LOD) And Quantification Research Articles

Copper-modified carbon nano-onions as electrode modifiers for the electroanalysis of the antiretroviral drug Efavirenz

The high prescription and consumption rate of antiretroviral drugs (ARV) such as Efavirenz (EFV) in South Africa for the treatment of the human immunodeficiency virus (HIV) has resulted in its presence in wastewater and surface water. Herein we report the electroanalysis of EFV at oxidised boron-nitrogen doped carbon nano-onions (oxi-BNCNO) and microscale branched copper cluster (CuC) modified glassy carbon electrodes. Potentiostatic electrodeposition of CuC on the oxi-BNCNO/GCE platform resulted in a stable and electrocatalytic surface that accelerated electron transfer between the analyte and the CuC/oxi-BNCNO/GCE surface, making quantification efficient. The electroactive surface area of CuC/oxi-BNCNO/GCE was estimated as being 3 times higher than bare GCE and twice that of oxi-BNCNO/GCE. The electrooxidation of EFV on a CuC/oxi-BNCNO/GCE sensor resulted in a pH-dependant anodic peak in the potential range of 0.8 to 1.2 V vs Ag/AgCl (3M KCl). The EFV voltammetric signal increased linearly with increasing concentration of EFV in the linear dynamic range (LDR) of 0.01 – 1.0 µM and 0.5 – 20 µM with a limit of detection (LOD) and quantification (LOQ) of 1.2 and 3.97 nM, respectively. Moreover, the sensor had a sensitivity of 23 µA ∙ cm−2 ∙ µM−1 and was selective to 100-fold of interferents including heavy metal ions and other ARVs with the exception of high concentrations of nevirapine. The developed electroanalytical method was successfully applied for the determination of EFV in real samples such as wastewater influent and effluent, drinking/tap water, and a pharmaceutical formulation with recovery ranging from 97.8% to 109.5%.

NADES-assisted sample preparation as a greener alternative for mycotoxins determination in apple-based products

While impressive advancements have been reported in mycotoxin analysis over the last decade, very little has been done to realign the sample treatment to the green sample preparation principles, which are arising more and more relevance in the current analytical chemistry. In this regard, this work proposes the first NADES-assisted sample preparation for the extraction of mycotoxins in food samples.Two protocols using dispersive liquid–liquid microextraction (DLLME) and DLLME with solidification of floating organic drop (DLLME-SFO) assisted with a natural deep eutectic solvent (NADES) were developed and assessed as green sample preparation procedures to extract mycotoxins from apple-based products prior to HPLC-MS/MS analysis. The selected mycotoxins were alternariol, alternariol monomethyl ether, tentoxin and ochratoxin A, which are known to occur in these food matrices. The main variables affecting the extraction efficiency, such as volume of dispersive and extraction solvents, as well as the salting-out effect were evaluated and optimized using a central composite design. In addition, both methodologies were examined and compared in terms of greenness using the newly released metric tool AGREEprep. Due to the use of NADES, the DLLME-SFO method achieved a higher greenness score, and it was selected for further characterization. Matrix-matched calibration curves were used, showing a satisfactory linearity (R2 > 0.99). Limits of detection (LODs) and quantification (LOQs) were below 0.25 and 0.8 µg kg−1, respectively. Recoveries were above 72 % for all the mycotoxins studied in both apple juice and apple puree samples. The validated DLLME-SFO-HPLC-MS/MS method was applied to the analysis of commercial apple juice and puree samples. All the samples analysed were contaminated with at least one mycotoxin with a total concentration ranging from 0.4 to 10.5 µg kg−1.

Micro-titer plate assay for measurement of total phenolic and total flavonoid contents in medicinal plant extracts

Total phenolic content (TPC) measured by using the Folin-Ciocalteu method and Total flavonoid content (TFC) based on a complex formation with AlCl3 assay are widely applied as part of herbal extract quality control. Conducting the assay measurements in microtiter plates may save resources and time. The objective of this study was to evaluate the validity of the micro-titer plates assay to determine the TFC and TPC in several medicinal plants’ extracts. To compare the developed TPC and TFC methods to the conventional assays, the confidence intervals of linear regression were used with a significance set as p < 0.05. Both of the standards showed good linearity in the range of 10–60 mg L−1 of gallic acid and 40–200 mg L−1 of quercetin, (R2 > 0.999). Based on the micro-titer plate assay, the limits of detection (LODs), and quantification (LOQs) for TPC ranged between 1.19 mg L−1 and 3.98 mg L−1 whereas for TFC, they were 1.47 mg L−1 and 4.90 mg L−1. The percent coefficient of variation (%CV) of the intra-day and inter-day assays were lower than 1.46% and 1.91%, respectively, showing adequate precision. The recovery ranged between 101.25% and 105.93% for the TPC assay and between 96.78% and 101.28% for the TFC assay. Twelve samples of medicinal extracts were analyzed by validated microplate assay for TPC and TFC and then compared with the conventional method. Notably, there were no significant differences in the TPC and TFC content detected between the microplate and conventional methods for all samples (p > 0.05). In conclusion, the microplate assay can be potentially used for TPC and TFC determinations.

Voltammetric Quantification of the Antibiotic Roxarsone using a Surface‐Modified Screen‐Printed Carbon Electrode

AbstractHerein, we report the electrochemical determination of roxarsone (ROX) on modified screen‐printed carbon electrodes (SPCE). Graphene oxide was reduced electrochemically on the working area of SPCE using cyclic voltammetry (CV) to form electrochemically reduced graphene oxide (ErGO), followed by electrochemical deposition of gold (Au) on ErGO/SPCE to get a final modified electrode Au/ErGO/SPCE. The modified electrode offered a significant surface area and improved electron transfer capability; hence it was used as an electrochemical sensor for the determination of ROX which is commonly used in meat production and poultry as a supplement to increase weight and improve feed efficiency. The effect of pH on the electrochemical behaviour of ROX on the Au/ErGO/SPCE was investigated by (CV) and square wave voltammetry (SWV). Under optimum experimental conditions, the linear calibration range, the limit of detection (LOD), and quantification (LOQ) were found to be 1 μmol L−1–1000 μmol L−1, 14.4 nmol L−1, and 47.9 nmol L−1 respectively. The proposed electrochemical sensor was successfully applied to determine low concentrations of ROX in lab samples as well as in real meat (spiked) samples. Overall, a good recovery rate and accuracy were obtained, endorsing onsite use of the developed sensor for quick and accurate analysis.

Determination of Rhodium in Soil by Dispersive Solid-Phase Extraction (DSPE) with Manganese Ferrite Nanoparticles and Flame Atomic Absorption Spectrometry (FAAS)

Manganese ferrite (MnFe2O4) nanoparticles-assisted dispersive solid-phase extraction (MF-DSPE) was developed for the determination of rhodium (Rh) in soil samples at low levels with good accuracy and precision by flame atomic absorption spectrometry (FAAS). The synthesis of MnFe2O4 nanoparticles was carried out in a microwave system by a rapid procedure. The pH, buffer volume, sorbent mass, sample volume, eluent volume/concentration, and mixing time were identified with univariate optimization. Under the optimal conditions, the limits of detection (LOD) and quantitation (LOQ) were 4.4 and 14.7 µg L−1, respectively. The sensitivity was improved by 121.9-fold based upon comparison of the limits of detection with and without preconcentration. The applicability was investigated by spiking rhodium into soil extracts, and good recovery results between 91.2% and 122.2% were achieved using matrix matching calibration. The results showed that MF-DSPE-FAAS determines low levels of rhodium in soil with good accuracy and precision.

Development and Validation of Analytical Method Using Gas Chromatography with Triple Quadrupole Mass Spectrometry for the Detection of Alkyl Halides as Potential Genotoxic Impurities in Posaconazole

Effective risk management and control methods for potentially genotoxic impurities (PGIs), including alkyl halides, are of significant importance in the medicinal (pharmaceutical) sector. The three alkyl halides in posaconazole are PGIs. The detection and assessment of genotoxic substances is a top priority for all regulatory organizations. Quantifying PGIs at trace levels using standard analytical techniques, such as gas chromatography (GC) and high-performance liquid chromatography (HPLC), is challenging for the pharmaceutical manufacturing industry. Thus, the detection of trace quantities of PGIs in posaconazole is essential for developing sensitive analytical methodologies. The objective of this study was to establish an analytical technique for quantifying the three PGIs (alkyl halides) in posaconazole and its intermediate. These alkyl halides are 1-(2,4-difluorophenyl) ethan-1-one (PGI-1), (Z)-1-(1-bromoprop-1-en-2-yl)- 2,4-difluorobenzene (PGI-2), and 1-bromo-2-(2,4-difluorophenyl) propan-2-ol (PGI-3). To identify trace quantities (parts per million (ppm)) of these impurities, we employed a gas chromatography (GC-MS/MS) equipped with a triple quadrupole mass spectrometry detector. The GC column was a USP phase G43, which is a mid-polar 6% cyanopropyl; 94% polydimethylsiloxane, with a 60 m length, 0.32 mm inner diameter, and 1.8 μm film thickness. Helium (He) was used as the carrier gas, with a flow rate of 1.5 mL/min. A thermal gradient elution program was used for this procedure. The method was calibrated for the three PGIs with limits of detection (LOD) and quantification (LOQ) of 0.01 and 0.025 ppm, respectively. The linear range of concentrations (25–150%) was maintained with respect to the specification level. This method was validated according to the ICH regulations and was shown to be specific, rugged, robust, precise, sensitive, accurate, linear, and stable. Therefore, in this newly developed method, the combination of suitable analytical techniques, such as GC-MS/MS and proper chromatographic conditions and column selection with the lowest LOD and LOQ, have allowed the induction of excellent ionization. These conditions have successfully facilitated the identification of PGI-1, PGI-2, and PGI-3 in posaconazole and its intermediate during routine analysis.

3D-printed device for the kinetic determination of As(III) in groundwater samples by digital movie analysis

High concentrations of inorganic arsenic in groundwater for human consumption is a worldwide common problem. Particularly, the determination of As(III) becomes important, since this species is more toxic than organic, pentavalent and elemental arsenic forms. In this work, a 3D-printed device that included a 24-well microplate was developed to perform the colourimetric kinetic determination of arsenic (III) by digital movie analysis. A smartphone camera attached to the device was used to take the movie during the process where As(III) inhibited the decolourization of methyl orange. The movie images were subsequently transformed from RGB to YIQ space to obtain a new analytical parameter called “d”, which was related to the chrominance of the image. Then, this parameter allowed the determination of the inhibition time of reaction (tin), which was linearly correlated with the concentration of As(III). A linear calibration curve (R = 0.9995) in the range from 5 μg L−1 to 200 μg L−1 was obtained. The method was precise (RSD = 1.2%), and the limits of detection (LOD) and quantification (LOQ) were 1.47 μg L−1 and 4.44 μg L−1, respectively. These values were lower than the limit established by the World Health Organization for total arsenic in drinking water (10 μg L−1). The accuracy of the method was assessed by a recovery study with optimal results (94.3%–104.0%). Additionally, the Analytical GREEnness metric approach was applied, obtaining a score 1.7 times higher than previously published works. The method is simple, portable and low-cost, being in compliance with various principles of green analytical chemistry.

Determination of 18 caine anesthetics in animal meat using solid phase extraction combined with ultra-performance liquid chromatography-tandem mass spectrometry

Because of the widespread application of anesthetic drugs in the fields of animal breeding and transportation, demand for the rapid, sensitive detection of anesthetic drugs in animal meat is increasing. The complex animal meat matrix contains various interfering substances, such as proteins, fats, and phospholipids, along with anesthetic drug residues at very low concentrations. Therefore, adopting appropriate pretreatment methods is necessary to improve the sensitivity of detection. In this study, a rapid, accurate analytical method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and solid phase extraction (SPE) was established to determine the contents of 18 caines in animal meat. The MS parameters, such as the collision energies of 18 caines, were optimized. Furthermore, the chromatographic separation conditions and response intensities of the caine in different mobile phases were compared. The effects of different pretreatment conditions on the extraction efficiencies of the 18 caines in meat samples and those of different purification conditions, such as extraction solvent, SPE column, and dimethylsulfoxide (DMSO) dosage, on their recoveries were investigated. Combined with the external standard method, the 18 caines in meat were successfully quantified. Sample pretreatment is a three-step process. First, in ultrasound-assisted extraction, 2.0 g samples were added to 2.0 mL water and extracted using 10 mL 0.1% (v/v) formic acid in acetonitrile under ultrasound conditions for 10 min. SPE was then performed using an Oasis PRIME HLB column. Finally, DMSO-assisted concentration was employed: the organic layer was collected and dried at 40 ℃ under a stream of N2 gas with the addition of 100 μL DMSO. Acetonitrile-water (1∶9, v/v) was added to the residue to yield a final volume of 1.0 mL for use in UPLC-MS/MS. The 18 caines were separated using an HSS T3 (100 mm×2.1 mm, 1.8 μm) column with 0.1% (v/v) formic acid in water (containing 0.02 mmol/L ammonium acetate) and methanol as mobile phases. Samples were detected using an electrospray ion source (ESI) in the positive ion and multiple reaction monitoring (MRM) modes during UPLC-MS/MS. Under the optimized conditions, the 18 target caine anesthetics displayed good linearities in the range of 1.00-50.0 μg/L, and the correlation coefficients (R2) were >0.999. The respective limits of detection (LODs) and quantification (LOQs) were 0.2-0.5 μg/kg, and 0.6-1.5 μg/kg. In pork, beef, and mutton samples, the recoveries obtained at three spiked levels were 83.4%-100.4% with relative standard deviations (RSDs) of 3.1%-8.5%. This simple, rapid, sensitive method may be applied in the detection of 18 caine anesthetics in animal meat and may provide technical support to the food safety department in China in monitoring the residues of caine anesthetics in animal meat.

Determination of 39 fatty acids in liver of rats by gas chromatography-mass spectrometry

Fatty acids not only form phospholipids that contribute to the formation of cell membranes but also participate in many metabolic activities, such as energy storage and cell signal transduction. The liver plays a key role in the synthesis and metabolism of fatty acids. The composition and contents of fatty acids in the liver are closely related to body health. Most fatty acid-detection methods require a large sample size and can detect only a small number of fatty acids. Therefore, a sensitive and efficient method to determine fatty acids in the liver is urgently required. Herein, a method based on gas chromatography-mass spectrometry (GC-MS) was established for the simultaneous determination of 39 fatty acids in 1.1 mg of liver tissue. Different extraction methods and derivatization conditions were compared to develop an optimal sample-treatment method. The performance of two different columns in separating the target fatty acids were also compared. A total of 10 mg of liver was added to 450 μL of normal saline and ground at -35 ℃ to obtain a homogenate. Next, 50 μL of the homogenate (equivalent to 1.1 mg of liver) was added with 750 μL of chloroform-methanol (1∶2, v/v) to extract total fatty acids. The fatty acid extracts were dried under nitrogen, and then derivatized at 100 ℃ for 90 min after being added with methanol containing 5% sulfuric acid. The fatty acid methyl esters were extracted with hexane and then separated on an SP-2560 capillary column (100 m×0.25 mm×0.2 μm; Supelco, USA) via GC-MS. The results revealed that all 39 fatty acid methyl esters detected had good linearities in the certain mass concentration ranges with correlation coefficients (R2) greater than 0.9940. The limits of detection (LOD) and quantification (LOQ) of these methyl esters in the liver were 2-272 ng/mg and 7-906 ng/mg, respectively. The accuracy and precision of the method were evaluated by spiking the liver homogenate with tridecylic acid and eicosanoic acid at low (0.09 μg/mg), moderate (0.90 μg/mg), and high (5.40 μg/mg) concentration levels. The recoveries ranged from 82.4% to 101.0% with an intraday relative standard deviations (RSDs) (n=5) of 3.2%-12.0% and interday RSDs (n=3) of 5.4%-13.4%. The method was successfully applied to detect fatty acids in the livers of four healthy male Sprague-Dawley (SD) rats and four male SD rats with abnormal liver function induced by perfluorooctane sulfonate (PFOS). PFOS is a persistent organic pollutant. Twenty-six fatty acids were detected in the livers of both groups. Among the fatty acids investigated, pentadecanoic acid (C15∶0), γ-linolenic acid (C18∶3n6), and elaidic acid (C18∶1n9t) cannot be detected by the methods reported in the literature. By contrast, the method developed in this study could separate the isomers of oleic acid (elaidic acid, C18∶1n9t; oleic acid, C18∶1n9c) and linolenic acid (linolelaidic acid, C18∶2n6t; linoleic acid, C18∶2n6c). In conclusion, the developed method is simple and can detect a large number of fatty acids using small sample amounts and few reagents. More importantly, it could successfully separate fatty acid isomers. These findings indicate that the developed method is suitable for the detection of fatty acid composition and contents in the liver in clinical and experimental research.

New spectrophotometric method for estimation of losartan potassium using Alizarin Red reagent

A simple, rapid, precise, and sensitive analytical method has been developed to identify losartan potassium in its pure and pharmaceutical dosage forms. This method involves a proton transfer between the losartan reagent and the Alizarin Red reagent in an acidic medium while standing to complete the reaction to obtain a colored product bound to the amount of losartan potassium, this product having a maximum absorption at 493 nm. A linear calibration curve was obtained over a concentration range of 1.5–12.5 gml–1 with a correlation coefficient of 0.9991. The molar absorptivity was 4.522104 lmol–1cm–1, and Sandell's sensitivity index was equal to 0.010 gcm–2. The limit of detection (LOD) and quantification (LOQ) values were 0.359 and 1.121 gml–1, respectively. The suggested approach was applied to estimate losartan potassium in the available pharmaceutical preparations (tablets). The results confirmed that the technique is successful by studying the recovery using the standard addition method.

Magnetic Adsorbent Decorated with Poly(N-Isopropylacrylamide) (PNIPAM) Brushes for the Vortex-Assisted Solid Phase Extraction (VASPE) of Lead in Water, Cigarettes and Soil with High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS) Detection

Here is reported the synthesis of a magnetic phosphorus-containing adsorbent decorated with poly(N-isopropylacrylamide) (PNIPAM) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) and its application for vortex assisted solid phase extraction of lead in water, cigarettes and soil. The adsorbent was characterized using Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive x-ray (EDX) spectroscopy. A high-resolution continuum source flame atomic absorption spectrometer (HR-CS FAAS) was used for the quantification of lead. All factors affecting the extraction efficiency including the solution pH, adsorbent dose, sample volume, vortex time, and elution protocols were optimized. The limits of detection (LOD) and quantification (LOQ) were determined to be 0.05 µg L−1 and 0.18 µg L−1, respectively. The preconcentration and enhancement factors were 20 and 18. Validation was performed using TMDA 64.3 fortified water and INCT-OBTL-5 tobacco leaves certified reference materials with satisfactory recoveries. The method was shown to be sensitive, efficient and reproducible.

What is the best spectroscopic method for simultaneous analysis of organic acids and (poly)saccharides in biological matrices: Example of Aloe vera extracts?

Several species of (poly)saccharides and organic acids can be found often simultaneously in various biological matrices, e.g., fruits, plant materials, and biological fluids. The analysis of such matrices sometimes represents a challenging task. Using Aloe vera (A. vera) plant materials as an example, the performance of several spectroscopic methods (80 MHz benchtop NMR, NIR, ATR-FTIR and UV–vis) for the simultaneous analysis of quality parameters of this plant material was compared. The determined parameters include (poly)saccharides such as aloverose, fructose and glucose as well as organic acids (malic, lactic, citric, isocitric, acetic, fumaric, benzoic and sorbic acids). 500 MHz NMR and high-performance liquid chromatography (HPLC) were used as the reference methods.UV–vis data can be used only for identification of added preservatives (benzoic and sorbic acids) and drying agent (maltodextrin) and semiquantitative analysis of malic acid. NIR and MIR spectroscopies combined with multivariate regression can deliver more informative overview of A. vera extracts being able to additionally quantify glucose, aloverose, citric, isocitric, malic, lactic acids and fructose. Low-field NMR measurements can be used for the quantification of aloverose, glucose, malic, lactic, acetic, and benzoic acids. The benchtop NMR method was successfully validated in terms of robustness, stability, precision, reproducibility and limit of detection (LOD) and quantification (LOQ), respectively.All spectroscopic techniques are useful for the screening of (poly)saccharides and organic acids in plant extracts and should be applied according to its availability as well as information and confidence required for the specific analytical goal. Benchtop NMR spectroscopy seems to be the most feasible solution for quality control of A. vera products.

Development and Validation of Spectrophotometric Methods for the Quantitative Determination of Doxycycline Hyclate in Pure Form and Pharmaceutical Formulations Using Flow‐Injection and Batch procedures: A Comparative Study

AbstractDoxycycline hyclate is an antibiotic drug with a broad‐spectrum activity against a variety of gram‐positive and gram‐negative bacteria and is frequently used as a pharmacological agent and as an effector molecule in an inducible gene expression system. A sensitive, reliable and fast spectrophotometric method for the determination of doxycycline hyclate in pure and pharmaceutical formulations has been developed using flow injection analysis (FIA) and batch procedures. The proposed method is based on the reaction between the chromogenic reagent (V4+) and doxycycline hyclate in a neutral medium, resulting in the formation of a yellow compound that shows maximum absorbance at 396 nm. In a batch procedure, the proposed method was validated over the concentration range of 1.0–80 μg mL−1with a sampling frequency of 30/h, and commercial pharmaceutical samples were successfully determined. The proposed method was successfully adapted with an FIA system where the peak heights are proportionally connected to doxycycline hyclate over the concentration range of 25–400 μg mL−1with a sampling frequency of 50/h. The limits of detection (LOD) and quantification (LOQ) were 0.9 and 10.44 μg mL−1and 3.01 and 34.81 μg mL−1for batch and FIA respectively. The samples were submitted to an HPLC analysis, and the outcomes demonstrated excellent agreement with the suggested procedures. The adopted FIA procedure allows fast monitoring of doxycycline hyclate in pharmaceutical formulations and it can be used for quality control purposes during the production processes of doxycycline hyclate.

Spectrophotometric Estimation of Phenylephrine Hydrochloride via Oxidative Coupling Reaction with p-Aminobenzophenone

In this research, a rapid, simple and accurate spectrophotometric approach was described for the estimation of phenylephrine hydrochloride in the pure and in its drug forms. The suggested method was based on the oxidative coupling reaction of phenylephrine hydrochloride with p-aminobenzophenone using potassium periodate as an oxidant. A taupe-red dye was formed at room temperature and showed maximum absorption at 512 nm. The linearity of the standard calibration curve was compatible with Beer's law within the concentration range of 2.0-20 μg/mL with a determination coefficient (r2=0.9986). The apparent molar absorptivity and the sensitivity of Sandell's index were calculated and found to be in the values of 0.552x104 L/mol.cm. and 0.0368 μg/cm2, respectively. The nature of the resulting dye has been studied between phenylephrine hydrochloride to p-aminobenzophenoneand and it was equal to 1:1. The limits of detection (LOD) and quantification (LOQ) were estimated and found to be 0.0094 and 0.0313 μg/mL, respectively. A relative standard deviation and a relative error were also calculated and they will be in the range of 0.0715 to 0.0216 and -0.0479% to -0.0145%, respectively. The recommended procedure was applied to assay phenylephrine hydrochloride in drops and injection and no interferences were observed from the common additives found in the drugs.

Screen-Printed Electrodes Based on Conductive Inks of Polyaniline/Graphene Hybrids and Their Application to Progesterone Detection

Screen-printed electrodes (SPEs) were produced using conductive inks based on hybrids of polyaniline (PAni) and reduced graphene oxide (rGO). Cyclic voltammetry (CV) showed peaks characteristic of the PAni redox behavior in acidic media for all the modified SPEs. Electrochemical impedance spectroscopy (EIS) showed a significant decrease in the charge-transfer resistances, from 930 Ω for SPE/G:PAni to 544 Ω for SPE/G:PAni-rGO1 and to 303 Ω for SPE/G:PAni-rGO2 with just 0.06% and 0.12% in mass of rGO, respectively, in the final mass composition of the conductive inks. The SPEs were evaluated in the determination of progesterone (P4) hormone in neutral medium (phosphate buffer solution, pH 7.0). The CV results showed higher current signals at SPE/G:PAni-rGO1 compared with SPE/G and SPE/G:PAni, indicating a synergistic effect of PAni-rGO1 in the determination of P4. EIS also showed significant changes in the electrochemical double-layer capacitances in the presence of P4. The limits of detection (LOD) and quantification (LOQ) were, respectively, 211 nmol l−1 and 703 nmol l−1. This method is a simple, scalable and low-cost alternative for the fabrication of electrodes based on PAni-rGO hybrids, with synergic properties, aiming for future applications in sensors.

An Improved Analytical Approach Based on µ-QuEChERS Combined with LC-ESI/MS for Monitoring the Occurrence and Levels of Patulin in Commercial Apple Juices

Patulin (PAT) is a mycotoxin produced in fruits, especially in apples, by diverse fungal species that can be transferred into industrial apple juice during processing. An accurate, effective, and selective method has been validated for the quantification of PAT in different commercial apple juices by combining a modified µ-QuEChERS procedure with high-pressure liquid chromatography (LC) equipped with a triple quadrupole mass spectrometer (QqQMS). This sample extraction procedure reduced interference from the sugar-rich matrix, and the separation was performed using the C18 Atlantis T3 column within 10 min. PAT was found by MS with electrospray negative ionization (ESI−) in the mode of multiple reaction monitoring (MRM). The correlation coefficient (R2 = 0.999) satisfied the prerequisite of linearity for PAT in the concentration range of 2–50 μg/kg. The limits of detection (LOD) and quantification (LOQ) of PAT were 0.32 and 1.15 μg/kg, respectively, which were compliant with the maximum levels settled in Commission Regulation (EC) No. 1881/2006. The recoveries were within the 92–103% range, at three fortified levels of 2, 20 and 50 μg/kg, with relative standard deviations lower than 7%. Based on analytical validation, it was confirmed that the µ-QuEChERS/HPLC-MS/MS method is an enhanced, reliable, and quick approach for determination of PAT in apple juice. The current approach proposes reduced sample preparation and analysis time. In addition, it is economical, environmentally friendly, and simpler to implement in comparison to traditional approaches.

Accurate Determination of Pesticide Residues in Milk by Sonication-QuEChERS Extraction and LC-LTQ/Orbitrap Mass Spectrometry

A modified, quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction procedure combined with sonication and Ultra-High Performance Liquid Chromatography–Orbitrap-Mass Spectrometry (UHPLC–Orbitrap-MS) was developed as a sensitive and reliable methodology for the determination of multiclass pesticides in full-fat milk. Different amounts of EMR-lipid sorbent were assayed for the cleanup step in order to achieve both acceptably high recoveries and low co-extractives in the final extracts. Accurate mass measurements of the analyte’s pseudo-molecular ions and tandem MS fragmentation were used to quantify and identify the target pesticides. Analytical performance characteristics of the method, such as linearity, recovery, precision, the limit of detection (LOD) and quantification (LOQ), matrix effects (ME), and expanded uncertainty, have been determined for method validation fulfilling all criteria for its use as a validated routine method. The method was successfully applied to real samples (by local farms and commercial), revealing the presence of carbendazim in one milk sample at a concentration level below the maximum residue limits.

A Facile and Rapid Strategy for Quantifying PCBs in Cereals Based on Dispersive Solid-Phase Extraction and Gas Chromatography-Mass Spectrometry: A Reference for Safety Concerns in Sustainable Textiles.

Cereals and their derivative products such as starch and cyclodextrin are significant natural materials for sustainable textile processing (e.g., sizing, dispersing, etc.). However, the contamination of cereals with polychlorinated biphenyls (PCBs) is often neglected, which has led to increasing concerns due to the adverse effects on end users. Therefore, monitoring PCBs in cereals is of great importance in preventing health risks. However, high starch, protein, and fat contents make cereals a complicated matrix and can challenge the analysis of PCBs in cereals. This work describes a facile and rapid strategy for quantifying 18 PCBs in cereals that included corn, wheat, and rice through dispersive solid-phase extraction and gas chromatography with mass spectrometry. Importantly, this was the first time that carboxyl-modified, multi-walled carbon nanotubes were incorporated in the detection of PCBs in cereals. The influences of several parameters on the extraction and clean-up efficiency were investigated; these included the type and volume of extraction solvent, sonication time, and the type and dosage of the adsorbent. The matrix effects on quantification were also evaluated. This approach exhibited a better clean-up performance. All the analytes showed weak matrix effects, and thus a solvent standard plot could be prepared for their quantification. Spiking experiments in the selected matrices at three concentration levels from 0.5 to 10 μg/kg resulted in satisfactory recoveries that ranged from 79.2% to 110.5% with relative standard deviations (RSDs; n = 6) less than 10.3%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.04 to 0.1 μg/kg and 0.1 to 0.4 μg/kg, respectively. The practical application of this method was investigated by analyzing actual cereal samples, which demonstrated that the proposed approach was a facile and efficient strategy for PCB determination and provided a reference for the safety evaluation of sustainable textiles. The method also could be generalized to other troublesome samples for testing of multiple PCBs.

Graded Atmospheres of Volatile Pyrethroid Overlaid on Host Cues Can Be Established and Quantified Within a Novel Flight Chamber for Mosquito Behavior Studies.

Spatial repellents are emerging as a promising approach to reduce vector-disease burden; however, the evolution of genetically resistant mosquitoes decreases repellent efficacy. The development of flight chambers to investigate spatial repellent application techniques is vital for sustainable mosquito control. We present an air-dilution chamber as a novel bioassay to study mosquito flight behavior responses to chemical gradients of the volatile, pyrethroid transfluthrin (TF). Air dilution was used to simulate a larger environment of stable concentration gradients verified with carbon dioxide (CO2) which was homogenously delivered and measured across the chamber to achieve a 5× inlet/outlet [CO2] ratio with 0.17 m/s outlet velocity. Female Aedes (Ae.) aegypti (Diptera: Culicidae, Linnaeus, 1762) were exposed to volatilized TF paired with heat, CO2, and Biogents-Sweetscent host-cues. Tandem solvent extraction-gas chromatography-mass spectrometry (SE-GC-MS) was used to quantify air samples taken during TF emanations with a limit of detection (LOD) and quantification (LOQ) of 2 ± 1 and 5 ± 2 parts-per-trillion (ppt) TF, respectively. Homogenous air diluted emanation of the spatial repellent TF was at least twice that of the 5× CO2 gradient with the same air flow in the chamber. The airborne TF concentrations the mosquitoes were exposed to range from 1 to 170 ppt. Video recordings of mosquito behavior during host-cues exposure revealed increased inlet activity, while exposure to TF protected host resulted in decreased inlet activity over time with inlet-outlet mosquito positional variation. This novel flight chamber design can simulate 'long'-range exposure with simultaneous quantitation of airborne spatial repellent to understand dose-dependent effects on mosquito behavior.

Green Synthesis and Encapsulation of Superparamagnetic Magnetite for Mercury (II) Removal: Adsorption Isotherms, Adsorption Kinetics, and Thermodynamic Studies

Mercury (II) ions have significant ecological impacts. In the current study, magnetized iron oxide (Fe3O4) nanoparticles were green synthesized and encapsulated with alginate (ALG). The nanoparticles were converted into a composite (Fe3O4/ALG). The Fe3O4/ALG beads were used to remove Hg (II) from industrial wastewater. Characterization was performed by X-ray diffraction (XRD), scanning electron microscopy—energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis-differential thermal analysis (TGA-DTA). A central composite design (CCD) approach was performed to define the experimental conditions providing the highest global adsorption efficiency and to optimize the pH, temperature and adsorbent mass. Hg (II) concentrations were determined by flame and electrothermal atomic absorption spectrometry (FAAS and ETAAS). The limits of detection (LOD) and quantification (LOQ) were 1.2 mg L−1 and 3.5 mg L−1 for FAAS and 0.2 µg L−1 and 0.5 µg L−1 for ETAAS, respectively. Additionally, Langmuir, Freundlich, and Temkin isotherm models were employed to determine the adsorption mechanism. The adsorption capacity of Fe3O4/ALG was determined to be 49.18 mg g−1 by the Langmuir model. Kinetic studies revealed that the adsorption of Hg (II) best fitted the pseudo-second order model. The Gibb’s free energy (ΔG°) values showed that the adsorption of Hg (II) on Fe3O4/ALG occurred spontaneously.