How can I combine a carbon filtering element with the MSR Guardian Purifier?

Question: How can I combine a carbon filtering element with the MSR Guardian Purifier? Why does the MSR Guardian Purifier not include one?

Answer: The Platypus GravityWorks Carbon Element can be attached to any hydration reservoir drink tube with a 0.25 inch internal diameter. While not an MSR product, it will serve the purpose of a broad spectrum chemical removal filter quite well. 
 
From an engineering standpoint, the size of the MSR Guardian Purifier is already so large that our design team figured it would make more sense to rely on a modular carbon/chemical removal filter element integrated elsewhere into the hydration system, such as into the drink tube. This setup would allow the user to bring the element along when necessary, and leave it behind when not.
 
It is important to note that while activated carbon is capable of reducing some heavy metals, pesticides, herbicides, and pharmaceutical byproducts, its efficacy is highly dependent on factors such as water temperature, concentration of contaminants, pH, and the presence of other contaminants. Additionally, there isn’t a good way of knowing when the carbon element has been used up and is no longer functioning in removing chemicals. Our team of microbiologists are working on a solution to address these limitations at our on-site water lab here in Seattle, WA. We currently have a product in the Research & Development pipeline that is being designed specifically for broad spectrum mitigation of chemicals.