ASTM D6596 Ampulization and Storage of Gasoline and Related Hydrocarbon Materials
4. Summary of Practice
4.1 The physical and chemical characteristics (for example, volatility, reactivity, flammability, and so forth) of a gasoline or related hydrocarbon mixture is first assessed to determine the appropriate procedures for sample handling, sample transfer, and ampulization. Then a uniform quantity of gasoline or hydrocarbon mixture is dispensed into suitably sized glass ampules (purged with an inert gas), and the ampules are flame-sealed with a torch. A number of ampules from throughout the filling and sealing process are selected and tested by appropriate test methods to determine homogeneity across the lot. Additional ampules are retained for later testing to determine stability and shelf life.
4.2 This practice addresses the common difficulties associated with the ampulization and storage of gasoline and similar liquid hydrocarbon materials, which may contain volatile components. The process of ampulization, whether performed using manual or automated equipment, involves the same fundamental issues, namely, assessment of the characteristics of the material to be ampulized, sources of contamination, sampling of the bulk container, volume dispensing accuracy, inert atmosphere blanketing, flame sealing, sequential ampule labeling, packaging homogeneity sampling, and homogeneity testing. Failure to adequately consider any of the above issues may negatively impact the quality, consistency, and value of the ampulized material as an RM.
4.3 Confidence in the homogeneity of the ampulized product can only be established through homogeneity testing, which involves the sampling, analysis, and statistical treatment of data from randomly selected ampules obtained from the beginning, middle, and end of the ampulized lot. Determination of ampulization homogeneity requires that the order in which the ampules have been filled and sealed be maintained. Homogeneity testing reveals the variability of the product introduced during the ampulization process. Homogeneity results must be within acceptable limits of the ARV or consensus value for the RM.
4.4 Ampulization does not necessarily guarantee sample stability or indefinite shelf life of the RM. Initial homogeneity data establish reference values for future tests of sample stability and determination of shelf life.
5. Significance and Use
5.1 Ampulization is desirable in order to minimize variability and maximize the integrity of calibration standards or RMs, or both, being used in calibration of analytical instruments and in validation of analytical test methods in round-robin or interlaboratory cross-check programs. This practice is intended to be used when the highest degree of confidence in integrity of a material is desired.
5.2 This practice is intended to be used when it is desirable to maintain the long term storage of gasoline and related liquid hydrocarbon RMs, controls, or calibration standards for retain or repository purposes.
5.3 This practice may not be applicable to materials that contain high percentages of dissolved gases, or to highly viscous materials, due to the difficulty involved in transferring such materials without encountering losses of components or ensuring sample homogeneity.
