When measuring "aluminum content," why is "aluminum" different from "aluminum phosphate"?

[KLM99]

Copied from the insert for Pentacel:

"1.5 mg aluminum phosphate (0.33 mg aluminum)"

I've read that Pentacel has a higher aluminum content than the separate vaccines, so I was trying to find exact numbers of the separate parts, but what's the difference between aluminum phosphate and just aluminum?

[harli]

Aluminum phosphate has this molecular formula....

AlPO4

That means that the aluminum atom (Al) is attached to a phosphate group (PO4) The phosphate group contains one phosphorus atom and 4 oxygen atoms.

Those phosphorus and oxygen atoms all add to the weight of the compound. So 1 molecule of aluminum phosphate is going to weigh more then 1 Aluminum atom. Therefore 1.5 mg of AlPO4 (aluminum phosphate) will weigh more then just the aluminum in that compound.


It's kind of like saying a batch of chocolate chip cookie dough will weigh more then just the chocolate chips that are in that cookie dough. Make sense?

[ma2two]

Just compare the aluminum content.

The only way to get less aluminum using separate components of Pentacel is to use the Tripedia brand of DTaP, but that brand contains mercury.

All the vaccine package inserts can be found here. http://www.fda.gov/BiologicsBloodVac.../ucm093833.htm