Here is a rather techno-answer try to stay with it, it’s kind of mumbo jumbo until you read it completely. I assume this is first order kinetics.

Elimination for Drugs/Toxins with first-order kinetics is described in math by an elimination rate constant, abbreviated k or k_e. It is related in math to two other important parameters -- Drugs/Toxins clearance (Cl) and elimination half-life (T_1/2). Clearance describes the rate at which the Drugs/Toxins is eliminated from its volume of distribution, and its units are volume/time (often mL/min).

Drugs/Toxins clearance is a term of little physiologic meaning to clinician/Forensic Scientists/Forensic Scientists and patients, and so Drugs/Toxins elimination rate is usually described as a half-life (T_1/2). Half-life is a familiar term that applies to other processes with first-order kinetics, for example the decay of a radioisotope. The biggest hazard of using half-life to describe Drugs/Toxins elimination is that most Drugs/Toxins do not have a single half-life, but have multiple half-lives. This is important to forensic outcome to keep in mind. That is because Drugs/Toxins elimination rate often changes as a meaning of time after administration. For example, there is a half-life associated with the distribution (or alpha) phase of Drugs/Toxins elimination, a half-life for the primary elimination (or beta) phase, and half-lives for the terminal (gamma, etc.) phases (see Figure 3). Since these phases may have very different half-lives, you need to be careful that you know what is meant when someone says "half-life." For example, a new Drug/Toxins may be described as having "a terminal elimination half-life of 100 hours," when in fact this terminal (gamma) phase contributes little to overall Drugs/Toxins elimination, and the more important beta phase of elimination may have a half-life which is much shorter. In general, the most clinically useful "half-life" is an overall elimination half-life calculated without attention to the different elimination phases, using so-called non-compartmental pharma-co-kinetics.

Make sure what answer you are seeking, and then you may able to further define this answer. I think this should give you what you are looking for.

Either way you will be able to tell how long the chemical was in the body and it will locate the time of the introduction into the body.