TOC-TNb Analyzer for Combined Carbon and Nitrogen

What is the TOC-TNb Analyzer for Combined Carbon and Nitrogen?

A TOC-TNb analyzer measures total organic carbon and total bound nitrogen from the same injection, using NDIR for CO2 and chemiluminescence for nitric oxide. It is used in wastewater and nutrient studies where carbon and nitrogen loads are evaluated together.

Overview

The TOC-TNb analyzer adds a nitrogen detection branch to a high-temperature combustion system. In the furnace at about 720–800 °C, organic carbon becomes CO2 and all bound nitrogen, including ammonium, nitrate, nitrite, and organic nitrogen, is converted to nitric oxide. A portion of the gas stream feeds the NDIR cell for carbon, while NO reacts with ozone in a chemiluminescence detector, where emitted light at 600–3000 nm is proportional to nitrogen concentration. The design delivers simultaneous TOC, TC, TIC, and TNb results in about 4 minutes. Measurement range for nitrogen is typically 5 µg/L to 10,000 mg/L. Because nitrogen is not measured by NDIR, catalysts and carrier gas must be compatible with nitrogen oxide formation, and ozone generators need air or oxygen supply. Calibration uses potassium nitrate alongside potassium hydrogen phthalate.

How does it work?

A TOC analyzer separates carbon into inorganic carbon (carbonate and bicarbonate) and organic carbon. In the NPOC method, the sample is acidified to pH below 2 with hydrochloric or phosphoric acid and sparged with carrier gas so inorganic carbon leaves as CO2, then the remaining organic carbon is oxidized. High-temperature catalytic combustion injects the sample into a furnace at 680–1200 °C with a platinum or cobalt catalyst, converting organic carbon to CO2. Wet chemical oxidation uses persulfate and ultraviolet light to generate hydroxyl radicals at lower temperatures. The resulting CO2 is dried, halogens are scrubbed, and the gas passes through an NDIR cell at about 4.26 µm. Peak area is proportional to carbon mass and is calibrated with potassium hydrogen phthalate. Total nitrogen bound can be measured by chemiluminescence after combustion.

What are the key features?

• Simultaneous TOC and TNb from one injection saves time and sample volume.
• Chemiluminescence detector provides sensitive nitrogen detection down to 5 µg/L.
• Combustion converts ammonium, nitrate, nitrite, and organic nitrogen to nitric oxide.
• Ozone generator with destructor protects the operator from ozone and NOx emissions.
• Dual calibration software handles carbon and nitrogen standards separately.

What are the technical specifications?

A typical toc-tnb analyzer for combined carbon and nitrogen configuration offers carbon range of 4 µg/L–30,000 mg/L, nitrogen range of 5 µg/L–10,000 mg/L, furnace temperature of 720–800 °C, carbon detector of NDIR, nitrogen detector of Chemiluminescence and injection volume of 20–500 µL. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The TOC-TNb Analyzer for Combined Carbon and Nitrogen is used in wastewater treatment process control, nutrient load assessment in rivers and lakes, agricultural runoff monitoring and fermentation and bioprocess media. Across the wider TOC Analyzers class, laboratories also deploy it for drinking water and surface water monitoring, wastewater and effluent compliance testing and soil and sediment organic carbon analysis.

Which standards and certifications apply?

Relevant standards and methods include ISO 8245, EN 1484, ASTM D7573, ASTM D4129, USP <643>, Ph. Eur. 2.2.44, ISO 10694 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Use carbon-free glassware or pre-baked vials and keep samples acidified and refrigerated if not analyzed immediately, because volatile organics are lost and microbial activity changes carbon. Ultra-pure carrier gas and low-blank water for calibration standards are essential at low ppb levels. Replace the combustion catalyst, halogen scrubber, and humidity trap based on sample load, and check the furnace tube for salt build-up with high-salt samples. Verify linearity with potassium hydrogen phthalate and check inorganic carbon recovery with sodium carbonate. System suitability in pharmaceutical use is performed with sucrose and 1,4-benzoquinone standards. Maintain calibration records and blank logs, and ensure ventilation for exhaust gas and acid fumes.

How do I select the right TOC-TNb Analyzer for Combined Carbon and Nitrogen?

Choose this variant when total nitrogen bound is a required parameter alongside TOC, for example in discharge permits or eutrophication studies. If only carbon is needed, a standard TOC analyzer is simpler. Specify nitrogen range, detector type, ozone supply, and methods such as EN 12260 or ISO 20236.

How does it compare with other TOC Analyzers variants?

The main selection criterion is the oxidation technique. High-temperature catalytic combustion handles particulate-laden, high-salt, and difficult organics, and covers ranges from 4 µg/L to 30,000 mg/L with suitable catalyst and injection volumes. UV-persulfate oxidation suits clean waters such as ultrapure and pharmaceutical water, with detection limits near 0.5 µg/L. Decide whether total nitrogen is needed and whether solid samples such as soils, sediments, or powders must be analyzed, because that requires a solid sample module with a furnace up to 900–1000 °C. Online process analyzers need continuous sampling, automatic calibration, and relay outputs. Consider autosampler capacity of 30–90 vials, sample volume, and the acid and catalyst consumption. Verify compliance with EN 1484, ISO 8245, and USP <643> when applicable.