Analyzing difficult samples with your Total Organic Carbon (TOC) analyzer can put a lot of wear and tear on the instrument, especially if you’re running samples like those high in salt. As the project manager on the OI Analytical 1080 TOC project, I worked as part of the engineering team to evaluate typical problem spots in maintaining a combustion TOC analyzer, and together, we developed solutions to be proactive in combatting these issues to extend the overall life of the instrument and make routine maintenance as quick and painless as possible.
Let’s take a look at preventative techniques you can utilize in your lab to get the most life out of your combustion TOC analyzer. I’ll also share some unique features we built into the 1080 TOC Analyzer to automate these techniques for easier and quicker laboratory instrument maintenance.
- Minimize the Total Salt Mass – This tip is as straightforward as they come. Prior to running samples, be mindful of what type of sample it is. If you know it’s a more difficult matrix, plan to adjust your sample size according to what your TOC analyzer can reasonably manage. In the case of salt samples, it’s all about total salt mass injected into the furnace. The less salt mass injected for each sample, the more total samples can be analyzed before requiring maintenance. The 1080 TOC Analyzer provides an automatic dilution feature for difficult samples, where the Method protocol allows.
- Condition the Furnace and Catalyst – When running high-salt samples, it is important to have frequent conditioning of the furnace tube and catalyst to maximize throughput between maintenance cycles. In the 1080 TOC Analyzer, we added a user-selectable furnace conditioning feature called “Acid Conditioning,” which injects an acid blank sample after each sample has run. When alkali-organic compounds are analyzed, the non-volatile alkali oxides are left in the combustion tube as a deposit. These deposits build up and readily absorb and desorb carbon dioxide. This leads to a background of carbon dioxide being present in the gas when the gas elutes from the reactor relative to the background of carbon dioxide observed when the reactor is in bypass mode. When an acid blank is injected, the alkali oxides react with the acids forming non-volatile salts (e.g. alkali chlorides are generated from the alkali oxides by “hydrochloric acid blanks,” or alkali sulfates are generated from the alkali oxides by “sulfuric acid blanks”). These acid blanks release carbon dioxide from the alkali carbonates present in the reactor. Multiple injections are typically used in an attempt to fully convert all of the carbonates in these layers of the alkali deposits within the combustion tube without having to remove the tube and physically dissolve the deposits and repack the combustion tube.
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