Teflon bomb

Human placenta (20 g) was completely dried at 105°C, crumbled, and a portion (5 g) was minerahzed by treating with nitric acid (12 M, 15 ml) at 110°C in a Teflon bomb. After mineralization, the contents were evaporated to dryness and the residue was dissolved in 1.0 ml of distilled water (termed sample A). An aliquot (10 pi) was chromatographed on RP-18 using MeOH -f HjO + CH3COOH (25 15 2) as the mobile phase. The separated spots of the metals were visualized by spraying the... 

Until recently, the pressures used in MW reactions in sealed Teflon containers have been restricted to 600-700 kPa (6-7 atm) for safety reasons. However CEM [21] have developed computerized systems with pressure and temperature control using vessels capable of withstanding pressures of 1500 kPa or more. Teflon bombs produced by Parr [22] can accommodate pressures up to 8 MPa (80 atm) and temperatures up to 250 °C. However it has been reported that repeated use of the vessels above 150 °C can lead to distortions which reduce the safe pressure level [7]. For safety reasons, the vessels used in these higher pressure reactions are equipped... 

Two methods were examined for digestion of biological samples prior to trace element analysis. In the first one a nitric acid-hydrogen peroxide-hydrofluoric acid mixture was used in an open system, and in the second one nitric acid in a closed Teflon bomb. The latter method was superior for Ge determination, however, germanium was lost whenever hydrogen fluoride had to be added for disolving sihcious material. End analysis by ICP-AES was used for Ge concentrations in the Xg/g range13. 

Hydrothermal transformation of ferrihydrite in a teflon bomb at 180 °C for several days yields platy crystals up to several pm in size (Schwertmann and Cornell, 2000). 

Another analytical procedure for sample preparation including analyte separation and enrichment is the coprecipitation of the trace elements to be determined. The co-precipitation behaviour of Ti, Mo, Sn and Sb under two different fluoride forming conditions (at < 70 °C in an ultrasonic bath and at 245 °C using a Teflon bomb) has been studied to improve the accuracy of the trace analysis of these elements in Ca-Al-Mg fluorides, by ICP-MS.14 The applicability of this analytical method (including isotope dilution technique) was demonstrated for four carbonaceous chondrites and silicate reference materials of basalt or andesite.14... 

Quality assurance. Tin is leached (dissolved) into canned foods from the tin-plated steel can.24 For analysis by inductively coupled plasma atomic emission, food is digested by microwave heating in a Teflon bomb (Figure 28-8) in three steps with HN03, H202, and HC1. 

Chemical Analyses. Subsamples (<20 mg) of standing-crop-trap particulate matter were solubilized by acid digestion in sealed all-Teflon bombs (Bombco Inc.) in a procedure modified from Eggiman and Betzer (13). National Institute of Standards and Technology (NIST) standard reference materials River Sediment (SRM 1645), Urban Particulate Matter (SRM 1648), and mixed-element liquid spikes were used to check bomb performance. 

Zeolite samples were digested using a mixture of HF, HNO3 and HCIO4 in screw-top teflon bombs (Savillex). Ruthenium analyses were performed using a VG PlasmaQuad II Inductively Coupled Plasma Mass Spectrometer. All samples were spiked with indium to serve as an internal standard. Atomic absorption was used to determine aluminum content. The results from the chemical analyses are shown in Table 1. 

Typically, these will be alloys, rocks, fertilisers, ceramics, etc. These materials are taken into solution using suitable aqueous/acid media, according to solubility hot water, dilute acid, acid mixtures, concentrated acids, prolonged acid digestion using hydrofluoric acid if necessary, alkali fusion (e.g. using lithium metaborate), Teflon bomb dissolution. Fusion and bomb methods are usually reserved for complex siliceous materials, traditionally reluctant to yield to solubilisation. 

Laboratory-made all-Teflon bombs, used for low- or medium-pressure work, are also appropriate for microwave-heated digestion [82], especially when fitted with pressure-relief holes, valves, or membranes (rupture discs). 

Matusiewicz, H. Development of a high pressure/temperature focused microwave heated Teflon bomb for sample preparation. Anal. Chem. 66, 751-755 (1994)... 

Hydrothermal transformation of various Fe oxides. Ferrihydrite (2-line), lepidocrocite, akaganeite and goethite (if poorly crystalline) can be converted to large (1-3 am) hexagonal plates of hematite if kept under water in a teflon bomb at 180 °C for 10 days. 

Eor total metal solubilization a representative unfrozen sample of 0.5 g, dried at 110°C and finely powdered, is dissolved in a Teflon bomb by an acid mixture of 5 ml of 40% HE, 1 ml of aqua regia (HNO3-HCI 1 3 v/v) and 5 ml of MQ water, heated at 180°C for 90 min and then cooled to room temperature. 5 ml of saturated H3BO3 solution are then added to the Teflon bomb and, after dilution to 50 ml in a volumetric flask, the solution is analyzed by ICP-AES. To test the accuracy of the total solubilization method several certified reference materials in sediment matrices are always analyzed along with the unknowns, obtaining results in a good agreement with certified values, as reported in Table 8.2. 

Sediment (total) Digestion of sample with HCI/HN03 and heat in Teflon bomb oxidation with potassium permanganate solution reduction with sodium borohydride purging to plasma ICP/MS 2 ng/g 96 Haraldsson et al. 1989... 

Oxidizing acids in PTFE (Teflon ) bomb, sealed quartz vessels/tubes, other vessels [WDCCV]... 

Total elemental concentrations-Total concentration of each metal in an unfiltered sample was determined after digestion. The unfiltered sample was carefully mixed, and a known amount (approximately 10 g) was weighed into the Teflon bomb of the microwave digestion system. Five milliliters of concentrated ( 36N) trace-metal grade nitric acid were added to each sample and the mixture was digested at high temperature and pressure in a microwave digestion unit... 

Another variation on the acid digestion procedure used a mixture of hydrofluoric acid, nitric acid, and perchloric add in a sealed Teflon bomb heated at 150°C for 4 h... 

Heat and pressure have little influence on the effectiveness of the digestion procedure. Good results have been attained using Teflon bombs in a microwave oven (Knapp etal., 1997). The Teflon bombs can be cleaned to a high level of purity and are pressure-resistant up to some 10 bars (10 Pa). The decomposition of the filter material (polycarbonate) and, to a varying extent, of the organic sample material, leads to the release of CO2. To attain a slow, controllable pressure increase, the temperature programmeme has to raise the micro-wave power stepwise. 

A stock of sub-boiled and blank-controlled acids is prepared and a dilution of a metal standard solution e.g., 100mg/L of gallium). Several separation procedures are performed to clean the Teflon bombs (refer to next section), until the blank values are constant and low. 

Amounts of 20 to 100 mg of a dried sediment sample are transferred into the Teflon bomb and the procedure given for samples of suspended material should be followed. 

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