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Pressure Digestion
The clear solution for your sample is already here!

The PDS-6 Pressure Digestion System

The safest, most accurate und cost effective method of sample preparation available!


This pressure digestion system was developed by a team of physical chemists and geochemists at the University of Göttingen in 1985. It has been fully described in the German journal, Zeitschrift für Pflanzenernährung und Bodenkunde 149, 350-353 (1986).

PDS-6 System

1: Top plate2: Clamping screw with
Allen-wrench fitting
3: Central colums4: Base plate
5: Aluminium support disk
for plastic lid
6: Plastic lid
7: Plastic beaker8: Aluminium support for
plastic beaker
9: Indentation in support disk
(for clamping screw)
10: Completely non-metallic offset
plastic/plastic closure
11: High pressure relief path12: Broadened plastic flanges
(beaker and cover) providing
additional protection from

The PDS-6 System

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Free Standing Seal In contrast to the normal 'digestion bomb', the PDS-6 seal is entirely plastic and is not completely enclosed in a metal container. This permits a very tight closure of the lid/beaker seal without overstressing the plastic. Diffusable gases pass through the plastic, the beaker is able to 'breathe'.
C-Clamp Retainer The C-clamp retention of the lid is intentionally wide enough to keep all metallic parts away from the seal. This significantly reduces the risk of contamination. The force of the clamping screw is exerted directly from the cover disc through the flanges of the plastic lid and beaker to the top edge of the cylindrical support. Since the beaker is not in close contact with either the base plate or the interior of the cylindrical support, the plastic is free to expand and contract with the temperature.
High Pressure Safety Relief Valve The clamping screw is slightly off-center so that increases in internal pressure raise one side of the Teflon cover slightly, thus permitting the release of excess pressure through the otherwise snug seal. Thus, thermal 'blasts' can be effectlively vented without any permanent deformation of the plastic materials.

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Accurate The PDS-6 gives extremely accurate results. The unique design means that potential for contamination of the sample is vastly reduced. The beaker seal is completely plastic and all metal parts are well away from the seal.
Safe Using a conventional thermal oven is far safer than using a microwave. The rate of heating is more gradual and the risk of thermal blasts is further reduced because the plastic container is not fully enclosed in metal. Non-polar gasas diffuse out through the plastic.
Cost Effective Thermal ovens are much less expensive than microwave ovens and do not need to be replaced as often due to the reduced risk of explosion. In addition, the sturdy construction of the PDS-6 ensures it has a long lifetime.
Efficient and Space Saving Using two thermal ovens, 48 samples can be processed every night using a timer. The ovens can be installed on a bench in a fume hood. This ensures the oven is adequately vented and the work surface of the fume hood is still accessible.

fume hood
2 thermal ovens on a bench in a fume hood
for sample processing using PDS-6

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Except for the screws which are stainless steel, all metal parts are made of aluminium that has been electrolytically treated to render the surface chemically inert. The plastic parts are made of a PTFE (Hostaflon, Hoechst AG).

Beaker Volume 30 ml
Maximum Temperature 220C
Maximum Pressure 100 bar
Diameter of 6 pack 16 cm
Height 10 cm
Weight of entire 6 pack 3 kg

High Pressure Safety Relief Valve

Relief pressure as a function of temperature

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The unique features of the PDS-6 have been patented both in Germany and in the United States (DBP 36 20 381, U.S.P. 4,944,923).

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Test Results

A customer sent the following results to compare the PDS-6 to a conventional digestion bomb. He measured blank values of a digestion with concentrated nitric acid. The physical unit of the values given is mg/l.

Print version

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List of references

Print version

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