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stability test
If I want to be sure about the stability of my leave in hair lotion (stability=just being one phase) for one year which test I should do? I know about putting sample in 45C for 8weeks and if it passes this test It will be stable for one year, but I have time limitation, is there any other scientific test which is lasting for 2 or 3 days?
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16 Replies
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Not really. You could test it @50C and do freeze/ thaw cycles. Most unstable formulations separate in a couple of days, but it is no guarantee.. .What I do if I have time limitation is to use my chemistry knowledge + my experience to do a qualified guess and then discuss it with the customer. Usually the customer prefers to wait instead of taking that risk.
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some one says me put the sample in oven and when it starts to melting set aside and see if it separates or not!!!!
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Nasrins,
The stability testing protocols have been developed and used by industry for decades … if there was a legitimate 2 to 3 day shortcut that really gave you results that you could rely on, it would be in common use.But, if you have access to a centrifuge, you can heat your sample up to 50C and centrifuge at 3,000 RPM for 30 minutes and see if you get any separation.You will always know if your product fails well in advance of the point in time that you can conclude that it passes! -
yes I have but could I rely on?, is it scientific method or it is obtained experimentally?
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No, I would not rely on it for a commercial launch. It is a quick test for emulsion stability, but you also need to do freeze/thaw cycles. It’s about as much as you can do in 2 to 3 days.
If you are using a proven combination of emulsifiers at the proper amounts and you are aware of other products using that combination that are on the market, that can give you some confidence, but short of doing your own testing, you are never going to be certain. -
Right. The only thing you can rely on is doing an actual stability test. (8 week minimum)
Even stability tests are only approximations of what will happen and they are not guarantees that your formula will be stable. -
so there is no guranteed way
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@markbroussard
“You will always know if your product fails well in advance of the point in time that you can conclude that it passes”
what does it mean? -
There is no guaranteed way. But, as @Perry says, even an eight week stability test is not guaranteed. The only thing that you can do is make your best guess.A long while back, I worked for a contract manufacturer who would sell a formula to a client based on only 3 or 4 days stability results. We would keep the samples on stability and pray - and 90% of the time, a sample that passed 3 days stability at 45C would pass 1 month stability at 45C easily. 2 months was a little less likely.In my humble opinion, the best thing to do is be upfront about the risk - tell the customer: “we’ve tested for 3 days, and it passed. That means that there’s a 90% chance that it will be stable for at least a year, and an 80-85% chance that it will be stable for two years or more.”
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What I mean by that is that only time will tell you whether your formula is stable or not. You just have to do the testing … if your formula fails prior to the proscribed 8 week testing period, that is definitive. You won’t know if it’s a pass until your testing is complete.
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@markbroussard thanks alot
@perry is there any valid website or test method for 8weeks test(such as ASTM test methods), I want to report it and I cant say I got it from chemist corner,
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The PCPC publishes stability test guidelines but they charge for it.
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IFSCC monograph no. 2 (“Fundamentals of Stability Testing”) covers this subject as well; like the PCPC, the IFSCC charges for copies
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I’ll offer this Nasrins: for quick determination of emulsion or liquid product integrity, Mark’s centrifuge test is more than adequate. Actually running that test at a sample temperature of 50C is downright brutal - if it passes you can be 99.9% sure your product will not separate or “cream” for several years! Running it at RT is good enough. What you will not determine, however, is the product’s stability as it relates to other attributes and variables such as pH, viscosity, scent deterioration, general appearance, color fastness, etc. Only a full 90-day accelerated test as described in the IFSCC monograph Bill Toge mentions will give you that.
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@chemicalmatt thanks … my stability test issue was solves but I face another problem. I write it in another discussion..
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