ASTM D4424 Standard Test Method for Butylene Analysis by Gas Chromatography
5. Apparatus
5.1 Chromatograph - Any chromatographic instrument having either a thermal conductivity or flame ionization detector with an overall sensitivity sufficient to detect at least 0.05 % of each of the components listed in 1.3.
5.2 Detector - Either a thermal conductivity or flame ionization detector may be used.
5.3 Sample Valve - Either a constant-volume gas sampling valve or a liquid sampling valve may be used. Ifa gas sampling valve is used, greater care must be taken to ensure that the vaporized butylenes that are injected into the chromatograph are a true representation of the sample.
5.3.1 If the liquid sample valve is used, the sample cylinder must be pressured up to at least 1100 kPa (160 psig) with an inert gas, such as nitrogen or helium. (Warning - Compressed gas under high pressure. Gas reduces oxygen available for breathing.) Also a valve must be installed in the purge line downstream of the liquid sample valve to ensure the butylenes sample in the sampling valve is entirely in the liquid phase prior to injection into the column. (Warning - Extremely flammable liquefied gas under pressure. Vapor reduces oxygen available for breathing.)
5.4 Column - Any chromatographic column may be used, providing the components listed in the scope can be separated sufficiently for the accurate determination of component concentration. Resolution between peaks must afford a resolution such that the depth of the valleys between peaks are no less than 50 % of the peak height of the lesser component. A list of satisfactory columns is given in Appendix X3.
5.5 Recorder - A recorder with a full-scale response of 2 s or less and a maximum rate of noise of +/- 0.3 % of full scale.
6. Preparation of Apparatus
6.1 Set up the chromatograph in accordance with the manufacturer's recommendations. Install the analytical column and adjust the carrier gas flow and column temperature so that the components will elute within the time desired for the analysis.
7. Calibration
7.1 A standard blend containing the components to be analyzed may be either made or purchased from a commercial source. Inject the calibration blend under identical conditions as will be used for the samples. Record the chromatogram and calculate the factors to be used for analysis by using the peak areas as measured by either manual, mechanical, or electronic means.
7.2 Relative response factors may be used if they are available.
NOTE 1 - Practice E260 procedures may be helpful to those using this test method.
