Sodium benzoate is a salt widely used in industry as preserver. Its activity coefficients in aqueous solutions can be estimated by Pitzer theory, once the necessary parameters are known. Electromotive force (emf) measurements on galvanic cells without liquid junction have been used for the determination o f mean activity coefficients of sodium chloride in the ternary system sodium chloride + sodium benzoate (NaB) + water. Pitzer theory has been applied to this system and those data enabled the evaluation of the specific parameters for sodium benzoate at 298.15 K by linear regression. The values obtained f o r / B(0) NaB and B(1) NaB parameters, respectively 0.177 kg mol-1 and 0.34 kg mol-1 are close to those published already for other carboxylic acid salts.

Potentiometric chemical sensors for the detection of paralytic shellfish toxins have been developed. Four toxins typically encountered in Portuguese waters, namely saxitoxin, decarbamoyl saxitoxin, gonyautoxin GTX5 and C1&C2, were selected for the study. A series of miniaturized sensors with solid inner contact and plasticized polyvinylchloride membranes containing ionophores, nine compositions in total, were prepared and their characteristics evaluated. Sensors displayed cross-sensitivity to four studied toxins, i.e. response to several toxins together with low selectivity. High selectivity towards paralytic shellfish toxins was observed in the presence of inorganic cations with selectivity coefficients ranging from 0.04 to 0.001 for Na+ and K+ and 3.6*10-4 to 3.4*10-5 for Ca2+. Detection limits were in the range from 0.25 to 0.9 μmolL-1 for saxitoxin and decarbamoyl saxitoxin, and from 0.08 to 1.8 μmolL-1 for GTX5 and C1&C2, which allows toxin detection at the concentration levels corresponding to the legal limits. Characteristics of the developed sensors allow their use in the electronic tongue multisensor system for simultaneous quantification of paralytic shellfish toxins.

At olive oil industrial extraction, water addition is a practice overcoming the formation of thick pastes. The effect of water addition (0 to 6.2%, kgadded water/kgolives), during the industrial milling of cv. Arbequina olives, on the oils’ chemical-sensory quality, was evaluated. Despite the extra virgin olive oil classification, compared with the water incorporation (1.2–6.2%), extraction without water addition resulted into oils that showed less primary oxidation (lower peroxide values and K232), greater total phenolic content (+12–22%) and higher oxidative stability (+22–31%). No water addition increased the oils secoiridoids content (+5–13%), mainly oleacein (+27–79%). Oils extracted without water addition had a more intense ripe fruity sensation (≥ +11%) but lower fruit intensities (at least - 4%). Thus, the quality and stability of the cv. Arbequina oils can be favoured if extracted without adding water during the olives industrial milling.

Olive oil is highly appreciated due to its nutritional and organoleptic characteristics. However, a huge compositional variation is observed between olive oils, requiring the use of diverse analytical techniques for its classification including titration, spectrophotometry and chromatography, as well as sensory analysis. Chemical analysis is usually time-consuming, expensive and require skilled technicians, while the sensorial ones are dependent upon individual subjective evaluations, even if performed by trained panellists. This work evaluated and demonstrated the feasibility of using a potentiometric electronic tongue, comprising non-specific lipid polymeric and cross-sensitive sensor membranes, coupled with chemometric tools based on different sub-sets of sensors (from 11 to 14 sensors), to predict key quality parameters of olive oils based on single-run assays. The multivariate linear models established for 23 centenarian olive trees from different cultivars allowed predicting peroxide value, oxidative stability, total phenols and tocopherols contents, CIELAB scale parameters (L*, a* and b* values), as well as 11 gustatory-retronasal positive attributes (green, sweet, bitter, pungent, tomato and tomato leaves, apple, banana, cabbage, fresh herbs and dry fruits) with satisfactory accuracy (0.90 ± 0.07 ≤ R2 ≤ 0.98 ± 0.02 for the repeated K-fold-CV procedure, which ensured that 25% of the data was used for internal-validation purposes). The electronic tongue device had an accuracy statistically similar to that achieved with standard analytical techniques, pointing out the versatility of the device for the fast and simultaneous chemical and sensory analysis of olive oil.

The work describes a new procedure for cetylpyridinium chloride determination in oral disinfectants, based on a flow-injection system with potentiometric detection. The determination was based on the measurement of picrate concentration decrease as result of ion-pair reaction with the analyte present in the injected sample. In the optimised set-up the sample injection volume was kept at 400 µL and merged downstream with the reagent solution containing 1,0 x10-5 mol/L of picrate adjusted to pH 5.0 with citrate/citric acid buffer. The flow rate was fixed at 8 mL/min and the reactor length at 40 cm. The proposed procedure enables the determination of cetylpyridinium in the analytical range of 5,0x10-6 – 7,5x10-5 mol/L at a sampling rate of 60/h. The results for real samples had a precision better than 3% and were comparable to the labelled values.

Honey-rich composition in biologically active compounds makes honey a food products highly appreciated due to the nutritional and healthy properties. Food-manufacturing is very prone to different types of adulterations and fraudulent labelling making it urgent to establish accurate, fast and cost-effective analytical techniques for honey assessment. In addition to the classical techniques (e.g., physicochemical analysis, microscopy, chromatography, immunoassay, DNA metabarcoding, spectroscopy), electrochemical based-sensor devices have arisen as reliable and green techniques for food analysis including honey evaluation, allowing in-situ and on-line assessment, being a user-friendly procedure not requiring high technical expertise. In this work, the use of electronic tongues, also known as taste sensor devices, for honey authenticity and assessment is reviewed. Also, the versatility of electronic tongues to qualitative (e.g., botanical and/or geographical origin assessment as well as detection of adulteration) and quantitative (e.g., assessment of adulterants levels, determination of flavonoids levels or antibiotics and insecticides residues, flavonoids) honey analysis is shown. The review is mainly focused on the research outputs reported during the last decade aiming to demonstrate the potentialities of potentiometric and voltammetric multi-sensor devices, pointing out their main advantages and present and future challenges for becoming a practical quality analytical tool at industrial and commercial levels.

Invasive candidiasis has become a major global health concern in the past years, due to both the lack of effective systemic antifungals with low drawbacks and the increasing number of multi-drug resistant yeasts. Macrocyclic compounds have been identified as key-points in the correct functioning of a variety of fundamental biological systems; as well have shown highly favourable drug-like proprieties. Thus, in the last decades, macrocyclic scaffold-based pharmaceuticals have been developed for a diversity of medical applications. In this work, a novel macrocycle with in vitro activity against the Candida genus was developed, the dioxo-[14]aneN3S (1-thia-4,8,12-triaza cyclotetradecane-3,13-dione). Dioxo-[14]aneN3S was synthesised by reacting dimethyl thiodiglycolate with dipropylenetriamine in a large excess of dry methanol at 40 ºC under nitrogen atmosphere for 9 days, and then purified by column chromatography (η = 76.8%). This procedure was based on Tabushi’s method for macrocyclisation and the introduced improvements increased the yield up to four fold comparatively to other macrocycles obtained by the non-modified methodology. The chemical structure and purity were confirmed by FT-IR, 1D/2D NMR and ESI-MS techniques. The acid-base behaviour of dioxo-[14]aneN3S in aqueous solution was studied by potentiometry and 1H NMR spectroscopy. Despite this compound has three ionisable centres, only one value of protonation constant was determined in the adopted experimental conditions (log⁡〖K_1^H 〗 = 9.43), corresponding to the protonation of the amine group. Moreover, for pH values below 8, the single-charged monoprotonated species (HL+) is the major form of dioxo-[14]aneN3S, which means that, according to the pH-partition hypothesis, this compound displays an unfavourable acid-base profile for oral administration, but good characteristics for parenteral formulation. The antifungal activity of dioxo-[14]aneN3S was evaluated in vitro against clinical isolates of multi-drug resistant Candida yeasts by broth microdilution method, according to the CLSI M27-A3 guidelines. By comparison with the reference antifungal fluconazole, dioxo-[14]aneN3S shows higher activity against several species from the Candida genus, which means that it has the potential to be developed as a promising new antinfungal agent.

The consumption of carotenoids has several health benefits. It is known that the fortification of olive oils with carotenoids, namely β-carotene or lutein, enhanced the oils’ physicochemical properties, being a possible strategy to increase carotenoids intake. This study showed that a lab-made potentiometric electronic tongue, comprising lipid sensor membranes, could discriminate non-fortified olive oils from those fortified with different levels β-carotene or lutein (repeated K-fold cross-validation sensitivities: 87 ± 8%), confirming the impact of the fortification on the oils’ phenolic contents and sensory sensations. Moreover, the device could, semi-quantitatively, discriminate oils fortified with different amounts (0, 0.05, 0.10, and 0.15 mg/mL) of each carotenoid (repeated K-fold cross-validation sensitivities: 94 ± 9% and 97 ± 7%, for β-carotene and lutein, respectively). This could be related to the capability of detecting increasing levels of the carotenoids and to the ability to assess the changes induced by the addition of carotenoids on the total phenols’ contents and on the intensities of the basic taste sensations. Indeed, satisfactory first- or second-order correlations could be established between the centroids of the first discriminant functions of the linear discriminant models and the carotenoid fortification levels, the total phenols contents, as well as with the sweetness, bitterness, and pungency intensities of the fortified oils (0.865 ≤ R2 ≤ 0.998). The successful qualitative and (semi-)quantitative performance of the electronic tongue may foresee its future application as a practical and cost-effective tool for assessing the impact of the fortification of olive oils with carotenoids at the carotenoids, phenols, and basic taste levels.

The development of bioinspired sensors has emerged and grown in recent decades, given their broad and exciting applications to pharmaceutical formulations, medical diagnosis and health care. These sensor-based technologies, owing to their function and to the elements involved in their design, potentially generate fast, selective, sensitive, safe and green analysis solutions. Their applications have evolved into mainly two fields. The first comprises sensor array systems like the electronic tongues (E-tongues), which are innovative (bio)sensing devices that, combined with chemometric tools, provide highly specialized responses, enabling the discrimination of thousands of possible targets. The second line of action involves the application of biosensors, namely aptasensors, which are highly specific against a target biomarker. In this chapter, the concept, design and application of electrochemical sensor approaches, such as E-tongues and aptasensors, for (bio)sensing applications, will be discussed and the main trends in medical and pharmaceutical applications will be highlighted.