Extraction Of Analytes Research Articles

Quantitative assay for farnesol and the aromatic fusel alcohols from the fungus Candida albicans

The dimorphic fungus Candida albicans is a commensal and opportunistic fungal pathogen of humans. It secretes at least four small lipophilic molecules, farnesol and three aromatic fusel alcohols. Farnesol has been identified as both a quorum sensing molecule (QSM) and a virulence factor. Our gas chromatography (GC)-based assay for these molecules exhibits high throughput, prevention of analyte loss by avoiding filtration and rotary evaporation, simultaneous cell lysis and analyte extraction by ethyl acetate, and the ability to compare whole cultures with their cell pellets and supernatants. Farnesol synthesis and secretion were separable phenomena and pellet:supernatant ratios for farnesol were high, up to 12:1. The assay was validated in terms of precision, specificity, ruggedness, accuracy, solution stability, detection limits (DL), quantitation limits (QL), and dynamic range. The DL for farnesol was 0.02 ng/µl (0.09 µM). Measurement quality was assessed by the relative error of the whole culture versus the sum of pellet and supernatant fractions (WPS). C. albicans strain SC5314 grown at 30 °C in complex and defined media (YPD and mRPMI) was assayed in biological triplicate 17 times over 3 days. Farnesol and the three aromatic fusel alcohols can be measured in the same assay. The levels of all four are greatly altered by the growth medium chosen. Significantly, the three fusel alcohols are synthesized during stationary phase, not during growth. They are secreted quickly without being retained in the cell pellet and may accumulate up to mM concentrations.Key points• Quantitative analysis of both intra- and extracellular farnesol, and aromatic fusel oils.• High throughput, whole culture assay with simultaneous lysis and extraction.• Farnesol secretion and synthesis are distinct and separate events.

Enzyme-free colorimetric sensor based on molecularly imprinted polymer and ninhydrin for methamphetamine detection

Digital image colorimetry was applied to introduce a rapid, portable, and non-enzymatic test for methamphetamine measurements in urine. Imprinted polymer was synthesized in a simple, low-cost process and utilized for selective extraction of analyte from the sample in combination with the well-known ninhydrin color test. Applying the digital camera on a mobile phone, RGB basic color data were obtained, and calibration curves were developed for different concentrations of methamphetamine. Optimization of the test condition was carried out by changing some effective parameters such as extraction time and pH. The results were compared with some similar structural compounds indicating great potential for use as a selective and semi-quantitative field test for this drug. An acceptable linear range (5–100 μM) and detection limit (1.44 μM) as well as good agreement with the reference method, makes this fast portable method, an easy and reliable test for the analysis of methamphetamine in biological samples.

Dispersive liquid–liquid microextraction with back extraction based on in situ deep eutectic solvent decomposition and air-assisted for determination of some antidepressant drugs in biological samples prior to HPLC-UV

ABSTRACT In this study, a dispersive liquid–liquid microextraction along with a back-extraction step (DLLME-BE) has been developed for the determination of thre antidepressant drugs (citalopram, sertraline, and venlafaxine) in biological samples prior to HPLC-UV. Briefly, the method involved two main steps: first, a deep eutectic solvent (DES) composed of tetrabutylammonium bromide (TBABr as a dispersive agent) and 1-dodecanol (as the extraction solvent) was decomposed in an aqueous phase and led to in situ dispersion of the organic phase and extraction of analytes. . Second, Air-assisted liquid–liquid microextraction (AALLME) was applied to back-extract analytes into 50 µL of an aqueous acceptor phase while many interferences were not able to extract into the acceptor solution. By performing this developed extraction method, a high sample clean-up was achieved. The maximum efficiency of analytes was obtained based on the optimisation of the main parameters. Validation of the method indicated that the limits of detection (LODs) and limits of quantifications (LOQs) were in the range of 0.7–3.9 µg L−1 and 2.1–9.8 µg L−1 respectively. The extraction recoveries and enrichment factors of analytes were obtained to be in the range of 87.1–99.1% and 89–102, respectively. Finally, the method was utilised for extraction of three antidepressant drugs in water, human urine and plasma samples.

Application of nanostructured supramolecular solvent based on C12mimBr ionic liquid surfactant to direct extraction of some chlorophenols in soil and rice samples

In the proposed research, ionic liquid surfactant (C12-mimBr)-based nanostructured supramolecular solvent (IL-SUPRAS) was applied for direct extraction and preconcentration of three chlorophenols (CPs) in soil and rice samples before using gas chromatography-flame ionization detection (GC-FID) analysis. Mainly for extraction of analyte from a solid sample, an initial extraction step is performed using harmful organic solvents. Then, after evaporation of those solvents, the secondary extraction method is applied. The purpose of this research is direct extraction of some analytes from solid samples without performing the initial extraction step and using an adverse organic solvent. At first, IL-SUPRAS aggregation was prepared in a water solution. After that, an appropriate amount of it was introduced to the Eppendorf vial containing the solid sample. In the next step, to effectively extract the analytes from samples to the SUPRAS phase, the Eppendorf vial was vortexed and centrifuged, respectively. Finally, to prevent the entrance of the SUPRAS phase into the GC instrument, a back extraction step of the analytes was performed. The influence of effective parameters (i.e., pH of sample solution, vortex time, centrifuge time, and volume of THF) on the extraction procedure was investigated. Under optimum experimental conditions, the enrichment factors were obtained in the reasonable range of 103.2–134.6. The calibration curves also were linear in the range of 1.0–2000 µg L-1 with coefficients of determination (R2) more than 0.9962 for all three analytes. Limits of detection (S/N = 3) of 0.3–0.7 µg L-1, thelimits of quantification (LOQ) of 0.99–2.1 µg L-1, the relative standard deviations (RSDs %) composed of inter-day RSD (7.6–8.7) and intra-day RSD (6.3–7.6),and relative recoveries in the range of 77.4–93.6 % were obtained. The proposed method (IL-SUPRAS-DME) was successfully applied, for direct and fast extraction of CPs analytes in soil and rice samples.

Determination of methanol-derivatives in drying oils after metal oxide-based dispersive solid phase extraction/QuEChERS clean-up

The determination of secondary volatile degradation products in drying oil extracts is substantial to prevent formation of undesirable metal formates in paintings and/or other artefacts. This study develops a simple, cost-effective, and reliable, high-performance liquid chromatography with diode array detector (HPLC–DAD) method to determine three secondary volatile degradation products (methanol, formaldehyde, and formic acid) in drying oils, including linseed, poppy-seed, and walnut oil. Extraction of analytes was performed using QuEChERS-based procedure followed by metal oxide-based dispersive solid-phase extraction (d-SPE) clean-up and presented a good performance for all of the volatile analytes of interest with recoveries in the range of 90–120% after application of the nanostructured cerium oxide-based (CeO2) and zirconia-based (ZrO2) sorbents prepared by favorable and ecological-friendly methods. With a new clean-up solution for samples with high-fat content, it was possible to achieve higher recoveries than with commercial Z-Sep/C18 sorbent. In all cases, relative standard deviations (RSD) of less than 10% were achieved. No significant matrix interference was observed due to the application of effective sorbents in nanostructured form. The developed method was applied to samples of drying oils, and it was found that after storage for three months, all methanol was most likely oxidized to formaldehyde and formic acid. The concentrations of formaldehyde were in the range of 260 - 304 μg∙g−1, while formic acid concentrations ranged between 72 - 386 μg∙g−1. The highest concentration of formaldehyde (304 μg∙g−1) and formic acid (386 μg∙g−1) was found in linseed oil.

Electromembrane extraction of clenbuterol from swine urine for monitoring illegal use in livestock.

The illegal use of clenbuterol seriously endangers food safety and human health. Accurate monitoring of the illegal use of clenbuterol in livestock can efficiently prevent the clenbuterol residue pork products from entering the consumer market. Thus, in this study, a simple, rapid, and sensitive method for the determination of clenbuterol in swine urine was developed using electromembrane extraction combined with liquid chromatography-tandem mass spectrometry. It should be noted that the electromembrane extraction method presented many advantages of simple operation, fast mass transfer rate, good sample clean-up capability, and less organic solvent consumption. The effect of important factors on the extraction efficiency of clenbuterol was investigated. Under the optimal conditions, good linearity was achieved for clenbuterol over the range of 1-1000ng/ml (linear correlation [R2 ] =0.9996). The recoveries of clenbuterol in swine urine at three spiked levels ranged from 83.7% to 110.0% with relative standard deviation values lower than 9.7% (n=4). The limits of detection and quantification for clenbuterol were 0.07 and 0.25ng/ml, respectively. These results suggested that the proposed method has great potential for the extraction and determination of trace analyte in a complex sample matrix for monitoring illegal use in livestock.

Can Direct-Immersion Aqueous–Aqueous Microextraction Be Achieved When Using a Single-Drop System?

For the analysis of biological analytes in complex matrices, it is difficult to achieve extraction of analytes and enrichment in an aqueous-aqueous single-drop microextraction system. In this study, we proposed a pH-dependent polydopamine (PDA)-coated vesicle/Fe3O4 magnetic aqueous-aqueous in a single-drop microreactor (SDMR) for the direct fluorescence detection of glutathione S-transferase (GST), a metabolic enzyme involved with crucial biological processes, in biological samples. After extracting and enriching the GST target from an aqueous-aqueous single-drop interface, the extraction process was conducted rapidly in 6 s in the SDMR system. The GST was first extracted from the sample solution via the GST-Aptamer on the polydopamine-coated vesicle/Fe3O4 nanospheres (Fe3O4@PDA@GST-Aptamer). Then, as the pH changed from weakly acidic to weakly alkaline in the SDMR system, the GST and GST-Aptamer were released from Fe3O4@PDA@GST-Aptamer nanospheres and captured by polydiacetylene vesicles via the capture probe. These changes altered the effective conjugation length and angle of the vesicle trunk, generating a highly enhanced fluorescence signal. This not only achieved the purpose of target enrichment but also reduced interferences posed by matrix effects. The approach can be used for the direct detection of GST in genuine urine and blood without any sample pretreatment. The linear range was 0.005 to 0.5 μg/mL, and the limit of detection was 0.834 ng/mL. The recoveries of GST in genuine blood samples ranged from 90.8 to 108.0% and in urine from 91.6 to 102.8%. The method has the capability of handling complex samples directly by enabling microextraction in an aqueous-aqueous single-drop system.

Fabric-to-cementitious matrix bond behavior in carbon fabric reinforced cementitious matrix (FRCM) composites with added short fibers

Fabric reinforced cementitious matrix (FRCM) composites are promising composite materials with useful properties, such as non-toxicity, fire resistance, corrosion resistance, and vapor permeability. However, the brittle failure mode, fabric efficiency, and tensile strength of FRCM composites require further improvement. Accordingly, the addition of short fibers to the matrix is proposed to improve the mechanical properties of FRCM composites, which are highly influenced by the fabric-to-cementitious matrix bond behavior. The objective of this study is to investigate the fabric-to-cementitious matrix bond behavior in carbon FRCM composites with added short fibers and to propose a method to evaluate the bond parameters. In total, 75 pullout specimens were designed to investigate the effects of short fiber type, short fiber volume content, and embedded length on the fabric-to-cementitious matrix bond behavior using double-sided pullout tests. The experimental results were evaluated in terms of the peak pullout force, displacement at peak pullout force, toughness, average bond strength, and initial stiffness. A closed-form solution was presented for the pullout force-displacement relationship based on a trilinear bond-slip model that accounted for the contribution of weft yarn. Furthermore, a method for the analytical extraction of bond parameters was proposed using the main characteristics of the experimental pullout force-displacement responses.

Analysis of persistent contaminants and personal care products by dispersive liquid-liquid microextraction using hydrophobic magnetic deep eutectic solvents

In this work, hydrophobic magnetic deep eutectic solvents (HMDESs) were used in the development of a simple and rapid dispersive liquid-liquid microextraction (DLLME) approach coupled to high performance liquid chromatography with UV detection (HPLC-UV) for the determination of ten organic contaminants including five polycyclic aromatic hydrocarbons, four UV filters, and a pesticide from water at trace levels. The HMDESs were prepared by mixing a hydrogen bond acceptor, metal halide salt, and hydrogen bond donor in suitable molar ratios. Two HMDESs, 2 tetraoctylammonium bromide ([N8888+][Br−]): cobalt chloride (CoCl2): 4 octanoic acid (OA) and 3 trioctylphosphine oxide (TOPO): neodymium chloride (NdCl3): 3 OA, offered the highest analyte extraction efficiency overall and were chosen as suitable solvents for validation of the microextraction method. Under optimized extraction conditions, the method required 30 µL of HMDES as extraction solvent, acetone (87.5 µL) as disperser solvent, a NaCl concentration of 30% (w/v), and an extraction time of 120 s at 20°C. Enrichment factors of the analytes ranged from 44.6 for 3-(4-methylbenzylindene) camphor to 66.0 for 2-ethylhexyl-4-(dimethyl)aminobenzoate. The method provided low limits of detection (LODs) ranging from 0.5 to 4.5 µg L−1, and acceptable precision, with RSD values lower than 9.6%. Furthermore, the validated method was successfully applied for tap and lake water analysis, resulting in relative recoveries of spiked samples ranging between 94.7 and 119.2%.

Use of solid phase microextraction in tips (SPME-Tips) for analysis of cocaine and biotransformation products in oral fluid by liquid chromatography tandem mass spectrometry (LC-MS/MS)

To develop and validate a method for analyzing cocaine and its metabolites using SPME-Tips and LC-MS/MS. Among the biological matrices used for analytical toxicology, oral fluid has advantages such as simplicity and non-invasive collection, the difficulty of adulteration, the low level of contamination risk and the possibility of recent abuse evaluation. Recently, nearly two million users have used cocaine in the US/Europe. When abused, cocaine is rapidly metabolized, mainly into methylecgonine and benzoylecgonine. Cocaethylene is formed in the concomitant use of cocaine with ethanol, and anhydroecgonine methyl ester (AEME) (in the crack abuse). Currently, in (green) analytical toxicology there is a growing interest in the use of new sample preparation techniques that are fast, efficient, automatable, and ecologically correct. Thus, methods based on microextraction processes have been developed, such as solid phase microextraction (SPME), a miniaturization of solid phase extraction. A variation of SPME technique was recently developed, consisting of a microfiber coated with extractor phase installed in a micropipette tip. In SPME-Tips, the extraction of analytes occurs in a extractor phase, allowing the direct immersion of the tip in biological fluids, causing the analytes to be adsorbed on the fiber and allowing the desorption to be carried out using small volume of more polar and less toxic solvents. The procedure was optimized, studying parameters such as salting-out effect, extraction time, sample agitation speed, elution solvent volume, and constitution. For extraction, SPME-Tips were immersed in 150 μL of oral fluid (collected with Quantisal) and kept under agitation at 500 rpm for 80 min. For the elution, 125 μL of methanolic solution with 0.1% formic acid was used, kept under agitation at 500 rpm for 30 min. The elution content was taken to LC-MS/MS, in which 5 μL were analyzed. The analyses were performed in a Nexera-UHPLC chromatographic system, coupled with a LCMS8060 mass spectrometer. The chromatographic separation was performed with Atlantis-T3 column (150 × 3.0 mm, 3.0 μm), maintained at 40 °C. The mobile phase consisted of ultra-pure water (A) and methanol (B), both containing formic acid (0.1%) and 2 mmol/L ammonium formate. The flow rate was set to 0.4 mL/min, and the elution gradient used started with 10%B for 1 min, followed by a linear increase to 100%B for 2 min and then maintained at 100%B for 2 min and returning to the proportion start in 0.1 min. This condition was maintained for another 3 min, completing a total of 8 min of chromatographic run. With this optimization, the method validation began, as recommended by the AAFS Standard Practices for Method Validation in Forensic Toxicology. For cocaine, benzoylecgonine, and cocaethylene, the correlation coefficient r 2 was greater than 0.98 (50 to 500 ng/mL). Good accuracy and precision results were obtained for low, medium and high QC. In this way, low extraction efficiency was observed to AEME and methylecgonine in C18 SPME-Tips. For the other analytes, the precision and accuracy values were in accordance to the criteria of the method validation guideline. Also, to prove the applicability of the method in real situations, 10 samples of oral fluid collected from individuals who participated in university parties will be analyzed. The samples were already collected and are stored in the Laboratory. A green analytical toxicology method was developed using SPME-Tips for the analysis of cocaine and its metabolites in oral fluid.

Micro-electromembrane extraction through volatile free liquid membrane for the determination of β-lactam antibiotics in biological and environmental samples

Micro-electromembrane extraction (μ-EME) was presented for the selective extraction of four main β-lactam antibiotics (penicillin, phenoxypenicillin, ampicillin, and amoxicillin) from complex samples. A volatile solvent (ethyl acetate or chloroform) was sandwiched between a plug of the complex sample and another plug of an aqueous acceptor solution in a transparent polymeric tube and formed the so-called free liquid membrane (FLM). The use of the FLM eliminated the evaporation of the solvent and enabled the μ-EME of the antibiotics, which was carried out by the application of DC voltage to the terminal aqueous solutions. The drugs in the complex sample were selectively transferred through the FLM to the acceptor solution, which was directly used for their determination by micellar electrokinetic chromatography with ultraviolet detection (MEKC-UV). The μ-EME was characterized by sub-μA electric currents, high elimination of matrix components, high stability of operational solutions, and suitability for extracting undiluted complex samples. The μ-EME/MEKC-UV method yielded good analytical repeatability (RSDs of peak areas ≤5%), extraction recoveries (40–84%), accuracy (92–105%) and linearity over one and a half order of magnitude (R2 ≥ 0.9998), and was applied to the determination of the four β-lactam antibiotics in human serum and waste water at clinically and environmentally relevant concentration levels. Further improvement in the method sensitivity was achieved by changing the μ-EME tube geometry (conical shape) and increasing the complex sample volume (100 μL). The analytes were enriched by factors of 7.6–11.5, the limits of detection dropped down to less than 18 ng/mL, and the modified μ-EME/MEKC-UV method enabled the trace determination of β-lactam antibiotics in complex samples.

A Strategy for Sample Preparation: Using Egg White Gel to Promote the Determination of Aflatoxin M1 Content in Milk Samples.

The analysis of food samples is a challenging task. The high complexity of food matrices hinders the extraction and detection of analytes from them. Therefore, the correct preparation of food samples is a crucial step for their subsequent analysis, as it achieves the proper isolation and preconcentration of analytes and removes the interfering proportion of the food matrix before instrumental analysis. We aimed to develop a method that not only satisfies the requirement of detecting trace compounds in complex matrices but also achieves a “greener” approach by reducing the use of organic solvents and non-degradable materials to minimize the health hazards posed to the operators as well as pollution to the environment. In this study, we prepared egg white as a concentrated gel and used this material for the biological purification of milk samples. After the milk protein was removed by acidification and salting, the residual amount of aflatoxin M1 in milk samples was quantitatively determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that the novel egg white purification method possessed advantages over the immunoaffinity technique used as the reference method in extraction recovery, sensitivity, repeatability, and operability. The limit of detection (LOD) was 0.001 μg/kg. In spiked samples containing 0.01 μg/kg to 2 μg/kg of AFM1, the average recovery was 88.3–94.7%, with a precision of 6.1–11.0%. Improved repeatability was obtained by significantly reducing the operation time and resource requirements compared with the immunoaffinity technique currently used internationally. This study provides a reference for the further improvement of the relevant international standards in place for the detection of aflatoxin M1 in milk.

Deep eutectic solvents-based headspace single-drop microextraction for the chromatographic determination of phenols and aliphatic alcohols in atmospheric air

In this work, the possibility for gas chromatography determination of volatile organic compounds in atmospheric air with preliminary microextraction into single drop of a deep eutectic solvent is presented for the first time. Highly toxic compounds (phenol, o-cresol) and aliphatic alcohols (methanol, n-butanol, n-pentanol) were selected as analytes for which low MPCs in the atmospheric air were established. A eutectic mixture of natural, environmentally friendly substances menthol and thymol was used as an extractant. The resulting eutectic solvent forms a stable drop that allows the rapid extraction of analytes from the gas phase. 30 min of sampling is enough to achieve sensitivity at the level of maximum permissible concentrations of these analytes in atmospheric air. At the same time, the volatility of the components of the eutectic compound themselves made it possible to introduce this solvent directly into the gas chromatograph without dilution. The developed procedure was used to analyze real air samples and standard gas mixtures. The limits of detection for analytes were in the range 0.001–0.01 mg L−1. The RSD for all analytes was <5 %. This sample preparation method can be easily and efficiently combined with subsequent chromatographic detection.

Selecting the Most Important Features for Predicting Mild Cognitive Impairment from Thai Verbal Fluency Assessments.

Mild cognitive impairment (MCI) is an early stage of cognitive decline or memory loss, commonly found among the elderly. A phonemic verbal fluency (PVF) task is a standard cognitive test that participants are asked to produce words starting with given letters, such as “F” in English and “ก” /k/ in Thai. With state-of-the-art machine learning techniques, features extracted from the PVF data have been widely used to detect MCI. The PVF features, including acoustic features, semantic features, and word grouping, have been studied in many languages but not Thai. However, applying the same PVF feature extraction methods used in English to Thai yields unpleasant results due to different language characteristics. This study performs analytical feature extraction on Thai PVF data to classify MCI patients. In particular, we propose novel approaches to extract features based on phonemic clustering (ability to cluster words by phonemes) and switching (ability to shift between clusters) for the Thai PVF data. The comparison results of the three classifiers revealed that the support vector machine performed the best with an area under the receiver operating characteristic curve (AUC) of 0.733 (N = 100). Furthermore, our implemented guidelines extracted efficient features, which support the machine learning models regarding MCI detection on Thai PVF data.

Stimuli-responsive polymer-based aqueous two-phase extraction of analytes in complex matrices

• Stimuli-responsive polymer-based ATPSs are effective green extraction techniques. • Temperature and pH are the common stimuli used in these ATPSs. • These ATPSs use less aggressive conditions during the extraction of analytes. • The stimuli-responsive polymers in the ATPS are recyclable after the extraction process. The use of aqueous two-phase systems (ATPSs) during extraction of analytes from complex matrices is increasingly gaining popularity. This can be attributed to the fact that these systems are generally simple, fast and environmentally friendly. The success of aqueous two-phase extraction largely depends on the good choice of materials to be used. The availability of smart materials such as stimuli-responsive polymers has facilitated the development of effective ATPSs for the extraction of analytes from complex matrices. This paper explores the utilisation of stimuli-responsive polymers during these biphasic systems. The stimuli-responsive polymers that are in common use in ATPSs include thermo-responsive and pH-responsive polymers. Other researchers used dual-stimuli-responsive ATPSs, which involve a combination of a thermo-responsive polymer and a pH-responsive polymer, during extraction of analytes from complex matrices. These biphasic systems composed of thermo-responsive and pH-responsive polymers are discussed in detail in this paper. In addition, this review explores the challenges associated with the use of stimuli-responsive polymers in ATPSs as well as the future prospects.

An efficient configuration for simultaneous electromembrane extraction of acidic and basic drugs on a chip

• An effective on-chip electromembrane extraction (CEME) was designed and coupled with HPLC. • This design does not require a syringe pump, so the system is simple and easy to handle. • The method was applied for simultaneous extraction and determination of acidic and basic analytes. • Efficient parameters on CEME of ibuprofen, disopyramide and lidocaine were optimized. • The preconcentration factors higher than 7.4 and RSDs% < 3.9% were obtained. In the present study, a new chip was designed for simultaneous electromembrane extraction (EME) of acidic and basic analytes. The method followed by the HPLC-UV analysis, was used for simultaneous extraction and determination of trace amounts of target analytes with different properties. Ibuprofen (IBU), as an acidic model analyte, and disopyramide (DIS) and lidocaine (LID), as basic model analytes, were selected. The chip was composed of three polymethylmethacrylate (PMMA) plates. The chamber for the sample solution was set in the middle plate. Two other chambers were carved on the other plates and they were acted as two acceptor phases’ reservoirs. Two stainless steel electrodes, which were responsible for applying a DC electrical potential on both sides of the supported liquid membranes (SLMs), were placed in the bottom of acceptor phases chambers and connected to a power supply. The two porous polypropylene membrane sheets, which were impregnated with different organic solvents, were used to separate the plates. Effective parameters such as SLM composition (1-octanol for acidic analyte and NPOE+5%DEHP for basic analytes), pH of donor phase and acceptor phases, applied voltage across SLM, and extraction time were optimized. Under the optimized conditions, the calibration curves were linear with coefficient of determinations (R 2 ) higher than 0.991 in the water, urine, and blood plasma samples. The obtained LODs were less than 5.0 µg L −1 and 1 µg L −1 for the basic and acidic analytes, respectively. The results demonstrated that on-chip EME would be used most effectively for extraction and determination of IBU, DIS, and LID in biofluids. Graphical Abstract .

Life Cycle Assessment and Life Cycle Cost of an Innovative Carbon Paper Sensor for 17α-Ethinylestradiol and Comparison with the Classical Chromatographic Method

Nowadays there is a growing concern with the environment and sustainability, which means that better methods, including pollutants analysis, with less consumption of materials, organic solvents, and energy, need to be developed. Considering the almost inexistent information about the topic, the main goal of this work was to compare the environmental impacts of two analytical methods, a traditional one based on liquid chromatography with fluorescence detection and a newly developed carbon paper sensor. The selected analyte was 17α-ethinylestradiol, which is a contaminant of emergent concern in aquatic ecosystems due to its endocrine disruptor behavior. The life cycle assessment data showed that the sensor detection presents an almost negligible environmental impact when compared with the extraction step (the same for both methods) and the liquid chromatographic determination (roughly 80 times higher than with the sensor). The sensor values for all categories of damage are below 3% of the total method impacts, i.e., 1.6, 1.9, 2.4, and 2.9% for resources, climate change, human health, and ecosystem quality. The extraction represents 98.1% of the sensor environmental impacts (and 99.6% of its life cycle costing) and 38.8% of the chromatographic method. This study evidences the need of developing and applying greener analytical (detection and extraction) strategies.

Investigation of stiffness and damping coefficients in fluid film bearing with bio-oils and mineral-based oil

Rotating machinery utilizes fluid film bearings because of their good load carrying capacity and inherent damping properties. Fluid film bearings offer stiffness and damping parameters to ensure dynamic stability. The damping and stiffness characteristics of oil film significantly change the critical speed and unbalance response of the rotor. The damping and stiffness coefficients (direct, cross-coupled) may lead to system instability, also known as self-excited vibrations. Bio-oils have good tribological and physiochemical properties. They are also environment-friendly and bio-degradable. In this work, bio-oils (rapeseed, palm olein, and soybean) are evaluated in terms of their dynamic characteristics to that of mineral-based SAE40 lubricant for journal-bearing applications. The analytical extraction of damping and stiffness coefficients is performed based on the experimental dynamic viscosity data at different temperatures. In comparison to SAE40, the bio-oils have shown improved responsiveness. Bio-oils showed lower cross-coupled stiffness coefficients than SAE40, the primary source of rotor instability. The main contribution of this study is that it provides damping and stiffness coefficients for various bio-oils at different eccentricity ratios and viscosities for different types of oils. This may be used to characterize the dynamic properties of the fluid film bearing under various operating circumstances. It is concluded that the difference in cross-coupled stiffness favors bio-oils. Whereas, the difference in cross-coupled damping favors SAE40 by around 6%. This discrepancy is decreased to less than 2% for all oil’s final eccentricity ratio values (bio-oils and SAE40).

Isoparametric singularity extraction technique for 3D potential problems in BEM

To solve boundary integral equations for potential problems using collocation Boundary Element Method (BEM) on smooth curved 3D geometries, an analytical singularity extraction technique is employed. By adopting the isoparametric approach, curved geometries that are represented by mapped rectangles or triangles from the parametric domain are considered. The singularity extraction on the governing singular integrals can be performed either as an operation of subtraction or division, each having some advantage.A particular series expansion of a singular kernel about a source point is investigated. The series in the parametric coordinates consists of functions of a type Rpxqyr, where R is a square root of a quadratic bivariate homogeneous polynomial with coefficients corresponding to the first fundamental form of a smooth surface, and p,q,r are integers, satisfying p≤−1 and q,r≥0. By extracting more terms from the series expansion of the singular kernel, the smoothness of the regularized kernel at the source point can be increased. Analytical formulae for integrals of such terms are obtained from antiderivatives of Rpxqyr, using recurrence formulae, and by evaluating them at the edges of rectangular or triangular parametric domains.Numerical tests demonstrate that the singularity extraction technique can be a useful prerequisite for a numerical quadrature scheme to obtain high order of convergence for the governing singular integrals in 3D collocation BEM with respect to the number of quadrature nodes or with respect to size of the discretization mesh cells.

A validated LC-MS/MS method for determination of antiviral prodrug molnupiravir in human plasma and its application for a pharmacokinetic modeling study in healthy Egyptian volunteers

A fully validated, simple, rapid and reproducible liquid chromatography-tandem mass spectrometry method was developed to determine NHC (N-hydroxycytidine), the active metabolite of Molnupiravir (MOL) in human plasma; one of the limited treatment options for SARS-CoV-2 in plasma of healthy volunteers. The internal standard (IS) used was ribavirin. The extraction of analyte and IS from plasma was performed using acetonitrile as a solvent for protein precipitation. Agilent Zorbax Eclipse plus C18, 4.6 × 150 mm, (5 µm) was used for chromatographic separation using a mixture of methanol0.2 % acetic acid (5:95, v/v) as a mobile phase that was pumped at a flow rate of 0.9 mL/min. Detection was performed on a triple quadrupole mass spectrometer operating in multiple reaction monitoring (MRM) employing positive ESI interface using API4500 triple quadrupole tandem mass spectrometer system, with the transitions set at m/z 260.10 → 128.10 and 245.10 → 113.20 for NHC and IS respectively. Method validation was performed in accordance with United States FDA bioanalytical guidance. The concentration range of 20.0–10000.0 ng/mL was used to establish linearity via weighted linear regression approach (1/x2). Moreover, the analyzed pharmacokinetic data from twelve Egyptian healthy volunteers were used to develop a population pharmacokinetic model for NHC. The developed model was used to perform simulations and evaluate the current MOL dosing recommendations through calculating the maximum concentration (Cmax) “the safety metric” and area under the curve (AUC0-12 h) “the efficacy metric” for 1000 virtual subjects. Geometric mean ratios (GMR) with their associated 90% confidence intervals (CI) compared to literature values were computed. Geometric means of simulation-based Cmax and AUC0-12 were 3827 ng/mL (GMR = 1.05; 90% CI = 0.96–1.15) and 9320 ng.h/mL (GMR = 1.04; 90% CI = 0.97–1.11), respectively indicating that current MOL dosage can achieve the therapeutic targets and dose adjustment may not be required for the Egyptian population. The developed model could be used in the future to refine MOL dosage once further therapeutic targets are identified.