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1.1 This test method describes an analytical technique to quantify lipid components that are often present in liposomal formulations as major components.

1.2 This test method uses high performance liquid chromatography (HPLC) to separate lipids in liposomal formulations and evaporative light-scattering detection (ELSD) to quantify the individual components.

1.3 This test method quantifies three major organic components in liposomal formulations: cholesterol, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG 2000), and hydrogenated soy L-α-phosphatidylcholine (HSPC).

1.4 This test method can estimate the absolute concentration of cholesterol, DSPE-PEG 2000, and HSPC and their ratio (DSPE-PEG 2000: HSPC: cholesterol) in liposomal formulations.

1.5 This test method describes preparation of calibration standards and samples, HPLC and ELSD instrumentation, method development and method validation, sample analysis, and data reporting.

1.6 The detection limits and quantitation limits for the analytes (lipid components) in this test method are in the range of 2 µg/g to 4 µg/g and 7 µg/g to 10 μg/g, respectively. The analytical measurement ranges for cholesterol, DSPE-PEG 2000, and HSPC are 10 µg/g to 165 µg/g, 10 µg/g to 300 µg/g, and 10 µg/g to 200 µg/g, respectively.

1.7 Significant digits and rounding of all reported values have been performed according to the guidelines as established in Practice D6026.

1.8 Units—The values stated in SI units are to be regarded as the standard. Where appropriate, c.g.s units in addition to SI units are included in this standard.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 Lipid composition in a liposomal formulation is an important aspect during synthesis of liposomes, which determines stability, surface characteristics, drug encapsulation, and drug release capabilities. The cholesterol component plays a key role in controlled drug release by adding stability to the liposome. A small variation in the lipid composition can significantly alter the parameters mentioned above (15).

5.2 Variation in the lipid composition in the liposomal formulation may influence the safety and efficacy of the product. Therefore, chemical composition of the liposomes shall be determined.

5.3 The pharmaceutical industry and regulatory agencies require QC, QA, specifications, thorough characterization, and quantification of lipid components (16, 17).

5.4 This test method can be used to ascertain variations in the lipid component profiling of various liposomal formulations. However, this test method does not intend to identify chemical degradation products (18).

5.5 Analyzing the stability of analytes and their chemical degradation profiles as a result of oxidation or hydrolysis is beyond the scope of this test method (18, 19).