The advantage of liquid chromatography for simultaneous separation and quantitative determination is particularly prominent in the detection of therapeutic drugs and pharmacokinetics. In order to achieve safe, effective, and reliable drug application, it is necessary to understand and study the processes of drugs and their formulations in the body (absorption, distribution, metabolism, excretion), in order to study the mechanism of action and pharmacodynamics of drugs. With the continuous advancement and development of drug analysis technology, quantitative analysis of the concentration of drugs and their metabolites in human and animal bodies (body fluids, tissues, and blood) can be carried out. It has important significance and practical needs for drug evaluation, guiding clinical rational drug use, and pharmacokinetic research.
The concentration of drugs in the body can be determined by liquid chromatography, and the data can be processed using certain statistical methods to study the pharmacokinetics of drugs.

Liu Xiangxin et al. administered single dose intravenous and oral administration of catechins at home, and measured their blood drug concentration using liquid chromatography. The drug time data after injection and administration followed a two compartment open model without absorption.
Zhang Zuoxin et al. used HPLC to determine the plasma drug concentration of ofloxacin (10mg/kg) in carp at different time points after a single oral mixed feeding. The results showed that its pharmacokinetic characteristics were consistent with the first-order absorption one compartment open model, and ofloxacin was suitable for the prevention and treatment of bacterial diseases in fish.