{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T13:22:08Z","timestamp":1777382528572,"version":"3.51.4"},"reference-count":56,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2018,2,27]],"date-time":"2018-02-27T00:00:00Z","timestamp":1519689600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Fast detection of heavy metals is very important for ensuring the quality and safety of crops. Laser-induced breakdown spectroscopy (LIBS), coupled with uni- and multivariate analysis, was applied for quantitative analysis of copper in three kinds of rice (Jiangsu rice, regular rice, and Simiao rice). For univariate analysis, three pre-processing methods were applied to reduce fluctuations, including background normalization, the internal standard method, and the standard normal variate (SNV). Linear regression models showed a strong correlation between spectral intensity and Cu content, with an      R 2      more than 0.97. The limit of detection (LOD) was around 5 ppm, lower than the tolerance limit of copper in foods. For multivariate analysis, partial least squares regression (PLSR) showed its advantage in extracting effective information for prediction, and its sensitivity reached 1.95 ppm, while support vector machine regression (SVMR) performed better in both calibration and prediction sets, where      R c 2      and      R p 2      reached 0.9979 and 0.9879, respectively. This study showed that LIBS could be considered as a constructive tool for the quantification of copper contamination in rice.<\/jats:p>","DOI":"10.3390\/s18030705","type":"journal-article","created":{"date-parts":[[2018,2,27]],"date-time":"2018-02-27T14:18:08Z","timestamp":1519741088000},"page":"705","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":51,"title":["Fast Detection of Copper Content in Rice by Laser-Induced Breakdown Spectroscopy with Uni- and Multivariate Analysis"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0266-6896","authenticated-orcid":false,"given":"Fei","family":"Liu","sequence":"first","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China"}]},{"given":"Lanhan","family":"Ye","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2842-170X","authenticated-orcid":false,"given":"Jiyu","family":"Peng","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"}]},{"given":"Kunlin","family":"Song","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"}]},{"given":"Tingting","family":"Shen","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6760-3154","authenticated-orcid":false,"given":"Chu","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6752-1757","authenticated-orcid":false,"given":"Yong","family":"He","sequence":"additional","affiliation":[{"name":"College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China"},{"name":"Key Laboratory of Spectroscopy Sensing, Ministry of Agriculture, Hangzhou 310058, China"}]}],"member":"1968","published-online":{"date-parts":[[2018,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1703","DOI":"10.1039\/c0an00387e","article-title":"Support vector machine regression (SVR\/LS-SVM)\u2014An alternative to neural networks (ANN) for analytical chemistry? Comparison of nonlinear methods on near infrared (NIR) spectroscopy data","volume":"136","author":"Balabin","year":"2011","journal-title":"Analyst"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"12138","DOI":"10.1038\/ncomms12138","article-title":"A heavy metal P-type ATPase OsHMA4 prevents copper accumulation in rice grain","volume":"7","author":"Huang","year":"2016","journal-title":"Nature Commun."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1158","DOI":"10.1016\/S1001-0742(10)60529-3","article-title":"Source attributions of heavy metals in rice plant along highway in Eastern China","volume":"23","author":"Feng","year":"2011","journal-title":"J. Environ. Sci.-China"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"843","DOI":"10.1016\/j.scitotenv.2013.08.090","article-title":"A review of soil heavy metal pollution from mines in China: Pollution and health risk assessment","volume":"468","author":"Li","year":"2014","journal-title":"Sci. Total Environ."},{"key":"ref_5","first-page":"355","article-title":"Current status of heavy metal contamination in Asia's rice lands","volume":"12","author":"Arunakumara","year":"2013","journal-title":"Rev. Environ. Sci. Biol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2542","DOI":"10.1016\/j.envpol.2009.03.002","article-title":"Risk assessment of potentially toxic element pollution in soils and rice (Oryza sativa) in a typical area of the Yangtze river delta","volume":"157","author":"Hang","year":"2009","journal-title":"Environ. Pollut."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1007\/s00604-012-0789-2","article-title":"Solid phase extraction of Cd(\u2161), Pb(\u2161), Zn(\u2161) and Ni(\u2161) from food samples using multiwalled carbon nanotubes impregnated with 4-(2-thiazolylazo) resorcinol","volume":"177","author":"ALOthman","year":"2012","journal-title":"Microchim. Acta"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"262","DOI":"10.1016\/S0169-4332(97)00787-3","article-title":"Laser ablation processes investigated using inductively coupled plasma atomic emission spectroscopy (ICP-AES)","volume":"127","author":"Mao","year":"1998","journal-title":"Appl. Surf. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"640","DOI":"10.1021\/ac303220r","article-title":"Laser-induced breakdown spectroscopy","volume":"85","author":"Fortes","year":"2013","journal-title":"Anal. Chem."},{"key":"ref_10","first-page":"2593","article-title":"Latest research on and applications progress in laser-induced breakdown spectroscopy","volume":"33","author":"Shao","year":"2013","journal-title":"Spectrosc. Spect. Anal."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"260","DOI":"10.1016\/j.trac.2016.08.015","article-title":"Challenging applications for multi-element analysis by laser-induced breakdown spectroscopy in agriculture: A review","volume":"85","author":"Peng","year":"2016","journal-title":"Trac.-Trend. Anal. Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"527","DOI":"10.1007\/s11483-011-9235-y","article-title":"LIBS: A quality control tool for food supplements","volume":"6","author":"Agrawal","year":"2011","journal-title":"Food Biophys."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/j.sab.2014.08.025","article-title":"Determination of inorganic nutrients in wheat flour by laser-induced breakdown spectroscopy and energy dispersive X-ray fluorescence spectrometry","volume":"100","author":"Peruchi","year":"2014","journal-title":"Spectrochim. Acta B"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"4453","DOI":"10.1364\/AO.54.004453","article-title":"Qualitative evaluation of Pb and Cu in fish using laser-induced breakdown spectroscopy with multipulse excitation by ultracompact laser source","volume":"54","author":"Alvira","year":"2015","journal-title":"Appl. Optics"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1216","DOI":"10.1016\/j.sab.2008.08.016","article-title":"Artificial neural network for Cu quantitative determination in soil using a portable laser induced breakdown spectroscopy system","volume":"63","author":"Ferreira","year":"2008","journal-title":"Spectrochim. Acta B"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1016\/S0584-8547(01)00186-0","article-title":"Optimization of the spectral data processing in a LIBS simultaneous elemental analysis system","volume":"56","author":"Body","year":"2001","journal-title":"Spectrochim. Acta B"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"955","DOI":"10.1366\/13-07345","article-title":"Application of a spectrum standardization method for carbon analysis in coal using laser-induced breakdown spectroscopy (LIBS)","volume":"68","author":"Li","year":"2014","journal-title":"Appl. Spectrosc."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"489","DOI":"10.1039\/b315588a","article-title":"LIBS limit of detection and plasma parameters of some elements in two different metallic matrices","volume":"19","author":"Ismail","year":"2004","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_19","first-page":"46","article-title":"Study of the matrix effect on the plasma characterization of six elements in aluminum alloys using LIBS with a portable echelle spectrometer","volume":"2","author":"Tawfik","year":"2007","journal-title":"Prog. Phys."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1016\/j.sab.2015.11.002","article-title":"Sample treatment and preparation for laser-induced breakdown spectroscopy","volume":"115","author":"Jantzi","year":"2016","journal-title":"Spectrochim. Acta B"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1016\/j.optlastec.2012.08.011","article-title":"Laser-induced breakdown spectroscopy for quantitative analysis of copper in algae","volume":"47","author":"Garcimuno","year":"2013","journal-title":"Opt. Laser Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"642","DOI":"10.1016\/j.sab.2010.04.009","article-title":"A review of normalization techniques in analytical atomic spectrometry with laser sampling: From single to multivariate correction","volume":"65","author":"Zorov","year":"2010","journal-title":"Spectrochim. Acta B"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1039\/C6JA00322B","article-title":"Impact of laser-induced breakdown spectroscopy data normalization on multivariate classification accuracy","volume":"32","author":"Porizka","year":"2017","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/j.sab.2013.01.005","article-title":"Quantitative analysis of oxide materials by laser-induced breakdown spectroscopy with argon as an internal standard","volume":"82","author":"Lasheras","year":"2013","journal-title":"Spectrochim. Acta B"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1111\/1475-4754.00119","article-title":"Evaluation of the analytical potential of laser-induced breakdown spectrometry (LIBS) for the analysis of historical glasses","volume":"45","author":"Muller","year":"2003","journal-title":"Archaeometry"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1039\/b411719k","article-title":"Laser-induced breakdown spectroscopy of liquid droplets: Correlation analysis with plasma-induced current versus continuum background","volume":"20","author":"Huang","year":"2005","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"598","DOI":"10.1007\/s11432-011-4198-7","article-title":"Nondestructive determination of nutritional information in oilseed rape leaves using visible\/near infrared spectroscopy and multivariate calibrations","volume":"54","author":"Liu","year":"2011","journal-title":"Sci. China-Inform. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1016\/j.sab.2015.09.022","article-title":"Evaluation of the standard normal variate method for laser-induced breakdown spectroscopy data treatment applied to the discrimination of painting layers","volume":"114","author":"Syvilay","year":"2015","journal-title":"Spectrochim. Acta B"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/S0003-2670(02)00054-5","article-title":"Characterization of jewellery products by laser-induced breakdown spectroscopy","volume":"457","year":"2002","journal-title":"Anal. Chim. Acta"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/j.aca.2004.01.003","article-title":"Minimum value assured by a method to determine gold in alloys by using laser-induced breakdown spectroscopy and partial least-squares calibration model","volume":"515","author":"Ortiz","year":"2004","journal-title":"Anal. Chim. Acta"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.sab.2009.11.007","article-title":"Comparison of univariate and multivariate calibration for the determination of micronutrients in pellets of plant materials by laser induced breakdown spectrometry","volume":"65","author":"Braga","year":"2010","journal-title":"Spectrochim. Acta B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/S0169-7439(02)00085-0","article-title":"Transfer of multivariate calibration models: A review","volume":"64","author":"Feundale","year":"2002","journal-title":"Chemometr. Intell. Lab."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1453","DOI":"10.1039\/c003620j","article-title":"Optimization and validation of a LIBS method for the determination of macro and micronutrients in sugar cane leaves","volume":"25","author":"Nunes","year":"2010","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"8883","DOI":"10.1021\/jf072057b","article-title":"Use of visible and near infrared spectroscopy and least squares-support vector machine to determine soluble solids content and pH of cola beverage","volume":"55","author":"Liu","year":"2007","journal-title":"J. Agric. Food Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1088\/0256-307X\/33\/8\/085201","article-title":"Monitoring the heavy element of Cr in agricultural soils using a mobile laser-induced breakdown spectroscopy system with support vector machine","volume":"33","author":"Gu","year":"2016","journal-title":"Chin. Phys. Lett."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1088\/1009-0630\/17\/8\/17","article-title":"Nondestructive determination of Cu residue in orange peel by laser induced breakdown spectroscopy","volume":"17","author":"Hu","year":"2015","journal-title":"Plasma Sci. Technol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"116","DOI":"10.1016\/j.colsurfb.2007.11.013","article-title":"Potato peels as solid waste for the removal of heavy metal copper(\u2161) from waste water\/industrial effluent","volume":"63","author":"Aman","year":"2008","journal-title":"Colloid Surf. B"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"837","DOI":"10.1039\/b919485a","article-title":"Spatial confinement of laser-induced plasma to enhance LIBS sensitivity for trace elements determination in soils","volume":"25","author":"Popov","year":"2010","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1109\/TPAMI.2004.1261097","article-title":"Two-dimensional PCA: A new approach to appearance-based face representation and recognition","volume":"26","author":"Yang","year":"2004","journal-title":"IEEE T Pattern Anal."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1443","DOI":"10.1007\/s00216-011-5287-6","article-title":"Multivariate classification of pigments and inks using combined Raman spectroscopy and LIBS","volume":"402","author":"Hoehse","year":"2012","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"14","DOI":"10.1080\/05704928.2011.622327","article-title":"Assessment of LIBS for spectrochemical analysis: A review","volume":"47","author":"Pathak","year":"2012","journal-title":"Appl. Spectrosc. Rev."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"25872","DOI":"10.1039\/c3ra44946g","article-title":"Analytical predictive capabilities of laser induced breakdown spectroscopy (LIBS) with principal component analysis (PCA) for plastic classification","volume":"3","author":"Unnikrishnan","year":"2013","journal-title":"Rsc. Adv."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1193","DOI":"10.1021\/ac00162a020","article-title":"Partial least-squares methods for spectral analyses. 1. Relation to other quantitative calibration methods and the extraction of qualitative information","volume":"60","author":"Haaland","year":"1988","journal-title":"Anal. Chem."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2323","DOI":"10.1039\/C4JA00217B","article-title":"A novel approach for the quantitative analysis of multiple elements in steel based on laser-induced breakdown spectroscopy (LIBS) and random forest regression (RFR)","volume":"29","author":"Zhang","year":"2014","journal-title":"J. Anal. Atom. Spectrom."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/j.chemolab.2004.01.002","article-title":"Comparing support vector machines to PLS for spectral regression applications","volume":"73","author":"Thissen","year":"2004","journal-title":"Chemometr. Intell. Lab."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"1381","DOI":"10.1016\/j.asoc.2007.10.007","article-title":"A distributed PSO-SVM hybrid system with feature selection and parameter optimization","volume":"8","author":"Huang","year":"2008","journal-title":"Appl. Soft Comput."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1021\/ci0342472","article-title":"The problem of overfitting","volume":"44","author":"Hawkins","year":"2004","journal-title":"J. Chem. Inf. Comp. Sci."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.aca.2009.03.001","article-title":"Classification of brazilian soils by using LIBS and variable selection in the wavelet domain","volume":"642","author":"Pontes","year":"2009","journal-title":"Anal. Chim. Acta"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"339","DOI":"10.1016\/S0584-8547(01)00398-6","article-title":"A procedure for correcting self-absorption in calibration free-laser induced breakdown spectroscopy","volume":"57","author":"Bulajic","year":"2002","journal-title":"Spectrochim. Acta B"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"545","DOI":"10.3788\/COL20090706.0545","article-title":"Correction and analysis of lead content in soil by laser-induced breakdown spectroscopy","volume":"7","author":"Xie","year":"2009","journal-title":"Chin. Opt. Lett."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1016\/j.pss.2003.08.012","article-title":"Investigation of LIBS feasibility for in situ planetary exploration: An analysis on martian rock analogues","volume":"52","author":"Colao","year":"2004","journal-title":"Planet. Space Sci."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"369","DOI":"10.1016\/j.sab.2009.04.003","article-title":"Evaluation of laser induced breakdown spectroscopy for the determination of micronutrients in plant materials","volume":"64","author":"Trevizan","year":"2009","journal-title":"Spectrochim. Acta B"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1016\/j.envres.2009.02.005","article-title":"Heavy metal concentrations in soils as determined by laser-induced breakdown spectroscopy (LIBS), with special emphasis on chromium","volume":"109","author":"Senesi","year":"2009","journal-title":"Environ. Res."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"688","DOI":"10.1016\/j.sab.2010.05.005","article-title":"Quarry identification of historical building materials by means of laser induced breakdown spectroscopy, X-ray fluorescence and chemometric analysis","volume":"65","author":"Colao","year":"2010","journal-title":"Spectrochim. Acta B"},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"2124","DOI":"10.1002\/jps.20109","article-title":"Figures of merit for the determination of the polymorphic purity of carbamazepine by infrared spectroscopy and multivariate calibration","volume":"93","author":"Braga","year":"2004","journal-title":"J. Pharm. Sci."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1364\/AO.55.000254","article-title":"Laser-induced breakdown spectroscopy determination of toxic metals in fresh fish","volume":"55","author":"Ponce","year":"2016","journal-title":"Appl. Optics"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/3\/705\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T14:56:35Z","timestamp":1760194595000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/3\/705"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,2,27]]},"references-count":56,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2018,3]]}},"alternative-id":["s18030705"],"URL":"https:\/\/doi.org\/10.3390\/s18030705","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,2,27]]}}}