soli TOC cube The versatile instrument for temperaturedependent differentiation of carbon in solids

soli TOC cube — Temperature‑dependent differentiation of carbon in solids: expert summary

Importance of the topic

Determination of carbon fractions in solid materials (total organic carbon, total inorganic carbon, and refractory/elemental carbon) is critical across environmental monitoring, waste management, soil science, construction materials QA/QC and research. Accurate differentiation of TIC, TOC and refractory organic carbon (ROC) informs biodegradability assessments, pollutant source identification and compliance with regulatory standards. Instruments that deliver high sensitivity, robust sample throughput and flexible protocols reduce laboratory workload while improving data quality for heterogeneous solid matrices.

Objectives and overview

This document presents the soli TOC cube, an elemental analyzer designed for automated, temperature‑programmed carbon fractionation in solids. The device aims to: measure TOC, TIC and ROC with high sensitivity across a wide dynamic range; support multiple standardized protocols (DIN 19539, DIN 15936, DIN 13137); enable simple sample handling for inhomogeneous materials; and offer optional simultaneous nitrogen measurement and carrier gas switching for improved separation of carbon fractions.

Methodology

The soli TOC cube implements two complementary analytical approaches:

• Classical acidification/drying TOC: direct acidification of solid samples in ceramic crucibles followed by combustion at constant temperature for TOC determination.
• Temperature programming (ramped combustion): progressive heating of the sample in the crucible to separate carbon fractions by their evolution temperatures. Typical protocol described: heat at 70 °C·min−1 with defined holds at 400 °C (TOC400), 400–600 °C (ROC fraction), and 600–900 °C (TIC900).

The unit can be operated in a three‑step temperature program or a two‑step program that incorporates carrier gas switching (oxygen to inert gas and back) to enhance separation of TIC and ROC. Post‑combustion catalysis is used to ensure quantitative oxidation of evolved carbon even for high carbon loads. Sample sizes from hundreds of milligrams to gram scale can be analyzed using reusable ceramic crucibles and an automated 89‑position autosampler.

Used instrumentation

The system components and options described include:

• soli TOC cube elemental analyzer (Elementar).
• High accuracy temperature control measured at the crucible for minimized thermal artifacts.
• Post‑combustion catalyst for complete oxidation of evolved carbon.
• Automated 89‑position autosampler and reusable ceramic crucibles with automatic ash removal.
• Carrier gas switching hardware to alternate between oxygen and inert gas (e.g., N2) during a run.
• Optional EC detector to simultaneously determine nitrogen (via an additional detector channel) or elemental carbon signal.
• Tool‑free clamp connections and robust consumables designed for long lifetime.

Main results and discussion

Performance features and measured behavior reported in the material include:

• Analytical range: 0.001–100% carbon, indicating suitability from trace to high‑carbon matrices.
• High sensitivity and stable calibration from state‑of‑the‑art combustion and detection technology.
• Temperature programming combined with carrier gas switching improves temporal separation between TIC and ROC peaks: pyrolysis in inert atmosphere at high temperature leaves ROC in the crucible while TIC evolves as CO2 prior to re‑oxidation of ROC when oxygen is reintroduced.
• Direct measurement at the crucible tip for precise temperature control avoids thermal lag and improves reproducibility.
• Representative dataset (soil types and industrial residues) illustrates the capability to quantify TOC400, ROC and TIC900 across diverse sample types: e.g., coal mine tailings showed very high TOC and ROC (~17% and ~19%, respectively), while typical soils had lower TOC (0.2–3.6%) and minor TIC fractions; industrial wastes (slag, incinerator ash) exhibited variable distributions emphasizing the need for fractionation.

Graphs described in the source show IR signal (CO2 detector) versus time under both three‑step and two‑step gas‑switched protocols, demonstrating distinct CO2 evolution peaks corresponding to TOC, ROC and TIC temperature windows and illustrating improved peak separation with gas switching.

Benefits and practical applications

Key advantages of the soli TOC cube for laboratory practice include:

• High throughput and automation: 89‑position autosampler and reusable crucibles reduce manual handling and allow reliable analysis of inhomogeneous samples.
• Flexibility: supports DIN‑compliant methods, customizable heating rates and hold times, two‑step or three‑step temperature programs, and optional gas switching and N‑analysis.
• Simplified sample preparation: direct acidification in crucibles for the DIN method or direct analysis without acids using temperature programming.
• Robustness and longevity: tool‑free connectors, certified consumables and automatic ash removal improve uptime and lower maintenance.
• Trace to bulk capability: measurement range enables both environmental trace analyses and characterization of high‑carbon industrial residues.

Future trends and possibilities

Potential developments and applications that build on the soli TOC cube approach include:

• Integration of multi‑detector arrays (e.g., simultaneous CO2, CO, NOx channels) for enhanced speciation and cross‑validation of combustion products.
• Automation of pre‑treatment workflows (acidification, drying) for fully unattended DIN workflows.
• Improved data processing algorithms (deconvolution of overlapping peaks) to further resolve complex matrices with overlapping carbon evolution ranges.
• Miniaturized or field‑deployable variants for on‑site soil and waste screening combined with cloud‑based QA/QC management.
• Expanded standardization to harmonize temperature‑programmed fractionation methods across regions and disciplines.

Conclusion

The soli TOC cube combines precise, crucible‑referenced temperature control, optional carrier gas switching and post‑combustion catalysis to deliver reliable fractionated carbon analysis for solids. Its wide dynamic range, automation, and conformity with DIN standards make it a practical solution for environmental labs, waste assessment, construction materials testing and research groups requiring robust TOC/TIC/ROC data. The instrument’s flexibility and upgrade paths (e.g., N detection) support diverse laboratory needs while simplifying routine operation.

Reference

Elementar Analysensysteme GmbH. soli TOC cube product information and technical specifications. Elementar‑Straße 1, 63505 Langenselbold, Germany. Document date indicated 02/2017. Standards referenced: DIN 19539, DIN 15936, DIN 13137.