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.
ACID REFLUX CLEANING SYSTEM
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.
CLEAN CHEMISTRY TOOLS FOR ATOMIC SPECTROSCOPY
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
The use of microwave heating for dry ashing applications has been represented a breakthrough in the process and quality control of samples like polymers, petroleum, food and feeds, pulp paper and pharmaceuticals.