Light Stress/Degradation Study

[sdo7575]

I need some advice on light stress/degradation studies. Our group performs light stress studies by exposing our samples to over 1000ft candles over a maximum period of 5 days.

What is the standard maximum light stress conditions the sample is exposed before you can justify the product is stable??

If the product is stable for two days in which there is peak purity and no degradation is found, but unstable at five days, does this mean that the test methods must require low actinic glassware for sample preparation??

If peak purity is not met after three days under light stress conditions, does that mean that you don't have a suitable method and need to modify it so that peak purity is met??

[ym3142]

I guess most people put the sample under a short wavelength UV. I am not sure about the specifictions.

For your two , five days cases, if you peak was not pure when got 10% degradation, you need improve the method; if pure, the method is OK;

For stability, you may need the sample to be stable for two to three day. otherwise you try new approaches to get a condition when your sample is stable enough for 2-3 days,
hope this helps, jim

[hema]

The ICH Guideline Q1B might be a help for you. This guideline defines the spectrum, the intensity and the duration of light exposure.

If you are performing photostability tests according to this guideline, you need both, UV and visible light to simulate artificial daylight and it needs to have a certain intensity (illumination of not less than 1.2 MegaLux h for visible light and at least 200 Wh/m2 of UV-irradiation) It’s a bit tricky to determine the illumination and irradtiation but the guideline Q1B describes some methods to do that.

However, the guideline does not tell you anything about the stability of your sample. You have to judge from your results whether the sample can be considered stable (Do they meet their specifications? Do they meet the expectations of your QA/customer?)

Hope it helped!

M

[Karan]

Ther are two things:

1) Stability study of test prepatration

2) Stability study of Product


If your concern is point no. 1 then you can improve the stability in many ways like 1) using low actinic glasswares 2) storing the test preparation at low temperature, 3) using sample cooler, 4) by selecting other suitable solvent, etc


If your concern is point no. 2 then Hema is right

Thanks,

Karan