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A simple and reliable methodology for the detection of paralytic shellfish toxins (PSTs) in bivalve tissues using potentiometric chemical sensors was developed. Five methods of PST extraction from mussel and oyster tissues were evaluated, including the AOAC-recommended method, which served as the reference. The main objective was to minimize the matrix effect of the extracts on the sensors' responses and ensure efficient toxin recovery. Extraction procedures using acetic acid with heating and water yielded the highest responses from the potentiometric chemical sensors to PSTs. The highest recovery of PSTs from bivalve tissues was achieved with extraction using acetic acid and heating. Further extract purification, which is indispensable for liquid chromatography with fluorometric detection (LC-FLD) analysis, was found to be unnecessary for analysis with chemical sensors. While water extraction can also be used as a rapid and simple PST extraction method, the lower recoveries should be considered when interpreting the results. Further research is needed to identify the compounds remaining in the extracts that cause a decrease in sensor responses and to develop procedures for their elimination. [ABSTRACT FROM AUTHOR]

The performance of an electronic tongue can be optimized by varying the number and types of sensors in the array and by employing data-processing methods. Sensor selection is typically performed empirically, with sensors picked up either by analyzing their characteristics or through trial and error, which does not guarantee an optimized sensor array composition. This study focuses on developing a method for sensor selection for an electronic tongue using simulated sensor data and Lasso regularization. Simulated sensor responses were calculated using sensor parameters such as sensitivity and selectivity, which were determined in the individual analyte solutions. Sensor selection was carried out using Lasso regularization, which removes redundant or highly correlated variables without much loss of information. The objective of the optimization of the sensor array was twofold, aiming to minimize both quantification errors and the number of sensors in the array. The quantification of toxins belonging to one of the groups of marine toxins—paralytic shellfish toxins (PSTs)—using arrays of potentiometric chemical sensors was used as a case study. Eight PSTs corresponding to the toxin profiles in bivalves due to the two common toxin-producing phytoplankton species, G. catenatum (dcSTX, GTX5, GTX6, and C1+2) and A. minitum (STX, GTX2+3), as well as total sample toxicity, were included in the study. Experimental validation with mixed solutions of two groups of toxins confirmed the suitability of the proposed method of sensor array optimization with better performance obtained for the a priori optimized sensor arrays. The results indicate that the use of simulated sensor responses and Lasso regularization is a rapid and efficient method for the selection of an optimized sensor array. [ABSTRACT FROM AUTHOR]

Port wine's prominence worldwide is unequivocal and the grape spirit, which comprises roughly one fifth of the total volume of this fortified wine, is also a contributor to the recognized quality of this beverage. Nonetheless, information about the influence of the grape spirit on the final aroma of Port wine, as well as its volatile composition, is extremely limited. Moreover, the aroma characteristics of Port wines are modulated mainly by their volatile profiles. Hence, this review presents a detailed overview of the volatile composition of the fortification spirit and Port wine, along with the methodologies employed for their characterization. Moreover, it gives a general overview of the Douro Demarcated Region (Portugal) and the relevance of fortification spirit to the production of Port wine. As far as we know, this review contains the most extensive database on the volatile composition of grape spirit and Port wine, corresponding to 23 and 208 compounds, respectively. To conclude, the global outlook and future challenges are addressed, with the position of the analytical coverage of the chemical data on volatile components discussed as crucial for the innovation centered on consumer preferences. [ABSTRACT FROM AUTHOR]

The evaluation of the variety suitability regarding each appellation's specificities should be a strategy for maximizing the varieties' oenological potential while contributing to the sustainable production of quality wines, keeping their typicity and rationalizing winemaking costs. Thus, the combination of several grape physicochemical attributes, modulated by climate and vineyard characteristics, providing knowledge for each grape variety's oenological potential, is a relevant and reliable support for winemakers' decisions. To prove this hypothesis, six mature grape varieties from three harvests, each one from three vineyard parcels with different topographical conditions from Bairrada Appellation (Portugal), were studied using analysis of variance–simultaneous components analysis (ASCA). The effects of harvest year and parcel on grape berry weight, pH, titratable acidity, total sugars, total phenolics, antiradical activity, and volatile composition in free and glycosidically-linked forms were analyzed. The compositional plasticity of autochthonous varieties (white Arinto and Bical and red Baga, Castelão, and Touriga Nacional) was observed. Sauvignon Blanc grape composition was significantly modulated by harvest. This study represents an important contribution for the maintenance of varieties' biodiversity while contributing to establishing their peculiarities. Autochthonous varieties, if accurately exploited, can provide higher characteristic diversity than worldwide used varieties, an aspect to be more objectively taken into consideration by winemakers. [ABSTRACT FROM AUTHOR]

Out of control proliferation of toxic phytoplankton, called harmful algal blooms (HABs), have a significant economic impact on bivalve aquaculture and harvesting in coastal waters. Some phytotoxins, such as paralytic shellfish toxins (PSTs), are of concern due to the life-threatening symptoms they can cause. Development of rapid and low-cost screening tools would be a welcome addition to the laboratory methodologies employed in routine monitoring programs. However, most of the assays and biosensors for the screening of PSTs, are restricted to a single target, saxitoxin (STX), which is the most potent PST. The present study aimed at developing an assay for the detection of N-sulfocarbamoyl PST—GTX5, which is one of the most abundant toxins in bivalves during G. catenatum blooms as found on the Portuguese coast. Enzymatic assay employing PSTs’ transforming enzyme—carbamoylase—was proposed. Carbamoylase was extracted and purified from the surf clam S. solida. Carbamoylase displayed similar specificity to both carbamate (STX) and N-sulfocarbamate toxins (GTX5 and C1+2) converting them into decarbamoyl saxitoxin (dcSTX) and decarbamoyl gonyautoxins 2+3 (dcGTX2+3), respectively. The enzymatic assay involved hydrolysis of GTX5 by carbamoylase and quantification of the product of enzymatic reaction, dcSTX, using a potentiometric chemical sensor. A potentiometric sensor with plasticized PVC membrane that displayed sensitivity to dcSTX and selectivity in the presence of GTX5 was employed. Enzymatic assay allowed determination of GTX5 in the concentration range from 0.43 to 3.30 µmolL−1, which encompasses levels of GTX5 in contaminated bivalve extracts with toxicities above PSTs regulatory limits. The feasibility of the carbamoylase-based potentiometric assay for detection of GTX5 was demonstrated. [ABSTRACT FROM AUTHOR]

Aging is associated with oxidative stress that may increase susceptibility to respiratory infections (RIs). We aimed to assess the impact of exercise training on the risk of RIs in older adults and on a targeted metabolomic profile of stress oxidative lipid peroxidation-related metabolites. Methods: In an 8-month clinical trial, 38 participants over 60 years of age were allocated to an exercise group (EG), in which participants underwent 90-min training sessions three times/week(n = 20), or a control group (CG), in which participants maintained daily physical activities(n = 18). Daily respiratory symptoms and RIs number and severity were collected. Serum by-products were assessed by comprehensive two-dimensional gas chromatography coupled to mass spectrometry with time of flight analyzer. Serum metabolomic profiling comprised 76 metabolites (alcohols, aldehydes, alkanes, and ketones). Principal components analysis and ANOVA-simultaneous component analysis were used to evaluate the metabolomic profile change. Results: The odds ratio of RIs for the EG was 2.0 CI 95% [0.2;25]. The incidence of RIs was 47% [23;70] in the EG vs. 44%[12;77] in the CG. The metabolomic profiling showed that alkanes and aldehydes classes differed between the EG and the CG before and after intervention. A calibration model showed a relation between the metabolites from four main classes (ketones, alcohols, alkanes and aldehydes) and the prediction of the number of RIs. Conclusion: Moderate exercise training, in older adults, compared with no exercise in controls, did not show a difference in the risk of RIs. A pattern of lipid peroxidation was associated with the number of RIs. [ABSTRACT FROM AUTHOR]

We hypothesize that oxidative stress induced by trichloramine exposure during swimming could be related to etiopathogenesis of asthma among elite swimmers. Aim To investigate the effect of a swimming training session on oxidative stress markers of asthmatic compared to non-asthmatic elite swimmers using exhaled breath ( EB) metabolomics. Methods Elite swimmers annually screened in our department (n=27) were invited and those who agreed to participate (n=20, of which 9 with asthma) had EB collected (Tedlar® bags) before and after a swimming training session. SPME fiber ( DVB/ CAR/ PDMS) was used to extract EB metabolites followed by a multidimensional gas chromatography analysis ( GC× GC-To FMS). Dataset comprises eight metabolites end products of lipid peroxidation: five aliphatic alkanes (nonane, 2,2,4,6,6-pentamethylheptane, decane, dodecane, and tetradecane) and three aldehydes (nonanal, decanal, and dodecanal). To assess exercise impact on lipid peroxidation markers, data were analyzed using principle component analysis ( PCA), which was run on the original data set and on the data set constructed using differences in the metabolite total areas before and after exercise session. Results Heatmap representation revealed that metabolites content decreased after exercise, both for control and asthma groups; however, the greater decrease was observed for controls. Asthmatics and controls did not form separated clusters; however, control swimmers demonstrated a more varied response to the exercise being dispersed along all score plot. Conclusion In well-trained athletes, swimming is associated with a decrease in oxidative stress markers independently of the presence of asthma, although a more pronounced decrease was seen in controls. [ABSTRACT FROM AUTHOR]

One of the obstacles to the practical use of the multisensor systems – electronic tongues is a drift, i.e. gradual change of the sensor characteristics occurring in the process of their exploitation. Sensor drift leads to the deterioration of the performance of the calibration model that was calculated before changes in the sensor responses occurred. Two approaches can be employed to deal with this phenomenon. One consists of regular re-calibration of the sensor array, which is effective but time and labor consuming. Alternatively, multivariate statistical methods can be applied to the calibration model update using small subset of the standard samples. While significant efforts have been directed to the development of the calibration transfer and calibration update techniques, they were mostly applied to the near infrared spectroscopic instruments. Very few works addressed this issue for the potentiometric sensor arrays. In the present study, applicability of calibration update methods including slope and bias correction, direct standardization using PLS2 regression and auto-associative neural network, calibration update by weighting, Tikhonov regularization and Joint Y-PLS regression to the sensor array data was evaluated. Calibration models for copper and lead quantification in mixed solutions of transition metals using an array of 7 potentiometric sensors was used as an example. Of all studied methods, weighting and JYPLS regression were shown to be the most effective permitting to reduce prediction error for new data to the level of cross-validation error for the initial data. [ABSTRACT FROM AUTHOR]

We report the optimization of the length of a D-shaped plastic optical fiber (POF) sensor for refractive index (RI) sensing from a numerical and experimental point of view. The sensing principle is based on total internal reflection (TIR). POFs with 1 mm in diameter were embedded in grooves, realized in planar supports with different lengths, and polished to remove the cladding and part of the core. All D-shaped POF sensors were tested using aqueous medium with different refractive indices (from 1.332 to 1.471) through intensity-based configuration. Results showed two different responses. Considering the refractive index (RI) range (1.33-1.39), the sensitivity and the resolution of the sensor were strongly dependent on the sensing region length. The highest sensitivity (resolution of 6.48 × 10-3 refractive index units, RIU) was obtained with 6 cm sensing length. In the RI range (1.41-1.47), the length of the sensing region was not a critical aspect to obtain the best resolution. These results enable the application of this optical platform for chemical and biochemical evanescent field sensing. The sensor production procedure is very simple, fast, and low-cost. [ABSTRACT FROM AUTHOR]

Chalcogenide glass electrode was applied to the detection of mercury(II) activity in the saline bromide buffers and artificial seawater at the activity levels corresponding to the acute toxicity. Mercury(II) toxicity in artificial seawater buffers and estuarine water was assessed using bioassay based on the luminescence of the marine bacterium A. fischeri. Electrode could detect mercury activity in the artificial seawater at the level of acute toxicity, which corresponded to pHg 23.2 (time of exposure 5 min.). Both electrode and bioassay indicated higher Hg2+ activity/toxicity in the estuarine water collected in the contaminated area. Quantification of Hg2+ activity in estuarine water using the mercury-selective electrode requires calibration procedure to account for matrix effects. [ABSTRACT FROM AUTHOR]

Hardwood and softwood lignins obtained from industrial sulphite and kraft and laboratory oxygen-organosolv pulping processes were employed in co-polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol). The obtained lignin-based polyurethanes were doped with 0.72 w/w% of multiwall carbon nanotubes (MWCNTs) with the aim of increasing their electrical conductivity to the levels suitable for sensor applications. Effects of the polymer doping with MWCNTs were assessed using electrical impedance (EIS) and UV-Resonance Raman (UV-RR) spectroscopy. Potentiometric sensors were prepared by drop casting of liquid polymer on the surface of carbon glass or platinum electrodes. Lignin-based sensors displayed a very low or no sensitivity to all alkali, alkali-earth and transition metal cations ions except Cr(vi) at pH 2. Response to Cr(vi) values of 39, 50 and 53 mV pX−1 for the sensors based on kraft, organosolv and lignosulphonate lignins, respectively, were observed. Redox sensitivity values close to the theoretical values of 20 and 21 mV pX−1 for organosolv and lignosulphonate based sensors respectively were detected in the Cr(iii)/Cr(vi) solutions while a very low response was observed in the solutions containing Fe(CN)63−/4−. Conducting composite lignin-based polyurethanes doped with MWCNTs were suggested as being promising materials for Cr(vi)-sensitive potentiometric sensors. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical impedance spectroscopy was applied to the study of conducting lignin-derived polymers to be used in all-solid-state potentiometric chemical sensors. Conducting polymers were produced by step-growth polymerization of modified eucalyptus kraft lignin with isocyanate and doped by multi-wall carbon nanotubes (MWCNTs). Lignin possesses ion-exchange properties due to the presence of a variety of functional groups, which makes it an attractive active substance for chemical sensing. Co-polymerization allows fixing lignin inside polymer matrix ensuring high stability of the resulting material. Doping of the lignin-based polyurethane with multi-wall carbon nanotubes (MWCNTs) was adopted as a mean to obtain electrically conductive system with low mass of filler. The direct current (DC) electrical conductivity and the dielectric properties of the conducting polymers have been evaluated at MWCNTs contents from 0 to 0.72% (wt.) at the frequencies between 40Hz and 100MHz in the temperature range −100 to 100°C. The percolation model theory was used to describe DC and the low frequency behaviour, where the electrical conductivity and the dielectric constant were expressed by scaling laws near the threshold conduction. The lignin-based polyurethane presented low critical concentration of MWCNTs around 0.18wt.%. The dielectric analysis was carried out using the modulus formalism and the dielectric relaxation behaviour was modelled using the Cole–Cole expression. [Copyright &y& Elsevier]

Modified eucalyptus kraft lignin doped with multiwall carbon nanotubes (MWCNTs) was used as a macromonomer in step-growth polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol) with the aim of producing a conductive copolymer for all-solid-state potentiometric chemical sensor applications. The crosslinked elastomeric polyurethane obtained was characterized by Fourier transform infrared attenuated total reflection spectroscopy, scanning electron microscopy, tunnelling electron microscopy and atomic force microscopy. Doping of lignin-based polyurethane with MWCNTs produced a significant enhancement of its electrical conductivity without deterioration of thermal and viscoelastic properties. The polymer composite displayed a low percolation threshold at an MWCNT concentration of 0.18% (w/w), which was explained by the oriented distribution of MWCNTs along lignin clusters. All lignin-based polyurethanes doped with MWCNTs at concentrations above the percolation threshold are suitable for sensor applications. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]