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- Haglund, Peter, et al.
(author)
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Determination of the gas chromatographic elution sequences of the (+)- and (-)-enantiomers of stable atropistomeric PCBs on Chirasil-Dex
- 1996
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In: HRC Journal of High Resolution Chromatography. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 0935-6304 .- 1521-4168. ; 19:7, s. 373-376
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Journal article (peer-reviewed)abstract
- Pure enantiomers of chiral (atropisomeric) polychlorinated biphenyls (PCBs) obtained by high-performance liquid chromatography were used to establish the gas chromatographic elution sequences of the (+)- and (−)-enantiomers of six PCB atropisomers on Chirasil-Dex. The elution order was found to be (−/+) for PCBs 84, 132, 136, and 176 and (+/−) for PCBs 135 and 174. The retention characteristics of all 19 tri- and tetra-ortho atropisomeric PCBs were also investigated. Nine of the atropisomers could be separated using this chiral selector. PCBs 95, 132, and 149 were completely resovled and PCBs 84, 91, 135, 136, 174, and 176 were partially separated (R = 0.7–0.9). All of the separated congeners are 2,3,6-substituted in at least one ring, and conversely – none of the congeners that lacks 2,3,6-substitution could be separated. Thus, chiral recognition and enantiomer separation seems to be strongly governed by 2,3,6-substitution.
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- Marriott, PJ, et al.
(author)
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Comparison of thermal sweeper and cryogenic modulator technology for comprehensive gas chromatography
- 2000
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In: HRC-Journal of High Resolution Chromatography. - 0935-6304. ; 23:3, s. 253-8
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Journal article (peer-reviewed)abstract
- The two current technologies for achieving comprehensive gas chromatography (GC x GC) - the thermal sweeper and the cryogenic modulator - are compared in an interlaboratory study using a multicomponent semi-volatile aromatic compound sample, The same column set (phases, film thickness, dimensions of columns) and conditions of oven temperature program were used, Carrier gas flow settings however were different for the data reported here. The thermal sweeper has a longer overall length due to the extra ca. 30 cm length of narrow bore tubing used for the modulator/accumulator section. Data reveal that the two methods behave in an analogous manner in respect of delivering GC x GC results, with key peak parameters of peak widths and symmetry measures showing good correlation Retention time dissimilarity on the first dimension columns in the two systems arises from different flow rates used, however the second column retention is similar, and this is due to the resulting different elution temperatures that peaks elute on the first dimension in each system. Overall, the two approaches to GC x GC appear to produce equivalent results within the scope of the application studied. Each system does have its experimental limitations; the thermal sweeper has what may be called a 'thick film effect', where at high temperature it can be difficult to sufficiently trap the migrating bands in the accumulator column, and the pulsing of solutes in the cryogenic system may suffer from a 'thick wall effect' if a column with too thick a wall dimension is used at low oven temperature.
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