Improvement of multivariate calibration through instrument standardization

Wang, Yongdong; Lysaght, Michael J.; Kowalski, Bruce R.

doi:10.1021/ac00029a021

Cited by 145 publications

(93 citation statements)

References 2 publications

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“…The spectrometers used to collect calibration and validation data are the same instruments installed in the facility. While there are several techniques for transferring a calibration from one instrument to another 13,16 , they tend to lead to a degradation in the prediction quality, due to the added effects of spectral noise from both instruments. The other components of the spectrophotometer, e.g.…”

Section: Methodsmentioning

confidence: 99%

On Line Spectrophotometric Measurement of Uranium and Nitrate in H Canyon

Lascola¹

2002

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Successful and timely completion of the Highly Enriched Uranium Blend Down Project requires an aggressive processing schedule. One of the requirements for meeting the schedule is the use of on-line instrumentation to eliminate the delays associated with the analysis of samples extracted from process tanks. The Analytical Development Section of the Savannah River Technology Center has developed on-line spectrophotometers to measure uranium and nitric acid concentrations in tanks in H Canyon. Development areas addressed in this report include air-lift samplers, instrument control and analysis software, and diode array spectrophotometers. A total of nine tanks will be analyzed using two spectrophotometers. The acquired spectra are interpreted using partial leastsquares models which are valid for solutions with uranium concentrations up to 11 g/L and nitrate concentrations as high as 6 M. Concentration-dependent measurement uncertainities (2σ) are less than 0.30 g/L for uranium and 0.32 M for nitrate, and are comparable to the uncertainties of available diode array spectroscopy methods at the Analytical Laboratory (AL) facility. The models incorporate corrections for the spectral effects of Fe (<3 g/L) and Hg (<1 g/L), which are expected to be present in some process streams. Analyses with the on-line instrumentation can be performed in less than one minute, a large time savings compared to the many hours required for sampling, transport, and analysis of grab samples by AL. Other benefits of the on-line instrumentation include the reduction of radiological exposure to personnel and cost savings associated with fewer demands on AL and faster processing rates. SUMMARYThis report describes the on-line instrumentation developed by the Analytical Development Section of Savannah River Technology Center (SRTC) in support of Highly Enriched Uranium (HEU) Blend Down processing in H Canyon. The system provides measurements of uranium and nitrate concentrations for nine tanks located before and after the mixer-settler separation banks. An air-lift sampler/flow cell system attached to each tank provides access to the contents of each tank. Absorption spectra of the solutions are obtained with one of two diode-array spectrophotometers that are coupled to the flow cells by fiber optics. The spectra are analyzed using partial least-squares analysis models, and the results are reported to the H Canyon Distributed Control System. This instrument replaces a spectrophotometer system developed and installed in the late 1980's 1 which was eventually abandoned after a redefinition of the site's priorities. Recent development work at SRTC incorporated improvements to the samplers, spectrophotometers, control software, and analysis models. This report describes those technical improvements and serves as an operating, design, and performance guide for the system. INTRODUCTION Measurement PrincipleThe basis of diode array spectroscopy as an analytical technique is the determination of the concentration-and wavelength-dependent li...

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Section: Methodsmentioning

confidence: 99%

On Line Spectrophotometric Measurement of Uranium and Nitrate in H Canyon

Lascola¹

2002

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“…These correction models are of course wavelength channel dependent, and therefore i vectors must be computed to correct each complete hypercube. This is equivalent to piecewise direct standardization (PDS) with a window width of one [11]. It is assumed that spatial variation dependencies have been previously removed by the external standard-based reflectance transform.…”

Section: Internal Standardsmentioning

confidence: 99%

Hyperspectral NIR image regression part I: calibration and correction

Burger

Geladi

2005

Journal of Chemometrics

111

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Hyperspectral imaging instruments produce large amounts of raw data. These raw data in A/D converter counts have a number of errors that can be corrected by calibration. The use of multiple Spectralon calibration standards is shown to correct for both spectral and spatial variations. Optimal results are achieved using a two-step calibration and correction process. A series of full field of view or external calibration standards is used to transform raw data counts to reflectance values. A grayscale series of internal standards embedded within each hyperspectral image is used to compensate for instrument instability. Second-order regression models based on these multiple standards provide maximum accuracy. The external standards allow for standardization within a hyperspectral image. The internal standards permit instrument standardization or calibration transfer between hyperspectral images.

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“…Furthermore, for multiple instruments, differences among instruments introduce the calibration model transfer problem [3]. Much work has been published regarding the standardization of probe-based NIR spectroscopic instruments and the transfer of multivariate calibration models [3][4][5][6]. The general idea of standardization is to model the instrumental differences.…”

Section: Introductionmentioning

confidence: 99%

“…The spectral response of a subset of samples measured on the primary instrument is regressed against the same subset measured on the secondary instrument. Thus, changes in the response variables between the two instruments can be corrected and the original model can be used for prediction on the secondary instrument without having to compute new regression coefficients [4].…”

Section: Introductionmentioning

confidence: 99%

Standardization of line‐scan NIR imaging systems

Liu

MacGregor

2007

Journal of Chemometrics

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A simple and easy to use method is proposed for standardizing NIR imaging systems for differences among detectors in the charge-coupled device (CCD) array and illumination unevenness. The standardization equations are then used to pre-treat NIR image data to reduce the systematic errors introduced by a line-scan NIR imaging system. The method requires only easily available homogeneous standards with relatively uniform spectral response. The effectiveness of the standardization in reducing the pixel-to-pixel biases and other systematic effects is illustrated with examples, and the improved sensitivity in results obtained from a multivariate image analysis (MIA) based on multi-way principal component analysis (MPCA) is demonstrated.

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Improvement of multivariate calibration through instrument standardization

Cited by 145 publications

References 2 publications

On Line Spectrophotometric Measurement of Uranium and Nitrate in H Canyon

On Line Spectrophotometric Measurement of Uranium and Nitrate in H Canyon

Hyperspectral NIR image regression part I: calibration and correction

Standardization of line‐scan NIR imaging systems

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