LOD) And Quantification Research Articles

Integrating theoretical and experimental insights into nanoporous gold electrochemistry for enhanced baicalein sensing performance

We introduce an innovative electrochemical sensing method for the sensitive detection of Baicalein (BAI), emphasizing a simple surface modification process. The study encompasses both practical and theoretical investigations into the electrochemical behavior of nanoporous gold. Our theoretical analysis, based on advanced quantum-mechanical calculations, demonstrates that the adsorption of BAI molecule on gold-based substrates is energetically favorable, with adsorption energy increasing from an unmodified surface to a more porous substrate. BAI physisorbs on unmodified regions in a horizontal alignment, while it chemisorbs more strongly on nanoporous regions by penetrating the pores. On less modified surfaces, interaction energy predominates, whereas on heavily modified surfaces, distortion energies become more significant due to increased substrate reactivity. These results align with physicochemical characterizations, which reveal that nanoscale modifications, induced by different anodization times, explain the variations in electrode performance. Experimentally, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed using both a gold electrode (GE) and a nanoporous gold electrode (NPGE). The GE was subjected to surface treatment by immersion in H2SO4 and potential control at ca. +2.0 V for 40 seconds, resulting in a nanoporous configuration. Following optimizations, Adsorptive Stripping Voltammetry (AdSV) was used to determine BAI. The method achieved detection (LOD) and quantification (LOQ) limits of 0.015 µmol L-1 and 0.045 µmol L-1, respectively (Edeposition=-0.25 V; tdeposition=50 s). Additionally, the standard addition method was applied to the NPGE for recovering BAI from spiked synthetic human plasma and urine, with success rates ranging from 93.4% to 106%. This approach exhibited excellent stability, precision, and accuracy, with minimal interference from other substances. Moreover, the theoretical findings provided deeper insights into the selective electrochemical detection of BAI on nanoporous gold surfaces, offering new perspectives on this field.

Determination of three methylimidazole compounds in cosmetics by high performance liquid chromatography-tandem mass spectrometry

Methylimidazole compounds are byproducts formed during the caramel-coloring process and are used in various cosmetics. In addition metronidazole is an antibacterial and anti-inflammatory drug commonly used in modern medicine and is used in cosmetics to treat acne in the short-term. The illegal addition of metronidazole during cosmetics production can result in residual 2-methylimidazole (2-MEI), which, along with 4-methylimidazole (4-MEI), is a class 2B carcinogen. Therefore, establishing efficient, accurate, and sensitive analytical techniques for analyzing methylimidazole compounds in cosmetics is an urgent objective. In this study, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for simultaneously determining 1-methylimidazole (1-MEI), 2-MEI, and 4-MEI in cosmetics was developed. Cosmetics samples were extracted via ultrasonication in acetonitrile and purified using a mixed cation-exchange (MCX) solid-phase extraction (SPE) column, with subsequent drying under a stream of nitrogen and redissolution in acetonitrile. The resulting solution was then filtered through a 0.22 μm organic filter membrane for further testing. The analytes were separated using an XBridge® shield RP18 chromatographic column (150 mm×4.6 mm, 3.5 μm) and isocratically eluted with 20 mmol/L ammonium formate solution (containing 0.1% formic acid)-acetonitrile (98∶2, v/v). The target compounds were ionized by electrospray ionization (ESI) source, analyzed in multi-reaction monitoring (MRM) mode, and quantified using the external standard method, with the peak area of the quantitative ion and the mass concentration of the compound taken as the longitudinal and transverse coordinates, respectively. Matrix-matching working curves were also constructed. 1-MEI exhibited good linear relationships in the range of 5-200 μg/L, with correlation coefficients (r2)≥0.9994, while 2-MEI and 4-MEI showed good linearities in the range of 2-100 μg/L with r2≥0.9984. The three methylimidazole compounds exhibited limits of detection (LODs) and quantification (LOQs) of 10-30 μg/kg and 25-100 μg/kg, respectively. Under three spiked levels (LOQ, 2LOQ, 10LOQ), the recoveries of three methylimidazole compounds were 80.9%-107.9%, with relative standard deviations (RSDs, n=6) of 1.2%-12.8%. The practicability of the method was examined using 48 cosmetic samples; 4-MEI was detected in nine samples at contents of 26-1000 μg/kg, while two samples contained 240 and 267 μg/kg of 2-MEI, respectively. 1-MEI was not detected in any of the 48 samples tested. The developed method is simple, fast, and highly sensitive, and provides methodological support for assessing risks and monitoring the three methylimidazole compounds in cosmetics through screening.

Effective magnetic nanoadsorbent based on natural carboxymethyl cellulose/polyaniline nanotube/graphene oxide for aflatoxin B1 and B2 adsorption in rice utilizing a novel synthesis method

A magnetic nanoadsorbent was prepared via a novel one-pot magnetization method by employing natural carboxymethyl cellulose (CMC), polyaniline (PANI) nanotube, and graphene oxide (GO) for the effective adsorption of aflatoxins B1 (AFB1) and B2 (AFB2) from rice samples. This synthesized adsorbent combines the multifunction of CMC, PANI, and GO and shows improved extraction performance. FT-IR, XRD, FE-SEM, VSM, and TGA analyses were used to investigate the successful synthesis of the nanocomposite. The adsorption mechanism was ascribed to π-π interactions, hydrogen bonding, and hydrophobic interactions. Under optimized conditions, the method achieved extraction recoveries ranging from 78 % to 89 %. Low limits of detection (LODs) and quantification (LOQs) were obtained in the ranges of 0.07 and 0.01 ng g−1, and 0.20 and 0.04 ng g−1 for AFB1 and B2, respectively. This method showed an acceptable precision with intra- and inter-day relative standard deviations (RSDs) of less than 15 %. Comparative studies with other adsorbents used in extraction methods such as solid phase extraction (SPE), magnetic dispersive solid phase extraction (MDSPE), and matrix solid-phase dispersion (MSPD) demonstrated that the proposed method outperforms the existing procedures; it is promising in efficient AFs monitoring in rice.

An Efficient Fluorescent Chemosensing Probe for Total Determination and Speciation of Ultra-Trace Levels of Mercury (II) Species in Water.

The current study reports a novel fluorescent chemosensor based on the tagging agent 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein (Rose Bengal, RB) for detection of trace levels of Hg2+in environmental water. The established probe has been based upon liquid-liquid extraction (LLE) of the developed ternary complex ion associate {[Hg (bpy)2]2+.[RB]2-} of Hg2+ -2,2- bipyridyl complex [Hg (bpy)2]2+ and RB at pH 9.0 onto chloroform and measuring the resulting fluorescence enhancement signal intensity at λex/em = 570/ (580-600) nm. The limits of detection (LOD) and quantification (LOQ) of for Hg2+ was calculated to be 6.06 and 20 nM with a linear dynamic range (LDR) of 0.02-20µM, respectively. The stability constant, stoichiometry, chemical equilibria, and the thermodynamic parameters (ΔH, ΔS, and ΔG) of the developed ion associate were evaluated and assigned. Student's t and F tests at 95% confidence were fruitfully used for validation of the proposed methodology for Hg2+ detection in water samples with the aid of inductively coupled plasma-optical emission spectrometry (ICP-OES). The established strategy was successfully applied for detection of trace levels of Hg2+ in water samples with acceptable results. The proposed probe was satisfactorily applied for total determination and speciation of Hg in various water samples. Integrating the functional chelating agent onto associate formation to improve the selectivity and sensing properties of the LLE combining sensing probe towards target analyte in water represent the main interest.

Determination of seven phenoxy carboxylic acid herbicides in water using dispersive solid phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry based on metal-organic framework composite aerogel

Phenoxy carboxylic acid herbicides (PCAs) are difficult to degrade and, thus, pose significant threats to the environment and human health. The limit for 2,4-dichlorophenoxyacetic acid is 30 μg/L in China's standards for drinking water quality, 70 μg/L in the United States' drinking water standards, and 30 μg/L in the World Health Organization's guidelines for drinking water quality. Therefore, the development of an effective detection method for trace PCAs in water is a crucial endeavor. Metal-organic frameworks (MOFs) are novel porous materials that possess advantages such as a large specific surface area, adjustable pore size, and abundant active sites. They exhibit excellent adsorption capability for various compounds. However, the applications of MOFs as adsorbents are limited. For example, the process of isolating powdered MOFs from aqueous solutions is laborious, and microporous MOFs exhibit limited surface affinity, which decreases their mass transfer efficiency in the liquid phase. MOF crystals can be embedded in a substrate to overcome these limitations. Aerogels are obtained by drying hydrogels, which are hydrophilic polymers with a three-dimensional crosslinked network structure. Spongy aerogel materials exhibit unique structural properties such as high porosity, large pore volume, ultralow density, and easy tailorability. When MOFs are combined with an aerogel, their efficient and selective adsorption properties are preserved. In addition, MOF aerogels exhibit a hierarchical porous structure, which enhances the affinity and mass transfer efficiency of the MOF for target molecules. At present, MOF aerogels are primarily prepared by freeze-drying or using supercritical carbon dioxide. These drying processes require significant amounts of energy and time. Hence, the development of greener and more efficient methods to prepare skeleton aerogels is urgently needed. In this study, we prepared an environment-friendly aerogel at ambient temperature and pressure without the use of specialized drying equipment. This ambient-dried MOF composite aerogel was then used for the dispersive solid phase extraction (DSPE) of seven PCAs from environmental water, followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The key parameters affecting the efficiency of DSPE, including the extraction conditions, ratio of MIL-101(Fe)-NH2 to sodium alginate, pH of the aqueous samples, extraction time, ionic strength (salinity), and elution conditions, such as the elution solvent ratio, elution time, and elution volume, were investigated to obtain optimal extraction efficiency. The adsorbent could adsorb the target contaminants within 12 min, and the analytes could be completely desorbed within 30 s by elution with 4 mL of 1.5% (v/v) formic acid in methanol solution. The water samples could be analyzed without pH adjustment. The main adsorption mechanisms were electrostatic interactions and π-π conjugation. Thus, a new method based on MOF aerogels coupled with UHPLC-MS/MS was developed for the determination of the seven PCA residues in water. The calibration curves for the seven PCAs showed good linearity (r2≥0.9986), with limits of detection (LODs) and quantification (LOQs) ranging from 0.30 to 1.52 ng/L and from 1.00 to 5.00 ng/L, respectively. Good intra- and inter-day precision values of 6.5%-17.1% and 7.4%-19.4%, respectively, were achieved under low (8 ng/L), medium (80 ng/L), and high (800 ng/L) spiking levels. The developed method was applied to the detection of PCAs in surface water, seawater, and waste leachate, and the detected mass concentrations ranged from 0.6 to 19.3 ng/L. Spiked recovery experiments were conducted at mass concentrations of 8, 80, and 800 ng/L, and the recoveries ranged from 61.7% to 120.3%. The proposed method demonstrates good sensitivity, precision, and accuracy, and has potential applications in the detection of trace PCAs in environmental water.

Colorimetric and fluorometric sensing of polar E120 in juice and environmental water samples using mannitol-functionalized magnetic nanoparticles and nitrogen-doped carbon dots

In this study, mannitol-functionalized magnetic nanoparticles (MMNPs) as a unique nanosorbent and N-doped fluorescent carbon dots (N-CDs) as a cost-effective nanosensor were created and utilized, for the first time, for dispersive micro-solid-phase extraction (Dµ-SPE) to determine carmine (E120) dye in water samples and juices. The modification of the magnetic nanoparticles with mannitol was designed to enhance the responsive potential for adsorption of the polar E120 dye from complex sample matrices through electrostatic interaction. The as-fabricated N-CDs fluorescent probe exhibited a high fluorescence quantum yield (Φs) of 43.1 %, allowing for accurate fluorometric detection of E120 dye. The as-synthesized MMNPs nanosorbent and fluorescent N-CDs nanoprobe were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Energy Dispersive X-ray (EDX), Thermogravimetric analysis (TGA), and Vibrating-sample magnetometer (VSM). Density Functional Theory (DFT) studied the E120 dye structure using Gaussian 09 to explore the interactions between E 120 dye molecules and MMNPs/N-CDs. The impact of the critical adsorption and detection experimental factors was investigated and adjusted. A minimal amount of MMNPs nanosorbent (150 mg) is sufficient for E120 extraction in an acceptable time of 15 min. Furthermore, with a high determination coefficient, the adsorption characteristics fit with the models of Langmuir isotherm and first-order kinetics. The adsorption capacity (qe) of the as-fabricated MMNPs was 87.7 mg.g−1. After adsorption, E120 dye was fluorometrically analyzed using nitrogen-doped carbon dots as a fluorescent nanosensor via the inner filter effect (IFE) mechanism. Under the optimized conditions, the proposed fluorometric procedures showed a linear increase in the fluorescence ratio with increasing the E120 concentration in the range of 1.0 – 160.0 μg.mL−1 with detection (LOD) and quantitation (LOQ) limits of 0.27 and 0.83 μg.mL−1, respectively. The relative standard deviation (%RSD) did not exceed 2.34 %. The proposed methodology was successfully applied to determine E120 dye in juice and environmental water samples with % recovery ranged from 89.2-106.1 % and 92.9–107.2 %, respectively offering a reliable and environmentally friendly alternative to traditional detection methods with potential applications across various industries.

Simultaneous extraction and deglycosylation for flavonoid analysis in Ginkgo biloba products using a two-phase deep eutectic solvent system

Total flavonoid content is one of the most important quality indicators of Ginkgo biloba leaves and its products, but the complex pretreatment procedures and the excessive use of organic solvents complicate the detection process. In response, an innovative and efficient two-phase deep eutectic solvent (DES) system—composed of an acidic hydrophilic DES and a hydrophobic DES—was developed to quantify flavonoids for quality control of G. biloba products. High-performance liquid chromatography (HPLC) detection conditions were optimized, followed by systematic screening and design of the two-phase DES system through adjustments to polarity, hydrophilicity, and acidity. Optimal pretreatment conditions were established through operating condition optimization. This approach enabled simultaneous extraction, deglycosylation, and enrichment of all flavonoids from G. biloba samples into the hydrophobic phase in a single step. Method validation showed strong linearity with a correlation coefficient (R2 > 0.9995). The detection (LOD) and quantification (LOQ) limits were between 0.35 and 0.37 mg/kg, and 0.92 and 0.96 mg/kg, respectively. The method also exhibited high sensitivity and accuracy, with a recovery rate of 96.91–100.39%. A greenness assessment with the ComplexGAPI tool confirmed this method’s eco-friendly advantages over conventional techniques, aligning well with green chemistry and economic principles. Ultimately, this technique effectively measured flavonoid levels in different G. biloba products. The method developed in this work not only enhances the efficiency of simultaneous extraction and deglycosylation by modifying the polarity, hydrophilicity, and acidity of the two-phase DES system, but also offers valuable insights for the advancement of environmentally friendly analysis technology for flavonoids.

Determination and Quantification of Folpet in Barley using HPLC-DAD Analysis

Although rоutinе pesticide analysеs are mostly performed using GC-MS, GC-MS/MS and/or LC-MS/MS, some pesticides especially those with relatively high MRLs and good detector response could also be precisely quantified with less sensitive equipment which gives the opportunity to some laboratories to expand their scope of work. The study focuses on HPLC-DAD method development for detection of folpet in barley grain. QuEChERS method was performed for extraction after which, additional clean-up was performed using PSA and polypropylene filtration. Pesticide separation was achieved using mobile phase of acidified CAN (pH 2.5) and water. The initial mobile phase was 60:40% (v/v), the elution gradient starts from 80:20% (v/v) to 100:0% (v/v) in 7 min and holds 100:0% (v/v) up to 8.5 min at a flow rate of 1 ml/min after which in the next 6.5 min the column was re-equilibrated to 40% phase-B. Calibration was performed using matrix-matched calibration standards. The obtained limits of detection (LOD) and quantification (LOQ) were 0.18 and 0.55 mg/kg, respectively, and the linear regression coefficient was 0.9973. Recovery, repeatability and reproducibility were investigated at three fortification levels (0.1 mg/kg, 0.6 mg/kg, and 1.6 mg/kg) and were found acceptable with relative standard deviation less than 10%. The method was applied for the analysis of three barley grain samples obtained from different producers and showed that folpet was present in one sample below the LOQ. Overall, the developed method is suitable for the determination of folpet in barley grains at levels below the established MRL of 1 mg/kg.

Evaluation of in-house-built pipette-tip micro-solid-phase extraction devices for sample preparation in the analysis of amino compounds by liquid chromatography-tandem mass spectrometry

Amino compounds are of significant interest in dietary, clinical, and quality control fields. Efficient extraction is crucial for comprehensive metabolomics, especially for amino acids and biogenic amines, but traditional solid-phase extraction (SPE) methods are costly and require large solvent volumes. Miniaturized SPE techniques, like pipette-tip micro-solid-phase extraction (PT-µ-SPE), offer promising alternatives by improving throughput and reducing solvent and sorbent usage. This study presents PT-µ-SPE for the screening and quantification of amino compounds in bee products, particularly honey. The method involves derivatization with diethyl ethoxymethylenemalonate (DEEMM) and analysis using liquid chromatography-triple quadrupole mass spectrometry. Silica-based SCX sorbents were effective for a broad range of amino compounds, while WCX sorbents were better for aliphatic amines. The method's extraction efficiency was assessed across sample loading, washing, and elution solution, with recovery rates of 70 - 120% in oat bran, sea buckthorn leaves, and honey extracts. Matrix effects were observed for four amino compounds in honey. Limits of detection (LoD) and quantification (LoQ) ranged from 0.37 to 57 µg L⁻¹ and 1.13 to 174 µg L⁻¹, respectively. Covering 48 amino compounds under different PT-µ-SPE conditions, this method has been applied to several samples, demonstrating accuracy, environmental sustainability, cost-effectiveness, portability, and versatility in amino compound analysis.

A novel method for the simultaneous determination of flavonoids in Pteridium aquilinum via SPE combined with UPLC-DAD via QAMS

A novel analytical method based on ultra-performance liquid chromatography-diode array detector (UPLC-DAD), solid-phase extraction (SPE), and quantitative analysis of multiple components by single marker (QAMS) was developed for the first simultaneous determination of 8 flavonoids in Pteridium aquilinum. The combination of QAMS and SPE demonstrated the convenient and economic advantages of the QAMS method while also exhibiting straightforward and cost-efficient advantages in terms of both the time and solvent usage of the SPE. The contents of the 8 flavonoids in P. aquilinum ranged from 0.59 to 697.08 μg/g. There were no substantial differences in the quantification when comparing the QAMS method and the external standard method (ESM). The standard deviations (SDs, %) obtained by QAMS and ESM were all less than 5 %. SPE increased the concentration of flavonoids by 4.18–18.9 times. The limits of detection (LODs) and quantification (LOQs) were in the ranges of 0.01–0.15 and 0.06–0.33 ng/g, respectively. Method validation revealed the linearity of the calibration curves (R2 ≥ 0.9989), with recoveries between 97.02 % and 105 %, and the relative standard deviations (RSD) were all lower than 5 %. In addition, rhoifolin (4), apigenin (6), and amentoflavone (8) were first reported in P. aquilinum. The results suggested that this method was simple, reliable, and feasible for determining the flavonoids in P. aquilinum samples and could be further applied to various foods and herbal medicine samples.

A New LC-MS/MS-Based Method for the Simultaneous Detection of α-Tocopherol and Its Long-Chain Metabolites in Plasma Samples Using Stable Isotope Dilution Analysis

Background: Our study presented a novel LC-MS/MS method for the simultaneous quantification of α-tocopherol (α-TOH) and its phase II metabolites, α-13′-COOH and α-13′-OH, in human serum using deuterium-labeled internal standards (d6-α-TOH, d6-α-13′-COOH, d6-α-13′-OH). Methods: The method addresses the analytical challenge posed by the significantly different concentration ranges of α-TOH (µmol/L) and its metabolites (nmol/L). Previous methods quantified these analytes separately, which caused an increase in workflow complexity. Results: Key features include the synthesis of stable isotope-labeled standards and the use of a pentafluorophenyl-based core-shell chromatography column for baseline separation of both α-TOH and its metabolites. Additionally, solid phase extraction (SPE) with a HybridSPE® material provides a streamlined sample preparation, enhancing analyte recovery and improving sensitivity. By utilizing deuterium-labeled standards, the method compensates for matrix effects and ion suppression. This new approach achieves precise and accurate measurements with limits of detection (LOD) and quantification (LOQ), similar to previous studies. Calibration, accuracy, and precision parameters align well with the existing literature. Conclusions: Our method offers significant advantages in the simultaneous analysis of tocopherol and its metabolites despite concentration differences spanning up to three orders of magnitude. In contrast to earlier studies, which required separate sample preparations and analytical techniques for tocopherol and its metabolites, our approach streamlines this process. The use of a solid-phase extraction procedure allows for parallel sample preparation. This not only enhances efficiency but also significantly accelerates pre-analytical workflows, making the method highly suitable for large-scale studies.

Evaluating BTEX in vehicle exhaust gas: A fast and efficient approach using SPME and GC-BID

Benzene, toluene, ethylbenzene, and the xylene isomers (m, p, and o-xylene) (BTEX) are known for their harmful effects on human health and have been extensively studied across various environmental matrices. However, quantifying BTEX in exhaust gases poses challenges due to the complexity of the matrices. In this study, we investigated a method development strategy involving solid-phase microextraction (SPME) and gas chromatography coupled with a dielectric barrier discharge ionization Detector (BID) for quantifying BTEX emitted from internal combustion engines operating at idle. Sampling was conducted using 1.0 L Tedlar bags, followed by withdrawal of aliquots and dilution with atmospheric air using a novel device (graduated vial) designed for gaseous samples. The SPME-GC-BID method was developed and validated for the conditions: BTEX extraction in CAR/PDMS 75 μm fiber at a contact time of 5.0 min at a temperature of 27 °C, followed by GC-BID analysis. Method validation to ensure the reliability of quantitative results used the merit figures e.g., limits of detection (LOD) and quantification (LOQ), precision, and accuracy (recovery). LOD varied from 0.194 to 0.340 mg m−3, LOQ varied from 0.587 to 1.03 mg m−3, precision ranged from 1.47 to 7.14 %, and recovery varied from 82.34 to 109.5 %. BTEX concentration in vehicle exhaust varied from 3.40 to 16.4 mg m−3. The results showed, concerning the figures of merit analyzed, that the SPME-GC-BID method provides good sensibility, precision, and accuracy for evaluating the presence of BTEX in the exhaust of internal combustion engines, contributing to the understanding of health risks associated with vehicle emissions.

Selective quantification of estrogens in serum with aptamer-affinity and LC-MS/MS analysis

In the previous study, we developed an accurate and automated immunologic mass spectrometry (iMS) method for the simultaneous quantification of multiple steroid hormones by target capturing with monoclonal antibodies and LC-MS/MS analysis. However, antibodies are less accessible to a wide variety of low-molecular-weight analytes, which limited the application of iMS method. At the same time, multiple monoclonal antibodies needed also increased the complexity and cost of the iMS assay. In the present study, we developed an aptamer-affinity and LC-MS/MS analysis method with a class-specific aptamer for the selective enrichment and simultaneous determination of estrogens (estrone (E1) and estradiol (E2)) in human serum. The DNA aptamer was coupled to magnetic beads to enrich the target estrogens from serum sample after protein precipitation. The magnetic beads were then washed and eluted with acetonitrile solution, and targets were analyzed with LC-MS/MS. The sample preparation process of enrichment, washing and elution works in an automatic manner. Matrix effect was negligible as the high specificity of target recognition and enrichment by the aptamer. The aptamer-affinity assay for estrogen quantification was validated for sensitivity, linearity, accuracy and precision. The limit of detection (LOD) and quantification (LOQ) were0.01 ng/mLand0.02 ng/mL for E1 and E2, respectively. Satisfactory coefficients of variation (CVs) were obtained, with the intra-batch CVs of5.5 %-7.3 % and 5.2 %-6.0 % for E1 and E2, respectively, and inter-batch CVs of 3.8 %-10.0 % and 5.2 %-6.3 % for E1 and E2, respectively. Recoveries were in the range of99.1 %-107.0 % and 94.9 %-107.7 % for E1 and E2, respectively. Quantification results of 40 serum samples by the aptamer-affinity and solid-phase extraction (SPE) LC-MS/MS method showed good consistency, with the correlation coefficient of 0.93 and 0.98 for E1 and E2, respectively. Clinical application of the aptamer-affinity and LC-MS/MS method was further demonstrated for quantifying serum estrogen levels of 170 pregnant women at different gestational weeks.

Microextraction by packed sorbent: Introducing a novel hybrid silica-based chitosan-graphene oxide biosorbent for the evaluation of pesticides and antibiotics in food matrices

This study introduces a novel silica-graphene oxide@chitosan (SiGO@CS) material as a packed biosorbent for microextraction by packed sorbent (MEPS), followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of pesticides (atrazine and thiamethoxam) and antibiotics (ceftiofur and sulfonamide) in food samples. The graphene-based aerogel was modified with varying percentages of silica-graphene oxide/chitosan (w/w) and characterized to confirm successful chitosan incorporation. Optimization of the MEPS protocol, using 24–1 and 23 experimental designs, identified draw/eject and washing cycles as the most influential parameters for extraction efficiency. The SiGO@CS biosorbent with 80 % CS/SiGO (w/w) exhibited superior extraction efficiency compared to other ratios and commercial sorbents. The method demonstrated excellent linearity for all analytes (R² > 0.9900), with low limits of detection (LOD) and quantification (LOQ) ranging from 0.020 to 0.045 µg l-1 and 0.045 to 1.0 µg l-1 for pesticides, respectively, and 5 to 15 µg l-1 and 15 to 20 µg l-1 for antibiotics, respectively. Trueness values were within 82 % to 109 %. The method's green credentials were confirmed using AGREEprep and the Green Analytical Procedure Index (GAPI) approach, highlighting sorbent reusability (over 15 times) and rapid analytical throughput (5 min per sample) with low use of pre-treated sample extract volume (500 µL). The application to local corn, tomato, and milk samples confirmed the detection and quantification of thiamethoxam and atrazine at concentrations above the recommended ingestion per day for one sample of tomato and corn out of the three samples analyzed. Furthermore, using the novel SiGO@CS biosorbent in the MEPS protocol offers a green, high-performance analytical alternative to traditional sorbent phases, with the potential for evaluating trace levels of pesticides and antibiotics in food matrices.

Determination of three dechloranes in environmental water by magnetic solid-phase extraction-gas chromatography-negative chemical ionization mass spectrometry based on the covalent organic framework material

Dechloranes are additive-type chlorine flame retardants that are widely used in processing industrial products, such as electronic equipment and textiles. Dechloranes, which can enter the human body through various routes, pose significant health risks because of their toxicity, persistence, and bioaccumulation. In 2023, dechlorane plus was listed in the Stockholm Convention on Persistent Organic Pollutants. In the same year, China recognized this compound as a priority-controlled substance. Dechloranes are commonly found at trace levels in water, which is extremely harmful to the environment and human health. Therefore, the development of detection methods for dechloranes is crucial. Magnetic solid-phase extraction (MSPE) has attracted considerable attention because of its low organic solvent consumption, simplicity of adsorbent separation, and ease of operation. In general, the selectivity and efficiency of MSPE depend on the characteristics of the adsorbent. Covalent organic frameworks (COFs) have regular porosity, structural predictability and stability, high specific surface areas, and adjustable pore sizes, which are advantageous for a wide range of separation and analysis applications. In this study, Fe3O4 magnetic nanoparticles and a COF material (TpBD) were combined to prepare Fe3O4@TpBD as an adsorbent for dechloranes. Subsequently, an effective method for analyzing dechlorane in environmental water was established by coupling MSPE with gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The successful synthesis of Fe3O4@TpBD was confirmed using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. A single-factor method was used to optimize the extraction conditions, including the Fe3O4@TpBD dosage, pH of water sample, elution solvent type and volume, extraction time, elution time, and ionic strength. The target analytes were separated on a TG-5SILMS column (30 m×0.25 mm×0.25 μm) and quantified using the external standard method in the selected-ion monitoring (SIM) mode. Under the optimal extraction conditions, the method validation results showed a linear range of 2-1000 ng/L. The limits of detection (LODs) and quantification (LOQs) were 0.18-0.27 ng/L and 0.60-0.92 ng/L, respectively, for the three analytes. The intra-day and inter-day precisions at three spiked levels were 4.2%-16.2% and 6.9%-15.7%, respectively. This method was successfully applied to the determination of dechloranes in environmental water samples (laboratory tap water, reservoir water, wastewater treatment plant effluent, and landfill leachate treatment effluent). The recoveries of the three dechloranes at different spiked levels ranged from 77.8% to 113.3% with relative standard deviations (RSDs) of 2.5%-16.3% (n=3). With the advantages of operational simplicity, high sensitivity, and good reproducibility, the proposed method is suitable for the qualitative and quantitative determination of dechloranes in environmental water.

Miniaturized dual-wavelength β-correction spectrophotometric probe for sensitive detection of cyanide in water via formation of cyano dithizone adduct

Cyanide toxicity in water significantly threatens public health and the environment. To address this, a miniaturized simple, low-cost, selective and sensitive direct dual wave β-correction spectrophotometric probe has been established for cyanide detection in water. The dual-wavelength β-correction spectrophotometry enhances the selectivity and sensitivity of the probe in the presence of interfering species. The assay relies a highly selective nucleophilic addition of cyanide ions to dithizone (H2Dz) as chromogenic reagent in aqueous media of pH 6.8–7.2, forming a red-colored cyano H2Dz adduct. The electronic spectrum of the formed adduct displays a sharp absorption peak at λmax = 480 nm, enabling precise colorimetric detection. The molar absorptivity and Sandell’s sensitivity index for the cyano H2Dz adduct with and without β-correction spectrophotometry were 5.62 × 103, and 1.79 × 103 L mol−1 cm−1, and 0.002 and 0.0033 µg cm−2, respectively. Beer’s law and Ringbom’s plots are valid in the range 0.01–5.0 and 0.06–2.0 µg mL−1 CN– concentration, respectively. The limits of detection (LOD) and quantification (LOQ) improved from 1.03 × 10−1 and 3.13 × 10−1 μg/mL using ordinary spectrophotometry to 2.8 × 10−2 and 8.7 × 10−2 μgmL−1 employing β-correction spectrophotometry. The probe offers rapid response, good anti-interference ability, reproducibility, and cost-effectiveness. The probe was successfully applied for detection of trace levels of cyanide ions in water with good repeatability. It has been also validated in water samples with good recoveries (99.2 ± 5.02 %). The experimental Student t test (texp = 1.2–1.5) was lower than the critical (texp = 2.78) at 95 % probability (n = 5). The stoichiometry and mechanism of formation of the cyano adduct were assigned and addressed.

Cloud point Extraction Of Methimazole By Direct (UV- Vis Spectrophotometer) And Indirect (Flame Atomic Absorption) methods

Abstract A new technique based on the formation of a chelate Methimazole-Fe(III) at 400 nm was used for the determination of Methimazole 114 as a surfactant in some pharmaceuticals using indirect flame atomic absorption spectroscopy (FAAS) and UV-visible methods based on Triton turbidity extraction. The optimal turbidity extraction temperature was 75.0°C after 25 min of extraction of the complex [MET-Fe(III)] with ethanol. The structure of the Methimazole-Fe(III) chelate was determined by the molar ratio method. A 1:1 L:M (ligand:metal) ratio was produced. The Beer law was employed in the concentration range of 2.5-30 and 2.5-32.5 g/mL for the UV and FAAS, respectively.. The limits of detection (LOD) and quantification (LOQ) were (0.3784) g/ml and (1.2612) g/ml, respectively, for these techniques. The technique has been approved and successfully used in the production of pharmaceutical preparations such as: B. Methimazole capsules sold in Iraq. The analytical results were validated by statistical and recycling studies with satisfactory results.

Laser‐scribed graphene toward scalable fabrication of electrochemical paper-based devices for lidocaine detection in forensic and pharmaceutical samples

Lidocaine (LID), a tertiary amine drug, is widely used as a local anesthetic for topical anesthesia and also presents antiarrhythmic and analgesic properties. Given its use can induce a temporary loss of sensory, motor, and autonomic function, it has been associated with criminal instances of drug-facilitated sexual assault. Herein, we manufactured an electrochemical paper-based analytical device (ePAD) using the laser-scribed graphene (LSG) technique for LID detection in pharmaceutical and forensic applications. The paper-based devices were characterized by scanning electron microscopy (SEM) and Raman spectroscopy, confirming the porosity and graphene-derived nature of the LSG material. In addition, to enhance the electrocatalytic properties, the LSG electrode was modified with a nanocomposite based on the mixture of multi-walled carbon nanotubes (MWCNT) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Electrochemical characterizations of the non-modified and MWCNT/PEDOT:PSS-modified electrodes by impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV), revealed the enhancement of the electrochemical properties of the modified electrode, providing higher detectability for LID detection. An analytical curve was built using DPV technique and exhibited a linear response in the concentration range of 31 to 248 µmol L−1 LID. The limits of detection (LOD) and quantification (LOQ) of the method were 0.72 µmol L−1 and 2.39 µmol L−1, respectively. The manufacturing reproducibility of the method was assessed by testing 8 sensors from different batches and provided a relative standard deviation (RSD) of 4.92 % (n = 8). The developed sensor was applied to LID determination in a commercial anesthetic sample and, as proof of the applicability of potential use in crime scenes of drug-facilitating crimes, we analyzed spiked LID in alcoholic drinks (vodka and tequila samples). The recovery percentages ranged from 79 % to 109 %, highlighting the practical use of our portable method for in-field analysis. In addition, four seized cocaine samples containing LID were successfully analyzed to demonstrate the potential use as a LID screening tool in street drug samples.

RP-HPLC-PDA-Based Simultaneous Estimation of Ramipril and Hydrochlorothiazide in Combined Dosage Forms: A Validated Approach

A rapid, highly sensitive High-Performance Liquid Chromatographic method has been developed for the simultaneous determination of Ramipril (RMP) and Hydrochlorothiazide (HCT) in bulk drug and in tablets. Ramipril (RMP) and Hydrochlorothiazide (HCT) were eluted from an Eclipse plus C18 (250 mm × 4.6 mm I.D.) with particle size 5 µm reversed phase column with a mobile phase consisting of acetonitrile and potassium dihydrogen ortho-phosphate pH 3 (40: 60 v/v) at a flow rate of 1 mL/min with UV detection at 210 nm. The retention time for RMP and HCT was found to be 3.31 ± 0.02 min and 6.64 ± 0.02 min, respectively. The linear response (r2 <0.99) was observed in the range of 2 - 12 μg/mL for RMP and 4 - 24 μg/mL of HCT with low values of limits of detection (LOD) and quantification (LOQ) for both drugs. The method shows good recoveries and intra and inter-day relative standard deviations were less than 1.0%. Validation parameters as specificity, accuracy, ruggedness and robustness were also determined. The proposed method provides accurate and precise quality control tool for routine simultaneous analysis of Ramipril and Hydrochlorothiazide in bulk and in tablet dosage form.

Enhanced chemiluminescence by carbon dots for rapid detection of bisphenol A and nitrite

Herein, a novel chemiluminescence (CL) sensor was successfully developed based on chlorine doped carbon dots (Cl/CDs) for the rapid determination of bisphenol A (BPA) and nitrite. The Cl/CDs were synthesized through a hydrothermal method, using ascorbic acid as the precursor and hydrochloric acid as the dopant. It was found that Cl/CDs significantly enhanced the CL intensity of the acid-KMnO4 system, while BPA and nitrite quenched the CL intensity of the Cl/CDs-sensitized acid-KMnO4 system. Under optimal conditions, BPA exhibited a linear detection range of 0.05–10 μM, with limits of detection (LOD) and quantification (LOQ) of 0.86 nM and 2.8 nM, respectively. Nitrite showed a linear detection range of 0.7–100 μM, with LOD and LOQ of 22.5 nM and 75 nM, respectively. The CL sensor was successfully use to determine BPA in water samples and nitrite in pickles, ham and celery, with spike recovery rates of 96.3 %–104.8 % and 96.0 %–104.9 %, respectively.