A standardised intensity scale for Fourier transform Raman spectra of liquids

Petty, Chris; Hendra, P.J.; Jawhari, T.

doi:10.1016/0584-8539(91)80206-x

Cited by 24 publications

(14 citation statements)

References 19 publications

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“…The intensity correction does provide a meaningful signal magnitude, which depends on the cross section and concentration of the scatterer. [17][18][19] The signal magnitudes reported here are still in arbitrary units, since the Kopp glass emission was itself normalized before its polynomial was determined. 14 However, the signal magnitude does indicate scattering strength relative to the standard and will correct for day to day variations in laser power, optics transmission, and, to some extent, alignment.…”

Section: Discussionmentioning

confidence: 99%

Noninvasive Identification of Materials inside USP Vials with Raman Spectroscopy and a Raman Spectral Library

McCreery

Horn

Spencer

et al. 1998

Journal of Pharmaceutical Sciences

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A commercial dispersive Raman spectrometer operating at 785 nm with a CCD detector was used to acquire spectra of USP reference materials inside amber USP vials. The laser and collection beams were directed through the bottom of the vials, resulting in a 60% loss of signal. The Raman shift was calibrated with a 4-acetamidophenol standard, and spectral response was corrected with a luminescent standard. After these corrections, the Raman spectra obtained inside the USP vial and on open powders differed by less than 5%. A spectral library of 309 reference materials was constructed, with spectral acquisition times ranging from 1 to 60 s. Of these, 8% had significant fluorescent background but observable Raman features, while 3% showed only fluorescence. A blind test of 26 unknowns revealed the accuracy of the library search to be 88-96%, depending on search algorithm, and 100% if operator discretion was permitted. The tolerance of the library search to degraded signal-to-noise ratio, resolution, and Raman shift accuracy were tested, and the search was very robust. The results demonstrate that Raman spectroscopy provides a rapid, noninvasive technique for compound identification.

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Section: Discussionmentioning

confidence: 99%

Noninvasive Identification of Materials inside USP Vials with Raman Spectroscopy and a Raman Spectral Library

McCreery

Horn

Spencer

et al. 1998

Journal of Pharmaceutical Sciences

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“…As these requirements, especially the last one, are dif® cult to ful® ll, several alternative techniques have been used. 18±20 Am ong them, the use of an external standard 21,22 that compensates for not only excitation intensity¯uctuations but other parameters, such as sample positioning changes, has been proposed. In this work, data were normalized by dividing with the intensity of the cyclohexane 802 cm 2 1 band and multiplying by 100.…”

Section: Resultsmentioning

confidence: 99%

“…Approximately 2 min was allowed for laser p o w er stabilizatio n betw een su b sequ en t m easu rem ents. 21 For the 2951, 1065, 661, and 604 cm 2 1 bands, the range of precision was 0.57±4.7 and 0.4 ±6.8% RSD (n 5 4) for band intensity and band area m easurement, respectively, while for 568 cm 2 1 it was 0.92±8.0 and 1.8±8.8% RSD (n 5 4), respectively. The good reproducibility of FT-Raman spectrom eters has been attributed to the large entrance aperture, which perm its focusing the laser into a relatively large sample volum e. 22 The effect of excitation intensity on calibration data was studied at 0.57, 0.81, and 1.01 W laser excitation intensity.…”

Section: Q Uantitative Analysis Of Fenthion Formulationsmentioning

confidence: 88%

“…Am ong the factors affecting precision are positioning changes when samples are exchanged, as well as differences in sam ple tubes, 23 while the dom inant one is the laser instability that results in exciting power¯uctuations within the time scale of the experim ent. 21 The uncertainty in sample positioning and laser power is also re¯ected in detection limit values. 24 Precision values were determined by changing the position of the NMR tube between the acquisition of successive spectra.…”

Section: Q Uantitative Analysis Of Fenthion Formulationsmentioning

confidence: 99%

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Quantitative Determination of Fenthion in Pesticide Formulations by FT-Raman Spectroscopy

1999

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The Raman spectrum of the organophosphorus pesticide fenthion is presented, and a novel Fourier transform (FT)-Raman method for the quantitative determination of fenthion in pesticide formulations is proposed. Calibration curves based on Raman intensity and band area at 2951, 1065, 661, and 604 cm−1 were linear (correlation coefficients: 0.991–0.998) in the concentration range of 0.4–4.36 M. Detection limits ranged between 0.14 to 0.36 M and precision from 0.4 to 6.8% relative standard deviation (RSD) (n = 4). Spectra normalization against the 802 cm−1 cyclohexane band proved to be effective in minimizing the effect of excitation intensity fluctuations and sample positioning changes in calibration data, resulting in improved long-term stability of the calibration curves. Results obtained during the analysis of the Lebaycid formulation compare well with those obtained by the gas chromatography (GC) reference method. The proposed FT-Raman method is fast, simple, and safe, avoids sample pretreatment, and minimizes handling of toxic samples.

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“…Intensity correction of m ultichannel Raman spectra has been the subject of a number of reports. [1][2][3][4][5][6][7][8] The effect of intensity correction on noise has been brie y addressed in a recent report. 9 This report raises the issue of whether the pattern noise of multichannel detectors is dependent on the intensity of the incident radiation.…”

Section: Introductionmentioning

confidence: 99%

Effect on Noise of Intensity-Axis Correction of Spectra Recorded with Charge-Coupled Device Detectors

et al. 2002

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We have examined the effect of intensity-axis correction on noise in white light spectra recorded with charge-coupled device (CCD) detectors. Measurements were made with five detectors in Raman spectrometers. Detectors were both liquid-nitrogen and thermoelectrically cooled devices and one room temperature device. Both random and pattern noise have been considered. We used cross-correlation of noise sets to provide an indicator of a fixed pattern in the spectra and an assessment of the efficacy of the correction procedure in removing this pattern. For four of the five detectors intensity-axis correction provided a significant improvement in signal-to-noise ratio. Correction was particularly important for measurements made with lower-cost CCD detectors of the kind proposed for process control instruments.

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A standardised intensity scale for Fourier transform Raman spectra of liquids

Cited by 24 publications

References 19 publications

Noninvasive Identification of Materials inside USP Vials with Raman Spectroscopy and a Raman Spectral Library

Noninvasive Identification of Materials inside USP Vials with Raman Spectroscopy and a Raman Spectral Library

Quantitative Determination of Fenthion in Pesticide Formulations by FT-Raman Spectroscopy

Effect on Noise of Intensity-Axis Correction of Spectra Recorded with Charge-Coupled Device Detectors

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