DTGS detector

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

The source is usually a temperature-stabilized ceramic filament operating around 1500K. The detector in FTIR is usually a deuterium triglycine sulphate (DTGS) detector, although in RAIRS experiments the liquid nitrogen-cooled mercury cadmium telluride (MCT) detector is employed. 

Depending on the source of the graphite, one obtains distinctly different IR/PA spectra (frequently caused by adsorbed species) and the response of the DTGS detector of an IR spectrometer turns out to be a more accurate measure of variable source intensity (12). A normalization technique (13) requiring measurement of the spectrum at two different mirror velocities and corrected by black body spectra taken at the same two velocities appears to be the best normalization method reported thus far. 

The pyroelectric DTGS detector is a very useful low-cost, general purpose, wideband NIR detector well suited for use in FT-based analyzers. It is not normally used in scanning monochromators where higher sensitivity detectors are needed to match the lower optical throughput and discrete wavelength scanning requirements. 

First, the availability of high optical throughput in an FT-NlR analyzer means that lower-cost, more robust and also more linear DTGS detectors can be used routinely. These in turn allow (through the choice of suitable beamsplitter materials and source characteristics) a wider range of operation than the conventional... 

Sources and detectors Specific discussions of sources and detectors have been covered elsewhere in this article. The issues here are more service and performance related. Most sources have a finite lifetime, and are service replaceable items. They also generate heat, which must be successfully dissipated to prevent localized heating problems. Detectors are of similar concern. For most applications, where the interferometer is operated at low speeds, without any undesirable vibrational/mechanical problems, the traditional lithium tantalate or DTGS detectors are used. These pyroelectric devices operate nominally at room temperature and do not require supplemental cooling to function, and are linear over three or four decades. 

ETIR Measurements. FTIR spectra were recorded using a Nicolet model 870 spectrometer (Madison, WI) equipped with a deuterated triglycine sulfate (DTGS) detector. 

IR spectra of starch can be obtained with an IR spectrometer such as a Digilab FTS 7000 spectrometer, Digilab USA, Randolph, MA, equipped with a thermoelectrically cooled deuterated tri-glycine sulfate (DTGS) detector using an attenuated total reflectance (ATR) accessory at a resolution of 4 cm by 128 scans. Spectra are baseline-corrected, and then deconvoluted between wavenumbers 1200 to 800 cm . A half-band width of 15 cm and a resolution enhancement factor of 1.5 with Bessel apodization are employed. Intensity measurements are performed on the deconvoluted spectra by recording the height of the absorbance bands from the baseline. 

Sample Characterization. Infrared spectra of the adsorbed films were obtained with a Perkin-Elmer 1710 FTIR Spectrometer, equipped with a DTGS detector and a nitrogen-purged sample chamber. The transmission IR spectra (high frequency range >2000 cm 1) of the adsorbed species were directly measured on the glass slides. The... 

A Bomem Michelson 102 FTIR equipped with a Csl beamsplitter and DTGS detector was used to collect spectra. Spectra were collected at 4 cm-1 resolution requiring approximately 6 seconds per scan and processed using Spectra-Calc software on a PC AT type system. 

FTIR Spectroscopy. Infrared spectra were recorded on a Perkin Elmer Spectrum One FTIR spectrometer equipped with a Deuterated Triglycine Sulfate (DTGS) detector and KBr optics. Data collection was performed at 4 cm-1 spectral resolution in the region of 4000-450 cm-1 and averaged over 5 scans. All samples were measured in transmission mode. 

Samples were prepared by using a KBr cell. Salt plates were cleaned before the experiments using Acetone. Using a micropipette, a drop of the CWA was place on one salt plate. Then the second plate was put over it and the liqnid was spread into a thin film. Samples were analyzed in a Bruker Vector 22 FUR with a DTGS detector. The Infiared experimental conditions were 20 scans and a 4 cm resolntion. A scanned backgronnd spectmm was acquired before each measurement session using a clean test salt plate at the same instramental conditions used for sample spectra acquisition. All spectra were recorded in absorbance mode. 

Gas phase experiments of the six CWAS were performed in a Bruker Optics FTIR model IFS 66v/S spectrometer equipped with a DTGS detector and a potassium bromide (KBr) beamsplitter. A gas cell was placed in the macro compartment and adapted to a micro pump that removed background air and transferred the sample to the cell. DMMP and DIMP were used for these analyses. One gram of the CWAS was deposited on an Erlemneyer. A typical spectroscopic measurement averaged 20 scans at a resolution of 4 cm in the range of 400 - 7500 cm. Gas phase IR spectra were also acquired using Bruker Optics OPUS , Version 4.2. A background of air in the cell was recorded before each run of the CWAS experiments. 

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