As part of our effort at defining a set of standard stationary phases for gas chromatography we have previously reported specific retention volumes Vt [l] and retention indices I [2] of high accuracy [3-61 for upwards of 60 hydrocarbon solutes with poly(dimethylsi1oxane) solvents (PDMS), including OV-1 and SE-30 [7] and OV-101 and SP-2100 [8], overthe temperature-range 30-80°C. Since that time, the retention indices for47 C5-C8 olefins with OV-101 at 50° and 7OoC have been published by Boneva and Dimov [9]. Unsaturated hydrocarbons comprise a class of compounds that is of course of considerable importance e.g., in the petrochemical industry particularly as regards reforming and catalysis [lo], yet for which there is a scarcity of absolute GCdata. Accordingly, and in order to bring the olefin data into our library of high-accuracy retentions, we convert in this work the retention indices of Boneva and Dimov to specific retention volumes, the latter being in any event required in the calculation of, for example, retention ratios (alphavalues). We also establish the likely limits of accuracy of the results.
2 Results
The retention indices of ref. [9] were converted to specific retention volumes V : using the absolute retention data reported in ref.
[8] together with the relation [2], van't Hoff plots of In Vivs. T-' were then employed to calculate the retentions at 30-80°C at 10' increments.
The results for the solutes in common with those of ref.
[8] are provided in Table 1. Comparison of the two sets of data yields a mean overall agreement o f t 0.5%, the largest deviation, -2.5%, arising with the most-volatile (ie., least-retained) compound, cis-2pentene. Presuming that the average of the extrema is likely to be representative of the level ofscatterthroughout, we estimate that the specific retention volumes calculated in the manner described for the remaining solutes, reported in Table 2, are accurate on average to no worse than ca. rt 1.5%.