@sameer while FDA has not provided general guidance on these terms, may I suggest looking at the post made by @Yosukemino with the recent update from EMA on these concepts and general guidance.
Temporary Limit:
To protect public health, to inform decisions on required market actions while ensuring at the same time availability of medicines while a formal AI is established, a temporary AI (t-AI) of 178 ng/day (total nitrosamines) can be adopted by the relevant authorities for marketed medicines identified to contain one or more nitrosamines exceeding the TTC of 18ng/day. This t-AI has been derived using TD50 values calculated in the Lhasa carcinogenic potency database and is based on a probabilistic approach that there is a 33% risk that the “true” AI is below the t-AI. It is expected that the t-AI would be used for a period of less than 12 months.
Analytical Target:
The t-AI should not be used as a target for development of validated analytical methods to quantify new nitrosamines since the long-term limits adopted by CHMP might ultimately be lower than the t-AI