PTFE vessel

Again, fluoro and oxo complexes of rhenium predominate. The reaction of KF and ReFe in an inert PTFE vessel yields pink K2[ReFs], the anion of which has a square-prismatic structure hydrolysis converts it to K[ReOFs]. 

Another advantage of PTFE vessels is low adhesivity, which can help to reduce detergent and organic solvent usage during cleaning operations that would otherwise generate considerable effluent [6]. 

The aquatic samples in 8 M HN03 are evaporated and the dry residue is dissolved in 20 mL 0.5 M HC1. After the addition of approximately 50 mg of ascorbic acid (reduction of Fe3+ to Fe2+), the solution is transferred to PTFE vessels equipped with a silver sheet bottom. Polonium is electrodepos-ited at 90°C for 4 h.34-36... 

This kind of contamination was carefully evaluated by using various labware glass and quartz tubes, polytetrafluoroethylene (PTFE) vessels, fluorinated ethylene propylene (FEP) and perfluoroalkoxy (PFA) tubes. Ideally, all trace element determinations should be carried out in clean rooms in which the incoming air is filtered and special clothing is worn. 

An MW-digestion system with a closed PTFE vessel was used to improve the leaching of inorganic constituents from biological samples with TMAH [2]. This new digestion method has been applied to the NIST SRM 1577b Bovine Liver... 

Minimum quantities of acids are needed if dissolution is carried out in a PTFE pressure dissolution vessel which is capable of operating at temperatures up to 180° C. With organic matrices, however, only the special versions of this apparatus capable of withstanding very high pressures should be used. For completely inorganic dissolutions, there is also an all-PTFE vessel, which is limited to temperatures below 120° C, but which completely removes the risk of contamination from the metal outer-casing. 

Various fluorides may be precipitated from aqueous solution for use as constituent powders in solid state reactions. Co-precipitation offers very elegant access to intimate mixtures, but the actual products are strongly dependent on the fluoride ion activity within the solution but also on the stability constants of the respective metal complexes. Accordingly, not only anhydrous fluorides are obtained, but also hydrated fluorides or hydroxide fluorides, which may be very difficult to convert to pure fluorides. As noted already [3], reactive compounds, e.g. carbonates, acetates, oxalates, hydroxides etc., which quite easily dissolve in acidic HF solutions, are the preferred starting materials for fluoride syntheses. In contrast, many oxides which have been heated to rather high temperature are frequently unreactive and may not dissolve at all. To enhance reactivity but also improve crystallinity of the product, it has proved useful to perform reactions above the boiling point of water in adapting the hydrothermal method, which has already been shown to be useful in the recrystallisation of materials which are more or less insoluble at ambient temperatures and pressures. Up to about 240°C even PTFE vessels may be used. A number of selected examples with respective reaction conditions are listed in Table 3. 

Useful for releasing a volatile product good oxidizing properties for ores, metals, alloys, oxides and hydroxides. Often used in combination with HNO3. Note Sulphuric acid must never be used in PTFE vessels (melting point 327 °C)... 

Microwave-assisted distiller Microwave energy has also been used to facilitate the distillation of various compounds from solid samples [11,63-65]. Figure 5.12A depicts a typical microwave-assisted distillation apparatus. It consists of a laboratory-made poly-tetrafluoroethylene (PTFE) vessel of 120 ml inner volume and 10 mm wall thickness, and a 60 ml collector flask. The screw cap of the vessel includes a drilled PTFE disc located on its upper part that avoids sample ejection during distillation. A hole made in the vessel cap provides a means for evacuating volatile compounds via a PTFE tube that is passed through the vent holes of the microwave cavity and is then adapted to a glass line finished by a bubbler which is inserted in the collector flask. A domestic microwave oven equipped with a 2450 MHz magnetron is normally used for this purpose, altered only as required to connect the sample vessel with the collector flask. 

Aysola,P., Anderson, P. and Langford, C.H.(1987). Wet ashing biological samples in a microwave oven under pressure using PTFE vessels. Anal. Chem. 59,1582-1583 Barrett, P., Davidowski, LJ.Jr., Penaro, K.W.and Copeland. T.R. (1978). Microwave oven based wet digestion techniques. Anal. Chem. 50.1021-1023 Bate, L.C. (1966). Adsorption and elution of trace elements on human hair, Int.J. App. Radiation 17.417-423... 

Weighed tissue samples (kidney, liver, meat, bone and wool) of approximately 1 and 0.5 g CRM 185 bovine liver were placed in PTFE vessels, 5 ml of concentrated HNO3 and 5 ml of distilled H2O were added. A microwave oven program with temperature and pressure settings of 150°C and 130 p.s.i., respectively, was performed for all analyzed matrices. The digestion solutions were diluted to a final volume of 50 ml all dilution, excluding blood samples, were performed with 1% HNO3. Zinc analysis was performed on a Flame AAS 2100 (Perkin-Elmer), with an air-acetylene flame. Lead and cadmium analysis was performed on a GF-AAS 5100 ZL (Perkin-Elmer). Analysis on GF-AAS were carried out under stabilized temperature platform furnace (STPF) conditions. 

The use of expanded tetrafluoroethylene (PTFE) prostheses (Gore-Tex ) has permitted the replacement of vessels as small as mm. The neointima layer is thinner in this system. Experimental work in dogs has used PTFE vessels as small as 3 mm successfully kO, ill). Unfortunately, most of the blood vessels in the human body are smaller than this size and no suitable material is yet available although many experimental materials show considerable promise. These include various hydrogels (12) and certain polyether polyurethane ureas (PEUUs) (h2, i+3). 

For storage, the solutions should be transferred to polyethylene or PTFE vessels. Silver solutions are stable only in dark flasks. 

The whole-blood samples are decomposed under pressure in polytetrafluoroethylene (PTFE) vessels. For this purpose 1 mL whole blood is pipetted into a 25-mL PTFE vessel together with 1.1 mL 65% nitric acid and 0.1 mL 96% sulfuric acid. The vessel is then sealed and heated to 140°C in the pressure vessel for 3 hr. After evaporating off the nitric acid at 120 C the residue is taken up in 0.9 mL 1% hydrochloric acid solution. A clear, yellow-colored solution is generally obtained under these conditions. If this is not the case the hydrochloric acid should be evaporated off and the mineralization step repeated. 

It is reported that LiCo02 can be renovated by the hydrothermal reaction [51]. In the hydrothermal process for LiCoO renovation [52], the spent LiCoO electrodes were located in a small polytetrafluoroethylene (PTFE) vessel. And the small PTFE vessel was immersed in LiOH solution. The lid of the small PTFE vessel has a lot of holes 1 mm in diameter in order to make the possible exchange of the inside and outside solutions. The hydrothermal experiment was carried out at 200 °C for 20 h. And the... 

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