TOC Analyzer NPOC Analysis

In total organic carbon analyses, total carbon (TC) and inorganic carbon (IC) measurement is required. The TOC analyzers used for TOC analysis are capable of measuring only the total carbon; therefore, some method needs to be adopted to measure the inorganic carbon. One such method is total NPOC Analysis. It’s a common method that directly measures TOC by re-acidification of the sample to a pH value of two or less. This releases IC gas in the TOC analyzer chamber; however, in this method the gas is released to air. The remaining non-purgeable carbon dioxide gas present in the liquid aliquot is then oxidized to release the gases which are detected by the detector.

Stages of NPOC Analysis by the TOC Analyzer

NPOC analysis can be divided into the following stages:

Acidification

By the process of acidification and sparging, IC and POC gases are removed from the liquid sample.

Oxidation

This is the stage in which oxidation of the carbon that remains in the sample takes place. It results in the formation of carbon dioxide and other gases within the TOC analyzer. There are several ways in which oxidation can be perfumed, such as photo oxidation. Here is a look at how a TOC analyzer that utilizes this process works.

Photo Oxidation (UV Light)

Within a TOC analyzer that utilizes this method of oxidation, ultra-violet light alone oxidizes the carbon within the sample and CO2 is produced. The advantage of using a TOC analyzer that utilizes this method is that it is most low maintenance, reliable way of analyzing total organic carbon in ultra-pure waters.

Detection and Quantification

Many TOC analyzer manufacturers commonly use detection methods, conductivity and NDIR for total organic carbon analysis.

Conductivity

TOC analyzers that measures using conductivity measures carbon dioxide either by the direct method or the membrane method. The benefits of direct conductivity are that it is an inexpensive and uncomplicated method of measuring carbon dioxide. Although membrane conductivity is more robust than direct conductivity, the analysis time is slow. There is no difference in the measurement procedure as both types of conductivity analyze the sample before and after oxidation; the difference created by oxidation is attributed to the total organic carbon of the sample.

NDIR Technology

NDIR or non-dispersive infrared is the only method of total organic carbon analysis that provides practical interference-free technique of detecting carbon dioxide.