Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils
Mid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of th...
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MDPI AG
2018-03-01
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| Series: | Sensors |
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| Online Access: | http://www.mdpi.com/1424-8220/18/4/993 |
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| author | Christopher Hutengs Bernard Ludwig András Jung Andreas Eisele Michael Vohland |
| author_facet | Christopher Hutengs Bernard Ludwig András Jung Andreas Eisele Michael Vohland |
| author_sort | Christopher Hutengs |
| collection | DOAJ |
| description | Mid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of the Agilent 4300 Handheld FTIR (DRIFT spectra) in comparison to a Bruker Tensor 27 bench-top instrument in terms of (i) spectral quality and measurement noise quantified by wavelet analysis; (ii) accuracy of partial least squares (PLS) calibrations for soil organic carbon (SOC), total nitrogen (N), pH, clay and sand content with a repeated cross-validation analysis; and (iii) key spectral regions for these soil properties identified with a Monte Carlo spectral variable selection approach. Measurements and multivariate calibrations with the handheld device were as good as or slightly better than Bruker equipped with a DRIFT accessory, but not as accurate as with directional hemispherical reflectance (DHR) data collected with an integrating sphere. Variations in noise did not markedly affect the accuracy of multivariate PLS calibrations. Identified key spectral regions for PLS calibrations provided a good match between Agilent and Bruker DHR data, especially for SOC and N. Our findings suggest that portable FTIR instruments are a viable alternative for MIR measurements in the laboratory and offer great potential for on-site applications. |
| first_indexed | 2024-04-14T04:46:18Z |
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| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-04-14T04:46:18Z |
| publishDate | 2018-03-01 |
| publisher | MDPI AG |
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| spelling | doaj.art-2a2cee31c9ab4874a25b0c40c59ed4152022-12-22T02:11:26ZengMDPI AGSensors1424-82202018-03-0118499310.3390/s18040993s18040993Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of SoilsChristopher Hutengs0Bernard Ludwig1András Jung2Andreas Eisele3Michael Vohland4Geoinformatics and Remote Sensing, Institute for Geography, Leipzig University, Johannisallee 19a, 04103 Leipzig, GermanyDeparatment of Environmental Chemistry, Kassel University, Nordbahnhofstr. 1a, 37213 Witzenhausen, GermanyTechnical Department, Szent István University, Villányi út 29-43, 1118 Budapest, HungarySphereOptics GmbH, Gewerbestrasse 13, 82211 Herrsching, GermanyGeoinformatics and Remote Sensing, Institute for Geography, Leipzig University, Johannisallee 19a, 04103 Leipzig, GermanyMid-infrared (MIR) spectroscopy has received widespread interest as a method to complement traditional soil analysis. Recently available portable MIR spectrometers additionally offer potential for on-site applications, given sufficient spectral data quality. We therefore tested the performance of the Agilent 4300 Handheld FTIR (DRIFT spectra) in comparison to a Bruker Tensor 27 bench-top instrument in terms of (i) spectral quality and measurement noise quantified by wavelet analysis; (ii) accuracy of partial least squares (PLS) calibrations for soil organic carbon (SOC), total nitrogen (N), pH, clay and sand content with a repeated cross-validation analysis; and (iii) key spectral regions for these soil properties identified with a Monte Carlo spectral variable selection approach. Measurements and multivariate calibrations with the handheld device were as good as or slightly better than Bruker equipped with a DRIFT accessory, but not as accurate as with directional hemispherical reflectance (DHR) data collected with an integrating sphere. Variations in noise did not markedly affect the accuracy of multivariate PLS calibrations. Identified key spectral regions for PLS calibrations provided a good match between Agilent and Bruker DHR data, especially for SOC and N. Our findings suggest that portable FTIR instruments are a viable alternative for MIR measurements in the laboratory and offer great potential for on-site applications.http://www.mdpi.com/1424-8220/18/4/993portable FTIR spectrometermid-infrared soil spectroscopybenchmarkingnoise analysiscontinuous wavelet transformmultivariate calibrationpartial least squaresspectral variable selection |
| spellingShingle | Christopher Hutengs Bernard Ludwig András Jung Andreas Eisele Michael Vohland Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils Sensors portable FTIR spectrometer mid-infrared soil spectroscopy benchmarking noise analysis continuous wavelet transform multivariate calibration partial least squares spectral variable selection |
| title | Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils |
| title_full | Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils |
| title_fullStr | Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils |
| title_full_unstemmed | Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils |
| title_short | Comparison of Portable and Bench-Top Spectrometers for Mid-Infrared Diffuse Reflectance Measurements of Soils |
| title_sort | comparison of portable and bench top spectrometers for mid infrared diffuse reflectance measurements of soils |
| topic | portable FTIR spectrometer mid-infrared soil spectroscopy benchmarking noise analysis continuous wavelet transform multivariate calibration partial least squares spectral variable selection |
| url | http://www.mdpi.com/1424-8220/18/4/993 |
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