Oxygen combustion, sample preparation using

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). 

Sample Preparation Using Oxygen Bomb Combustion Method... 

Table 5.18 Results of comparative study of analysis of 250 ggkg-1 of spiked toxic metals after sample preparation using microwave acid digestion and oxygen bomb combustion. Results in brackets are percentage recovery...

The Parr oxygen combustion bombs were used for a rapid ash determination and for sample preparation for IC. About 0.5 g of shale or shale oil was mixed with 0.5 g of white oil in a stainless steel cup. Five mL of water was placed in the bottom of the bomb which was then assembled and pressurized to 30 atmospheres of oxygen. After combustion, the bomb was allowed to cool for ten minutes and then opened slowly. The inside walls of the bomb were washed with water, and all the washings were combined, filtered if necessary, and diluted to 50 mL. The residue in the cup was dried at 110°C for 15 minutes and reweighed for ash determination. 

Table 20.2. Degradation data for samples prepared using screen-printing and combustion methods. Conditions 0.5 A/cm, 80 C, hydrogen-oxygen, 30 psi backpressure each side. (Reproduced courtesy of nGimat)...

Biological material in a polythene bag filled with oxygen and being prepared for analytical combustion exploded. Diethyl ether used to anaesthetise the experimental animal from which the sample was derived may have still been present, and ignition from static charge on the plastics bag may have been involved. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

The first step in analysing plastics for metals content in polymers by ICP-AES technique is that they must be prepared in solutions that are suitable for nebulization. There are four general methods applicable for sample preparation for metal analysis by ICP-AES and they are solvent dissolution of some plastics dry ashing using a muffle furnace acid digestion using a microwave oven and oxygen bomb combustion. 

Digestion of samples using high pressure oxygen bomb combustion is an excellent technique for sample preparation, particularly trace metal analysis. This technique can be applied to most plastics provided that small sample ( 0.25 g) of fine grain sizes of plastics are used. The solutions obtained are clean and easily analysed for metal content against standards prepared in the same solution added to bomb. 

Sample Preparation of Anaerobic Adhesive Using Oxygen Bomb Combustion... 

---