Robert S. Green11.01.01
The Laboratory Notebook
Answering important questions about quality.
By Robert S. Green
This month we tackle questions on product expiration dating (which leads nicely into a discussion on accelerated stability testing), the benefits and pitfalls of using pre-production samples, use of the measurement “I.U.” and testing for potency.
Q. I’m ready to produce a multi-component product and want my label to include an expiration date. May I use a two-year term that I see on so many supplements?
A. Expiration dating is like everything else on your label—it should accurately represent your product’s characteristics. If your product carries a two-year term you are warranting that the product will meet its specifications for two years. To make that statement you should be able to demonstrate that it’s a fact.
So how do you do this? The most direct way is to put a sealed bottle aside for two years, at the end of which time you test it. But this, of course, means you cannot sell your product during this testing period, which is not a realistic approach. Fortunately, once again science comes to our aid.
Science brings us the accelerated stability study, which some also refer to as stress testing. Quite simply, by cycling a product through temperature and humidity extremes we can duplicate a two-year shelf life in a matter of months (the testing is accelerated). We do this with the use of a computer-controlled environmental chamber that will cycle through the temperature and humidity settings we designate. While the accelerated equivalent of a two-year shelf life depends on several factors, a rule of thumb is that we can duplicate one year of shelf life with one month in the chamber. Now we have a realistic approach to the shelf life issue.
The accelerated stability study will include product testing at designated points. Generally speaking, the product is tested at the outset (no point conducting the study if the product does not initially meet specifications) and at the end of each month of the study. Since we are testing the shelf life of sealed bottles, the chamber should contain one bottle for each test point (if you used only one bottle, once it is opened for the first test point the subsequent results are no longer valid). Obviously, if the product fails to meet specs at any test point the study is terminated.
While you could go test crazy, a knowledgeable customer-oriented lab will design a study requiring the least amount of testing to get the job done. For example, when studying a multi-component product there may be no need to test every ingredient. Rather, an experienced lab can designate one or more ingredients that are subject to degradation and only test them on the theory that they will fail first (and once one item fails the test is over). For example, vitamin C, metals, minerals and synthetic ingredients like MSM are very stable, while sugars and glycosides are unstable. In a product containing both groups you can be sure the unstable items will be the first to fail so you can focus on them. The form of the product is also important, as for example liquids and gels tend to be less stable. The effects of components on one another must also be considered; valerian contains valerenic acid that can degrade an otherwise stable component.
The points to make is that (a) nutritional supplements are chemical entities and therefore we should look to science for the answers to our questions and (b) it does not have to cost a small fortune to employ science; a qualified lab acting in your best interests can make science work for you in a commercially reasonable manner.
Q. Planning to buy a raw material from a new manufacturer, I asked for and then tested a pre-production sample; it was perfect. I then had the order drop-shipped to my customer and it failed their testing. What happened?
A. Pre-production samples can be useful. If you are buying from a new vendor you want to be sure its product will meet your specifications. A pre-production sample provides you the opportunity to do this without waiting for the completion of the production run. However, an acceptable pre-production sample is no guarantee the material delivered will be likewise.
To begin with, “bait and switch” is an old game played in every industry and the nutritional supplement industry is no exception. You hook the buyer on the perfect sample and then deliver something less. But even without this corruption, there is always the possibility that something goes awry in any manufacturing process. Or the material is exposed to unfavorable environmental conditions after manufacture. Or the material is contaminated, whether intentionally or not. Or any number of other events could transpire between your order and the delivery of the material that adversely affect it. The only answer to this dilemma is to test the actual product at the point you know nothing else will happen to it.
There is actually a larger lesson to be learned here. Analytical results are sample-specific; you cannot automatically apply a product analysis of one sample to any other material. An analytical lab can only test the sample in its possession and the results only apply to that sample. The fact that there is material elsewhere with the same lot number does not necessarily mean that the lab analysis applies to it. This is especially important when you are buying material based on a product analysis conducted by a lab for another party. You have to be absolutely certain that the material you are buying is the same material tested by the lab and that nothing adverse happened to that material since the date of the analysis.
Q. My formulator certified that my vitamin A product contains 100 milligrams as I specified. As a responsible company we sent a sample to an independent testing lab and they reported that my product contains 18,170 I.U. Which one is correct?
A. They both are. An international unit (I.U.) is a standard unit of measurement of biological activity that is used for fat-soluble vitamins (A, D and E) and some other compounds. It was established by the International Conference for Unification of Formulae and is recognized internationally. One I.U. represents a different amount for each substance. The weight equivalents for fat-soluble vitamins are as follows:
Vitamin A—1 milligram = 181.7 I.U.
Vitamin D—1 microgram = 40 I.U.
Vitamin E—1 milligram = 1.36 I.U.
To avoid confusion it is always a good idea to let your lab know in which unit of measure you want your results to be reported. And before anyone calls, 1000 micrograms = 1 milligram.
Q, Can you test the potency of my standardized St. John’s Wort product?
A. “Potency” is a confusing term to use. If what you mean is purity (i.e., what percentage of my raw material is standardized St. John’s Wort) then, of course, no problem. However, sometimes the word “potency” is used to mean “efficacy.” That is an entirely different matter. Efficacy is the age-old question of “does it work?” That is not a question for an analytical lab, but rather, an organization that conducts pharmacological studies. And this is going to cost you!NW