<p><strong>Dimethyl carbonate (DMC) plays a critical role in lithium-ion battery electrolytes, where solvent purity directly impacts performance, safety, and lifetime. Even trace-level impurities can contribute to degradation of solid electrolyte interfaces, consumption of lithium ions, or gas formation—effects that compromise both efficiency and safety.</strong></p><p>As battery materials continue to evolve, analytical approaches must provide both high sensitivity and high-confidence identification. A recent LECO application study demonstrates how combining two GC-MS platforms enables a more complete characterization of DMC impurities than either approach alone.</p><h3><strong>Why Impurity Characterization in DMC Is Challenging</strong></h3><p>Battery-grade solvents demand detection of contaminants across a wide concentration range, starting from major byproducts to trace-level species. In DMC, impurities may include oxygenated compounds, hydrocarbons, and nitriles, many of which arise from synthesis or handling processes.</p><p>These compounds can co-elute or exist at levels below typical detection thresholds, making comprehensive analysis difficult with a single analytical technique. In addition, electron ionization (EI) spectra do not always provide a clear molecular ion, complicating compound confirmation.</p><h3><strong>A Complementary Analytical Strategy: Sensitivity + Confidence</strong></h3><p>The application note demonstrates a combined workflow using the approach:</p><ul><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/1097"><strong>Pegasus BTX (GC-TOFMS)</strong></a>&nbsp;for high-sensitivity detection</li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/products/38"><strong>Pegasus HRT (high-resolution GC-MS)</strong></a>&nbsp;for accurate mass confirmation</li></ul><p>The<strong> Pegasus BTX </strong>enables detection of impurities at<strong> below parts-per-billion levels</strong>, ensuring that even low-abundance analytes are captured.</p><p>Following detection, the<strong> Pegasus HRT</strong> provides high-resolution, accurate mass data in both EI and positive chemical ionization (PCI) modes. PCI is particularly valuable when EI spectra lack a clear molecular ion, allowing confirmation through common adduct species such as protonated molecular ions [M+H]⁺.</p><p>Because both ionization modes can be accessed without hardware changes, the workflow supports efficient, multi-dimensional confirmation of analyte identity.</p><h3><strong>Observations</strong></h3><p>Using this combined approach, multiple classes of impurities were identified in the DMC sample. These included:</p><ul><li>Oxygenated reaction byproducts</li><li>Alcohols, carbonates, and ethers</li><li>Hydrocarbons and aromatic species</li><li>Additional low-level analytes detected with high library match scores</li></ul><p>Importantly, the high sensitivity of the Pegasus BTX revealed a broader set of low-concentration compounds, while the Pegasus HRT increased confidence in compound identification through accurate mass measurements and confirmation of molecular formulas. &nbsp;</p><p>The study also highlights cases where co-eluting compounds were successfully deconvoluted, allowing individual components to be identified even without complete chromatographic separation.</p><h3><strong>Why This Matters for Battery Materials Analysis</strong></h3><p>This work illustrates a key principle for advanced materials characterization: detection and identification are distinct challenges that often require complementary solutions.</p><ul><li>Detection alone&nbsp;is insufficient without confident identification</li><li>High-resolution confirmation&nbsp;is limited if low-level species are not first detected</li></ul><p>By combining these capabilities, laboratories can gain deeper insight into solvent purity, production processes, and potential performance risks in battery systems.</p><h3><strong>Explore the Complete Study</strong></h3><p>This short overview highlights only a portion of the findings. The full application note provides:</p><ul><li>Detailed acquisition parameters and workflows</li><li>Chromatographic and spectral data examples</li><li>Confirmed impurity lists with retention times and similarity scores</li><li>Examples demonstrating EI/PCI complementarity and accurate mass confirmation</li></ul><p>To better understand how complementary GC-MS techniques can improve confidence in battery solvent analysis, download the full application note: <a target="_blank" rel="noopener noreferrer" href="https://www.leco.com/documents/203-821-731/"><strong>“Battery Solvent Characterization: Identifying Impurities in Dimethyl Carbonate”</strong>.</a></p>

 Confident Identification of Battery Solvent Impurities Using Complementary GC-MS Techniques

<p><strong>The international standard ISO/IEC 17025 [1] clause 7.7.2 with regards to ensuring the validity of results, requires a laboratory to participate in proficiency testing (PT) and/or to participate in interlaboratory comparisons (ILCs) other than PT. However, no guidance as to what these other ILCs might be, or indeed how they might compare in relation to PT, is provided. This leaflet aims to outline other ILCs available, pointing out some of the limitations as compared to PT.&nbsp;</strong></p><p>There are three major types of ILCs in which a group of laboratories analyses identical portions from a homogeneous, stable test sample, with each type being characterized by its intended purpose [2,3]:</p><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Eurachem_Interlaboratory_comparisons_other_than_proficiency_testing_2_d9263807fb.jpg" alt="Eurachem: Interlaboratory comparisons other than proficiency testing" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Eurachem_Interlaboratory_comparisons_other_than_proficiency_testing_2_d9263807fb.jpg 245w," sizes="100vw" width="1507" height="607"></p><p>A key point is that PT is an ILC that is designed to specifically evaluate the performance of participants, providing them with an infrastructure to monitor and assess the validity of their results. This is not the key purpose of the two other ILCs, and thus depending on their intended purpose they have a number of limitations that laboratories need to be aware of when using them rather than PT. Only proficiency testing should have been conducted in full compliance to the competency standard ISO/IEC 17043 [4].&nbsp;</p><h4><strong>Evaluation of measurement procedure performance&nbsp;</strong></h4><p>These ILCs, are designed to assess how a particular measurement procedure performs and whether it is fit for its intended purpose. These ILCs are often referred to as a ‘method performance study’ or a ‘collaborative study’ [2]. Some limitations of using such ILCs for monitoring laboratory performance as an alternative to PT are:&nbsp;</p><ul><li>All participants use the same measurement procedure i.e. the measurement procedure that is being validated. Unless the measurement procedure is being routinely used by the participating laboratory such an ILC will not assess the routine performance of the laboratory using their own routine measurement procedure. Nor does it enable them to compare their performance with other laboratories using alternative measurement procedures.&nbsp;</li><li>The measurement procedure is likely to be new, so participants may not have established stable procedures and quality control, so performance may not reflect routine use.&nbsp;</li><li>The report from such an ILC would not provide information on the performance of the participant, if the statistical model used makes the assumption that all laboratories perform with equal variability.</li><li>The design of the study may require the participants to assess multiple samples and/or to undertake multiple replicate analysis on the test materials. This may not be representative of the routine measurements or tests undertaken by the laboratory.&nbsp;</li><li>The conclusion of the ILC might be that the measurement procedure being assessed is not valid.&nbsp;</li></ul><p><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Eurachem_Interlaboratory_comparisons_other_than_proficiency_testing_3_a53ecd2f5d.jpg" alt="Eurachem: Interlaboratory comparisons other than proficiency testing" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Eurachem_Interlaboratory_comparisons_other_than_proficiency_testing_3_a53ecd2f5d.jpg 157w," sizes="100vw" width="570" height="566"></p><h4><strong>Characterisation of candidate reference materials&nbsp;</strong></h4><p>These are ILCs that assign a property value to a candidate reference material, usually with a stated measurement uncertainty. These are often referred to as a ‘material certification study’ [2]. Limitations of using such ILCs as an alternative to PT are:&nbsp;</p><ul><li>The analysis of the candidate reference material is likely to require additional care in exercising the routine measurement procedure, such as substantially more replication, and/or may require quite different reporting formats (e.g. all valid replicates instead of a mean result). Thus, such an ILC will not necessarily provide an evaluation of the performance of the laboratory based on the routine use of their measurement procedures.&nbsp;</li><li>The report from such an ILC may include the results from the participating laboratories but would not provide information on the performance of each laboratory.&nbsp;</li><li>Participating laboratories may be required to assess multiple samples and/or to undertake multiple replicate analysis on the candidate reference materials. Thus this may not be representative of the routine measurements or tests undertaken by the laboratory.&nbsp;</li></ul><h4><strong>Other ILCs&nbsp;</strong></h4><p>Some other ILCs, whilst not being conducted in full compliance of the requirements of ISO/IEC 17043, may be designed to evaluate participant performance. These would include small ILCs as defined by EA‑2/21 [5] or split sample ILCs i.e. where a portion of a single sample is sent to two or three laboratories. Whilst these ILCs are specifically designed to evaluate participant performance, they may not provide a comprehensive comparison that a PT might provide. In such cases the laboratory needs to evaluate carefully the competence of the organization managing the ILC and the suitability of the service externally provided (ISO/IEC 17025 clause 6.6).</p>

Interlaboratory comparisons other than proficiency testing

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Eurachem is a European network promoting international traceability of chemical measurements and good analytical practice. It provides expert guidance, supports method validation, uncertainty evaluation, proficiency testing, and facilitates discussion on technical and policy issues in analytical quality.

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In 1936, the Laboratory Equipment Company introduced the first rapid carbon determinator for the American iron and steel industry.  Today, almost 80 years later, LECO is recognized globally as a leader in the development of high-quality analytical instrumentation, mass spectrometers, comprehensive two-dimensional chromatography, metallography & optical equipment as well as consumables.

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Interlaboratory comparisons other than proficiency testing

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