How to Get More From Your Combustion TOC Analyzer

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.

  1. 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.

  2. 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 OIA-1080-TOC-300x400.jpgfeature 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.

  3. Run ‘Clean-Ups’ – After cooking a pot full of chili, you don’t leave the residue in the pot until the next time you want to cook, do you? Why not? For one thing, the longer you leave the residue, the more stubborn it will become to clean. Equally as important, the last batch of chili will influence the new batch’s flavor. Running difficult samples with a combustion TOC analyzer is no different. Running a ‘clean-up’ sample greatly improves the accuracy of each analysis by reducing any background (or carryover) between samples and also contributes to the life of the instrument overall. Knowing the importance this step contributes, we implemented a “clean-up” sample type in the 1080 TOC Analyzer, which the user can insert anywhere in the sequence, without taking up a vial in the auto-sampler tray.

  4. Maximize the Furnace Tube and Catalyst Lifetime – Due to the total salt mass accumulation in the furnace tube with high-salt samples, a typical Combustion TOC failure mode is a clogged or failed furnace tube.  As the furnace tube begins to clog, the back-pressure in the furnace will increase.  The 1080 TOC Analyzer provides an on-screen reading of this backpressure so that it can be easily monitored by the operator.

    The furnace tube itself can also be slowly attacked by the salt samples and lead to premature failure.  In the 1080 TOC Analyzer, we provide a large-diameter, thick-walled combustion tube with a high-porosity bottom frit standard with every unit., and our layered blend of quartz chips and catalyst maximize the salt-loading capability of the furnace tube.  No expensive “High Salt” Kit needs to be purchased!

    Additionally, we provide a patent-pending “catalyst guard” tube.  This easily-replaced sacrificial tube not only takes the initial thermal stress of the liquid injection, but also provides a surface for the salt to preferentially attack before attacking the furnace tube.

    Ultimately, the catalyst and tube will need to be removed and rinsed when the backpressure increases significantly. However, the more conscious you are of the backpressure, the easier it is to remember to perform routine “clean-up” samples to help extend the catalyst lifetime.

  5. Clean the Injector Cap and Slider – This tip is very important for high-salt samples.  As high-salt samples are injected into the furnace, there is a natural tendency for salt crystals to form wherever micro droplets of the salt solution comes in contact with a sufficiently hot surface, causing the droplets of a salt solution to lose water. This can result in crystals forming on the furnace cap/slider assembly, which can ultimately damage the sealing surfaces and cause leaks.  Thus, it is important to routinely inspect and clean this cap/slider assembly to maximize the performance of the 1080 TOC.

  6. Keep the Scrubber and Dryer Fresh – This tip is simple yet important. Hydrochloric acid vapor can result by running samples stabilized with hydrochloric acid, or running samples containing chloride salts that are stabilized with sulfuric acid. Keeping the halide scrubber and sample-gas dryer fresh and always having backups on hand is a preventative measure that saves a lot of trouble as the instrument ages. Failing to take care of this can cause a domino-type effect in other parts of the instrument, namely the irreversible destruction of the flow path of the NDIR detector.

While there are plenty of tips to share for keeping your combustion TOC analyzer at the top of its game, the most important thing to remember is to be aware of the samples you are running and the condition of the analyzer’s components after each run. Begin making a mental checklist to check the following things at the start of each new sequence: reagent levels, humidifier levels, gas cylinder, halide scrubber and dryer.

We mindfully designed our 1080 Combustion TOC Analyzer with high visibility for maintenance, fully expecting it to be used to analyze extremely difficult samples that could potentially be harder on the instrument. Just remember, when you expect your analyzer to work harder for you, you need to give it the attention it deserves. Luckily for you, that attention is in the simple form of maintenance tricks that take little effort and time on your part, but yield a high-performing solution for low-cost analysis.

Click here to learn more about how we incorporated special components in our 1080 Combustion TOC Analyzer to help users keep maintenance costs down and productivity at its peak. Want to ask our engineering expert Noel Bauman a question? Email him!

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