Why not use units of µg/g or µg/mL?
When performing elemental analysis most sample preparation and data workup is done in units of µg/g, µg/mL, µg/L, etc. However, when working with pharmaceutical samples the Permitted Daily Exposure (PDE) limits are reported in units of µg/day. Since different pharmaceutical products have different maximum dosages, it is critical to convert the conventional units used by elemental analysts into something that can be equated back to the PDE limit unit of µg/day. The J Value is used to perform this conversion.
What is a J Value?
If you are testing pharmaceutical samples using USP <232> / <233> and/or ICH Q3D, then you may be familiar with the concept of the J value. The J value is defined below:
PDE limits are determined by USP <232> and ICH Q3D, but the dilution factor and maximum daily dose is determined by you and your sample. The reason that the PDE limit is converted to a J