This review discusses the results of research in the use of bulk liquid membranes in separation processes and preconcentration for analytical purposes. It includes some theoretical aspects, definitions, types of liquid membranes, and transport mechanism, as well as advantages of using liquid membranes in laboratory studies. These concepts are necessary to understand fundamental principles of liquid membrane transport. Due to the multiple advantages of liquid membranes several studies present analytical applications of the transport through liquid membranes in separation or preconcentration processes of metallic cations and some organic compounds, such as phenol and phenolic derivatives, organic acids, amino acids, carbohydrates, and drugs. This review presents coupled techniques such as separation through the liquid membrane coupled with flow injection analysis.

The transport of p-nitrophenol (PNP) through an agitated bulk liquid membrane (ABLM) was investigated. A kinetic model of two consecutive irreversible first order reactions was applied in order to describe pertraction. The influence of PNP concentration in the feed solution, NaOH concentration in the stripping phase, and the type of solvent on the transport parameters (k′ _f , k′ _s , t _max, , J _max) was studied. To describe transport kinetics, the apparent mass transfer coefficient (k′ [cm/s]) as a parameter independent of volume and a membrane area was proposed. The results indicated that pertraction efficiency decreases in the series: benzene > toluene > p-xylene. In the investigated range of concentrations, the influence of the feed phase concentration (PNP) on pertraction efficiency is much higher than the stripping phase concentration (NaOH). It was also found that pertraction is controlled by PNP diffusion and sorption (extraction) at the feed/liquid membrane interface. The average value for the overall mass transfer coefficient is equal to 3.564(±0.047) × 10⁻⁴ cm/s which is characteristic for the studied system.

The paper presents experimental data obtained in the study of liquid–liquid partition equilibriums in biphasic system in order to optimize the process of transport through bulk liquid membranes (triphasic partition systems). The partition equilibriums of some nitrophenols using chloroform as extraction solvent and membranary solvent, respectively, were studied. The influence of the pH on the partition equilibriums was investigated. The repartition constants and the pKa values of the studied nitrophenols were calculated. Nitrophenols were transferred in triphasic system from a feed phase with pH 2, through a chloroform liquid membrane, into a receiving phase with pH 12, with efficiencies over 90%

Analytical results represent a very important part in a quality control program. Uncertainty estimation is an important step in method validation. The objective of this paper is to study the uncertainty of measurement estimation in the quantitative determination of codeine phosphate from pharmaceutical formulations using UV-VIS spectrophotometry. The uncertainty estimation was performed using the Ishikawa diagram. The estimation of uncertainty components proved to be a good way for the experimental model to obtain low contribution of uncertainty to the analytical result.