Division 5.2.2 Choice of operating conditionsF1

The operating conditions are generally as follows:

• column temperature:

  	20 °C/minute		5 °C/minute		20 °C/minute
  Initially 80 °C (1′)	→	240 °C	→	325 °C (6′)	→	340 °C (10′)

• detector temperature: 350 °C;

• quantity of substance injected: 1 μl of the n-heptane solution (2-4 ml);

• carrier gas: helium or hydrogen at the correct linear velocity for the gas selected (see Appendix);

• instrument sensitivity: suitable for the following conditions:

The conditions may be modified according to the characteristics of the column and the GC apparatus to obtain separation of all the waxes and a satisfactory peak resolution (see figure); the internal standard C ₃₂ retention time must be 18 ± 3 minutes. The most representative wax peak must be at least 60 % of the full scale.

The peak integration parameters must be established so as to obtain a correct evaluation of the areas of the peaks in question.