Numerical Simulation and Experimental Validation of Calibrant-Loaded Extraction Phase Standardization Approach.

We present the kinetics of calibrant release and analyte uptake between the sample and calibrant-loaded extraction phase, CL-EP, with a finite-element analysis (FEA) using COMSOL Multiphysics software package. Effect of finite and infinite sample volume conditions, as well as various sample environment parameters such as fluid flow velocity, temperature, and presence of a binding matrix component were investigated in detail with the model in relation to the performance of the calibration. The simulation results supported by experimental data demonstrate the suitability of the CL-EP method for analysis of samples with variation of the sample environment parameters. The calibrant-loaded approach can provide both total and free concentrations from a single experiment based on whether the partition coefficient (Kes) value being used is measured in a matrix-matched sample or in a matrix-free sample, respectively. Total concentrations can also be obtained by utilizing CL-EP in combination with external matrix-matched calibrations, which can be employed to automate the sampling process and provide corrections for variations in sample preparation, matrix effects, and detection processes. This approach is also suitable for very small volumes of sample, where addition of an internal standard in the sample is either troublesome or can change the sample characteristics.