Fluorpolymer pressure vessels

Table of Contents

Isostatic pressing is a basic requirement for manufacturing pressure vessels without a support jacket from high-purity TFM™ PTFE. Vessels manufactured by this process are characterized by high purity of the material and a long service life.

Fluoropolymers and mercury analysis

In the past, the applicability of PTFE vessels for the wet chemical digestion of mercury-containing samples was repeatedly discussed. However, in recent years, the acceptance towards the materials increased due to the use of modified fluoropolymers with improved properties. To investigate the memory effects in TFM™-PTFE digestion vessels, mercury content was determined in pine needles with a certified total mercury content of 0.0338 ± 0.010 mg/kg.

For digestion, 500mg of sample material was weighed into each TFM™-PTFE vessel. Samples were mixed with 3.0mL of HNO3 (65%), 1.0 mL of H2O2 (30%), 0.5 mL of HCl (37%), and 10 mL of double distilled H2O and digested at 210°C using the microwave digestion apparatus. Mercury content was analyzed by ICP-MS. To obtain information on possible carryover or contamination of mercury, mercury concentration in pine needles was tested. For this purpose, a blind digestion was performed at the beginning and at the end of the test series. Between the individual digestions, the vessels were simply rinsed with double-distilled water. The digestions were carried out on four consecutive days. Analysis of the blank values showed that mercury concentrations were below the detection limit at all times. Carryover, as could occur due to adsorption effects, was not detectable and thus no mercury contamination from preceding samples is to be expected.

Note on the digestion of mercury

If samples containing mercury are digested, volatile mercury compounds may form which may lead to insufficient recoveries. This is particularly the case if digestion vessels are opened while still hot. To bring mercury back into solution from the gas phase, the vessels should only be opened well cooled, at room temperature.