{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T04:18:43Z","timestamp":1791519523914,"version":"4.3.4"},"reference-count":39,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2025,4,12]],"date-time":"2025-04-12T00:00:00Z","timestamp":1744416000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Alexander von Humboldt Foundation"},{"name":"Escuela Polit\u00e9cnica Nacional"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Cocoa is a major commodity in the global food industry. Heavy metal contamination, particularly cadmium (Cd), raises significant concerns. This work demonstrates the use of laser-induced breakdown spectroscopy (LIBS) for fast Cd quantification in commercial cocoa powder across a wide range of concentrations (70\u20135000 ppm). Cocoa powder presents unique challenges due to its physical properties, such as the tendency to soften and liquefy at elevated temperatures, which complicates sample preparation. To address these issues, a mechanical mixing and pelletization protocol was implemented to ensure uniformity. Pellets were doped with known cadmium concentrations for calibration. Cadmium atomic lines at 340.36 and 361.05 nm were used to construct quantification curves. A special algorithm for background subtraction was implemented, and the LIBS plasma was characterized to ensure local thermodynamic equilibrium conditions. Out of eighteen samples, five double-blinded unknowns were evaluated. The concentrations agreed well within normalized standard deviations of 9.73% and 5.88% for the two cadmium lines. The limits of detection for the lines were 0.4 and 0.08 \u03bcg\/g, respectively. LIBS is confirmed as a rapid and versatile analytical tool for Cd detection and quantification in complex food matrices, with potential applications in field-based and industrial monitoring systems.<\/jats:p>","DOI":"10.3390\/s25082434","type":"journal-article","created":{"date-parts":[[2025,4,14]],"date-time":"2025-04-14T04:42:07Z","timestamp":1744605727000},"page":"2434","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Assessing the Sensitivity and Efficiency of Laser-Induced Breakdown Spectroscopy (LIBS) for High-Concentration Cadmium Detection in Cocoa Powder"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1364-8960","authenticated-orcid":false,"given":"Juan","family":"Molina M.","sequence":"first","affiliation":[{"name":"Consejo Nacional de Investigaciones Cient\u00edficas y T\u00e9cnicas (CONICET), Calle Godoy Cruz 2290, Buenos Aires 1425, Argentina"},{"name":"Laboratorio de Ecolog\u00eda Evolutiva Humana (LEEH), Facultad de Ciencias Sociales (FACSO), Universidad Nacional del Centro de la Provincia de Buenos Aires (UNICEN), Calle 508 881, Quequ\u00e9n, Buenos Aires 7631, Argentina"},{"name":"Mass Spectrometry & Optical Spectroscopy Group, Departamento de F\u00edsica, Escuela Polit\u00e9cnica Nacional (EPN), Ladr\u00f3n de Guevara E11\u2013253, Ed. #6, Piso 1, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Raquel","family":"Pincay","sequence":"additional","affiliation":[{"name":"Mass Spectrometry & Optical Spectroscopy Group, Departamento de F\u00edsica, Escuela Polit\u00e9cnica Nacional (EPN), Ladr\u00f3n de Guevara E11\u2013253, Ed. #6, Piso 1, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6616-3193","authenticated-orcid":false,"given":"V\u00edctor","family":"Santos","sequence":"additional","affiliation":[{"name":"Departamento de Automatizaci\u00f3n y Control Industrial, Escuela Polit\u00e9cnica Nacional, Ladr\u00f3n de Guevara E11-253, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-0209-4770","authenticated-orcid":false,"given":"Jos\u00e9 Luis","family":"Gonz\u00e1lez","sequence":"additional","affiliation":[{"name":"Mass Spectrometry & Optical Spectroscopy Group, Departamento de F\u00edsica, Escuela Polit\u00e9cnica Nacional (EPN), Ladr\u00f3n de Guevara E11\u2013253, Ed. #6, Piso 1, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7250-6479","authenticated-orcid":false,"given":"Mar\u00eda Fernanda","family":"Trujillo Guerrero","sequence":"additional","affiliation":[{"name":"Departamento de Automatizaci\u00f3n y Control Industrial, Escuela Polit\u00e9cnica Nacional, Ladr\u00f3n de Guevara E11-253, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Diego","family":"D\u00edaz Pace","sequence":"additional","affiliation":[{"name":"Consejo Nacional de Investigaciones Cient\u00edficas y T\u00e9cnicas (CONICET), Calle Godoy Cruz 2290, Buenos Aires 1425, Argentina"},{"name":"Laboratorio de Ecolog\u00eda Evolutiva Humana (LEEH), Facultad de Ciencias Sociales (FACSO), Universidad Nacional del Centro de la Provincia de Buenos Aires (UNICEN), Calle 508 881, Quequ\u00e9n, Buenos Aires 7631, Argentina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5242-1892","authenticated-orcid":false,"given":"C\u00e9sar","family":"Costa-Vera","sequence":"additional","affiliation":[{"name":"Mass Spectrometry & Optical Spectroscopy Group, Departamento de F\u00edsica, Escuela Polit\u00e9cnica Nacional (EPN), Ladr\u00f3n de Guevara E11\u2013253, Ed. #6, Piso 1, Quito 170525, Ecuador"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,4,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1879","DOI":"10.1038\/s41559-018-0697-x","article-title":"The use and domestication of Theobroma cacao during the mid-Holocene in the upper Amazon","volume":"2","author":"Zarrillo","year":"2018","journal-title":"Nat. Ecol. Evol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2972","DOI":"10.1038\/s41598-024-53010-6","article-title":"A revisited history of cacao domestication in pre-Columbian times revealed by archaeogenomic approaches","volume":"14","author":"Lanaud","year":"2024","journal-title":"Sci. Rep."},{"key":"ref_3","unstructured":"Lippi, D., and Vannozzi, G. (2019). Cacao bioactive compounds: Chemistry, analysis, and bioavailability. Chocolate in Health and Nutrition, Humana."},{"key":"ref_4","unstructured":"International Cocoa Organization (ICCO) (2025, January 20). Quarterly Bulletin of Cocoa Statistics, Volume XLVIII, No. 1\u20134. Available online: https:\/\/www.icco.org\/categorie-produit\/qbcs\/."},{"key":"ref_5","unstructured":"(1995). General Standard for Contaminants and Toxins in Food and Feed (Standard No. CXS 193-1995)."},{"key":"#cr-split#-ref_6.1","unstructured":"European Commission (2006). Regulation"},{"key":"#cr-split#-ref_6.2","unstructured":"(EC) No 1881\/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs. Off. J. Eur. Union, L364, 5-24."},{"key":"ref_7","first-page":"45","article-title":"Critical evaluation of selected atomic absorption techniques for the determination of metals in plants","volume":"48","author":"Smith","year":"1976","journal-title":"Anal. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"362","DOI":"10.1016\/j.trac.2008.11.011","article-title":"Application of X-ray fluorescence spectrometry to determination and quantitation of metals in vegetal material","volume":"28","author":"Queralt","year":"2009","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1016\/j.jfda.2015.04.010","article-title":"Determination of Pb (Lead), Cd (Cadmium), Cr (Chromium), Cu (Copper), and Ni (Nickel) in Chinese tea with high-resolution continuum source graphite furnace atomic absorption spectrometry","volume":"24","author":"Zhong","year":"2016","journal-title":"J. Food Drug Anal."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1017","DOI":"10.1007\/s12161-020-01722-6","article-title":"Direct determination of Ca, K, and Mg in cocoa beans by laser-induced breakdown spectroscopy (LIBS): Evaluation of three univariate calibration strategies for matrix matching","volume":"13","author":"Gamela","year":"2020","journal-title":"Food Anal. Methods"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"963","DOI":"10.1177\/0003702819853252","article-title":"Laser-induced breakdown spectroscopy (LIBS) of organic compounds: A review","volume":"73","author":"Moros","year":"2019","journal-title":"Appl. Spectrosc."},{"key":"ref_12","unstructured":"Douglas, A.S., Holler, F.J., and Crouch, S.R. (2013). Fundamentals of Analytical Chemistry, Cengage Learning."},{"key":"ref_13","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. Spectrochim","volume":"115","author":"Jantzi","year":"2016","journal-title":"Acta Part B At. Spectrosc."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"39635","DOI":"10.1039\/C8RA07799A","article-title":"Detection of cadmium in soils using laser-induced breakdown spectroscopy combined with spatial confinement and resin enrichment","volume":"8","author":"Fu","year":"2018","journal-title":"RSC Adv."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1016\/j.foodchem.2018.07.214","article-title":"High-sensitivity determination of cadmium and lead in rice using laser-induced breakdown spectroscopy","volume":"272","author":"Yang","year":"2019","journal-title":"Food Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"599616","DOI":"10.3389\/fpls.2020.599616","article-title":"Application of laser-induced breakdown spectroscopy in detecting cadmium content in rice stems","volume":"11","author":"Wang","year":"2020","journal-title":"Front. Plant Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"929","DOI":"10.1016\/j.sab.2006.07.003","article-title":"Analysis of heavy metals in liquids using laser-induced breakdown spectroscopy by liquid-to-solid matrix conversion","volume":"61","author":"Bertuccelli","year":"2006","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1125","DOI":"10.1016\/j.envpol.2019.06.027","article-title":"Fast visualization of chromium in rice leaves using dual-pulse LIBS and chemometric methods","volume":"252","author":"Peng","year":"2019","journal-title":"Environ. Pollut."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1072","DOI":"10.1016\/j.talanta.2005.11.023","article-title":"Detection of heavy metals in Arabian crude oil residue using LIBS","volume":"69","author":"Gondal","year":"2006","journal-title":"Talanta"},{"key":"ref_20","unstructured":"Tognoni, E., Palleschi, V., Corsi, M., Cristoforetti, G., Omenetto, N., Gornushkin, I., Smith, B.W., and Winefordner, J.D. (2006). From Sample to Signal in laser-Induced Breakdown Spectroscopy: A Complex Route to Quantitative Analysis. Laser-Induced Breakdown Spectroscopy (LIBS) Fundamentals and Applications, Cambridge University Press."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/j.sab.2014.08.039","article-title":"Good practices in LIBS analysis: Review and advice","volume":"101","author":"Canioni","year":"2014","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_22","unstructured":"Kramida, A., Ralchenko, Y., Reader, J., and NIST ASD Team (2023, August 07). NIST Atomic Spectra Database (Ver. 5.10), Available online: https:\/\/physics.nist.gov\/asd."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.sab.2016.10.018","article-title":"Comparison of baseline removal methods for laser-induced breakdown spectroscopy of geological samples","volume":"126","author":"Dyar","year":"2016","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1457","DOI":"10.1177\/0003702817695624","article-title":"A fully customized baseline removal framework for spectroscopic applications","volume":"71","author":"Giguere","year":"2017","journal-title":"Appl. Spectrosc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"16171","DOI":"10.1364\/OE.26.016171","article-title":"Continuous background correction using effective points selected in third-order minima segments in low-cost laser-induced breakdown spectroscopy without intensified CCD","volume":"26","author":"Liu","year":"2018","journal-title":"Opt. Express"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Palleschi, V. (2023). Chemometrics and Numerical Methods in LIBS, Wiley Online Library.","DOI":"10.1002\/9781119759614"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Cremers, D.A., and Radziemski, L.J. (2013). Handbook of Laser-Induced Breakdown Spectroscopy, John Wiley & Sons.","DOI":"10.1002\/9781118567371"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Noll, R. (2012). Laser-Induced Breakdown Spectroscopy, Springer.","DOI":"10.1007\/978-3-642-20668-9"},{"key":"ref_29","unstructured":"Singh, J.P., and Thakur, S.N. (2020). Laser-Induced Breakdown Spectroscopy, Elsevier."},{"key":"ref_30","unstructured":"National Institute of Standards and Technology (NIST) (2023, August 07). Atomic Spectra Database, Available online: http:\/\/physics.nist.gov\/PhysRefData."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1016\/j.sab.2009.11.005","article-title":"Local Thermodynamic Equilibrium in Laser-Induced Breakdown Spectroscopy: Beyond the McWhirter Criterion","volume":"65","author":"Cristoforetti","year":"2010","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"893","DOI":"10.1016\/j.sab.2008.05.010","article-title":"Characterization of laser-induced plasmas by optical emission spectroscopy: A review of experiments and methods","volume":"63","author":"Aguilera","year":"2008","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"16","DOI":"10.1016\/j.sab.2012.06.026","article-title":"Hydrogen Balmer lines for low electron number density plasma diagnostics","volume":"76","author":"Sakan","year":"2012","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"79","DOI":"10.4236\/opj.2015.53007","article-title":"Self-Absorption Effects on Electron Temperature Measurements Utilizing Laser-Induced Breakdown Spectroscopy (LIBS) Techniques","volume":"5","author":"Mansour","year":"2015","journal-title":"Opt. Photonics J."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"C1","DOI":"10.1364\/JOSAB.479557","article-title":"\u03c4-algorithm for gathering spectroscopic information by modeling emission line shapes: Application to laser-induced plasmas","volume":"40","author":"Molina","year":"2023","journal-title":"J. Opt. Soc. Am. B"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1259","DOI":"10.1366\/0003702991945506","article-title":"Improvements in Quantitative Analysis of Steel Composition by Laser-Induced Breakdown Spectroscopy at Atmospheric Pressure Using an Infrared Nd:YAG Laser","volume":"53","author":"Aguilera","year":"1999","journal-title":"Appl. Spectrosc."},{"key":"ref_37","first-page":"1841","article-title":"Quantitative Analysis of Aluminum Alloys by Laser-Induced Breakdown Spectroscopy and Plasma Characterization","volume":"50","author":"Sabsabi","year":"1995","journal-title":"Spectrochim. Acta Part B"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1016\/j.scitotenv.2018.08.292","article-title":"Soil Properties and Agronomic Factors Affecting Cadmium Concentrations in Cacao Beans: A Nationwide Survey in Ecuador","volume":"649","author":"Montalvo","year":"2019","journal-title":"Sci. Total Environ."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/8\/2434\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:13:22Z","timestamp":1760030002000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/8\/2434"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,4,12]]},"references-count":39,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2025,4]]}},"alternative-id":["s25082434"],"URL":"https:\/\/doi.org\/10.3390\/s25082434","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,4,12]]}}}