This work focuses on the development, validation and application of an analytical method for the determination of twenty organochlorine pesticides (OCPs) in human tissues using salting-out liquid–liquid extraction and dispersive liquid–liquid microextraction for sample preparation and gas chromatography–mass spectrometry to analyze the obtained extracts. Measurement of the concentration levels of these toxics in tissues can be used to assess the risk of the population to exposure. The linearity of the proposed method was verified in the 10–1,000 ng/g range. The sensitivity was evaluated calculating the limits of detection (LODs) for 20 OCPs (α-, β-, γ- and δ-hexachlorocyclohexane (HCH), α- and β-endosulfan, endosulfan sulfate, aldrin, dieldrin, endrin, endrin ketone, endrin aldehyde, α- and γ-chlordane, 4,4′-dichlorodiphenyltrichloroethane, 4,4′-dichlorodiphenyldichloroethylene (DDE), 4,4′-dichlorodiphenyldichloroethane, heptachlor, heptachlor epoxide and methoxychlor), most of them being found between 1.0 and 16 ng/g. The intra- and interday precisions were <12% for relative standard deviation values. The accuracy of the method was evaluated by recovery studies, which gave recovery percentages in the 85–109% range. Seven different tissues (liver, kidney, heart, spleen, lung, brain and abdominal fat) from eight autopsies were analyzed, and only three cases were seen to have β-HCH and 4,4′-DDE in abdominal fat, while 4,4′-DDE was also detected in the heart of one case. The rest of the samples were free of the studied OCPs at least above the corresponding LODs.

A study of the transient potential signals obtained with a cation-selective electrode based on an ion-exchanger was carried out for solutions of the following individual cations at different concentrations: H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Mg²⁺, Ca²⁺, choline (Ch⁺), acetylcholine (AcCh⁺), and procaine (Pr⁺). Three different general types of transient signals were distinguished depending on the value of the selectivity coefficient of the corresponding ion. A principal component analysis (PCA) was performed on the signals, finding that the qualitative identification of the corresponding ion from the scores of two principal components is possible. The study was extended to the transient signals of solutions containing an analyte in the presence of an interfering ion. The PCA of the corresponding signal allows for the detection of the presence of interfering ions, thus avoiding biased results in the determination of the analyte. Moreover, the two principal components of the transient signals obtained for each of the ions at different concentrations allow for the construction of calibration graphs for the quantitative determination of the corresponding ion. All the transient signals obtained experimentally in this work can be reconstructed accurately from principal components and their corresponding scores.

This study investigates the potential of transient potentiometric signals generated by an array of ion-selective electrodes (ISEs) as the basis for a potentiometric electronic tongue capable of identifying and quantifying a range of inorganic and organic cations. Six distinct polymeric membrane ISEs were fabricated, differing in plasticizer type (either NPOE or DEHS), and in the presence or absence of a lipophilic ion exchanger (KTClPB) and/or an ionophore (DB18C6). Transient potential responses were recorded following the exposure of the electrode array to various cations at different concentrations. A total of 810 transient signals were analyzed through visual inspection and principal component analysis (PCA), revealing characteristic dynamic patterns influenced by membrane composition, ion type, and ion concentration. PCA was conducted both on the transient signals from each individual electrode and on the aggregated dataset comprising signals from the full six-electrode array (electronic tongue). The electronic tongue exhibited a markedly enhanced capacity for discriminating and quantifying ion concentrations in comparison to any single electrode.

This review examines the reported research on the potential responses of ion-selective electrodes over time when exposed to sudden changes in the concentration of the primary ion (ion initially present in the ion-selective electrode membrane) and/or foreign interfering ions. Particular attention is given to the responses of liquid- and plasticized polymeric membrane-based ion-selective electrodes to foreign ions. The review provides an in-depth discussion of the theoretical models proposed to describe transient potential signals obtained experimentally with these ion-selective electrodes. In chronological order, the different contributions are presented and commented on in terms of their assumptions and mathematical treatments. The final equations obtained in each case, as well as some stages of their derivations, are presented. Additionally, the various models are classified and critically commented upon. Lastly, the review discusses the analytical applications reported for identifying and quantifying ions using the transient potential signals.