Gas chromatographic separation of perfluorocarbons

The use of cyclic perfluoroalkanes and SF6 in atmospheric dispersion experiments

“…Perfluorocarbons (PFCs) are essentially hydrocarbons in which all of the hydrogen atoms have been replaced by fluorine atoms. A more rigorous definition allows the exception of those hydrogen atoms 'whose substitution would affect the nature of the functional group' (O'Mahony et al, 1993). The PFCs have very different properties, both physical and chemical, to their hydrocarbon equivalents.…”

“…The third point concerns their toxicity; they generally fall into two categories regarding toxicity, being either completely non-toxic or highly toxic. For example, perfluoroisobutene, the most toxic PFC, is lethal even at concentrations in the ppmv (parts per million by volume) range (Lovelock and Ferber, 1982;O'Mahony et al, 1993). The compounds used as tracers are a specific type of perfluorocarbon called perfluoroalkylcycloalkanes, based around a carbon ring.…”

“…The separation of perfluorocarbons by gas chromatography (GC) has been the subject of an extensive review paper (O'Mahony et al, 1993). Even though the review paper was published in 1993, by which time the use of PFC tracers had become relatively widespread, only three examples of Table I.…”

Activity coefficients of hydrocarbons at infinite dilution in di-n-octyltin dichloride. Comparison with results obtained in other alkyltin solvents

“…Obtaining the thermodynamic results. Experimental results obtained on each column were fitted to the equation ln V° = -A H° / RT + constant (2) where A H°, the heat of sorption, corresponds to the transfer of one mole of solute from an ideal vapour phase at a partial pressure of 1 atm to an stationary phase of yet undefined characteristics. Regression analysis of the results obtained in a given column showed that: a) valúes of percent standard deviation of the heats of sorption, 100 s(A ) / A , were smaller than 1.5 % for all the solutes; b) retention volumes obtained in a just conditioned column differed by less than 0.8 % from those obtained under identical conditions after two or more weeks of column use, and the differences between the corresponding heats of sorption was smaller than 4 %.…”

“…Perfluorinated substances have been sporadically employed as stationary phases in gas chromatography, and this mostly for the separation of substances of high chemical reactivity or perfluorocompounds and freons. Excellent review articles have been written by Pomaville and Poole [1] and by O'Mahony et al [2].…”