Teledyne 6750 operating instructions Subsystems Principles of Operation, Sample Handling

Total Organic Carbon Analyzer Theory of Operation

2.4 Subsystems Principles of Operation

The Model 6750 TOC Analyzer is comprised of five subsystems:

1.Sample Handling

2.Inorganic Carbon Removal

– OR –

Inorganic Carbon Analysis/TOC-True Method

3.Oxidation

4.NDIR CO2 Gas Detection

5.Electronic Signal Processing, Display and Control

The sample system is designed to accept the liquid sample and any required reagents, transporting them through the analyzer to the appropriate components. For TOC (actually, NPOC) analysis, the sample is pumped initially to the sparger, where it is mixed with acid to lower the pH between 2.0 and 3.0. At that pH, all inorganic carbon/carbonates are converted to dissolved CO2 gas, which is sparged out of the liquid solution by the air/O2 carrier gas. At this point, any volatile organic carbon is also sparged out and lost for inclusion in the “TOC” analysis, unless a TOC-True analysis is performed, as described below.

2.4.1 Sample Handling

The sample is processed through the analyzer in two phases: liquid and gaseous

2.4.1.1LIQUID PHASE SAMPLE HANDLING

Referencing Figures 2-6 and 2-7, the sample is introduced to the analyzer with a self-priming peristaltic pump (P-4). It is then initially directed to the Inorganic Carbon (IC) Sparger, where it is mixed with acid delivered by pump (P-2). The pH of the solution is lowered to approximately 2, converting the inorganic carbon to CO2, which is sparged out by the carrier gas and measured as Total Inorganic Carbon (TIC) by an infrared analyzer (NDIR-2) in the “TOC-True” mode.

The “TOC-True” mode is the preferred method of use if volatile hydrocarbons are present, which would otherwise be lost in the sparging process. Thus, through subsequent analysis of Total Carbon (TC) and

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