System suitability solution— Add 0.2 g of methyl heptadecanoate to 0.3 g of Dibutyl Sebacate, and mix to dissolve.

Chromatographic system (see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector and a 2-mm × 1.8-m column packed with 10% liquid phase G41 on 100- to 120-mesh support S1A. The carrier gas is helium, flowing at a rate of about 30 mL per minute. The chromatograph is programmed as follows. Initially, the column temperature is maintained at 150 for 2 minutes, then increased at a rate of 4 per minute to 280, and maintained at 280 for 30 minutes. Make adjustments if necessary. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between dibutyl sebacate and methyl heptadecanoate, at relative retention times of about 1.0 and 0.8, respectively, is not less than 1.8; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject about 1.0 µL of Dibutyl Sebacate into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of C18H34O4 in the portion of Dibutyl Sebacate taken by the formula: in which A is the peak response for dibutyl sebacate; and B is the sum of the responses of all the peaks.