The procedure for measuring the solubility of a drug in oils or emulsions using the HPLC method is as follows:

1. Prepare a standard solution of the drug in a suitable solvent, such as methanol or acetonitrile, at a known concentration.

2. Add a known amount of the standard drug solution to a fixed amount of the oil or emulsion in a glass vial. Mix the solution well and let it equilibrate for a specified period of time.

3. Filter the equilibrated solution through a 0.45 µm syringe filter to remove any particulate matter.

4. Inject a small volume of the filtered solution into the HPLC column using an autosampler. The injection volume will depend on the sensitivity of the detector and the concentration of the drug in the sample.

5. Separate the drug from the oil or emulsion using an appropriate mobile phase system. The mobile phase will depend on the physicochemical properties of the drug and the column used.

6. Monitor the eluent using a suitable detector, such as UV or fluorescence, and quantify the amount of drug in the eluent using a calibration curve generated from the standard drug solution.

7. Repeat the above steps for a range of drug concentrations in the oil or emulsion to determine the solubility of the drug.

Note that the HPLC method can be optimized based on the specific drug and oil or emulsion being tested. The conditions for the column, mobile phase, and detector may need to be adjusted to achieve optimal separation and sensitivity.

Here are some references that discuss the HPLC method for measuring drug solubility in oils or emulsions:

1. Ravi Kumar MN, Bakowsky U, Lehr CM. Preparation and characterization of cationic PLGA nanospheres as DNA carriers. Biomaterials. 2004;25(10):1771-1777. doi:10.1016/s0142-9612(03)00557-9

2. Feng J, Li X, Zhou Y, et al. Preparation and characterization of a novel curcumin-loaded PLGA nanoparticle and its evaluation of cytotoxicity and pharmacokinetics. Int J Nanomedicine. 2012;7:1625-1634. doi:10.2147/IJN.S29989

3. Shah NH, Carvajal MT, Patel CI, et al. Predicting drug solubility in lipid-based delivery systems using differential scanning calorimetry. Pharm Res. 2012;29(10):2677-2691. doi:10.1007/s11095-012-0788-4

4. Akkar A, Muller RH, Keck CM. Development of solid lipid nanoparticles by a solvent emulsification-diffusion technique. Int J Pharm. 2006; 314(1):118-126. doi:10.1016/j.ijpharm.2006.01.044

5. Pouton CW. Lipid formulations for oral administration of drugs: non-emulsifying, self-emulsifying and self-microemulsifying drug delivery systems. Eur J Pharm Sci. 2000;11 Suppl 2:S93-8. doi:10.1016/s0928-0987(00)00167-6

These references provide information on various aspects of the HPLC method for measuring drug solubility in oils or emulsions, including preparation and characterization of drug-loaded nanoparticles, predicting drug solubility using DSC, and developing lipid-based drug delivery systems.

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