Total Organic Carbon Analyzers | TOC/TNb Analyzers

The new multi N/C x300 series sets a new benchmark in efficiency, matrix tolerance, and user-friendliness for TOC/TN_b analysis. With its clever design, advanced technologies, modern software interface, and diverse automation options, it ensures smooth workflows, precise results, and low overall operating costs. Whether you're dealing with wastewater samples with high particle levels or ultrapure water, high throughput or specialized applications, solid or liquid samples – our product range has the device you need. The modular design allows for customization to meet your specific requirements.

High-temperature catalytic combustion or UV digestion?

Devices equipped with high-temperature catalytic combustion provide outstanding particle handling and exceptional sensitivity. Our UV devices deliver impressive precision and persulfate-free digestion at the ultra-trace level, ensuring rapid and complete sample oxidation, even for complex matrices. 

With decades of experience in developing analytical equipment and supporting our successful customers globally, we understand the demands of TOC/TN_b analysis. Let us help you find the perfect analyzer to ease the daily workload in your lab.

TOC analysis / TNb analysis

TOC/TN_b analysis is a method for measuring total organic carbon (TOC) and total bound nitrogen (TN_b) in samples. This method is suitable for both liquid and solid materials. It is primarily used in environmental analysis to assess water and soil quality, in the pharmaceutical industry for evaluating ultrapure water quality and cleaning validation, and across various other industries, including power generation, chemical manufacturing, and the oil and gas sector.

Sum parameters and their significance in chemical analysis

TOC/TN_b analysis is one method of sum parameter analysis. Under defined analysis conditions, it quantifies groups of substances collectively without measuring individual parameters. The main advantage of this method over single substance analysis is its speed: instead of quantitatively detecting each substance individually, TOC/TN_b analysis measures the total amount of organic carbon and bound nitrogen. For instance, water can contain millions of different organic molecules. Rather than identifying and quantifying each one, TOC/TN_b analysis measures them collectively, allowing for a reliable assessment of water quality in just a few minutes.

The TOC sum parameter

Total Organic Carbon (TOC) and Dissolved Organic Carbon (DOC) are crucial parameters in environmental analysis for assessing quality standards and identifying undesirable foreign substances in samples. TOC represents the total organic carbon content in a sample, excluding inorganically bound carbon. TOC measurements can be performed on liquid samples such as drinking water, groundwater, wastewater, and surface water, as well as on solid samples like soils, sediments, and waste.

The analytical measurement of TOC values adheres to specific technical standards that outline procedural guidelines. For water analysis, the DIN EN 1484 standard is followed. This standard provides instructions for TOC measurements in various water types, including drinking water, groundwater, surface water, seawater, and wastewater, within a range of 0.3 mg/L to 1,000 mg/L. It also includes stipulations for sample pretreatment and measurement procedures.

On an international level, the DIN EN ISO 20236 standard is applicable. This standard addresses water analysis and specifies requirements for measuring TOC, Total Nitrogen bound (TN_b), DOC, and Dissolved Nitrogen bound (DN_b) after catalytic oxidative high-temperature combustion.

For measuring the TOC sum parameter in sludge, treated biowaste, soil, and waste, the DIN EN 15936 standard is used.

Oxidation methods in TOC measurement

Various methods for determining Total Organic Carbon (TOC) have been established in analytical chemistry. All these methods share a common principle: the organic compounds in the sample are oxidized to carbon dioxide (CO₂), which is then recorded and quantified. TOC measurement methods can be categorized into two main types:

• Wet chemical UV oxidation: In this method, the sample is mixed with an oxidizing agent and oxidized in a reactor at around 80°C while a carrier gas is passed through. Alternatively, the sample can be irradiated with UV light, producing hydroxyl (OH) radicals that convert organic substances to CO₂. Many modern TOC analyzers combine these two methods to achieve a higher oxidation rate, even for samples with complex matrices.
• Catalytic combustion oxidation: In this method, the sample is mixed with an oxidizing agent and oxidized in a reactor at around 80°C while a carrier gas is passed through. Alternatively, the sample can be irradiated with UV light, producing hydroxyl (OH) radicals that convert organic substances to CO₂. Many modern TOC analyzers combine these two methods to achieve a higher oxidation rate, even for samples with complex matrices.

Detection of CO2 content and methods for measuring TOC

After oxidation, the CO₂ content of the sample must be quantified to calculate the TOC. Infrared spectrometry, known for its high selectivity and sensitivity, is the preferred method. The CO₂ produced during oxidation is carried by a carrier gas through a non-dispersive infrared (NDIR) detector. The measured CO₂ concentration is recorded over time, and the resulting area integral allows quantification of the total carbon dioxide released from the sample.

There are three different calculation methods for quantification:

• Differential method (TOC = TC – TIC): This method is particularly suitable for large TOC concentrations, such as in wastewater analysis. Two measurements are performed: one for total carbon (TC) and one for total inorganic carbon (TIC). The difference between these values gives the TOC concentration.
• Direct method: In this method, inorganic carbon compounds are removed from the sample by acidification, leaving only the organic component to be quantified. This method is widely used due to its ease of implementation, speed, and reliability. However, volatile organic compounds may escape during TIC removal, so the measured value is referred to as non-purgeable organic carbon (NPOC). Since such compounds are rare in most water samples, NPOC is typically equated with TOC
• Additive method: If highly volatile compounds are present in the sample, they can be quantified separately as purgeable organic carbon (POC). Adding POC to NPOC gives the TOC value. This method is more theoretical and is rarely used in practice.

The TNb sum parameter

Total Bound Nitrogen (TN_b) includes nitrate, nitrite, ammonium, and organic nitrogenous compounds, but excludes elemental nitrogen (N2).

Similar to TOC analysis, TN_b  is measured in a single analysis run without separating the individual components. This analytical method is standardized under DIN EN ISO 20236, which supersedes the older DIN EN 12260. The standard outlines procedures for measuring Total Organic Carbon (TOC), Dissolved Organic Carbon (DOC), Total Bound Nitrogen (TN_b), and Dissolved Bound Nitrogen (DN_b) following catalytic oxidative high-temperature combustion.

Catalytic combustion oxidation and detection for TNb measurement

Similar to TOC measurements, TN_b measurements in analytical chemistry also utilize a combustion process. In this process, nitrogen-containing substances in the sample are converted into nitrogen monoxide (NO) at temperatures exceeding 720°C. The nitrogen monoxide is then detected and measured quantitatively.

The chemiluminescence method is widely used for detecting bound nitrogen. During this process, the nitrogen monoxide produced during combustion is oxidized with ozone, forming nitrogen dioxide (NO₂). The NO₂ is initially in an energetically excited state and then returns to its ground state, emitting light quanta. These light quanta are detected by a photomultiplier, where the measured radiation intensity is proportional to the NO concentration in the sample gas, and thus to the nitrogen concentration in the sample.

In addition to chemiluminescence detection, electrochemical detection is also commonly used. In this method, the resulting NO dissolves in a solid-phase electrolyte. The changing cell potential is "titrated back" to its initial state by the formation of electrons. The resulting current is proportional to the nitrogen concentration in the sample. This method is particularly advantageous due to its lower overhead costs compared to chemiluminescence detection.

Advantages and limitations of TOC/TNb analysis

In modern analytical chemistry, TOC/TN_b analysis can be effectively combined into a versatile and economical method. Advanced machines, such as the multi N/C Series, can reliably measure sum parameters quickly and in compliance with standards. Besides TOC and TOC/TN_b these machines can measure other significant parameters like NPOC, DOC, POC, TC, and TIC.

Sum parameter analysis offers several advantages over the complex analysis of individual substances. It saves considerable time and money, is easy to use, and provides highly comparable measurements. In practice, sum parameter analysis often serves as a preliminary stage before more specific analytical methods. It allows for the rapid identification of potential hazards, functioning as an early warning system, for example, to detect contaminated water.

However, TOC/TN_b analysis has limitations. Both parameters are conventional, meaning the lack of detailed information about individual components can be misleading regarding the composition and hazard potential of substances. Therefore, single substance analysis should also be included as a further, specific analytical method depending on the application.

Applications and industries

TOC/TN_b analysis has become firmly established in various applications and industries as a fast, reliable, and economical method. Some typical fields of application for this method of sum parameter analysis include:

• Chemicals and materials: TOC measurement in material streams such as nickel, cobalt, manganese, and lithium salts for the production of cathodic materials (e.g., lithium-ion batteries) and product quality monitoring of hydrogen peroxide and phosphoric acid.
• Geology, Mining, and Metals: TOC measurement in oil shale serves as a relevant quality parameter for evaluating source rock in oil and gas production.
• Power Plants and Energy Technology: TOC measurement in ash, slag, and filter dust from coal combustion, as well as in boiler feed and cooling water in thermal power plants.
• Food and agriculture: TOC measurement in agricultural soils, dried manure, and sediments, and for quality assessment of drinking water.
• Environment: TOC/ TN_b measurement in municipal wastewater treatment plants and industrial wastewater (e.g., pulp and paper industry); TOC/ TN_b and DOC/DN_b analysis for assessing surface water and characterizing waste for landfill classification.
• Oil & gas: TOC/ TN_b measurement in refinery wastewater and TOC measurement in brine samples from the crude oil desalting process.

In conclusion, TOC/ TN_b analysis is suitable for a wide range of liquid and solid substances. In environmental engineering and water resources management, this method can be applied to drinking water, groundwater, surface water, seepage water, and wastewater. In process applications, it is used for analyzing cooling water, boiler feed water, pure water in the semiconductor industry, and electroplating baths.

In solids analysis, the method has proven especially effective in waste recycling and testing contaminated sites, where soils, sediments, building rubble, sludge, filter cakes, ash, and household waste must be scrutinized.