<p><strong>A team from CEITEC Masaryk University (MUNI) in collaboration with researchers from two research institutes in Norway has, for the first time, captured how echovirus 18, a member of the enterovirus genus, releases its genetic material into cells to initiate infection. The study provides a structural view of an early stage of viral infection under near-native conditions. Using cryo-electron microscopy, the researchers discovered that the virus does not release its RNA through a small pore in its capsid, as had long been assumed. Instead, its protein shell partially disassembles, creating a large opening through which the viral genetic material escapes into the host cell. A detailed understanding of this genome release mechanism could eventually help develop compounds preventing enteroviruses from infecting cells.</strong></p><p>Enteroviruses are common human pathogens causing diseases ranging from the common cold and gastrointestinal infections to severe neurological disorders. Echovirus 18, the virus investigated in this study, is known primarily as a cause of meningitis and encephalitis in children. It belongs to the picornaviruses, a family of small, non-enveloped viruses whose genetic material is protected by a protein shell, the capsid, organized with icosahedral symmetry.</p><p>To replicate within a cell, the enteroviruses must release their RNA – the molecule that carries viral genetic information – from the capsid, into the cell cytoplasm. Although this step is crucial for initiating infection, it has never been observed in infected cells.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_71d553bb0e.jpg" alt="CEITEC/Plevka Lab: CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection: View into a cell infected by echovirus 18. Echovirus 18 is shown in green and yellow, ribosomes in violet, and actin filaments in cyan. Scale 50 nm. " srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_71d553bb0e.jpg 221w," sizes="100vw" width="1600" height="1128"></p><p><i>“For a long time, two main theories existed about how picornaviruses deliver their RNA genomes into cells. One proposed that the genome leaves the capsid through a small opening. The other, supported by earlier work from our laboratory, suggested that the genome escapes from partially disassembled capsids missing pentamers of capsid proteins. However, both models were based on experiments with virus particles outside cells. We wanted to go one step further and see what really happens during infection inside a cell,”</i> says <a target="_blank" rel="noopener noreferrer" href="https://www.ceitec.eu/liya-mukhamedova-ph-d/u89248?page=publication"><strong>Liya Mukhamedova</strong></a><strong>, the study’s first author from CEITEC MUNI</strong>.</p><p>Using cryo-electron microscopy, which allows scientists to visualize biological structures at exceptionally high resolution, the researchers observed individual echovirus 18 particles directly within infected cells. They discovered that empty virus particles in infected cells lack parts of their capsids. It is through these openings that the virus releases its RNA.</p><p>The study also revealed the role of the FcRn receptor, a cell-surface molecule that enteroviruses use to enter cells. The binding of the virus to the receptor triggers structural changes in the viral particle that prime it for subsequent genome release. The team showed that receptor binding causes the loss of the so-called pocket factor, a small molecule that normally helps stabilize the virus particle. The virus otherwise remains largely intact, suggesting that receptor binding is only the first step toward uncoating, while additional factors within the cell are required to complete the process and trigger genome release.</p><p><i>“Infection is a complex process, during which enterovirus particles sense various interactions with cell components. The binding of echovirus 18 to the FcRn host-cell receptor triggers conformational changes in the virus, priming it for genome release.”</i> – explains <a target="_blank" rel="noopener noreferrer" href="https://www.ceitec.eu/pavel-plevka-ph-d/u26854"><strong>Pavel Plevka</strong></a><strong>, head of the Structural Virology Research Group</strong>.</p><p>The researchers did not observe the so-called activated particles that are key intermediates in the enterovirus uncoating process. This suggests that genome release in cells occurs much faster than previous experiments had suggested.</p><p>By combining structural data obtained from studies of virus particles outside living cells with observations of infected cells, the study offers a picture of how enterovirus infection begins. Moving beyond simplified experiments with isolated virus particles, it brings scientists closer to understanding the earliest stages of enterovirus infection as they occur in living cells. The study, was published in the <a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1073/pnas.2601182123"><strong>PNAS journal</strong></a>.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_2_3601bf1df9.jpg" alt="CEITEC/Plevka Lab: CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection: Reconstructions of E18 particles from infected cells. The particles are rainbow-colored based on the distance from the particle center. Scale 10 nm." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_CEITEC_Vedci_z_CEITEC_jako_prvni_zachytili_jak_enteroviry_spousteji_infekci_bunek_2_3601bf1df9.jpg 245w," sizes="100vw" width="1600" height="906"></p><blockquote><h4><strong>Article</strong></h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.pnas.org/doi/10.1073/pnas.2601182123"><strong>Particles of echovirus 18 open to release their genomes in vivo</strong></a></h4><p>Liya Mukhamedova, David Buchta, Zuzana Trebichalská, Yevgen Levdansky, Jana Moravcová, David Potěšil, Zbyněk Zdráhal, Dominik Hřebík, Lucie Nepovímová, Torleif Tollefsrud Gjølberg, Jan Terje Andersen, Jiří Nováček, Tibor Füzik, and Pavel Plevka</p><p><i><strong>Proc. Natl. Acad. Sci. U.S.A.</strong></i>, 2026, <strong>123</strong>, e2601182123</p><div>&nbsp;</div><div><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1073/pnas.2601182123">https://doi.org/10.1073/pnas.2601182123</a></div><h6>licenced under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/"><strong>CC-BY 4.0</strong></a></h6></blockquote><h4><strong>Abstract</strong></h4><p>Enteroviruses cause a broad spectrum of human diseases, ranging from mild respiratory or gastrointestinal infections to severe neurological disorders such as aseptic meningitis and encephalitis. Enterovirus cell entry involves receptor-mediated endocytosis followed by destabilizing rearrangements of the virus capsid that enable genome release. However, the mechanism of enterovirus genome release has not been visualized in infected cells. Here, we used cryoelectron tomography and microscopy to image echovirus 18 (E18) entry into host cells and its interaction with the neonatal Fc receptor (FcRn). 30 min postinfection, endosomes and cytoplasm contained empty capsids missing one or several pentamers of capsid proteins, providing evidence that in vivo E18 releases its genome through capsid opening. In vitro, FcRn binding induced the expulsion of pocket factors from hydrophobic pockets in VP1, priming the virus for uncoating. The cryoelectron microscopy reconstruction of genome-containing particles of E18 inside infected cells did not reveal pocket factors, indicating that receptor binding triggers the same priming process during infection. We did not detect activated particles in infected cells, suggesting that these intermediates are short-lived and rapidly release their genomes in vivo. Our results identify capsid opening as the in vivo mechanism of echovirus 18 genome release, providing structural evidence for a process previously only inferred from in vitro experiments.</p>

CEITEC Scientists Are the First to Capture How Enteroviruses Initiate Infection 

<p><strong>In the week from September 14, the following webinars await you in the field of atomic and molecular spectroscopy and spectrometry</strong></p><blockquote><h4><a target="_blank" rel="noopener noreferrer" href="https://icpms.labrulez.com/webinars"><strong>👉 DETAILS AND REGISTRATION IN THE WEBINARS SECTION</strong></a></h4><p><strong>👉 Search and filter in the largest global database</strong> with over <strong>6 000 GC, LC, MS and spectroscopy webinars</strong>.</p></blockquote><h5><strong>1. Technology Networks: Automating Microplastic Analysis To Support Water Quality Research</strong></h5><ul><li>Tu, 15.9.2026 16:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6471">Registration</a></li></ul><p>Join this webinar on automated microplastic analysis and learn how automated sample preparation can improve workflow efficiency and support water quality research.</p><h5><strong>2. C&amp;EN: Fast Track Closed-Loop Experimentation with AI-Driven Automation on Stuntman</strong></h5><ul><li>Tu, 15.9.2026 17:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6472">Registration</a></li></ul><p>Discover how the Stuntman platform integrates AI and laboratory automation to enable closed-loop experimentation and accelerate research and discovery workflows.</p><h5><strong>3. Agilent Technologies: ICP-OES Preventive Maintenance: What to Clean, How, and When</strong></h5><ul><li>Tu, 15.9.2026 21:30 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6413">Registration</a></li></ul><p>Learn key ICP-OES cleaning procedures and maintenance schedules to prevent signal drift, instability, and unnecessary instrument downtime.</p><h5><strong>4. Bruker: From Pit to Port: XRF Solutions for Base Metal Mining Operations</strong></h5><ul><li>We, 16.9.2026 10:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6502">Registration</a></li></ul><p>Explore how EDXRF and WDXRF support base metal mining operations, from grade control and process monitoring to quality assurance across the production chain.</p><h5><strong>5. Bruker: AI-Assisted Analysis of Viscoelasticity with AFM</strong></h5><ul><li>We, 16.9.2026 17:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6503">Registration</a></li></ul><p>Learn how machine learning and the ViscoDirect module accelerate AFM-based viscoelasticity analysis and cell nanorheology workflows.</p><h5><strong>6. Anton Paar: Extreme-Temperature Stability of MXenes Revealed by In-Situ High-Temperature XRD</strong></h5><ul><li>We, 16.9.2026 18:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6429">Registration</a></li></ul><p>Discover how non-ambient XRD chambers enable in-situ characterization of MXene structural dynamics at temperatures up to 1200 °C.</p><h5><strong>7. Agilent Technologies: Accelerating Biopharmaceutical Development with the Agilent Cary 3500 UV-Vis Spectrophotometer</strong></h5><ul><li>Th, 17.9.2026 07:30 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6507">Registration</a></li></ul><p>Explore how the Agilent Cary 3500 UV-Vis spectrophotometer supports biopharmaceutical characterization from development through routine quality control.</p><h5><strong>8. Agilent Technologies: Landscape of Standardization and Overview of Analytical Techniques Used for Microplastics Analysis</strong></h5><ul><li>Th, 17.9.2026 11:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6539">Registration</a></li></ul><p>Explore current trends in microplastics analysis, including analytical standards, molecular spectroscopy, Py-GC/MS, TD-GC/MS, and future developments for reliable characterization.</p><h5><strong>9. SelectScience: Master EV profiling with Leprechaun – A case study from North Texas Eye Research Institute</strong></h5><ul><li>Th, 17.9.2026 17:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6506">Registration</a></li></ul><p>Explore advanced extracellular vesicle profiling and discover how the Leprechaun platform streamlines EV characterization for research applications.</p><h5><strong>10. Agilent Technologies: Analysis of High Purity Titanium Using an Agilent 9500 ICP-QQQ</strong></h5><ul><li>Th, 17.9.2026 20:00 CEST</li><li><a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/webinar/6414">Registration</a></li></ul><p>Learn how the Agilent 9500 ICP-QQQ overcomes titanium matrix effects to enable trace impurity analysis in high-purity titanium.</p>

Webinars LabRulezICPMS Week 38/2026

<p><span><strong>This study compares loss-on-ignition, acid decarbonation, and combustion elemental analysis for measuring organic carbon in sediments using certified reference materials and real samples. Loss-on-ignition conversions were inaccurate, while acid washing before elemental analysis caused significant organic carbon loss and poor precision.</strong></span></p><p><span>Combustion pretreatment followed by elemental analysis provided accurate and precise organic and inorganic carbon measurements, confirmed by temperature-dependent combustion. Across more than 150 intertidal sediment samples, acid decarbonation underestimated organic carbon by 37% ± 8%, supporting combustion-based elemental analysis as the preferred approach for reliable sediment carbon determination.</span></p><blockquote><h4><strong>The original article</strong></h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#s0055"><strong>Comparing loss-on-ignition, acid decarbonation and combustion elemental analysis for measuring organic carbon concentrations – recommendations for best practice</strong></a></h4><p>Robert B. Sparkes, Stuart A. Rae, Lucy McMahon, Hannah L. Mossman, David McKendry, Clare E. Dean, Graham Tinsley, Frances Fowden, Connor J. Grisdale, Hafiza Begum, Holly Hope, Charlotte McEnhill, Samuel O’Boyle, Nawal Sohail, Marvyn Wachira, Rachel M. Dunk</p><p>Organic Geochemistry, Volume 218, 2026, 105215</p><div><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1016/j.orggeochem.2026.105215"><span>10.1016/j.orggeochem.2026.105215</span></a></div><h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/"><strong>CC-BY 4.0</strong></a></h6></blockquote><p><strong>Selected sections from the article follow. Formats and hyperlinks were adapted from the original.</strong></p><div><div><div><div><div><p>Environmental and Earth scientists frequently require measurements of carbon contents, including both the total carbon concentration (TC) and the fractions contributed by carbon from organic matter (organic carbon; OC) and carbonate minerals (inorganic carbon; IC; <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0025"><span>Bendle et al., 2009</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0220"><span>Radabaugh et al., 2018</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0230"><span>Saderne et al., 2019</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0240"><span>Scheingross et al., 2019</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0260"><span>Smeaton et al., 2021</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0295"><span>Vonk et al., 2012</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0315"><span>Wood et al., 2021</span></a>).</p><p>Accurate, precise, and affordable carbon concentration measurements are critical to the drive towards net-zero emissions, which requires monitoring, reporting and verification of carbon burial and release from an array of global environments (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0210"><span>Post et al., 2001</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0265"><span>Smith, 2004</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0270"><span>Smith et al., 2020</span></a>). Carbon concentration measurements also underpin further analyses (e.g. normalising the concentration of individual biomarker compounds against the total organic carbon concentration, calculating elemental carbon to nitrogen ratios (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0290"><span>van Dongen et al., 2008</span></a>), determining the correct sample load for isotope ratio measurements). Despite carbon concentration measurements being ubiquitous throughout multiple disciplines there is no standard approach for making these, especially determining the organic component of the sedimentary carbon (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0080"><span>Fest et al., 2022</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0320"><span>Young et al., 2018</span></a>). Different disciplines have often generated their own consensus approach, which may not align with studies from another field, even those working on similar samples and asking similar questions (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0070"><span>Farmer et al., 2014</span></a>). Use of an agreed standard measurement protocol for carbon concentrations, or understanding the agreement/variability between protocols, is vital for regulatory monitoring, reporting and verification (MRV), such as the ongoing development of carbon offsetting standards that, if implemented robustly, could provide real-world benefits to climate mitigation (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0035"><span>Bonn et al., 2014</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0045"><span>Burden et al., 2023</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0105"><span>Guizar-Coutiño et al., 2022</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0190"><span>Needelman et al., 2018</span></a>, <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0205"><span>Pan et al., 2022</span></a>). Determining a standardised, verified approach to carbon measurement is important for those performing MRV, who may not have access to advanced and/or expensive analytical instrumentation.</p><p>This study compares three common methods for quantifying the total and organic carbon concentrations in sedimentary samples: i) loss-on-ignition, ii) elemental analysis combined with acid decarbonation, and iii) elemental analysis combined with organic matter combustion. The comparison focuses on assessing the accuracy, precision, and repeatability of each method, identifying their respective strengths and weaknesses, and independently confirming findings via a fourth method (temperature dependent combustion and infrared CO<sub>2</sub> measurement) to provide recommendations for best practice. A summary review of these methods is provided below.</p><h4><strong>2. Materials and methods</strong></h4><h5><strong>2.3. Independent testing of reference materials via TDC</strong></h5><p>Standards were analysed by the supplier (Elemental Microanalysis Ltd, UK) as part of the certification process: 15/30 elemental analysis measurements gave expected values of TC, OC and IC and the uncertainty for TC, following ISO/IEC17025. These values were independently checked using an <a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/icpms/library?mainauthorItems=16&amp;search=Soli+TOC"><strong>Elementar SoliTOC cube</strong></a> instrument at the instrument manufacturer’s headquarters (Elementar Analysensysteme, Hanau, Germany), which used the TDC method. Two combustion ramps were applied, first a two-step OC and IC determination at 500 °C and 900 °C, and then a three-step programme at 400 °C and 600 °C for easily-combustible and residual OC fractions and 900 °C for IC, with three repeat measurements of each. The SoliTOC cube instrument also analysed the agricultural soil sample, again making three repeat measurements of both the two-step and three-step temperature dependent combustion protocols (see Supplementary Table 3).</p><h5><strong>2.5. Elemental analysis</strong></h5><p>Total carbon concentrations were measured following the protocol described in <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0180"><span>Mossman et al. (2022)</span></a>. 20&nbsp;mg of either untreated or pre-treated sample was weighed into tin capsules (Elemental Microanalysis Ltd.) and analysed for carbon concentrations using a Vario EL cube elemental analyser (Elementar Ltd.). Before each analytical run, the instrument was cleaned using three blanks without oxygen and seven blanks with oxygen, and calibrated using five analyses of up to 14&nbsp;mg ethylenediaminetetraacetic acid (EDTA) standard (Elemental Microanalysis Ltd.) and three analyses of an independent Soil Standard (Clay) CRM, acquired separately to the Soil Standard (Clay) CRM used to create analytical samples for this study (Elemental Microanalysis Ltd.). Three analyses of the EDTA calibration standard were repeated after every twenty samples. Long-term drift was monitored by repeated measurements of an internal laboratory standard sample, which has been analysed since 2015. Over the course of 65 measurements across 10 instrument runs for this study the laboratory standard showed no systematic drift.</p><h4><strong>3. Results and discussion</strong></h4><h5><strong>3.1. Testing of certified reference materials (CRMs) using temperature dependent combustion (TDC)</strong></h5><p>Both two-step and three-step TDC protocols consistently measured carbon contents close to but slightly below the supplier-certified values (see <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#f0005"><span>Fig. 1</span></a>). For Soil Standard (Clay), the TDC instrument under-estimated OC by 0.10&nbsp;wt% (two-step) and 0.14&nbsp;wt% (three-step) and IC by 0.15&nbsp;wt% (two-step) and 0.087&nbsp;wt% (three-step). For Soil Standard (Peaty) the TDC instrument underestimated OC by 0.26&nbsp;wt% (two-step) and 0.34&nbsp;wt% (three-step), and IC by 0.021&nbsp;wt% (two-step) and 0.090&nbsp;wt% (three-step). Relative differences for OC are small, 5.1 – 7.0% for Clay and just 1.7 – 2.2% for Peaty, but higher for IC due to the small amount of IC present in the standards (25 – 44% for Clay, 7.0 – 30% for Peaty).</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Organic_Geochemistry_Volume_218_2026_105215_Fig_1_Comparison_of_organic_carbon_and_inorganic_carbon_measurements_on_two_certified_reference_materials_using_four_methods_31537717b3.jpg" alt="Organic Geochemistry, Volume 218, 2026, 105215: Fig. 1. Comparison of organic carbon and inorganic carbon measurements on two certified reference materials using four methods. Upper panel is Soil Standard (Clay) and lower panel Soil Standard (Peaty). Yellow diamonds show the certified value (Elemental Microanalysis Ltd) with manufacturer stated uncertainty in total carbon used as error bars for OC and IC (n = 30). White and grey symbols represent Loss-on-Ignition results using four different organic matter to organic carbon conversion equations (grey sqaures use the “van Bemmelen” scaling factor (Pribyl, 2010), grey circles the Craft et al. (1991) factor, white diamonds the Ouyang and Lee (2020) equation and white circles the Smeaton et al. (2022) equation. IC values for all LoI results use the C/CO2 mass fraction (Wang et al., 2011). Blue circles show the acid decarbonation and elemental analysis protocol, orange circles the combustion and elemental analysis protocol. Green and purple circles show mean results from temperature dependent combustion method (2-step and 3-step protocols respectively). Error bars represent one standard deviation after multiple measurements (n = 2 to n = 4). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Organic_Geochemistry_Volume_218_2026_105215_Fig_1_Comparison_of_organic_carbon_and_inorganic_carbon_measurements_on_two_certified_reference_materials_using_four_methods_31537717b3.jpg 116w," sizes="100vw" width="2756" height="3698"></p><h5><strong>3.4. Reproducibility tests</strong></h5><p>Having shown that combustion coupled with elemental analysis was the most robust method for measuring OC in pure and diluted standards, the next experiment tested the reproducibility of these protocols over multiple implementations. A dried, ground agricultural soil sample was repeatedly analysed using each method (separate aliquots were measured using LoI at 500 °C and 800 °C, separate untreated aliquots were analysed via EA, separate aliquots were combusted at 500 °C and analysed via EA, and separate acid decarbonations were carried out prior to EA measurements). This required a large amount of starting material, more than was available in the CRMs. Independent external measurement of the soil sample using temperature dependent combustion (Elementar, Germany) gave mean OC&nbsp;=&nbsp;2.50&nbsp;±&nbsp;0.002&nbsp;wt% and IC&nbsp;=&nbsp;1.29&nbsp;±&nbsp;0.008&nbsp;wt% for combustion to 500 °C (n&nbsp;=&nbsp;3), whereas combustion to 600 °C gave OC&nbsp;=&nbsp;2.52&nbsp;±&nbsp;0.075 and IC&nbsp;=&nbsp;1.12&nbsp;±&nbsp;0.010&nbsp;wt% (n&nbsp;=&nbsp;3).</p><div><p>LoI showed differences in mean OC depending on the equation chosen (<a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#f0010"><span>Fig. 2</span></a>). The conversions of <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0050"><span>Craft et al. (1991)</span></a> and <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0200"><span>Ouyang and Lee (2020)</span></a> were similar to the independent measurements (2.90&nbsp;±&nbsp;0.05&nbsp;wt% and 2.60&nbsp;±&nbsp;0.07&nbsp;wt% respectively; n&nbsp;=&nbsp;9 for each), but the equations of <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#b0255"><span>Smeaton et al. (2022)</span></a> and van Bemmelen over-estimated OC (4.19&nbsp;±&nbsp;0.05 and 4.21&nbsp;±&nbsp;0.08&nbsp;wt% respectively; n&nbsp;=&nbsp;9 for each). IC estimates using the C/CO<sub>2</sub> mass fraction conversion were higher than the expected value (1.91&nbsp;±&nbsp;0.06&nbsp;wt%, n&nbsp;=&nbsp;9). Note that the relative standard deviation for OC<sub>LoI</sub> was&nbsp;∼&nbsp;1.8%, and 3.2% for IC<sub>LoI</sub>, showing acceptable run-to-run precision.</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Organic_Geochemistry_Volume_218_2026_105215_Fig_2_Organic_and_inorganic_carbon_measurements_following_repeated_analysis_of_a_homogenised_soil_sample_via_multiple_methods_c5d62ece0b.jpg" alt="Organic Geochemistry, Volume 218, 2026, 105215: Fig. 2. Organic and inorganic carbon measurements following repeated analysis of a homogenised soil sample via multiple methods. Markers for each method are shown in the legend and are the same as Fig. 1. Small black circles and error bars show the mean and one standard deviation after multiple repetitions of each protocol (n = 9 for LoI, C-EA and AD-EA, n = 3 for TDC)." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Organic_Geochemistry_Volume_218_2026_105215_Fig_2_Organic_and_inorganic_carbon_measurements_following_repeated_analysis_of_a_homogenised_soil_sample_via_multiple_methods_c5d62ece0b.jpg 204w," sizes="100vw" width="2363" height="1815"></p><p>Since OC<sub>C-EA</sub> and IC<sub>AD-EA</sub> were calculated by subtraction from mean TC<sub>EA</sub>, all data from the C-EA and AD-EA methods plotted on a straight line in <a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S0146638026000902#f0010"><span>Fig. 2</span></a>, representing OC&nbsp;+&nbsp;IC&nbsp;=&nbsp;TC. However, position and scatter along that line varied between the two pre-treatment techniques. OC<sub>C-EA</sub> clustered just higher than the independent measurements using TDC (2.60&nbsp;±&nbsp;0.03&nbsp;wt%, n&nbsp;=&nbsp;9). Propagating the errors in TC and IC gave a combined error estimate of&nbsp;±&nbsp;0.1&nbsp;wt% for the repeated OC<sub>C-EA</sub> measurements. IC<sub>C-EA</sub> was also close to but slightly higher than the TCD results, 1.35&nbsp;±&nbsp;0.03&nbsp;wt%. AD-EA, however, gave mean OC values of 2.00&nbsp;±&nbsp;0.12&nbsp;wt% (n&nbsp;=&nbsp;9) which was more variable run-to-run than the other methods and gave a significantly (p&nbsp;&lt;&nbsp;0.0001) lower mean OC value than the TCD results. Once again, acid decarbonation results suggested that a large amount of organic matter was lost during the acid treatment, tested further in the next section.</p></div><h4><strong>4.3. Conclusions</strong></h4><p>An accurate, precise, efficient, and standardised method for measuring total, organic and inorganic carbon contents of sediment samples is critical for both scientific research and environmental monitoring and reporting and verification. We rigorously tested three methods for measuring carbon contents in soils and intertidal sediments, using certified reference materials and&nbsp;&gt;&nbsp;150 sediment samples. Loss-on-ignition (LoI) is cheap and easy but showed moderate run-to-run variability and, without careful calibration, it is not accurate.</p><p>Elemental analysis (EA) is an accurate and precise method for total carbon (TC) analysis. Measuring organic and inorganic carbon via EA requires pre-treatment of the sample, and this study tested both acid decarbonation and combustion preparation techniques. Acid decarbonation led to significant and variable organic carbon loss, meaning that true organic carbon concentrations are likely higher than those measured following acidification. Combustion pre-treatment was shown to efficiently remove organic matter, leading to accurate and precise results, and we would recommend making organic carbon measurements in this way.</p></div></div></div></div></div>

Comparing loss-on-ignition, acid decarbonation and combustion elemental analysis for measuring organic carbon concentrations – recommendations for best practice

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Comparing loss-on-ignition, acid decarbonation and combustion elemental analysis for measuring organic carbon concentrations – recommendations for best practice

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