Search results for "FOURIER TRANSFORM INFRARED SPECTROSCOPY"
showing 10 items of 394 documents
An Infrared Method, with Reduced Solvent Consumption, for the Determination of Chlorsulfuron in Pesticide Formulations
2003
A simple method has been developed for the determination of Chlorsulfuron in pesticide formulations by Fourier Transform Infrared (FTIR). Samples were diluted with CHCl3− , and the FTIR spectra of the samples and standards were obtained at a nominal resolution of 4 cm− 1 from 4000 to 900 cm− 1 with the accumulation of 25 scans. Chlorsulfuron determination was based on the measurement of peak area values from 1373 to 1363 cm− 1 which were corrected by use of a two points baseline defined from 1401 to 1302 cm− 1. The limit of detection achieved, which was of the order of 6 µg g− 1, was appropriate for the determination of Chlorsulfuron in commercially available formulations. FTIR results were…
Determination of caffeine in tea samples by Fourier transform infrared spectrometry
2002
A sustainable and environmentally friendly procedure has been developed for the FTIR determination of caffeine in tea leaf samples. The method is based on the extraction with ammonia and CHCl3 and direct determination of caffeine on the chloroform extracts using peak height absorbance measurements at 1658.5 cm(-1) and external calibration. The method provides a sensitivity of 0.2142 absorbance units mg(-1) mL and a limit of detection of 1 mg L(-1), corresponding to 0.002% m/m caffeine in tea leaves. As compared with a reference procedure, based on UV absorbance measurement at 276 nm after low pressure column chromatography, the developed procedure reduces the consume of CHCl3 by a factor of…
HPLC determination of oxadiazon in commercial pesticide formulations
2008
A simple, fast and precise high performance liquid chromatographic (HPLC) procedure has been developed for the determination of oxadiazon in emulsifiable concentrated pesticide formulations. 20 µL of diluted sample in acetonitrile were injected in a Kromasil C18 (250 ×am injetados em uma coluna Kromasil C18 4.6 mm, 5 µm) column, using acetonitrile:water (80:20) as mobile phase at 1 mL min-1 flow rate and oxadiazon determined by absorbance measurement at 292 nm. A theoretical limit of detection of 0.02 µg mL-1, a limit of quantification of 0.047 µg mL-1, corresponding to a 0.02 and 0.07% m/v in the original sample, and a relative standard deviation of 0.08% for three replicate analysis of sa…
Microwave-assisted vapour-generation Fourier transform infrared spectrometric determination of carbonate in waters
1998
Abstract A microwave-assisted vapour-generation Fourier transform infrared spectrometric procedure is proposed for the determination of total carbonate in waters. The method is based on the simultaneous injection of 100 μl of sample and 300 μl of 0.1 M nitric acid in a two-channel manifold with a merging zone; a coil located inside a microwave oven encourages the removal of CO 2 . The carbon dioxide is separated from the distilled water employed as carrier by means of gas–liquid separator and is introduced by a nitrogen carrier flow inside a long-path infrared absorption gas cell, from which the corresponding flow analysis recording is registered as a function of time in the wavenumber rang…
FTIR determination of Aspartame and Acesulfame-K in tabletop sweeteners.
2004
Two different strategies for sweeteners determination in tabletop samples by Fourier transform middle-infrared (FTIR) spectrometry, an off-line and a fully mechanized extraction of Aspartame and Acesulfame-K with different mixtures of chloroform and methanol, have been developed. The off-line method involves the extraction of both active principles by sonication of samples with 25:75 v/v CHCl3/CH3OH and direct measurement of the peak height values at 1751 cm(-1), corrected using a baseline defined at 1850 cm(-1) for Aspartame, and measurement of the peak height at 1170 cm(-1) in the first-order derivative spectra, corrected by using a horizontal baseline established at 1850 cm(-1), for Aces…
Direct ATR-FTIR determination of sucrose in beet root.
2000
A simple and fast procedure has been developed for the direct determination of sucrose in beet root samples through attenuated total reflectance Fourier transform infrared absorbance measurements (ATR-FTIR) at 1056 cm(-1) with a baseline established between 1187 and 887 cm(-1). The method only requires a previous crushing or liquefaction of samples and it is free from matrix effects and from the interference of minoritary sugars and fermentation molecules. Aqueous solutions of sucrose can be used as standards and recovery values from 101 to 103% were found for spiked concentration levels from 3.5 to 10.5% (w/w). The limit of detection provided by this method corresponds to 0.15% (w/w) of su…
Direct determination of ethanol and methanol in liquid samples by means of vapor phase-Fourier transform infrared spectroscopy
1997
Abstract A FTIR procedure is proposed for the direct determination of methanol and ethanol in liquid samples, such as alcoholic beverages and eau-de-cologne, based on vapor generation from small injected volumes of untreated samples into a heated Pyrex glass reactor in which, at a temperature of 80°C, ethanol and methanol are volatilized and introduced into a long-path IR gas cell by means of a N2 carrier flow. The IR spectra obtained present two characteristic ethanol bands (1050 and 880 cm−1) and a single characteristic methanol band (1030 cm−1). The measurement of the area of the transient recording obtained for the wavenumber range between 1025–950 and 950–820 cm−1 allows us the determi…
On-line gel permeation chromatography–attenuated total reflectance–Fourier transform infrared determination of lecithin and soybean oil in dietary su…
2007
Gel permeation chromatography (GPC) with attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometry detection has been proposed for the simultaneous determination of lecithin and soybean oil in dietary supplements. The method involves the extraction of analytes with dichloromethane in an ultrasound water bath and the injection of 2 ml of centrifuged and filtered extracts into the system integrated by two Envirogel GPC columns (19 mm x150 mm, 19 mm x 300 mm) coupled on-line. Dichloromethane was used as mobile phase. A method has been developed to select the most appropriated wavenumber to be used for the determination of each considered compound from the calculation of a…
Structural characterization of Nigerian coals by X-ray diffraction, Raman and FTIR spectroscopy
2010
Abstract The structural parameters of six Nigerian coals were determined by X-ray diffraction, Raman and FTIR spectroscopy. This study reveals that the coals contain crystalline carbon of turbostratic structure with some amount of highly disordered amorphous carbon. The average lateral sizes ( L a ), stacking heights ( L c ) and interlayer spacing ( d 002 ) of the crystallite structures calculated from the X-ray intensities range from 16.47 to 25.70, 8.12 to 13.25 and 3.48 to 3.58 A, respectively. The L a values derived from the Raman spectra analyses using the classical linear relationship between 1/ L a and the D/G band ratio are higher (27.53–34.67 A) than values obtained from X-ray diff…
ATR-FTIR and XRD quantification of solid mixtures using the asymptotic constant ratio (ACR) methods. Application to geological samples of sodium and …
2019
Two asymptotic constant ratio methods applied to the quantification of individual components of solid samples using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) are described. The methods involve the measurement of the peak current/peak areas of selected signals (diffraction peaks in XRD and absorption bands in ATR-FTIR) relative to the signal of standard added in constant proportion to the sample and the sample enriched with the analyte following the usual standard additions methodology. The proposed method compensates the absorption effects appearing in XRD and the presence of overlapping absorption bands of interferents by me…