Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a laboratory comparison, CCQM-P20.e, was coordinated by the Bureau International de Poids et Mesures (BIPM) in 2006/2007. Nine national measurement institutes, two expert laboratories and the BIPM participated in the comparison. Participants were required to assign the mass fraction of theophylline present as the main component in two separate study samples (CCQM-P20.e.1 and CCQM-P20.e.2).CCQM-P20.e.1 consisted of a high-purity theophylline material obtained from a commercial supplier. CCQM-P20.e.2 consisted of theophylline to which known amounts of the related structure compounds theobromine and caffeine were added in a homogenous, gravimetrically controlled fashion. For the CCQM-P20.e.2 sample it was possible to estimate gravimetric reference values both for the main component and for the two spiked impurities.In addition to assigning the mass fraction content of theophylline for both materials, participants were requested but not obliged to provide mass fraction estimates for the minor components they identified in each sample.The results reported by the study participants for the mass fraction content of theophylline in both materials showed good levels of agreement both with each other and with the gravimetric reference value assigned to the CCQM-P20.e.2 material. There was also satisfactory agreement overall, albeit at higher levels of uncertainty, in the quantification data reported for the minor components present in both samples. In the few cases where a significant deviation was observed from the consensus values reported by the comparison participants or gravimetric reference values where these where available, they appeared to arise from the use of non-optimal chromatographic separation conditions.The results demonstrate the feasibility for laboratories to assign mass fraction content with associated absolute expanded uncertainties in the range 0.05% to 0.5% for solid organic compounds of high purity (mass fraction of main component >995 mg/g) and in the range 0.1% to 1% for compounds of lower purity (mass fraction of main component >980 mg/g).Main text. To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Organic Analysis.
Several rhamnolipid preparations from Pseudomonas strains were studied by thin-layer chromatography/fast atom bombardment (TLC/FAB) mass spectrometry and TLC/FAB tandem mass spectrometry (MS/MS). The preparations were separated with normal-phase (Silica 60) and reversed-phase (RP-8) chromatography. Silica 60 plates appeared to be very useful in the separation of rhamnolipids according to the number of monosaccharide residues present. Spectra which show characteristic fragment ions could be obtained from components of mixtures with a total sample size of less than 200 ng. Chromatography on RP-8 plates gave a good separation of the rhamnolipids based on the length of the fatty acid alkyl chain. MS/MS of the sodium cationized molecules gave information about the sequence of the building blocks. Particularly, heterogeneity in beta-hydroxy fatty acid composition was determined for the principal as well as minor components present in natural rhamnolipid mixtures.
Gas chromatography/mass spectrometry (GC/MS) is a well-known instrumental technique used for the analysis of fire debris for accelerant detection. However, matrix problems, such as pyrolysis product interference, are still encountered. These interferences often lead to inconclusive interpretation of the chromatographic results obtained. This paper describes a method of analyzing arson accelerants using gas chromatography coupled with ion trap mass spectrometry/mass spectrometry (GC/MS/MS). Petrol was investigated as an accelerant. Analysis incorporated an ion preparation method (IPM) that manipulates the ion population in the ion trap following ionization but prior to ion analysis. Parent ions of selected mass-to-charge (m/z) values, characteristic for petrol, are stored within the ion trap. All other unwanted ions are physically removed from the trap by sophisticated electrostatic waveforms. The parent ions fill the trap and are then fragmented by means of collision-induced dissociation (CID). The resultant daughter ion spectra are obtained, which can be used for identification purposes. In this manner, ions of pyrolysis origin are removed.
When an accelerant is poured onto an absorbent material, such as carpet pile, it is absorbed into the material. Once ignited, the accelerant is heated and the carpet pile acts as a wick, which feeds evaporating accelerant into the fire plume. This paper deals with the analysis of the volatile material on the edge of the fire plume. Charcoal strips have been used to adsorb the volatiles and Gas Chromatography/Mass Spectrometry used to analyze the extracts from the charcoal strips. The technique has been used successfully to identify the accelerant burnt on the pile, from the chromatographic profile of the gases in the plume.
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