Oxygen flask combustion

Oxygen flask combustion methods have been used to determine chlorine in PVC [5] and traces of chlorine in polyolefins and chlorobutyl rubber [6]. 

Traces of chlorine have been determined in polyolefins [5] at 0-500 ppm. The Schoniger oxygen flask combustion technique requires a 0.1 g sample and a one litre conical flask. Chlorine-free polyethylene (PE) foil is employed to wrap the sample, which is then supported in a platinum wire attached to the flask stopper water is the absorbent. Combustion takes place at atmospheric pressure in oxygen. The chloride formed is potentiometrically titrated in nitric acid/acetone medium with 0.01 M mercuric nitrate solution. 

In the method for determining chlorine in chlorobutyl and other chlorine-containing polymers, [6] the sample is combusted in a 1-2 litre oxygen-filled combustion flask containing 0.01 M nitric acid. After combustion, the flask is allowed to cool and 0.01 M silver nitrate added. The combustion solution containing silver chloride is evaluated 

Determination of fluorine in fluorinated polymers such as polytetrafluoroethylene (PTFE) is based on decomposition of the sample by oxygen flask combustion followed by spectrophotometric determination of the fluoride produced by a procedure involving the reaction of the cerium(III) complex of alizarin complexan (l,2-dihydroxy-anthraquinone-3-ylmethylamine N,N-diacetic acid). The blue colour of the fluoride-containing complex (maximum absorption, 565 nm) is distinguishable from the yellow of the free dye (maximum absorption, 423 nm) or the red of its cerium(III) chelate (maximum absorption, 495 nm). 

A method has been described [7] for the determination of chlorine in polymers containing chlorine, fluorine, phosphorus and snlfnr that involves oxygen flask combustion over water, ethanol addition, and titration to the diphenylcarbazide indicator end point with 0.005 M mercuric nitrate  

Alternatively, to determine bromine, chlorine, iodine, or mixtures thereof, the combustion solution can be titrated with dilute standard silver nitrate solution or can be evaluated by ion chromatography (see Method 2.2). 

An oxygen flask combustion method for the determination of between 2 and 80% of chlorine, bromine and iodine in polymers is described in Methods 2.2 and 2.3 at the end of this chapter. 

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Another destructive method for the deterrmnation of organic fluonne is oxygen-flask combustion [3, 16, 17]... 

The simultaneous analysis of orthophosphate, glycerol phosphates, and inositol phosphates has been achieved by spectrophotometric analysis of the molybdovanadate complexes. Also, a sensitive and selective chemiluminescent molecular emission method for the estimation of phosphorus and sulphur is described, which is based on passing solutions into a cool, reducing, nitrogen-hydrogen diffusion flame. For organic compounds it was usually necessary to prepare test solutions by an oxygen-flask combustion technique. 

Micro amounts of sulfur in polymer are usually determined by oxygen flask combustion, sodium peroxide fusion in a metal bomb followed by titration [30], pyroluminescence [36] or ICP-AES. An oxygen flask combustion photometric titration procedure capable of determining total sulfur in polymers in amounts down to 50 ppm was reported. The repeatability of the sulfur determination in polyolefins in the oxygen flask is 40% at 50 ppm level, improving to 2% at the 1 % level [21]. Crompton [31] has also combined Schoniger flask combustion with a colorimetric procedure for the determination of phosphorous in polymers in various concentration ranges (0.01 to 2%, 2 to 13%). 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Procedure Bum 0.30 g, in three equal portions, by the method for oxygen-flask combustion (BP), using a 1 Litre flask and a separate 20 ml portion of DW as the absorbing liquid for each combustion, shaking the flask vigorously for about 15 minutes and transferring to the same 100 ml Nessler cylinder. Add 5 ml of acid zirconyl alizarin solution to the combined liquids, adjust the volume to 100 ml with DW and allow to stand for 1 hour. 

Prescribed Limit The colour of the resulting solution is greater than that obtained by repeating the operation with no substance enclosed in the successive portions of filter paper burnt in the method for oxygen flask combustion, but adding 3.0 ml of fluoride standard solution (10 ppm F) to the combined absorption liquids before adding the acid zirconyl alizarin solution. ... 

Macdonald AMG, Sirichanya P. 1969. The determination of metals in organic compounds by oxygen-flask combustion or wet combustion. Microchem J 14 199- 206. 

Sample Preparation Using a 1000-mL combustion flask and 25 mL of 0.5 N nitric acid as the absorbing liquid, proceed as directed under Oxygen Flask Combustion, Appendix I, using the amount of sample specified in the individual monograph (and the magnesium oxide or other reagent, where specified). 

Oxygen flask combustion (Schoniger flask) Oxygen bomb combustion Combustion in a dynamic system (Trace-O-Mat) Organic Organic Organic... 

Combustion in Closed Systems Oxygen Flask Combustion (Schoniger)... 

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