No abstract

Eight compounds from a Kentucky 1R4F reference cigarette smoke condensate have been determined by selected ion monitoring-mass spectrometry (SIM-MS) to confirm the validity of multidimensional gas chromatography (MDGC) as a quantitative tool in complex mixture analyses. Four electrostatically precipitated smoke condensate samples of 100 cigarettes each are dissolved individually in 25 mL of 2-propanol. The 2-propanol contains two methyl esters (C8 and C14) and seven deuterium-labeled compounds used as internal standards (IS). Analysis of the compounds of interest, pyridine; acetamide; acrylamide; phenol; o-, m-, and p-cresol; and quinoline, is accomplished by using two heartcuts. Heartcut times of the MDGC analysis are selected such that at least one IS is transferred with each group of compounds being analyzed. This study shows that the MDGC technique previously developed and described can be used for quantitative analyses. A comparison is made between the two types of internal standards. The results obtained for both types of internal standards agree within 20% of each other, on the average, with higher standard deviations for approximately 60% of the compounds where methyl esters are used as internal standards.

No abstract

The thermochemistry of benzoyl ion formation from a variety of sources has been examined by using the measured kinetic energy release for metastable ions to estimate the excess energy of the activated complex. A correlation is observed between this estimated excess energy and literature values of the heat of formation of the benzoyl ion. From this relationship and the observed correlation between the uncorrected heat of formation and the difference between the appearance potential of [C,H,CO]c and the ionization potential of the parent compound, the large range of reported values for AH,[C,H,CO]+ is seen to be due, at least in part, to variation in the kinetic shift with the critical energy of the reaction. With the exception of the ion generated from trifluoroacetophenone and possibly that from benzaldehyde, the fragmenting [C,H,O]+ ions are shown, from kinetic energy release data, to be structurally identical. The approach adopted here may have general merit in improving or testing the accuracy of thermochemical data based on appearance potential measurements. I N T R O D U C T I O NTHIS paper is concerned with the interpretation of thermochemical data derived from appearance potential (P,) measurements. The particular example discussed is the ion [C,H,CO]+ generated in the gas phase by fragmentation of benzoyl compounds. Several previous studies on the energetics of ionic gas phase reactions have discussed benzoyl and substituted benzoyl ions.1-12 The present study attempts to refine traditional (P,) data in the light of measured kinetic energy releases accompanying metastable ion fragmentations.An elementary precaution in discussing thermochemical data on polyatomic ions is to ensure that the species being compared are structurally identical. Methods for determining ion structures in the gas phase have developed ra~id1y.l~ The choice of the benzoyl ion for study was based in part on the evidence (see below) that a single structure is involved. Moreover, the reactions leading to [C,H,O]+ formation are all apparently simple bond cleavages at the carbonyl group, making the formation of different product ions unlikely.The heats of formation of ions, as determined from P, measurements, have often been used to characterize ion structure^.^.^^.^^ Such measurements always represent upper limits to ion enthalpies, because they include (i) the internal energy of the activated complex and (ii) the reverse activation energy. In cases where the reaction involves simple bond cleavage, the reverse reaction is an ion-radical combination for which activation energies are often negligibly small. In such instances the major source of error is likely to be the internal energy.In spite of independent evidence for a single [C,H,O]+ structure from all but one of the benzoyl compounds studied here, the most striking feature of the standard compilation of heats of formation of gaseous ions is the extraordinary range of values found for [C,H,O]+. The literature values range from 165 to 204 kcal mol-l'16 One must infer that P, measurem...

Distributions of the kinetic energy release have been determined for reactions of metastable ions leading to formation of the benzoyl cation. Although the reactions studied were all apparent simple bond cleavages, the shapes of these distributions varied widely, as did the magnitude of the most probable energy release. There is evidence that the shape of the distribution function is related to the mechanism of the reaction. In one case the distribution shows structure not seen in the metastable peak itself, suggesting that at least two reaction pathways are operative. Thus, the present measurements on energy distributions supplement the information concerning different elementary reactions that can be obtained from the study of metastable peaks.