Exercise 3: Determining the time-out in CPG The best-known method of estimating the dead time tM...
Exercise 3: Determining the time-out in CPG The best-known method of estimating the dead time tM consists in measuring the retention time of an unretained compound (commonly methane in GC). Another method is proposed here using the relation used in establishing retention indices, namely that in a homologous series of organic compounds one can write, if the temperature of the column does not vary: log (tr-t = an + b t represents the retention time of the compound with n carbon atoms, a and b are constants which depend on the class of solutes and on the stationary phase chosen. Calculate t from the following experiment: a mixture of linear alkanes with 6, 7 and 8 carbon atoms is injected. The retention times are respectively 271, 311 and 399 s in an isothermal regime at 80 °C.