n-alkanes (C12 to C36): n-dodecane (RI ), … n-hexatriacontane (RI )

 

GC/MS system

One µL of the derivatized sample is injected splitless by an Agilent autosampler into an Agilent gas chromatograph equipped with a 15 m x 0.18 mm i.d. fused silica capillary column with a chemically bonded 0.18 µm DB 5-MS stationary phase (J&W Scientific). The injector temperature is 270°C, the purge flow-rate is 20 ml min^-1 and the purge is turned on after 60 s. The gas flow rate through the column is 1 ml min^-1, the column temperature is held at 70°C for 2 minutes, then increased by 40°C min^-1 to 320°C, and held there for 1 min. The column effluent is introduced into the ion source of a Pegasus III time-of-flight mass spectrometer, GC/TOFMS (Leco Corp., St Joseph, MI, USA). The transfer line and the ion source temperatures are 250°C and 200°C, respectively. Ions are generated by a 70 eV electron beam at an ionization current of 2.0 mA, and 30 (15-30) spectra s^-1 are recorded in the mass range 60 to 800 m/z. The acceleration voltage is turned on after a solvent delay of 170 s. The detector voltage is V.

 

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