• Mirco Written by Mirco Rossetti, Application Specialist | July 21, 2023

What's the best approach to clean my digestion vessels?

What are some of the common mistakes to avoid when cleaning digestion vessels?

Cleaning various items used in ultra-trace analysis work is a critically important laboratory routine. To minimize contamination, traditional cleaning methods require soaking items in hot acids, often for several hours. To be effective, large volumes of acid are consumed and need to be changed regularly. There is also a substantial risk of exposure to hot acids and acid vapors using traditional soaking techniques. This is particularly the case when trying to achieve high-quality blanks when using microwave digestion procedures, as pre-cleaning the vessels is critically important.
However, it is not sufficient to simply wash or soak vessel liners in dilute acid. The surface of PTFE is porous and will take up trace amounts of digest solution at elevated temperatures, especially as it “ages” with continued use. Running a blank in a vessel previously used to digest a sample, without thorough cleaning, will lead to serious blank contamination.
To circumvent issues associated with acid soaks, and to more thoroughly clean microwave digestion vessels, labs may choose to perform a separate cleaning run (with blank acid) in the microwave prior to each sample digestion run. The downside is that this significantly reduces the sample processing capacity of the microwave system and impacts the vessel lifetime.


So in order to address these issues, Milestone has developed the traceCLEAN, a fully automated, self-contained, acid steam cleaning system that can not only be used for cleaning microwave digestion sample vessels and containers, but also for other accessories, glassware and components that are used with the ICP-OES and ICP-MS instrumentation.
So how does the system work? The items to be cleaned are placed in the traceCLEAN, where freshly distilled acid vapors continuously reflux within the sealed unit, thoroughly leaching any metal contaminants from the items. Various holders are available for vials, microwave digestion vessels, flasks, glassware, and ICP sample introduction components, such as torches, nebulizers, or spray chambers. Steam cleaning with nitric acid vapors is a highly effective cleaning method for preconditioning and routine cleaning of containers and apparatus. The component to be cleaned is placed over a PTFE-coated glass rod. Acid in the lower reservoir is heated, and purified acid vapor travels up through the glass rod and condenses on the container, removing surface contamination as shown in the video.


Ultratrace analysis is as dependent on minimizing contamination and controlling the analytical blank as it is on the accuracy and precision of the instrument carrying out the analysis. When working at ppb and ppt levels using ICP-OES or ICP-MS, the higher the blank and the worse the BG noise, the poorer the detection capability. To address these issues, Milestone has developed a wide range of products, accessories, and consumables to support clean chemistry sample preparation and address the multitude of challenges faced by the modern analytical laboratory when carrying out ultra-trace elemental analysis. MILESTONE