The Laboratory Notebook

Answering important questions about quality.

By Robert Green

This month we discuss the differences between capsule weight and capsule fill weight, and how we get to those amounts. We also discuss the issues surrounding the analysis of a non-standardized botanical in a finished product.

Q: I recently sent in my capsules for analytical testing and I don’t understand why the capsule fill weight on the report is different from the weight I recorded when I weighed the capsules. What happened?

A. We hear this comment often, and it is a simple misunderstanding of terms. The capsule fill weight is just that—the fill weight. This means that the contents of the capsule have been removed and weighed separately from the shell.

Generally speaking, for capsules, the supplement product is the material in the capsule. The capsule itself is merely the packaging, which holds the product. When determining a product’s ingredients we must separate it from the packaging. It is obviously critical that we recover the entire contents of the capsule for our analysis to be accurate. For hard shell capsules this is straightforward; we carefully empty the entire contents of the capsule, weigh the contents and then start our analysis from there. The capsule is discarded.

Extracting the contents and discarding the shell is also a practice employed for softgel capsules. However, as anyone who has tried to get the contents out of one knows, the process is a bit more complicated. Extra care must be taken to ensure we do indeed recover the entire contents. To do this we first weigh the softgel in its entirety (shell and contents). We then remove the contents the good old fashioned way—we cut the capsule and squeeze the contents out. Knowing this “high-tech” maneuver will not extract the entire contents, we wash the softgel with an appropriate solvent, which removes the remaining contents without adversely affecting it. The “squeezed-out contents” are then combined with the contents extracted through the solvent. The now clean softgel shell is weighed and then this weight is subtracted from the initial weight of the capsule (when it contained its contents). What you are left with is the capsule fill weight.

Determining tablet weight is a bit more direct. Here the tablet is the tablet; there is no exterior packaging to remove. As such, the tablet is weighed in its entirety. However, our initial processing of a tablet does not end there. Tablets are highly compressed products. Before analysis, the tablets must be physically broken down so the components are exposed to the extraction process. We accomplish this through another “high-tech” process—grinding (usually by hand).

As you can see, it is a lot more complicated to prepare a finished product for analysis than it is for a raw material, thus explaining why analyti­cal labs may charge more for finished products.

As we have discussed previously in this column, an accurate analysis starts with an accurate sample. Even with the best of manufacturing techniques there will be some variations between capsule/tablet weights for the same lot of product. It is therefore important that the lab use several tablets/capsules for its analysis and not rely on just one.

So the next question is: why is tablet weight and capsule fill weight important? In order to quantify the amount of a particular component in a product, you have to know how much product you are working with. If we were working with just one tablet or capsule that would be easy. But as mentioned, to be certain our analysis is representative of the product, we must work with several tablets/capsules. So we need to determine the average tablet or fill weight and use that in our calculations.

If your serving size is two capsules and you are trying to determine the amount of the ingredient at issue present per serving, the calculation would involve multiplying your average capsule weight by two and applying that as the unit weight. The same reasoning applies to tablets.

Q: I have a nutritional supplement in capsule form where the primary ingredient is Hoodia gordonii. I want to know how much Hoodia is in the capsule but I was told this was not possible because my Hoodia is not standardized. Is this true?

A. Sort of. As we have discussed in previous columns, botanicals are extremely complex materials with a multitude of components. Therefore, we can­­not measure a botanical in is entirety. Instead, we focus on one or more specific phytochemicals we can measure. However, the levels of these phytochemicals vary from plant to plant, so just measuring them still gives us no way to determine the amount of the material in the product. To solve this dilemma, most botanicals in use today are standardized extracts. Standardization is the pro­cess of concentrating a botanical so that one or more phytochemicals is present in a standard amount. With that, we can measure the amount of those standardized analytes and, knowing the standardization rate, calculate how much of the extract is in the product.

Without standardized Hoodia we are back to where we started. There is, however, something we can do. If you have the actual hoodia that went into your product we can first measure the amount of one or more phytochemicals in it. Next, we measure the amounts of those analytes in your product. Now that we know the levels of these analytes in the raw material, we can use this to calculate the amount of hoodia in the product. What we have done, in effect, is standardized the very hoodia you used in your product. The key here is that the raw material Hoodia must be the exact hoodia used in the product. The analysis of the raw material will not apply to the next batch of material incorporated in later products since, as we mentioned, the levels in non-standardized Hoodia will differ from lot to lot.NW