TOC/TN_b Determination in Particle-Containing Samples – Performing the "Cellulose Test"

User Benefits

- High Suspension mode ensures reliable, reproducible results of even heavily particle-laden samples. - Delivers robust accuracy and proven compliance with ISO 20236, EN 1484, and ISO 8245. - TOC-L simplifies the workflow and minimizes maintenance, letting users focus on secure, reliable results.

Introduction

Analyzing the total organic carbon (TOC) and total bound nitrogen (TN_b) content of water samples is a key requirement in environmental and industrial laboratories, especially for applications such as municipal and industrial wastewater treatment, where samples often contain particulate matter. TOC determination was originally specified in EN 1484 and ISO 8245 which addressed only carbon parameters, and is now more comprehensively defined in ISO 20236, which also includes nitrogen. This latest standard defines TOC as the sum of organically bound carbon, and TN_b as the sum of organically and inorganically bound nitrogen, present in a sample, regardless of whether these are dissolved or suspended. When required, the dissolved fractions (dissolved organic carbon, DOC, and dissolved bound nitrogen, DN_b) can be determined after membrane filtration (0,45 µm). Measuring TOC and TN_b in samples containing particulate material presents a unique analytical challenge. Accurate assessment of suspended material requires not only robust instrumentation, but also careful sample preparation and handling, as particles can settle, aggregate, or escape detection during analysis. One of the central challenges in such analyses is the reliable execution of the “particle processing control,” more commonly known as the “cellulose test.” Originally included in the standards EN 1484 and ISO 8245, and most recently detailed and mandated in ISO 20236, this test has become the primary benchmark for assessing instrument performance and operator proficiency in handling suspensions. Successfully passing the cellulose test is therefore required to demonstrate that both the system and laboratory procedures are fully fit for the analysis of real-world samples containing particulate material.​

July 29, 2025 GMT