visual inspection of the spectra is confirmed by principal component and linear discriminant projections of the spectra, as well as by statistical hypothesis testing. Principal component regression (PCR), using the regions of the IR spectra associated with the amide A/B, I, II, and III vibrational bands (3500-2800, 1650, 1540, and 1350 cm-1), was employed on the more uniform dip coated spectra to estimate limits of detection for blood on two of the four fabrics - acrylic and nylon. These results demonstrate that detection limits for blood on fabrics can be decreased significantly by controlling for the orientation and face of the fabric samples while collecting spectra. Limits of detection for acrylic and nylon were found to be 196 Ã and 227 Ã diluted blood, respectively.

DOWNLOAD

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is a well-known technique for thin film characterization. Since all asbestos species exhibit intense adsorptions peaks in the 4000-400 cm-1 region of the infrared spectrum, a quantitative analysis of asbestos in bulk samples by DRIFT is possible. In this work, different quantitative analytical procedures have been used to quantify chrysotile content in bulk materials produced by building requalification: partial least squares (PLS) chemometrics, the Linear Calibration Curve Method (LCM) and the Method of Additions (MoA). Each method has its own pros and cons, but all give affordable results for material characterization: the amount of asbestos (around 10%, weight by weight) can be determined with precision and accuracy (errors less than 0.1).

Fourier transform infrared (FT-IR) spectroscopy has been successfully applied for the identification of bacteria and yeasts, but only to a limited extent for discriminating specific groups of filamentous fungi. In the frame of this study, 73 strains - from different associated hosts/substrates and geographic regions - representing 16 taxa of the edible mushroom genus Pleurotus (Basidiomycota, Agaricales) were examined through the use of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A binary matrix, elaborated on the basis of presence/absence of specific absorbance peaks combined with cluster analysis, demonstrated that the spectral region 1800-600 cm(-1) permitted clear delimitation of individual strains into Pleurotus species. In addition, closely related species (e.g., Pleurotus ostreatus and Pleurotus pulmonarius) or taxa of the subgenus Coremiopleurotus demonstrated high similarity in their absorbance patterns, whereas genetically distinct entities such as Pleurotus dryinus, Pleurotus djamor, and Pleurotus eryngii provided spectra with noteworthy differences. When specific regions (1800-1700, 1360-1285, 1125-1068, and 950-650 cm(-1)) were evaluated in respect to the absorbance values demonstrated by individual strains, it was evidenced that this methodology could be eventually exploited for the identification of unknown Pleurotus specimens with a stepwise process and with the aid of a dichotomous key developed for this purpose. Moreover, it was shown that the nature of original fungal material examined (mycelium, basidiomata, and basidiospores) had an effect on the outcome of such analyses, and so did the use of different mycelium growth substrates. In conclusion, application of FT-IR spectroscopy provided a fast, reliable, and cost-efficient solution for the classification of pure cultures from closely related mushroom species.

High-throughput diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is an increasingly valuable technique used to reduce analytic costs, time, and labor when measuring soil properties. This technique can be used to analyze soil variables in large datasets for precision agriculture and landscape-to-watershed scales studies, and therefore help to increase the sustainability of agro-ecosystems.

Diffuse reflectance measurement of powdered samples typically results in relatively long pathlengths that increases the interaction of the infrared light with the sample. Concentrated samples may have absorbance values beyond the dynamic range of an instrument resulting in higher noise. In order to obtain the absorbance in the linear range, samples need to be diluted with nonabsorbing, diffusely reflecting salts such as potassium bromide.

The cold soils of northern regions contain vast amounts of carbon-rich, organic matter. To understand how warming these soils affects carbon storage, scientists need a fast, effective way to analyze organic matter. A team determined that a technique, called diffuse reflectance mid-infrared Fourier transform (DRIFT) spectroscopy, accurately estimates the quantity and chemical composition of organic matter. It can also assess the degradation state of the carbon-rich materials stored in the soil.

Abstract:Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.Keywords: palladium; DRIFTS; modulated excitation; phase sensitive detection; baseline; oxidation state; quickEXAFS

Another technique would be reflection. Here the IR light only interacts with the surface of a material to collect chemical information. Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) is a special reflection sampling technique that allows to collect great quality spectra of solid samples that are very difficult to analyze in transmission, like soil or concrete.

In this paper, the proposed method has been introduced for qualitative and quantitative determination of micropore volume in nano ZSM-5 zeolite samples based on diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy along with chemometric methods. For this purpose, a total of 72 samples were provided and DR-FTMIR spectra corresponding to the samples were obtained in the range of 400-4000 cm-1. In order to estimate total surface area from a nitrogen adsorption isotherm, Brauner Emmett Teller (BET) method as a reference method was used. The results are displayed that the significant adsorption peak of the mid-IR spectroscopy in 3660 cm-1 is corresponded to the Sisbnd OH groups of the zeolite external surface that is a criterion for the intensity of the mesoporosity. The intensity of the 3745 cm-1 peak is grown up with enhancing the external surface area. These changes were evaluated by non-negative matrix factorization -alternating least squares (NMF -ALS) chemometrics approach for estimating the microporosity in nano ZSM-5 zeolite samples. Back-propagation artificial neural network (BP-ANN) as a nonlinear multivariate regression technique was also used to determine the micropore volume of zeolites based on DRIFT spectroscopy. For BP-ANN model in these samples, R and minimum mean squared error (MSE) values of the testing set data with 5 hidden nodes were 9.95 Ã 10-1 and 4.11 Ã 10-7, respectively. The achieved results are presented that DRIFT spectroscopy coupled with chemometrics approaches is a precise, explicit and easy technique to analyze the volume of the micropore in ZSM-5 nano-catalyst samples.

The sorption and desorption of phenanthrene and pyrene on treated and untreated aspen wood fibers were studied to evaluate the sorption mechanisms of polycyclic aromatic hydrocarbons (PAHs). Those samples were characterized using elemental analysis, porosity analysis, Solid-state 13C nuclear magnetic resonance (NMR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and batch sorption experiments with phenathrene and pyrene. Results from NMR and FTIR spectra indicated that bleaching removed aromatic moieties, yielding the highest polarity and increased porosity, whereas hydrolysis removed parts of hemicelluloses and cellulose, producing a matrix with more aromatic moieties. All PAH isotherms on treated and untreated aspen wood fibers fitted well to the Freundlich equation and bleached (BL) had the highest N value, followed by untreated (UTR), low temperature hydrolyzed (LHY) and high temperature hydrolyzed (HHY). The results suggest aromatic moieties and polarity of wood fibers mainly contribute to PAH sorption and desorption.

d0d94e66b7