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Cielecki PP, Hardenberg M, Amariei G, Henriksen ML, Hinge M, Klarskov P. Identification of black plastics with terahertz time-domain spectroscopy and machine learning. Sci Rep 2023; 13:22399. [PMID: 38104201 PMCID: PMC10725460 DOI: 10.1038/s41598-023-49765-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 12/12/2023] [Indexed: 12/19/2023] Open
Abstract
Several optical spectroscopy and imaging techniques have already proven their ability to identify different plastic types found in household waste. However, most common optical techniques feasible for plastic sorting, struggle to measure black plastic objects due to the high absorption at visible and near-infrared wavelengths. In this study, 12 black samples of nine different materials have been characterized with Fourier-transform infrared spectroscopy (FTIR), hyperspectral imaging, and terahertz time-domain spectroscopy (THz-TDS). While FTIR validated the plastic types of the samples, the hyperspectral camera using visible and near-infrared wavelengths was challenged to measure the samples. The THz-TDS technique was successfully able to measure the samples without direct sample contact under ambient conditions. From the recorded terahertz waveforms the refractive index and absorption coefficient are extracted for all samples in the range from 0.4 to 1.0 THz. Subsequently, the obtained values were projected onto a two-dimensional map to discriminate the materials using the classifiers k-Nearest Neighbours, Bayes, and Support Vector Machines. A classification accuracy equal to unity was obtained, which proves the ability of THz-TDS to discriminate common black plastics.
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Affiliation(s)
- Paweł Piotr Cielecki
- Terahertz Photonics, Department of Electrical and Computer Engineering, Aarhus University, Finlandsgade 22, 8200, Aarhus N, Denmark
| | - Michel Hardenberg
- Terahertz Photonics, Department of Electrical and Computer Engineering, Aarhus University, Finlandsgade 22, 8200, Aarhus N, Denmark
| | - Georgiana Amariei
- Plastic and Polymer Engineering, Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, 8200, Aarhus N, Denmark
| | - Martin Lahn Henriksen
- Plastic and Polymer Engineering, Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, 8200, Aarhus N, Denmark
| | - Mogens Hinge
- Plastic and Polymer Engineering, Department of Biological and Chemical Engineering, Aarhus University, Aabogade 40, 8200, Aarhus N, Denmark
| | - Pernille Klarskov
- Terahertz Photonics, Department of Electrical and Computer Engineering, Aarhus University, Finlandsgade 22, 8200, Aarhus N, Denmark.
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Duchowny A, Ortiz Restrepo SA, Kern S, Adams A. Quantification of PVC plasticizer mixtures by compact proton NMR spectroscopy and indirect hard modeling. Anal Chim Acta 2022; 1229:340384. [PMID: 36156235 DOI: 10.1016/j.aca.2022.340384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/19/2022] [Accepted: 09/08/2022] [Indexed: 11/28/2022]
Abstract
A novel approach is introduced for the fast, reliable, and low-cost recognition and quantification of plasticizers in plasticizers mixtures. It uses benchtop 1H NMR spectroscopy and indirect hard modeling, a mechanistic multivariate regression technique. The approach is demonstrated on five different PVC plasticizers having similar spectral signatures in proton NMR spectra. With only 16 scans per spectrum, i.e., 2 min 40 s measurement time, quantification limits down to 0.14 mg mL-1, or 0.35 wt% plasticizer in PVC, were achieved. Apart from the rapid data acquisition, the use of spectral hard modeling enabled the quantification of plasticizer mixtures while using only 4 to 6 training samples per component. Despite strongly overlapping signals in the NMR spectra, various plasticizers were differentiated and quantified, as exemplarily demonstrated for binary mixtures. A commercial PVC specimen with three different layers was also examined, confirming the applicability of benchtop NMR spectroscopy. Additionally, the use of the proposed method to validate official regulations concerning the plasticizer content in PVC is assessed. The presented results demonstrate that the combination of benchtop NMR and spectral hard modeling is a very promising analytical tool for rapid PVC plasticizer recognition and quantification with high analytical throughput. Moreover, the results indicate a high potential for benchtop NMR and spectral hard modeling for microchemical analysis, even for complex samples.
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Affiliation(s)
- Anton Duchowny
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Templergraben 55, 52056, Aachen, Germany
| | | | - Simon Kern
- S-PACT GmbH, Burtscheider Str. 1, 52064, Aachen, Germany
| | - Alina Adams
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Templergraben 55, 52056, Aachen, Germany.
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da Silva IJG, Raimundo IM, Mizaikoff B. Analysis of sugars and sweeteners via terahertz time-domain spectroscopy. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:2657-2664. [PMID: 35699197 DOI: 10.1039/d2ay00377e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A THz-TDS spectrometer (terahertz time-domain spectroscopy) with ASOPS technology (asynchronous optical sampling) was employed in this study, aiming to explore the potential of the technique and to develop analytical applications for the identification of some saccharides. Analytical curves with linear responses were obtained in the saccharide concentration range from 1.7 to 11.7 (w/w). The characteristic peaks used for each sugar for univariate calibrations were fructose (1.704 THz), sucrose (1.827 THz), glucose (1.435 THz), lactose (1.373 THz), saccharin (2.664 THz), and sucralose (2.219 THz). Limits of detection around 1.0% (m/m) were obtained. Gaussian peak fitting was also employed as a tool to aid in the identification of saccharide components in mixtures and it was observed that the region between 0.5 and 2.0 THz is more adequate for such analysis since scattering is less evident. It was observed that in a mixture of sucrose, glucose and lactose (5% or 10% (m/m) each) in the range of 1.31 to 1.51 THz some sub-peaks of pure lactose and glucose can be identified.
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Affiliation(s)
- Igor J G da Silva
- Institute of Chemistry, UNICAMP, PO Box 6154, 13083-970, Campinas, Brazil.
| | - Ivo M Raimundo
- Institute of Chemistry, UNICAMP, PO Box 6154, 13083-970, Campinas, Brazil.
| | - Boris Mizaikoff
- Institute of Analytical and Bioanalytical Chemistry, Ulm University, 89081, Ulm, BW, Germany.
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Compact NMR Spectroscopy for Low-Cost Identification and Quantification of PVC Plasticizers. Molecules 2021; 26:molecules26051221. [PMID: 33668752 PMCID: PMC7956471 DOI: 10.3390/molecules26051221] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 02/21/2021] [Accepted: 02/22/2021] [Indexed: 11/17/2022] Open
Abstract
Polyvinyl chloride (PVC), one of the most important polymer materials nowadays, has a large variety of formulations through the addition of various plasticizers to meet the property requirements of the different fields of applications. Routine analytical methods able to identify plasticizers and quantify their amount inside a PVC product with a high analysis throughput would promote an improved understanding of their impact on the macroscopic properties and the possible health and environmental risks associated with plasticizer leaching. In this context, a new approach to identify and quantify plasticizers employed in PVC commodities using low-field NMR spectroscopy and an appropriate non-deuterated solvent is introduced. The proposed method allows a low-cost, fast, and simple identification of the different plasticizers, even in the presence of a strong solvent signal. Plasticizer concentrations below 2 mg mL-1 in solution corresponding to 3 wt% in a PVC product can be quantified in just 1 min. The reliability of the proposed method is tested by comparison with results obtained under the same experimental conditions but using deuterated solvents. Additionally, the type and content of plasticizer in plasticized PVC samples were determined following an extraction procedure. Furthermore, possible ways to further decrease the quantification limit are discussed.
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Hirata J, Kurokawa N, Okano M, Hotta A, Watanabe S. Evaluation of Crystallinity and Hydrogen Bond Formation in Stereocomplex Poly(lactic acid) Films by Terahertz Time-Domain Spectroscopy. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00237] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Junya Hirata
- Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Naruki Kurokawa
- Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Makoto Okano
- Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Atsushi Hotta
- Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Shinichi Watanabe
- Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
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Wang Y, Zhao Z, Qin J, Liu H, Liu A, Xu M. Rapid in situ analysis of l-histidine and α-lactose in dietary supplements by fingerprint peaks using terahertz frequency-domain spectroscopy. Talanta 2020; 208:120469. [PMID: 31816746 DOI: 10.1016/j.talanta.2019.120469] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/09/2019] [Accepted: 10/10/2019] [Indexed: 02/08/2023]
Abstract
A simple, green and nondestructive method based on terahertz fingerprint peaks has been developed for rapid in situ analysis of l-histidine and α-lactose in dietary supplements. Fingerprint absorption peaks of l-histidine and α-lactose located at 0.77 and 0.53 THz could be directly used for identification and quantitation of these analytes in commercial dietary supplements. Compared with the partial least squares regression model (PLSR), the linear least squares regression (LLSR) method based on peak areas presented better performance, with the linear correlation coefficients of 0.9899 and 0.9910 for l-histidine and α-lactose, respectively. Furthermore, analysis time per sample can be shortened to less than 1 min due to the narrower spectral acquisition region. The accuracies were 94.8-110% and 98.9-110%, comparable to those of ion chromatography for l-histidine and high-performance liquid chromatography for α-lactose. The results presented great potential of the developed method for rapid in situ analysis of nutrients in dietary supplements.
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Affiliation(s)
- Yongmei Wang
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
| | - Zongshan Zhao
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
| | - Jianyuan Qin
- Centre for Terahertz Research, China Jiliang University, Hangzhou, 310018, China.
| | - Huan Liu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
| | - Aifeng Liu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
| | - Mengmeng Xu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
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Adams A. Non-destructive analysis of polymers and polymer-based materials by compact NMR. Magn Reson Imaging 2018; 56:119-125. [PMID: 30243579 DOI: 10.1016/j.mri.2018.09.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 09/14/2018] [Accepted: 09/16/2018] [Indexed: 12/19/2022]
Abstract
Low-field nuclear magnetic resonance (NMR) based on permanent magnet technologies is currently experiencing a considerable growth of popularity in studying polymer materials. Various bulk properties can be probed with compact NMR tabletop instruments by placing the sample of interest inside the magnet. Contrary to this, compact NMR sensors with open geometries give access to depth-dependent properties of polymer samples and objects of different sizes and shapes truly non-destructively by performing measurements in the inhomogeneous stray-field outside the magnet system. Some of the sensors are also portable being thus well suited for onsite measurements. The gain of both bulk and depth-dependent microscopic properties are important for establishing improved structure-property relationships needed for the rational design of new polymer formulations. Selected recent applications will be presented to illustrate this potential of compact NMR.
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Affiliation(s)
- Alina Adams
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Templergraben 55, D-52056 Aachen, Germany.
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