Sealed samples

Although aimed at the introductory class, this simple experiment provides a nice demonstration of the use of GG for a qualitative analysis. Students obtain chromatograms for several possible accelerants using headspace sampling and then analyze the headspace over a sealed sample of charred wood to determine the accelerant used in burning the wood. Separations are carried out using a wide-bore capillary column with a stationary phase of methyl 50% phenyl silicone and a flame ionization detector. 

Sealed samples decompose exothermally above 136°C. See entry ISOXAZOLES See other N-O COMPOUNDS... 

Amino-3-isoxazolidinone [68-39-3] NH-O / i nh2 Sealed samples decompose exothermally above 78°C. See entry isoxazoles See other N-o compounds c3h4n2o2... 

Sealed samples decompose exothermally above 210°C. See entry isoxazoles See other N-o compounds... 

Several explosions occurred in vacuum-sealed samples kept at ambient temperature. Storage under air at —20°C, or as solutions up to 2 Mol appear safe. 

An interesting difference between the samples is found in the behaviour of the samples during destabilisation. While for the sample under a deuterium pressure, LiBD4 is not destabilised until both phases are molten, in the vacuum sample LiD is destabilised in the solid phase, and at much lower temperatures (ca. 360°C). This is primarily due to the improved diffusion kinetics of Li species over that of LiBD4. There is also the possibility that LiD precipitation out of the liquid phase at nucleation sites on the Mg particles allows improved mixing over the solid Mg and liquid LiBD4 observed in the sealed sample. 

Kajiwara, N., Ueno, D., Takahashi, A., Baba, N., Tanabe, S., 2004. Polybrominated diphenyl ethers and organochlorines in archived northern fur seal samples from the Pacific coast of Japan, 1972-1998. Environ. Sci. Technol. 38(14), 3804-3809. 

CDDs were determined in pooled samples of ringed seal (Phoca hispida) blubber, beluga whale (Delphinapterus leucas) blubber, and polar bear (Ursus maritimus) liver and fat collected from several areas throughout the Canadian north (Norstrom et al. 1990). All seal samples and all but one polar bear sample had detectable levels of 2,3,7,8-TCDD (wet weight) ranging from 2 to 37 ppt, but 2,3,7,8-TCDD... 

Based on ESR signal strength of a light-protected, sealed sample. 

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