Mass spectrometry in ocular drug research.

Mass spectrometry (MS) has been proven as an excellent tool in ocular drug research allowing analyzes from small samples and low concentrations. This review begins with a short introduction to eye physiology and ocular pharmacokinetics and the relevance of advancing ophthalmic treatments. The second part of the review consists of an introduction to ocular proteomics, with special emphasis on targeted absolute quantitation of membrane transporters and metabolizing enzymes. The third part of the review deals with liquid chromatography-MS (LC-MS) and MS imaging (MSI) methods used in the analysis of drugs and metabolites in ocular samples. The sensitivity and speed of LC-MS make simultaneous quantitation of various drugs and metabolites possible in minute tissue samples, even though ocular sample preparation requires careful handling. The MSI methodology is on the verge of becoming as important as LC-MS in ocular pharmacokinetic studies, since the spatial resolution has reached the level, where cell layers can be separated, and quantitation with isotope-labeled standards has come more reliable. MS will remain in the foreseeable future as the main analytical method that will progress our understanding of ocular pharmacokinetics.

Investigations into the concentrations and metabolite profiles of doping agents and antidepressants in human seminal fluid using liquid chromatography-mass spectrometry.

Exogenous substances, including drugs and chemicals, can transfer into human seminal fluid and influence male fertility and reproduction. In addition, substances relevant in the context of sports drug testing programs, can be transferred into the urine of a female athlete (after unprotected sexual intercourse) and trigger a so-called Adverse Analytical Finding. Here, the question arises as to whether it is possible to distinguish analytically between intentional doping offences and unintentional contamination of urine by seminal fluid. To this end, 480 seminal fluids from non-athletes were analysed to identify concentration ranges and metabolite profiles of therapeutic drugs that are also classified as doping agents. Therefore, a screening procedure was developed using liquid chromatography connected to a triple quadrupole mass spectrometer, and suspect samples (i.e. samples indicating the presence of relevant compounds) were further subjected to liquid chromatography-high-resolution accurate mass (tandem) mass spectrometry. The screening method yielded 90 findings (including aromatase inhibitors, selective estrogen receptor modulators, diuretics, stimulants, glucocorticoids, beta-blockers, antidepressants, and the non-approved PPARδ agonist GW1516) in a total of 81 samples, with 91 % of these suspected cases being verified by the confirmation method. Besides the intact drug, phase-I and -II metabolites were also occasionally observed in the seminal fluid. This study demonstrated that various drugs including those categorized as doping agents partition into seminal fluid. Monitoring substances and metabolites may contribute to a better understanding of the distribution and metabolism of exogenous substances in seminal fluid that may be responsible for the impairment of male fertility. Significance Statement This study demonstrates that doping agents as well as clinically relevant substances are transferred/eliminated into seminal fluid to a substantial extent and that knowledge about drug levels (and potential consequences for the male fertility and female exposure) is limited. The herein generated new dataset provides new insights into an important and yet little explored area of drug deposition and elimination, and hereby a basis for the assessment of contamination cases by seminal fluid in sports drug testing.

Results of the first international quality control programme for oral targeted oncolytics.

AIMS: With the rising number of oral targeted oncolytics and growing awareness of the benefits of therapeutic drug monitoring (TDM) within the field of oncology, it is expected that the requests for quantifying concentrations of these drugs will increase. It is important to (cross-)validate available assays and ensure its quality, as results may lead to altered dosing recommendations. Therefore, we aimed to evaluate the performance of laboratories measuring concentrations of targeted oral oncolytics in a one-time international quality control (QC) programme. METHODS: Participating laboratories received a set of plasma samples containing low, medium and high concentrations of imatinib, sunitinib, desethylsunitinib, pazopanib, cabozantinib, olaparib, enzalutamide, desmethylenzalutamide and abiraterone, with the request to report their results back within five weeks after shipment. Accuracy was defined acceptable if measurements where within 85%-115% from the weighed-in reference concentrations. Besides descriptive statistics, an exploratory ANOVA was performed. RESULTS: Seventeen laboratories from six countries reported 243 results. Overall, 80.7% of all measurements were within the predefined range of acceptable accuracy. Laboratories performed best in quantifying imatinib and poorest in quantifying desethylsunitinib (median absolute inaccuracy respectively 4.0% (interquartile range (IQR) 1.8%-6.5%) and 15.5% (IQR 8.8%-34.9%)). The poorest performance of desethylsunitinib might be caused by using the stable-isotope-labelled sunitinib instead of desethylsunitinib as an internal standard, or due to the light-induced cis(Z)/trans(E) isomerization of (desethyl)sunitinib. Overall, drug substance and performing laboratory seemed to influence the absolute inaccuracy (F = 16.4; p < 0.001 and F = 35.5; p < 0.001, respectively). CONCLUSION: Considering this is the first evaluation of an international QC programme for oral targeted oncolytics, an impressive high percentage of measurements were within the predefined range of accuracy. Cross-validation of assays that are used for dose optimization of oncolytics will secure the performance and will protect patients from incorrect advices.

Sensitive and selective determination of upadacitinib using a custom-designed electrochemical sensor based on ZnO nanoparticle-assisted molecularly imprinted polymer.

Upadacitinib (UPA) is a selective and reversible oral Janus kinase (JAK) 1 inhibitor and is of great importance in treating inflammatory bowel disease (Zheng et al., Int Immunopharmacol 126:111229, 2024; Foy et al., JAAD Case Rep 42:20-22, 2023). Although there are limitations to the effectiveness of UPA, it has received positive responses in clinical trials and is approved for the treatment of atopy dermatitis (AD) (Li et al., Int Immunopharmacol 125:111193, 2023). In this study, a nanoparticle-doped molecularly imprinted polymer (MIP)-based electrochemical sensor was developed for sensitive and selective detection of UPA. The developed sensor was designed as a thin film layer using the photopolymerization method on the surface of the prepared nanoparticle-doped polymerization solution glassy carbon electrode (GCE). Various nanoparticles, such as multi-walled carbon nanotube, titanium dioxide, oxide, and zinc oxide (ZnO) nanoparticles, were the most suitable for UPA. Surface characterization of the developed sensor was done by scanning electron microscopy (SEM), and electrochemical characterization was done by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The quantitative analysis of UPA was performed in 5.0 mM [Fe (CN)6]3-/4- solution using the differential pulse voltammetry (DPV) technique. Under optimum conditions, the calibration range was between 0.1 and 1 pM. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.005 pM and 0.017 pM, respectively. The sensor's accuracy was proven by performing a recovery study in serum. The sensor's selectivity was also evaluated using common interfering substances such as KNO3, CaCl2, Na2SO4, uric acid, ascorbic acid, dopamine, and paracetamol. According to the results obtained, the performance of the designed sensor was found to be quite sensitive and selective in determining UPA. The developed UPA-ZnO/3-APBA@MIP-GCE sensor showed high sensitivity and selectivity towards UPA. In addition, the selectivity, the most important feature of the MIP-based sensor, was confirmed by imprinting factor (IF) calculations using tofacitinib (TOF) and ruxolitinib (RUX). The sensor's unique selectivity is demonstrated by its successful performance even in the presence of UPA impurities.

Enantioselective separation and determination of ibuprofen: Stereoselective pharmacokinetics, pharmacodynamics and analytical methods.

Ibuprofen (IBP), the 29th most prescribed drug in the United States in 2019, is a widely used nonsteroidal anti-inflammatory drug (NSAID) comprising two enantiomers, (R)-IBP and (S)-IBP, collectively known as (RS)-IBP. This critical review examines analytical techniques for the enantioselective separation and determination of IBP enantiomers, crucial for pharmaceutical and clinical applications. The review focuses on state-of-the-art methods, including chromatographic techniques including high-performance liquid chromatography, gas chromatography, liquid chromatography-tandem mass spectrometry, and some other techniques. This review addresses pharmacokinetics, pharmacology, and side effects of each enantiomer, ensuring safe drug usage. By consolidating diverse analytical methods and their applicability in different matrices, this review serves as a valuable resource for researchers, analysts, and practitioners in pharmaceutical analysis, pharmacology, and clinical studies.

One-Pot Synthesis of Sustainable Fluorescent Nanomaterials via Microwave Irradiation as a Probe for the Determination of Metformin in Pure and Pharmaceutical Dosage Forms: Greenness and Whiteness Metrics.

A rapid, green and sensitive technique for the determination of metformin determination was developed based on the direct fluorescence enhancement of carbon dots (CDs) induced by the cited drug. The water-soluble CDs were prepared via a one-pot synthesis from avocado peels using domestic microwave. The prepared CDs exhibited strong fluorescence at 405 nm after excitation at 320 nm with a quantum yield of 51%. The fluorescence of CDs was enhanced linearly by increasing the concentration of metformin within the range 0.5-25 µg/mL with limit of detection 0.087 µg/mL and limit of quantification 0.263 µg/mL. The designed probe was proved to be selective toward metformin in the presence of other drugs such as vildagliptin and alogliptin and also in the presence of excipients in the pharmaceutical dosage form. The suggested and reported methods were compared with the help of the whiteness and greenness tools, specifically the white analytical chemistry and analytical greenness metric tools, for assessing hazardous solvents and reagents used.

Fabrication of a novel tantalum boride/vanadium carbide modified screen-printed carbon electrode for voltammetric determination of pimonidazole in bio-fluids.

For the first time, a tumour hypoxia marker detection has been developed using two-dimensional layered composite modified electrodes in biological and environmental samples. The concept of TaB2 and V4C3-based MXene composite materials is not reported hitherto using ball-milling and thermal methods and it remains the potentiality of the present work. The successful formation is confirmed through various characterisation techniques like X-ray crystallography, scanning electron microscopy photoelectron, and impedance spectroscopy. A reliable and repeatable electrochemical sensor based on TaB2@V4C3/SPCE was developed for quick and extremely sensitive detection of pimonidazole by various electroanalytical methods. It has been shown that the modified electrode intensifies the reduction peak current and causes a decrease in the potential for reduction, in comparison with the bare electrode. The proposed sensor for pimonidazole reduction has strong electrocatalytic activity and high sensitivity, as demonstrated by the cyclic voltammetry approach. Under the optimal experimental circumstances, differential pulse voltammetry techniques were utilised for generating the wide linear range (0.02 to 928.51 µM) with a detection limit of 0.0072 µM. The resultant data demonstrates that TaB2@V4C3/SPCE nano-sensor exhibits excellent stability, reliability, and repeatability in the determination of pimonidazole. Additionally, the suggested sensor was successfully used to determine the presence of pimonidazole in several real samples, such as human blood serum, urine, water, and drugs.

Analytical approaches for determination of COVID-19 candidate drugs in human biological matrices.

Since the outbreak of the COVID-19 pandemic, the use of antiviral and other available drugs has been considered to combat or reduce the clinical symptoms of patients. In this regard, it would be necessary to choose sensitive and selective analytical techniques for pharmacokinetic and pharmacodynamic studies, monitoring of drug concentration in biological fluids, and determination of the most appropriate dose to achieve the desired effect on the disease. In the present study, the analytical techniques based on spectroscopy and chromatography with different detectors for diagnosis and determination of candidate drugs in the treatment of COVID-19 in human biological fluids are reviewed during the period 2015-2022. Moreover, various sample preparation and extraction techniques, are being used for this purpose, such as protein precipitation (PP), solid-phase extraction (SPE), liquid-liquid extraction (LLE), and QuEChERS (quick, easy, cheap, effective, rugged, and safe) are investigated.

Stability for 6 months and accuracy of a specific enteral caffeine base preparation for a multisite clinical trial.

The 'Intermittent Hypoxia and Caffeine in Infants Born Preterm (ICAF)' study (NCT03321734) uses an extemporaneously compounded enteral caffeine base solution for its study drug. The primary aim of this report is to determine the stability of this specific enteral caffeine base preparation stored for up to 6 months and assess optimal storage temperature. To analyse stability, caffeine solutions were prepared and stored at 4°C and 25°C (room temperature). The caffeine concentrations were analysed over time using high-performance liquid chromatography (HPLC). To confirm the accuracy of compounded caffeine concentrations, study drug samples from three research pharmacies were analysed. Stability results showed that caffeine concentrations are within 5% of the expected concentration when stored for up to 6 months at room temperature. Our results also show that accurate caffeine concentrations were achieved by multiple research pharmacies.

Conductive vial electromembrane extraction of opioids from oral fluid.

The use of oral fluid as sample matrix has gained significance in the analysis of drugs of abuse due to its non-invasive nature. In this study, the 13 opioids morphine, oxycodone, codeine, O-desmethyl tramadol, ethylmorphine, tramadol, pethidine, ketobemidone, buprenorphine, fentanyl, cyclopropylfentanyl, etonitazepyne, and methadone were extracted from oral fluid using electromembrane extraction based on conductive vials prior to analysis with ultra-high performance liquid chromatography-tandem mass spectrometry. Oral fluid was collected using Quantisal collection kits. By applying voltage, target analytes were extracted from oral fluid samples diluted with 0.1% formic acid, across a liquid membrane and into a 300 µL 0.1% (v/v) formic acid solution. The liquid membrane comprised 8 µL membrane solvent immobilized in the pores of a flat porous polypropylene membrane. The membrane solvent was a mixture of 6-methylcoumarin, thymol, and 2-nitrophenyloctyl ether. The composition of the membrane solvent was found to be the most important parameter to achieve simultaneous extraction of all target opioids, which had predicted log P values in the range from 0.7 to 5.0. The method was validated in accordance to the guidelines by the European Medical Agency with satisfactory results. Intra- and inter-day precision and bias were within guideline limits of ± 15% for 12 of 13 compounds. Extraction recoveries ranged from 39 to 104% (CV ≤ 23%). Internal standard normalized matrix effects were in the range from 88 to 103% (CV ≤ 5%). Quantitative results of authentic oral fluid samples were in accordance with a routine screening method, and external quality control samples for both hydrophilic and lipophilic compounds were within acceptable limits.

Biomass derived nitrogen functionalized carbon nanodots for nanomolar determination of levofloxacin in pharmaceutical and water samples.

Binder-free and efficient electrochemical sensing of levofloxacin (LF) was successfully developed based on the nitrogen-doped carbon nanodots (NCNDs). The NCNDs were synthesized by hydrothermal carbonation (180°C for 12 h), and the heteroatom was embedded in aqueous solution of ammonia (NH3). Spectral and microscopic characteristization techniques were used to analyze the topological, crystallinity, and chemical binding behavior of synthesized biomass functional material. HR-TEM image revealed a uniform spherical dot (2.96 nm), and superior quantum yield efficiency (0.42 Φ). The NCNDs was drop coated on a glassy carbon electrode (GCE) and electrochemical sensing of LF was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve in phosphate-buffered saline (PBS; pH = 7.0). The NCNDs modified electrode showed a sharp oxidation peak at +0.95 V (vs. Ag/AgCl) with a four-fold higher current response than the bare GC electrode. The NCNDs/GCE surface not only increases the current response, but has lower detection potential, and facilitates electron transfer reaction. Under optimized working parameters, the NCNDs/GCE showed wide linear concentrations range from 200 nM to 2.8 mM and a low detection limit (LOD) of 48.26 nM (S/N = 3). The electrode modified with NCNDs has high electrochemical sensing stability (RSD = 1.284 ± 0.05% over 5 days), and superior reproducibility (RSD = 1.682 ± 0.06% (n = 3)). Finally, the NCNDs modified GC electrode was successfully applied to quantify the concentration of LF in drug and river water samples with acceptable recovery percentages of 96.60-99.20% and 97.20-99.00% (n=3), respectively.

Application of gas chromatography in the analysis of phytocannabinoids: An update (2020-2023).

INTRODUCTION: Cannabinoids are a group of compounds that bind to cannabinoid receptors. They possess pharmacological properties like that of the plant Cannabis sativa. Gas chromatography (GC) is one of the popular chromatographic techniques that has been routinely used in the analysis of cannabinoids in different matrices. OBJECTIVE: The article aims to review the literature on the application of GC-based analytical methods for the analysis of phytocannabinoids published during the period from January 2020 to August 2023. METHODOLOGY: A thorough literature search was conducted using different databases, like Web of Knowledge, PubMed, Google Scholar, and other relevant published materials including published books. The keywords used, in various combinations, with cannabinoids being present in all combinations, in the search were cannabinoids, Cannabis sativa, marijuana, analysis, GC, quantitative, qualitative, and quality control. From the search results, only the publications that incorporate the GC analysis of phytocannabinoids were reviewed, and papers on synthetic cannabinoids were excluded. RESULTS: Since the publication of the review article on GC analysis of phytocannabinoids in early 2020, several GC-based methods for the analysis of phytocannabinoids have appeared in the literature. While simple 1D GC-mass spectrometry (MS) and GC-flame ionisation detector (FID) methods are still quite common in phytocannabinoids analysis, 2D GC-MS and GC-MS/MS are increasingly becoming popular, as these techniques offer more useful data for identification and quantification of phytocannabinoids in various matrices. The use of automation in sample preparation and the utilisation of mathematical and computational models for optimisation of different protocols have become a norm in phytocannabinoids analysis. Pre-analyses have been found to incorporate different derivatisation techniques and environmentally friendly extraction protocols. CONCLUSIONS: GC-based analysis of phytocannabinoids, especially using GC-MS, remains one of the most preferred methods for the analysis of these compounds. New derivatisation methods, ionisation techniques, mathematical models, and computational approaches for method optimisation have been introduced.

On the Application of Microfluidic-Based Technologies in Forensics: A Review.

Microfluidic technology is a powerful tool to enable the rapid, accurate, and on-site analysis of forensically relevant evidence on a crime scene. This review paper provides a summary on the application of this technology in various forensic investigation fields spanning from forensic serology and human identification to discriminating and analyzing diverse classes of drugs and explosives. Each aspect is further explained by providing a short summary on general forensic workflow and investigations for body fluid identification as well as through the analysis of drugs and explosives. Microfluidic technology, including fabrication methodologies, materials, and working modules, are touched upon. Finally, the current shortcomings on the implementation of the microfluidic technology in the forensic field are discussed along with the future perspectives.

Synergism of Photo-Induced Electron Transfer and Aggregation-Induced Quenching Mechanisms for Highly Sensitive Detection of Silver Ion and Captopril.

Carbon-based nanoprobes, with excellent physicochemical performance and biocompatibility, are a kind of ideal nanomaterial for biosensing. Herein, we designed and prepared novel oxygen-doped nitrogen-enrichment carbon nanoribbons (ONCNs) with an excellent optical performance and uniform morphology, which could be used as a dual-mode fluorescence probe for the detection of Ag+ ion and captopril (Ctl) based on the synergism of photo-induced electron transfer and aggregation-induced quenching mechanisms. By recording the changes in fluorescent intensities of ONCNs, the Ag+ ion and Ctl concentrations can be easily tested in real samples. The results displayed that two good linear relationships existed between the change in fluorescent intensity of ONCNs and the concentrations of Ag+ ion and Ctl in the ranges of 3 µM to 30 µM and 1 µM to 30 µM, with the detection limit of 0.78 µM and 74 nM, respectively. The proposed sensing platform has also been successfully applied for the Ctl analysis in commercial tablet samples based on its high selectivity, proving its value in practical applications.

Chiral FexCuySe nanoparticles as peroxidase mimics for colorimetric detection of 3, 4-dihydroxy-phenylalanine enantiomers.

L-3,4-dihydroxy-phenylalanine (L-dopa) is the most widely used drug in Parkinson's disease treatment. However, development of cost-effective and high-throughput sensors to accurate enantioselective discrimination of L-dopa and D-dopa remains challenging to date. Herein, on the basis of the peroxidase-mimic activity of chiral FexCuySe nanoparticles, we demonstrated a novel colorimetric sensor for determination of chiral dopa. The surface chiral ligand, L/D-histidine (L/D-His), endowed the nanozymes with enantioselectivity in catalyzing the oxidation of dopa enantiomers. According to the values ofkcat/Km, the efficiency of L-His modified nanoparticles (L-FexCuySe NPs) towards L-dopa was 1.56 times higher than that of D-dopa. While, D-His can facilely reverse the preference of the nanozyme to D-dopa. On the basis of high catalytic activity and enantioselectivity of L-FexCuySe NPs in oxidation of L-dopa, the L-FexCuySe NPs-based system can be utilized for detection of L-dopa. The linear ranges for L-dopa determination were 5µM-0.125 mM and 0.125 mM-1 mM with a detection limit of 1.02µM. Critically, the developed sensor has been successfully applied in the quality control of clinical used L-dopa tablets. Our work sheds light on developing simple and sensitive chiral nanomaterials-based sensors for drug analysis.

Melanochrome-based colorimetric assay for quantitative detection of levodopa in co-presence of carbidopa and its application to relevant anti-Parkinson drugs.

In this paper is reported the selective detection and quantification of levodopa in co-presence of carbidopa. The method took advantage of the spontaneous oxidation and color development of levodopa at basic pH here driven by alkaline earth cations and co-solvent in solution. We have shown for the first time the generation and stabilization of the purple melanochrome from levodopa, by using magnesium acetate and dimethyl sulfoxide, which was here exploited for the development of a quantitative colorimetric assay for the active principle ingredient in commercial drugs for the treatment of Parkinson's disease. The calibration curves of levodopa in the two tablet formulations, containing carbidopa as decarboxylase inhibitor, showed a common linear trend between 10 mg L-1 and 40 mg L-1 with levodopa alone or in combination with carbidopa in standard solutions, with very good reproducibility (CVav%, 3.3% for both brand and generic drug) and very good sensitivity, with limit of quantification about 0.6 mg L-1 in any case. The colorimetric method here developed is very simple and effective, appearing as a rapid and low-cost alternative to other methodologies, involving large and expensive instrumentations, for drug estimation and quality control of pharmaceutical formulations.

A semi-covalent molecularly imprinted electrochemical sensor for rapid and selective detection of tiotropium bromide.

Tiotropium bromide (TIO) is a long-acting bronchodilator used in the treatment of chronic obstructive pulmonary disease (COPD) and asthma. Specifically, it is used to prevent patients from worsening breathing difficulties. In this study, a new TIO-imprinted electrochemical sensor was designed to detect TIO in serum and pharmaceutical samples. Methacryloyl-L-histidine-cobalt(II) [MAH-Co(II)] has been used as a metal-chelating monomer for synthesizing selective molecularly imprinted polymer (MIP). MIP film has been developed on glassy carbon electrodes using MAH-Co(II) as the functional monomer, 2-hydroxyethyl methacrylate (HEMA) as the basic monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linker in the photopolymerization method. The surface characterization of the developed MAH-Co(II)@MIP/GCE electrochemical sensor was done using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Also, the electrochemical behavior of the sensor was provided by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. Under optimized experimental conditions, the linearity range was in the range of 10-100 fM, and the limit of detection (LOD) and limit of quantitation (LOQ) values were calculated as 2.73 fM and 9.75 fM, respectively. The MAH-Co(II)@MIP/GCE sensor was used to precisely determine TIO in capsule and commercial serum samples. The results demonstrated that the MIP could specifically recognize TIO compared to structurally related drugs and could be reliably applied to the direct determination of drugs from real samples.

Chiral probe for mass spectrometric identification and quantitation of levodropropizine and its enantiomer, dextrodropropizine.

Acyl chlorides react rapidly with hydroxyl and amino groups in the absence of catalysts and therefore hold great promise for chiral mass spectrometry. Herein, a tandem mass spectrometry method based on derivatization with (-)-camphanic acid chloride as a simple chiral probe was developed for the highly sensitive detection and quantitation of levodropropizine and its enantiomer, namely, dextrodropropizine. The diastereomeric derivatization products were quantified based on the relative abundances of their fragment ions produced upon collision-induced dissociation in positive-ion mode. The reactive site was elucidated using nuclear magnetic resonance spectroscopy and two-dimensional total correlation spectroscopy, and the reaction mechanism was proved by stoichiometry studies. The degree of isomer recognition was investigated at different collision energies and determined as Rchiral  ≈ 1.5. Thus, this study gives the way to the mass spectrometric identification and quantitation of levodropropizine and its enantiomer, and the developed method represents a new and practical technique for rapid and sensitive determination and quality control of enantiomers of chiral drugs.

Preparation of bamboo-derived magnetic biochar for solid-phase microextraction of fentanyls from urine.

In this study, a biochar-based magnetic solid-phase microextraction method, coupled with liquid chromatography-mass spectrometry, was developed for analyzing fentanyl analogs from urine sample. Magnetic biochar was fabricated through a one-step pyrolysis carbonization and magnetization process, followed by an alkali treatment. In order to achieve desired extraction efficiency, feed stocks (wood and bamboo) and different pyrolysis temperatures (300-700°C) were optimized. The magnetic bamboo biochar pyrolyzed at 400°C was found to have the greatest potential for extraction of fentanyls, with enrichment factors ranging from 58.9 to 93.7, presumably due to H-bonding and π-π interactions between biochar and fentanyls. Various extraction parameters, such as type and volume of desorption solvent, pH, and extraction time, were optimized, respectively, to achieve the highest extraction efficiency for the target fentanyls. Under optimized conditions, the developed method was found to have detection limits of 3.0-9.4 ng/L, a linear range of 0.05-10 µg/L, good precisions (1.9-9.4% for intrabatch, 2.9-9.9% for interbatch), and satisfactory recoveries (82.0-111.3%). The developed method by using magnetic bamboo biochar as adsorbent exhibited to be an efficient and promising pretreatment procedure and could potentially be applied for drug analysis in biological samples.

Ultrasensitive Determination of Natural Flavonoid Rutin Using an Electrochemical Sensor Based on Metal-Organic Framework CAU-1/Acidified Carbon Nanotubes Composites.

Rutin, a natural flavonol glycoside, is widely present in plants and foods, such as black tea and wheat tea. The antioxidant and anti-inflammatory effects of flavonoids are well known. In this study, a new electrochemical rutin sensor was developed using multiwalled carbon nanotubes/aluminum-based metal-organic frameworks (MWCNT/CAU-1) (CAU-1, a type of Al-MOF) as the electrode modification material. The suspension of multiwalled carbon tubes was dropped on the surface of the GCE electrode to make MWCNT/GCEs, and CAU-1 was then attached to the electrode surface by electrodeposition. MWCNTs and CAU-1 were characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Due to the synergistic effect of CAU-1 and MWCNT-COOH, the prepared sensor showed an ultrasensitive electrochemical response to rutin. Under optimized conditions, the sensor showed a linear relationship between 1.0 × 10-9~3.0 × 10-6 M with a detection limit of 6.7 × 10-10 M (S/N = 3). The sensor also showed satisfactory stability and accuracy in the detection of real samples.