ASTM D2268 Test Method for Analysis of High-Purity n-Heptane and Isooctane by Capillary Gas Chromatography
4. Apparatus
4.1 Chromatograph - Gas chromatograph should be equipped with a split-stream inlet device for introducing minute quantities of sample without fractionation, a capillary column, and a hydrogen flame ionization detector. An electrometer to amplify the low output signal of the hydrogen flame ionization detector, and a strip-chart recorder for recording the detector signal are needed. The time constant of neither the electrometer nor the recorder should exceed 1 s. A ball and disk integrator or electronic integrator for peak area measurements should be used. The detection system must have sufficient sensitivity to produce a recorder deflection for cyclohexane of at least 8 divisions on a standard 0–100 scale chart using 0.10 volume percent of cyclohexane in n-heptane as defined in 7.1.

4.2 Microsyringe - A microsyringe is needed for injecting the sample into the split-stream inlet device.

4.3 Volumetric Pipet, 0.1-mL capacity.

4.4 Analytical Balance, 200-g capacity.

5. Reagents and Materials
5.1 Carrier Gas - Argon, Nitrogen, or Helium; 99.99% or greater purity. (Warning - See Note 1.)

NOTE 1 - Warning: Compressed gases under high pressure.

5.2 Fuel Gas - Hydrogen; 99.99% or greater purity. (Warning - See Note 2.)

NOTE 2 - Warning: Compressed gas under high pressure. Extremely flammable gas.

5.3 Oxidant Gas - Air; 99.99% or greater purity. (Warning - See Note 1.)

5.4 Cyclohexane - At least 99 mol % pure, to be used as internal standard. (Warning - See Note 3.)

NOTE 3 - Warning: Flammable liquid and harmful if ingested or inhaled.

5.5 n-Pentane - Commercial grade. (Warning - See Note 4.)

NOTE 4 - Warning: Volatile and flammable liquid, and harmful if ingested or inhaled.

5.6 Isooctane (2,2,4-trimethylpentane) - (Warning - See Note 3.)

5.7 Squalane - Liquid phase for gas chromatographic columns.

5.8 Tubing - Type 316, 321, or 347 stainless steel; 0.25 mm (0.010 in.) indise diameter.