Recovery Values Research Articles

Optimization of co-injecting CH4 with CO2 to enhanced oil recovery and carbon storage: A machine-learning based case study on H59 block of Jilin Oilfield, China

During CO2-EOR implementation, CH4 in the reproduced CO2-rich mixture are included in the recycle injection gas. However, improper injection gas composition and operation parameters can reduce the flooding performance.In this study, a machine-learning assisted framework combining Convolutional Neural Networks-Gate Recurrent Unit (CNN-GRU) and Non-dominated Sorting Genetic Algorithm II (NSGA-II) was proposed to obtain the optimal parameters for simultaneous maximum oil production, carbon storage efficiency, and net present value. A case study from the CO2-EOR project in the H59 block of Jilin oilfield, China, was carried out. Base cases were established to evaluate the effects of reinjection CH4 on flooding performance.Results show that the built CNN-GRU model has high prediction accuracy and computational efficiency, and thus can be used as an alternative tool to the reservoir simulator. The proposed framework can find the optimum parameters to improve oil recovery, carbon storage and net present value. The co-injection of CH4 and CO2 improves oil production, and carbon storage performance, but reduces the net present value. This work provides engineers with multiple strategies for decision-making to simultaneously promote flooding performance with CH4 being a co-injectant in CO2-EOR projects.

Applicability of QbD-assisted Analytical Method for Simultaneous Detection of Tetrahydrocurcumin and Folic Acid in Developed Nanostructured Lipid Carriers

Aims: Applicability of QbD-assisted analytical method for simultaneous detection of tetrahydrocurcumin and folic acid in developed nanostructured. Background: Diabetic foot ulcer (DFU) is a multifactorial disorder that involves chronic inflammation, oxidative stress and neuropathy. Current treatment therapies involving the use of growth factors and skin substitutes being costly, are out of reach for the majority of patients. The present research explored the usefulness of (5929IN008, application number 202211045937), a combination of tetrahydrocurcumin and folic acid-loaded nanostructured lipidic carriers. Objectives: To develop and validate a QbD-assisted method for simultaneous analysis of tetrahydrocurcumin (THC) and folic acid (FA). Applicability of the above method to determine total drug content (TDC) and entrapment efficiency (EE) of nanostructured lipid carriers (NLCs) loaded THC and FA. Methods: A high-performance liquid chromatographic (HPLC) method was developed, optimized and validated using Box-Behnken design for improved method performance. Chromatographic separation was conducted on a Supelco 250 x 4.6 mm (5 μm) column with optimized mobile phase composition containing tetrahydrofuran: citric acid buffer pH 3.5 (50:50) at a flow rate of 0.4 mL.min-1 and diode array detection between 210 and 360 nm. Results: The method developed in a concentration range of 1 to 100 μg.mL-1 was found to be linear (R2 0.999, p≤0.001), accurate (99.10-101.70%) and precise with high recovery values in intra and inter-day results. The system adaptability and robustness evaluation revealed that the percent recovery ranged from 96.90 to 102.80%, and the percent relative standard deviation (%RSD) values were less than 2%. Moreover, the method was further applied for the determination of TDC (86±6% and 96±8%) and drug EE (81±21% and 73±13%) for THC and FA, respectively. Conclusion: The investigation indicated the applicability of the developed and validated method for the estimation of THC and FA in the developed nanostructured lipidic carriers.

A hand-drawn graphite electrode for affordable analysis: Application to the enzymatic determination of tyramine in fish

The development of simpler and greener, but also reliable and efficient analytical sensors that meet the increasing global demands is a current challenge. In this work, a user-friendly and low-cost electrochemical cell was developed by combining two metallic wires (from a standard connector header) and a working electrode fabricated by pencil hand-drawing, which is one of the simplest, cheapest, and greenest ways of creating miniaturized electrodes. Graphite pencils with different degrees of hardness were tested and, using a 6B pencil, an electroanalytical platform with high precision (RSD < 5 %) was achieved. This platform was used as transducer for constructing an enzymatic biosensor for the determination of tyramine, using tyrosinase as the biological recognition element. After the optimization of several parameters, the biosensor showed a linear range between 5 and 150 mg·L−1, a limit of detection of 0.4 mg·L−1, and high selectivity for tyramine with no interference from other biogenic amines. This biosensor was successfully applied to the analysis of different fish species achieving recovery values between 87 % and 100 %. Its usefulness for monitoring tyramine concentration during the spoilage of a sardine sample was also demonstrated. Therefore, this cheap and miniaturized biosensor represents an interesting alternative for tyramine determination. Moreover, the good electrochemical features of the developed electrochemical cell demonstrated its potential for the development of future electrochemical sensors.

Vortex-Assisted Magnetic Solid-Phase Extraction of Heavy Metals in Water and Food Samples Using Iron Oxide Nanoparticle-Impregnated Carboxymethyl-β-Cyclodextrin.

The excessive accumulation of heavy metals has adverse effects on the human body. Here, magnetic iron oxide-impregnated carboxymethyl-β-cyclodextrin was synthesized. The synthesized material was employed as a magnetic solid-phase extracting adsorbent for specific heavy metals like lead (Pb), nickel (Ni), copper (Cu), and cobalt (Co). Characterization was performed by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, and Fourier-transform infrared spectroscopy. The analytical merits, like detection limits (Pb: 1.38ng/mL, Ni: 0.5ng/mL, Co: 0.14ng/mL, and Cu: 0.55ng/mL) andquantification limits (Pb: 4.14ng/mL, Ni: 1.62ng/mL, Co: 1.85ng/mL, and Cu: 1.82ng/mL) were calculated. Similarly, the preconcentration and enhancement factors (15) and relative standard deviation (Pb: 3.5, Ni: 0.92, Co: 2.7, and Cu: 1.5) were also calculated. The interfering study shows that the method is highly selective. For validation, it was applied to certified reference materials such as the Institute of Nuclear Chemistry and Technology ornamental Basma tobacco leaves and trace metal double addition 63.4 environmental water with good percent recovery values (92%-99%). Real water and food samples were also used with satisfactory (90%-99%) recovery results.

Azo Coupling Reaction for Spectrophotometric Determination of Sulfanilamide Using β -Naphthol as a Reagent

This research is based on one simple and good method for determining sulfanilamide in its pure state and in pharmaceutical preparations. Spectrophotometric determination of Sulfanilamide using the azo coupling reaction in an aqueous solution and several standard solutions were prepared. The optimal conditions were also studied. The effects of the type of acid and its volume, the influence of the base type and its volume, the effect of reagent volume (100 µg/ml), the effect of reaction time on the color stability of the product, the effect of adding sequence, the solvent effect, and the effect of temperature on the formation and stability of the colored product. The product for the Sulfanilamide drug is auburn at a wavelength of 489 nm; the method obeyed Beer's law in a range of concentrations ranging from 1–12 µg/ml; and the molar absorptivity was 28840.76 L/mol.cm. Sandal's sensitivity (0.00091 μg/cm), detection limit (0.2472 µg/ml), correlation coefficient value 0.9984, and RSD% value 0.01365, By applying the method to a pharmaceutical preparation containing Sulfanilamide, the recovery value ranged between 102.1306%.

Analysis of short-term self-healing performance of asphalt mixture under a three-point bending fatigue test

To evaluate the self-healing performance of asphalt mixture under repeated loads, indoor three-point bending fatigue tests and self-healing tests were conducted on asphalt mixture AC-13. The stress control mode was selected to test the fatigue resistance of the mixture, and the dissipated energy recovery value and visco-elastic ratio were proposed to evaluate the self-healing performance of the mixture. The experimental results show that there is a good linear relationship between fatigue life and fatigue stress, and the damage degree to the mixture is exponentially related to the load times. The numerical dispersion of flexural tensile modulus is large, which is not suitable for evaluating the self-healing performance of the mixture. As the number of loading cycles increases, the hysteresis dissipated energy of the mixture gradually decreases and tends to stabilize. After the loading interval, due to the self-healing effect, the visco-elastic performance of the asphalt material is partially restored. The initial dissipated energy before and after interval can be used as an evaluation index for self-healing behavior, and there is a good linear relationship between the initial dissipated energy and the damage degree. Due to the deformation migration of the mixture during the initial loading stage before and after interval, the visco-elastic ratio has changed, and this change becomes more pronounced with the damage degree of the mixture, indicating that the self-healing ability of the mixture has also been improved.

Nessler Method Verification for Determining Ammonia in Shrimp Pond Wastewater and Its Application in the Ammonia Adsorption Test with Lampung Natural Zeolite

Ammonia levels exceeding 0.50 mg/L can threaten organisms in aquatic environments. The Nessler method is one of the ammonia analysis methods based on the reaction between ammonia in a basic solution and Nessler reagent (K&lt;sub&gt;2&lt;/sub&gt;HgI&lt;sub&gt;4&lt;/sub&gt;), forming a colloidal dispersion with a brownish-yellow colour. The colour intensity is determined by spectrophotometry. This research aims to verify the Nessler method for determining ammonia levels in shrimp pond wastewater. The research results indicate that the Nessler method shows good linearity in the range of ammonia concentrations from 1 to 5 mg/L, with a correlation coefficient (R&lt;sup&gt;2&lt;/sup&gt;) value of 0.9962. The precision value was determined from repeatability, expressed as %RSD (Relative Standard Deviation), i.e., 1.92%, and it meets acceptance criteria, which should be less than 0.5 of the Horwitz RSD. The accuracy obtained from the standard addition method provides a percentage recovery value of 99.25%, meeting the AOAC acceptance criteria. The detection limit and quantification limit of the technique are 0.3883 mg/L and 1.2943 mg/L, respectively. The verified method is then applied to analyze shrimp pond wastewater samples from Sriminosari Village, East Lampung, resulting in an ammonia concentration of 1.52 mg/L. The ammonia levels were then reduced by adsorption with natural zeolite Lampung, decreasing ammonia levels by 20.30%. Meanwhile, adsorption with an activated zeolite reduced the ammonia levels by 45.30%.

Supramolecular Solvent Liquid Phase Microextraction of Voriconazole İn Pharmaceutical and Environmental Samples With High Performance Liquid Chromatography Detection

In this study, a new analytical method based on the supramolecular solvent liquid phase microextraction (Ss-LPME) and HPLC was developed for the analysis of voriconazole as an active drug in the class of antifungals with a wide spectrum of action at trace levels. Nano/micro sized supramolecular phase formed in 1-decanol, tetrahydrofuran and aqueous environment was used as extraction agent for separation and preconcentration of trace level of voriconazole. For the optimization of the Ss-LPME method, important analytical parameters such as the effect of sample solution pH, volume of 1-decanol, amount of THF, ultrasounic irridation time, centrifugation time and sample solution volume on the extraction efficiency were evaluated. Optimal conditions of the Ss-LPME; pH: 8, 1-decanol volume: 200 µL, THF volume: 300 µL, ultrasounic irridation time:10 min and centrifugation time: 8 min. For the developed Ss-LPME/HPLC procedure, the limit of detection (LOD), limit of quantification (LOQ) and enhancement factor (EF) were found 2.7 µg·L-1, 8.8 µg·L-1 and 36, respectively. The Ss-LPME/HPLC procedure was applied to waste water, lake water and drug samples. The fact that recovery values ranging from 100% to 108.5% were obtained for these real samples proved that this method can be used successfully in the matrix environments studied

Study on the deployment of differentiated well patterns for shale gas in southern Sichuan region

Shale gas blocks are of great geological differences in southern Sichuan, deploying differentiated well patterns accordingly is therefore significant. For two typical shale gas blocks in southern Sichuan, Dingshan normal pressure area and Yongchuan south area, a hydraulic fracturing interlayer law model based on the cohesive zone model and a fracture extension model based on rock damage theory were established. Hydraulic fracture height and length charts under different natural fracture density and operation parameters were drawn. Using these charts, fracture parameters in different areas were determined, and hydraulic and natural fracture models were established. By coupling an embedded discrete fracture model with geological models and fracture models, a complex fracture network simulation model was built to predict gas production. Horizontal well spacing, orientation, and length were optimized under different geological characteristics to maximize production and economic indicators, and a differentiated well pattern deployment strategy was proposed. Results show that, firstly, for Dingshan area, the fracture height range is 40-64 m with an average of 51 m, that of Yongchuan is 42-65 m with an average of 53 m. The fracture length range of Dingshan area is 215-350 m with an average of 300 m, whereas that of Yongchuan is 290-350 m with an average of 330 m. The optimal horizontal well spacing in Dingshan area is 300 m, the optimal well orientation is 60°-90°, and the optimal lateral length is 2000 m; and those of Yongchuan are 300 m, 90°, and 1680 m. Well pattern on-site can be adjusted according to the optimal parameters to achieve higher Estimated Ultimate Recovery (EUR) and Net Present Value (NPV).

Exploiting a carbon black paste electrode modified with palladium nanoparticles entrapped in aluminum hydroxide matrix for selective detection of 2(3)-t-Butyl-4-hydroxyanisole antioxidant in biodiesel samples

A simple and selective method for determination of 2(3)-t-Butyl-4-hydroxyanisole (BHA) based on carbon black (CB) paste electrode modified with Palladium nanoparticles entrapped in aluminum hydroxide matrix (PdNPAH) is described for the first time. The materials were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The composition of the paste was studied using different amounts of each material. The voltammetric studies of the behavior of BHA on PdNPAH/CBP electrode demonstrated a catalytic activity for the oxidation process of BHA. Also, the voltammetric studies showed that it is possible to determine BHA in presence of 3,5-Di-tert-butyl-4-hydroxytoluene (BHT) and 2-(1,1-Dimethylethyl)-1,4-benzenediol (TBHQ). Under optimized conditions, the method showed a linear response for BHA from 1-5000 µmol/L and a detection limit of 0.20 µmol/L. The proposed method presented good selectivity, precision and it was successfully applied for detection of BHA in biofuel with recovery values from 98.80 % to 105.29 %, showing a good accuracy for the proposed method.

Application of UHPLC-QqQ-MS/MS Method for Quantification of Beta-Adrenergic Blocking Agents (β-Blockers) in Human Postmortem Specimens.

Betablockers are one of the most frequently used medications in cardiology. They can lead to fatal drops in blood pressure and heart rhythm disturbances. Death is functional, and poisoning with this group of drugs can be difficult to detect. The liquid-liquid extraction (LLE) method developed using ethyl acetate at pH 9 successfully identified 18 β-blockers in human blood. The method's limit of quantification (LOQ) was in the range of 0.1 to 0.5 ng/mL. No carryover of substances between samples was detected, and no interfering ion current signals were observed in the biological samples at the retention times of the compounds or internal standards. All compounds had a coefficient of determination (R2) above 0.995. Intraday and interday precision (RSD%) and accuracy (RE%) for low and high QC levels were within 1.7-12.3% and -14.4 to 14.1%, respectively. Very good recovery (80.0-119.6%) and matrix effect (±20.0%) values were achieved for all compounds. In addition, fragmentation spectra were collected for all the examined substances, and high-resolution spectra were presented for landiolol and metipranolol, because they are not available in commercial HRMS spectra databases. The developed method was applied in authentic postmortem samples.

Heart rate response and recovery in cycle exercise testing - normal values and association with mortality.

Chronotropic incompetence and impaired heart rate (HR) recovery are related to mortality. Guidelines lack specific reference values for HR recovery. We defined normal values and studied blunted HR response and recovery, and mortality risk. We included 9,917 subjects (45% females) aged 18-85 years who performed a cycle exercise test. We defined normal values for peak HR, HR reserve, and HR recovery at 1 and 2 minutes (HRR1 and HRR2) based on individuals apparently healthy (N=2,242). Associations between blunted HR indices (<5th percentile) and mortality over a median follow-up of 8.6 years were analysed using Cox regression and competing risk analysis. All HR indices were age-dependent and independent predictors of all-cause and CV mortality. The 5th percentiles of HR reserve, HRR1, and HRR2 correlated weakly with existing reference values. HR recovery variables were the strongest predictors of all-cause mortality (HRR1, hazard ratio 1.70 [95% confidence interval, 1.49-1.94] and HRR2, 1.57 [1.37-1.79]), including in subjects with normal exercise capacity (HRR1, 1.96 [1.61-2.39] and HRR2, 1.76 [1.46-2.12]). Combining HR indices appeared to increase the risk of all-cause (HRR1 and HRR2, 1.96 [1.68-2.29] and peak HR and HRR1, 1.87 [1.56-2.23]) and CV mortality, although no specific combination was superior for predicting CV mortality. All HR variables were age-dependent and associated with all-cause and CV mortality. Blunted HR recovery variables were the strongest predictors of all-cause mortality, even in subjects with normal exercise capacity. Combined blunted HR indices appeared to add prognostic value.

Natural deep eutectic solvent-based dispersive liquid-liquid microextraction of pesticides in drinking waters combined with GC-MS/MS detection

The current research aims to develop a new analytical method applying a dispersive liquid-liquid microextraction (DLLME) assisted by vortex and using an environmentally friendly extractant for the preconcentration of organochlorine and organophosphorus pesticides followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. The extractant (i.e., natural deep eutectic solvent (NADES)) is safe, cheap, biodegradable and can be prepared by simply mixing DL-menthol and decanoic acid (molar ratio 2:1). The main experimental factors affecting the extraction of all analytes evaluated (19 organochlorine and organophosphorus pesticides) have been optimised using a multivariate analysis consisting in two steps: a Plackett-Burman design followed by a central composite design (CCD). Seven experimental factors have been evaluated: (i) sample volume; (ii) NADES volume; (iii) sample pH; (iv) extraction time; (v) centrifugation time; (vi) centrifugation speed; and (vii) ionic strength (NaCl %, w v−1). For the significant variables, the optimum values were 10 mL sample and 45 μL NADES. No pH adjustment as well as addition of NaCl were needed. The other variables were set at 3 min extraction time, 5 min centrifugation time and 900×g centrifugation speed, respectively. Under the optimised extraction conditions, the limit of quantification (LOQ) values ranged between 0.2 and 78 ng L−1 for all analysed pesticides. Furthermore, the proposed analytical method has been successfully applied to drinking water (bottled spring water). The recovery study (n = 3) has been evaluated at 0.1, 1.0 and 5.0 μg L−1 spiking levels, obtaining relative recovery values within the range of 70 % and 117 % and RSD values between 1 % and 20 % for all the analytes studied, except for p,p-DDT (56–77 % in high conductivity water samples).

Small Molecule Detection with Ligation-Dependent Light-Up Aptamer Transcriptional Amplification.

ATP and NAD+ are small biomolecules that participate in a variety of physiological functions and are considered as potential biomarkers for disease diagnosis. In this study, we developed a ligation-dependent light-up aptamer transcriptional amplification assay for the sensitive and selective detection of ATP and NAD+. This assay relies on a specific DNA ligase that catalyzes the ligation of a nicked DNA template in the presence of a specific small molecule. We prepared a nicked template consisting of a duplex fragment with an overhang for the T7 promoter region and a single-stranded DNA with a complementary overhang sequence for the Broccoli aptamer. The nicked template was connected using a DNA ligase in the presence of a specific small molecule. The ligation product was subjected to in vitro transcription to amplify the light-up aptamer-mediated fluorescence signals. By integrating the target-dependent ligation and transcription amplification, significant signal amplification was achieved with 5.9 and 142 pM detection limits for ATP and NAD+, respectively. Moreover, good selectivity to discriminate between the target and its analogues was also realized. The application of this method to biological samples was evaluated using human serum and exhibited excellent recovery values.

A non-enzymatic hydrogen peroxide biosensor based on cerium metal-organic frameworks, hemin, and graphene oxide composite

This study presents the development of a novel non-enzymatic electrochemical biosensor for the real-time detection of hydrogen peroxide (H2O2) based on a composite of cerium metal–organic frameworks (Ce-MOFs), hemin, and graphene oxide (GO). The Ce-MOFs served as an efficient matrix for hemin encapsulation, while GO enhanced the conductivity of the composite. Characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, and thermogravimetric analysis (TGA) confirmed the successful integration of hemin into the Ce-MOFs. The Ce-MOFs@hemin/GO-modified sensor demonstrated sensitive H2O2 detection due to the exceptional electrocatalytic activity of Ce-MOFs@hemin and the high conductivity of GO. This biosensor exhibited a linear response to H2O2 concentrations from 0.05 to 10 mM with a limit of detection (LOD) of 9.3 μM. The capability of the biosensor to detect H2O2 released from human prostate carcinoma cells was demonstrated, highlighting its potential for real-time monitoring of cellular oxidative stress in complex biological environments. To further assess its practical applicability, the sensor was tested in human serum samples, yielding promising results with recovery values ranging from 94.50 % to 103.29 %. In addition, the sensor showed excellent selectivity against common interfering compounds due to the outstanding peroxidase-like activity of the composite.

L-asparaginase-mediated pH shift and carbon dot fluorescence modulation: A sensitive ratiometric method for quantifying L-asparagine in diverse potato varieties under variable storage conditions

This study presents a novel and selective method for the determination of l-asparagine in diverse potato varieties under various storage conditions. L-asparagine levels serve as a crucial indicator for acrylamide formation, a hazardous substance in processed potato products. The fluorometric method utilized blue-emitting CDs (B-CDs), orange-emitting CDs (O-CDs), and the enzyme L-asparaginase for ratiometric detection of L-asparagine. Upon enzymatic hydrolysis of L-asparagine by L-asparaginase, liberated ammonia induced a pH increase in the reaction medium. This pH shift enhanced the fluorescence of B-CDs while simultaneously decreasing that of O-CDs, enabling sensitive and selective L-asparagine quantification. Comprehensive characterization of the CDs was performed using various spectroscopic techniques and transmission electron microscopy. The method demonstrated excellent sensitivity (LOD = 0.31 μM) and a wide linear range (1.0–50.0 μM). When the method was applied to potato samples, high recovery values (98.00–100.33 %) with low relative standard deviations (RSDs) were achieved, confirming the accuracy and precision of the method. The approach was employed to determine L-asparagine levels in three potato varieties (Lady Rosetta, Spunta, and Nicola) under different storage temperatures and durations. This method provides a valuable tool for monitoring L-asparagine content in potatoes, potentially aiding in the mitigation of acrylamide formation during processing. The robust performance and simplicity of the proposed technique make it suitable for routine analysis in both research and industrial applications within the potato industry.

A Reliable and Straightforward Combination of vortex-assisted Dispersive Magnetic solid-phase Extraction with Direct Sorbent Sampling for Highly Sensitive Silver Determination in Water Samples Using Flame and Metal Furnace AAS.

In the present paper, the assessment of vortex-assisted dispersive magnetic solid-phase extraction using amino-functionalized mesoporous combined with direct magnetic sorbent sampling (DMSS) in flame or furnace atomic absorption spectrometry (FAAS or FF-AAS) was demonstrated for highly sensitive silver determination in water samples. The developed method showed significant enrichment factors compared to conventional pneumatic nebulization by FAAS, 607 for DMSS-FF-AAS and 114 for DMSS-FAAS. The analytical curve showed linearity in the range from 5.0 to 70.0µg L- 1 and 1.0 to 15.0µg L- 1 and limits of detection of 0.59 and 0.09µg L- 1 for DMSS-FAAS and DMSS-FF-AAS, respectively. The intra and inter-day precision evaluated as a percentage of the relative standard deviation (RSD,%) ranged from 1.89 to 4.71% for levels of 25.0 and 65.0µg L- 1. The method was applied in different kinds of water samples without matrix effects, yielding recovery values from 90 to 110%.

Lab-on-a-chip paper-based electrochemically assisted solid-phase microextraction and ion selective sensor for determination of naproxen in biological fluid samples

BackgroundThe integration of paper-based analytical devices with lab-on-a-chip technology has opened up new possibilities for miniaturized, rapid, low cost and portable diagnostic testing in resource limited settings. This work introduces an integrated lab-on-a-chip platform coupling paper-based analytical devices (LOC-PADs) for dual usage: electrochemically controlled solid-phase microextraction (EC-SPME) and determination of naproxen (NAP) by potentiometric ion-selective electrode (ISE) in biological samples. ResultsConductive papers were successfully fabricated by a chemical procedure. Thereupon, a conducting molecularly imprinted polymer (CMIP) film based on PPy and an anionic model drug (NAP) as a template were applied to the conductive paper substrate via electrochemical methods. A microfluidic chip device was employed to assess the analytical performance of the fabricated paper-based CMIP. The designed chip is divided into two parts with a microfluidic channel between them. The first chamber is an extraction zone for EC-SPME of NAP by using the CMIP paper as a selective sorbent. The second chamber is the detection zone and consists of a paper-based NAP ion selective sensor for potentiometric detection of drug. The analytical process was investigated and optimized for each chamber. Remarkable selectivity towards NAP was achieved in the concentration range from 4.0 × 10−7 to 1.0 × 10−2 mol L−1 with determination coefficient (R2 = 0.99) and the limit of detection (LOD) was 2.0 × 10−7 mol L−1. Anionic Nernstian compliance was gained −58.5 ± 0.5 mV decade−1, and response time in the detection step was 7s for ISE. Satisfactory spiking recovery values within the acceptable range of 90–110 % with RSDs ≤7 % were achieved for the analysis of real samples with fully portable LOC device. SignificanceThe LOC-PADs were favorably used for selective extraction and determination of NAP in serum and saliva samples, respectively. EC-SPME caused sample clean-up, reduced or eliminated different interferences and enhanced selective response of ISE as detection zone of device. Integration of EC-SPME and ISE in a single chip enabled easy and fast determination of trace amounts of NAP in limited real sample volumes, and fully portable advantages.

Fluorescence-based determination of tobramycin using a portable smartphone-based device

The study presents the development of a robust portable smartphone-based device for determining tobramycin in drugs and urine by a fluorescence-based method. As existing analytical methods for the determination of tobramycin often require complex equipment and time-consuming procedures, the proposed approach offers simplicity, portability and real-time monitoring capabilities. The spectrofluorimetric method is based on the reaction of tobramycin and fluorescamine in an alkaline medium. The measurement of analytical signals was enabled with a specially designed device integrating a 3D printed adapter, LEDs, a macro lens, an Arduino-based microcontroller, and asmartphone. The traditional spectrofluorimetry was used as a reference method. Preliminary and optimisation studies were conducted to select the most suitable experimental conditions (e.g. reagent concentration and reaction time) as well as instrumental parameters (e.g. selection of the appropriate RGB model component, ISO, and white balance). The performance of the method was validated, and then verified against conventional spectrofluorimetry, showing comparable accuracy and precision. The method implemented in a smartphone-based device showed a linear range of 0.10–1.00 mgL-1 with a detection limit of 0.03 mgL-1. Synthetic samples were tested to verify analytical usability, followed by analysis of pharmaceutical and urine samples. The method showed good precision (CV<3.4 %) and recovery values (92.3–114.1 %), consistent with spectrofluorimetric results (CV<5.9 %, recovery 92.3–119.8 %). Comparison with other methods highlighted the simplicity and efficiency of the developed approach. The research reveals that it is competitive with existing well-established methods. The proposed device offers reliable results with low reagent and sample consumption, making itsuitable for on-the-go analysis in non-laboratory conditions.

Evaluation of the presence of emerging contaminants in wastewater and seawater using automated solid-phase extraction and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

The presence of emerging contaminants in water constitutes one of the main ways of human exposure to them, which can cause severe effects on health. In this sense, their adequate elimination through appropriate treatments plays a fundamental role, being necessary to monitor the effluents from wastewater treatment plants, as well as the areas close to their discharge. The aim of the present work has been the development and validation of an analytical methodology to determine 15 organic contaminants of emerging concern in wastewater as well as in seawater samples using an automated solid-phase extraction system and an ultra-high-performance liquid chromatography coupled to tandem mass spectrometry instrument. Matrix-matched calibration showed good linearity with determination coefficients ≥ 0.990. Likewise, matrix effect assessment showed a significant signal suppression in almost all the analytes demonstrating the need to consider such effect for a proper quantification of the analytes. Recovery values ranged from 74.7 to 109% with relative standard deviation values ≤ 20.5% for most analytes. Regarding seawater and wastewater samples, 11 of the target analytes were detected in, at least, one sample at concentrations from below limit of quantification of the method to 217 ± 92 ng l-1 in seawater and up to 2340 ± 107 ng l-1 in wastewater samples.