Heavy Metal Analysis with Perfluorinated PTFE Digestion Vessels

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Elementar Analysensysteme GmbH

Glatt Ingenieurtechnik GmbH

Angst+Pfister AG

For digestion 500 mg of sample material were weighed in the TFM-PTFE vessel in each case. The samples were mixed with 3.0 ml HNO₃ (65 %), 1.0 ml H₂O₂ (30 %), 0.5 ml HCl (37 %) and 10 ml bidistilled water and digested at 210 °C with the Speedwave Four microwave digestion unit.

Analysis of the mercury content was carried out using ICP-MS. In order to obtain information about possible carry-overs or contamination by mercury on the one hand reference materials with varying mercury contents were examined, while on the other hand blind digestion was undertaken at the start and finish of the test series. Between the individual digestions the vessels were simply rinsed with bidistilled water. The digestions were conducted on four consecutive days.

Examining the Mercury Concentration in Pine Needles

At the beginning and end of the series of experiments blind digestion was carried out in the digestion vessels. The blind values were under the detection limit, so that it may be presumed that there was no contamination by mercury. A total of four repeated digestions were undertaken in the same vessel on different days. Between the individual digestions the vessels were simply rinsed with bidistilled water.

The reproducibility of the methods employed was specified in order to determine the precision. The recovery rates of between 99 and 118 % are adequate and are within the acceptance criterion of ±30 %.

It can also be seen from the measurement data that there are no carry-overs or contamination whatsoever on the walls of the vessel that might lead to flawed results. Traces of mercury can therefore be determined to be fault-free even where isostatically compressed TFM-PTFE vessels are used. A rinsing of the vessels with water is also sufficient and additional blind digestions are not essential.

(ID:42501513)