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ANALYTICAL CHEMISTRY, VOL. 61, NO. 1, JANUARY 1, 1989
experimental values than those obtained by the simpler assumption that I is linear with T. A t least, this is true for Sadtler’s data when extrapolating from two lower temperatures to a third higher temperature. Replacing AS°CHz/mOcH,in eq 12 with an adjustable parameter produced a better fit, as might be expected. For SE-54 the value was 8 X lo4 (where ASo/AHo was 10 X lo4) and gave errors in the extrapolated values with a standard deviation of 1.5 units, irrespective of temperature. For OV-1, the value was again 8 X lo4 (instead of ASo f AHo= 14 x lo4), but the standard deviation was 6 units, which was worse than the uncertainty of the simple linear extrapolation. No opinion is offered as to whether the nonlinearity of IbT with T results from temperature dependence of ASOCH,/ or of I$ or e or from systematic error in Sadtler’s very short retention times at high temperature. Therefore, no opinion is offered as to whether it is significant that values extrapolated from low-temperature values of I to a higher temperature were always found to be higher than the experimental value and never lower, except when using the adjustable parameter 8 X
PRACTICAL ADVICE FOR THE ANALYST No better method of extrapolation from two temperatures can at present be offered than to assume that I is linear with T. The error in an extrapolated value is usually below (AI/A T ) f 6 index unit per degree and in all cases that were investigated it was below (AI/AT) f 3. LITERATURE CITED (1) Takacs, J.; Rockenbauer, M.; Olacsi, I . J . Chromatogr. 1989, 42. 19. (2) Mitra, G. D.; Saha, N. C. Technology (Slndri, In&) 1972, 9(4),
334-335. (3) Ettre, L. S.Chromafcgraphla 1974, 7 , 39-48. (4) Rang, S.;Kuninges. K.; Orav, A.; Eisen, 0. J . Chromatogr. 1076, 128, 53-58. (5) Shlyakhov, A. F.; Anvaer, 8. I.; Zolotareva, 0. V.; Romina, N. N.; Novikova, N. V.; Koreshkova, R. I. Z h . Anal. Khlm. 1975, 30(4), 788-792 Anal. Ab&. 1978. 30, 5C42. (6) The Sadtier Standad Gas chrometography Retention Index Lbrary; Sadtier Research Laboratories DMsion of Blo-Rad Laboratories: Philadelphia, PA, 1985. (7) Hawkes, S.J. Chromatographla 1988, 25, 313.
RECEIVED for review November 6, 1987. Accepted October 14, 1988.
C0RRECTI 0N Use of Secondary Equilibria for the Separation of Small Solutes by Field-Flow Fractionation Alain Berthod, Daniel W. Armstrong, Marcus N. Myers, and J. Calvin Giddings (Anal. Chem. 1988,60, 2138-2141). Equation 8 on p 2141 should read
