These results could be attributed to the analytes physical–chemical properties influencing the extraction efficiency of the CPE technique, and thus the analytical responses [26]. At the working pH 3 TC and ABC were in their molecular form, while EFV and NFV were in their ionic forms. They show different water solubility behavior (Table 1) coherent with their analytical responses. In this sense, it is expected to obtain the lowest responses for 3 TC and ABC since they are the most polar analytes and the surfactant is no-ionic, limiting thus the affinity between them and the micelles. The performance of EFV could be attributed to the fact that at the lowest surfactant concentration assayed, the extraction efficiency was the maximum. Higher concentration led to higher surfactant reach phase volume; therefore, concentration of the extracted analytes was lower due to a dilution effect. In this sense, NFV reported the highest analytical response at intermediate concentration, falling for dilution into the resulting coacervate phase when higher surfactant was used. The most polar analytes contain higher number of polar atoms into their structure. This leads to higher molecular effective radio due to the solvatation, reducing their interaction with micelles. Therefore, 3 TC and ABC require higher surfactant concentration to achieve a successful extraction and analytical response.
Based on these experiment results, 5% (w/v) Triton X-114 was adopted as working condition considering it as the best compromise concentration that lead to successful analytical response for the studied ARV. This fact is relevant for the development of an analytical methodology for a multi-component analysis.