Developing a new sensitive solid-phase microextraction fiber based on carbon nanotubes for preconcentration of morphine

Functionalized carbon nanotube-polyaniline composite coating for on-line microextraction on a screw coupled with high performance liquid chromatography to determine opium alkaloids

A novel and efficient on-line microextraction on a screw coupled with high-performance liquid chromatography with an ultraviolet-visible detector was developed to extract and determine trace quantities of five opium alkaloids. All detections of the analytes were achieved at 210 nm. The surface of the screw grooves was electrochemically coated with the carbon nanotubes-COOH/polyaniline composite. The surface characterization was assessed by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The prepared screw was inserted into a cartridge of a guard column, and then the constructed microextraction on a screw device was placed in the loop of a six-port HPLC injection valve. The parameters affecting the extraction efficiency of the analytes were optimized using the one variable-at-a-time method. The effective parameters for the extraction efficiency of the analytes, including sample volume, extraction time, sampling flow rate, desorption solvent type, ionic strength, and pH were investigated and optimized. Under optimal conditions, the detection limits were 3-10 μg L-1, and the linear dynamic ranges were 10-2000 μg L-1 with a coefficient of determination greater than 0.9940. The inter-day and intra-day (n = 3) relative standard deviations were less than 7% and 5%, respectively. The proposed method was simple and reproducible, with an acceptable relative recovery (90-108%) for determining opium alkaloids in water and urine samples.

Water-Soluble Pd6L3 Molecular Bowl for Separation of Phenanthrene from a Mixture of Isomeric Aromatic Hydrocarbons

Phenanthrene is a high-value raw material in chemical industries. Separation of phenanthrene from isomeric anthracene continues to be a big challenge in the industry due to their very similar physical properties. Herein, we report the self-assembly of a water-soluble molecular bowl (TB) from a phenothiazine-based unsymmetrical terapyridyl ligand (L) and a cis-blocked 90° Pd(II) acceptor. TB featured an unusual bowl-like topology, with a wide rim diameter and a hydrophobic inner cavity fenced by the aromatic rings of the ligand. The above-mentioned features of TB allow it to bind polyaromatic hydrocarbons in its confined cavity. TB shows a higher affinity for phenanthrene over its isomer anthracene in water, which enables it to separate phenanthrene with ∼93% purity from an equimolar mixture of phenanthrene and anthracene. TB is also able to extract pyrene with around ∼90% purity from an equimolar mixture of coronene, perylene, and pyrene. Moreover, TB can be reused for several cycles without significant degradation in its performance as an extracting agent. This clean strategy of separation of phenanthrene and pyrene from a mixture of hydrophobic hydrocarbons by aqueous extraction is noteworthy.

Amino-Functionalized Hierarchical Porous Carbon Derived from Zeolitic Imidazolate Frameworks for Ultrasensitive Electrochemical Sensing of Heavy Metals in Water

Electrochemical sensing provides a feasible avenue to monitor heavy metal ions (HMIs) in water, whereas the construction of highly sensitive and selective sensors remains challenging. Herein, we fabricated a novel amino-functionalized hierarchical porous carbon by the template-engaged method using ZIF-8 as the precursor and polystyrene sphere as the template, followed by carbonization and controllable chemical grafting of amino groups for efficient electrochemical detection of HMIs in water. The amino-functionalized hierarchical porous carbon features an ultrathin carbon framework with a high graphitization degree, excellent conductivity, unique macro-, meso-, and microporous architecture, and rich amino groups. As a result, the sensor exhibits prominent electrochemical performance with significantly low limits of detection for individual HMIs (i.e., 0.93 nM for Pb²⁺, 2.9 nM for Cu²⁺, and 1.2 nM for Hg²⁺) and simultaneous detection of HMIs (i.e., 0.62 nM for Pb²⁺, 1.8 nM for Cu²⁺, and 0.85 nM for Hg²⁺), which are superior to most reported sensors in the literature. Moreover, the sensor displays excellent anti-interference ability, repeatability, and stability for HMI detection in actual water samples.

Novel solid-phase microextraction fiber coatings: A review

The materials used for the fabrication of solid-phase microextraction fiber coatings in the past five years are summarized in the current review, including carbon, metal-organic frameworks, covalent organic frameworks, aerogel, polymer, ionic liquids/poly (ionic liquids), metal oxides, and natural materials. The preparation approaches of different coatings, such as sol-gel technique, in-situ growth, electrodeposition, and glue methods, are briefly reviewed together with the evolution of the supporting substrates. In addition, the limitations of the current coatings and the future development directions of solid-phase microextraction are presented.

Plant Extract and Herbal Products as Potential Source of Sorbent for Analytical Purpose: An Experimental Study of Morphine and Codeine Determination Using HPLC and LC-MSMS

Solid-phase microextraction (SPME) is an analytical method for microextraction of analytes, in which the analytes bind to the sorbent on the surface of the SPME fiber. Many types of chemical agents are used as sorbent; however, many of these sorbents cause secondary contamination or are not cost-effective. Here, aqueous extract of Ferula gummosa was evaluated as potential source of sorbent for simultaneous microextraction of morphine and codeine. For this purpose, multiwalled carbon nanotubes were carboxylated with H2SO4/HNO3 (3:1) and then functionalized with aqueous extract of F. gummosa. Functionalization was confirmed by Fourier transform infrared and Raman spectroscopy measurements as well as scanning electron microscopy analysis. Porous polypropylene hollow fibers were filled with the functionalized carbon nanotubes (CNTs) and used for analyte extraction in urine sample at 40°C and pH 6 for 2 min. Reversed-phase high-performance liquid chromatography (RP-HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed that the fiber could preconcentrate 1 ng/mL of morphine and 0.75 ng/mL codeine in urine sample and was successfully used for 30 times with no significant loss in the extraction efficiency. Limit of detection (LOD) and limit of quantification (LOQ) for morphine were 1 and 3.3 ng/mL, respectively. LOD and LOQ for codeine were determined 0.75 and 2.47 ng/mL, respectively. Recovery of the fiber was 80% and 93% for morphine and codeine, respectively. SPME fiber using extract of F. gummosa plant was used for the detection of a small amount of morphine in urine sample. Therefore, plants can be considered as abundant and cheap sources of sorbent for various analytical purposes.

Application of Microextraction-Based Techniques for Screening-Controlled Drugs in Forensic Context-A Review

The analysis of controlled drugs in forensic matrices, i.e., urine, blood, plasma, saliva, and hair, is one of the current hot topics in the clinical and toxicological context. The use of microextraction-based approaches has gained considerable notoriety, mainly due to the great simplicity, cost-benefit, and environmental sustainability. For this reason, the application of these innovative techniques has become more relevant than ever in programs for monitoring priority substances such as the main illicit drugs, e.g., opioids, stimulants, cannabinoids, hallucinogens, dissociative drugs, and related compounds. The present contribution aims to make a comprehensive review on the state-of-the art advantages and future trends on the application of microextraction-based techniques for screening-controlled drugs in the forensic context.

Sodium dodecyl sulfate-multi-walled carbon nanotubes-coated-membrane solid phase extraction of glucocorticoids in aqueous matrices

A membrane-based solid phase extraction (SPE)-ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the determination of nine glucocorticoids in water. This new hybrid SPE approach involved the deposition of sodium dodecyl sulfate (SDS)-multi-walled carbon nanotubes (MWCNTs) on a piece of polypropylene membrane that served as the extraction device. Hitherto, such a sample preparation procedure has not been applied to the analysis of water contaminants before. The use of the surfactant helped to disperse the MWCNTs effectively so that they were coated uniformly onto the polypropylene membrane. This increased the overall extraction efficiency of the procedure. Characterisation of the SDS-MWCNTs material was performed using transmission electron microscopy and scanning electron microscopy. The membrane device did not require a pre-conditioning step. The most favourable extraction parameters such as type of surfactant, percentage of surfactant, type of desorption solvent, stirring rate, desorption time, extraction time, temperature, salting-out effect, pH and diameter of MWCNTs were obtained. The method showed linearity ranges from 0.2 to 100 ng mL^-1 for hydrocortisone, dexamethasone, cortisone acetate and beclomethasone dipropionate, and 0.5-100 ng mL^-1 for the rest of the analytes. Limits of detection ranging from 0.019 to 0.098 ng mL^-1, and limits of quantification ranging from 0.065 to 0.326 ng mL^-1, were obtained for the analytes. The intra-day repeatability was between 1.77 and 3.56% while the inter-day reproducibility was between 2.69 and 9.53%, respectively. The method was used to analyse glucocorticoids as contaminants in the canal water samples.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Molecular modeling and experimental study of a new peptide-based microextraction fiber for preconcentrating morphine in urine samples

Antimicrobial peptides (AMPs) are best known for their bactericidal properties; however, due to their unique and flexible structures, they have also been proposed as potential selective sorbents for specific molecules. In the present study, we aimed to design and produce a new peptide-based microextraction fiber for preconcentrating morphine in urine samples. The binding of morphine to the peptide was first evaluated by computational simulation using the Molecular Operating Environment (MOE) 2015.10 software. A similar study was then performed using DS BIOVIA Materials Studio 2017 v17.1.0.48, which confirmed the results of the simulation carried out with MOE. Afterwards, those results were also confirmed by experimental research. In the experimental evaluation, carbon nanotubes (CNTs) were initially carboxylated with H₂SO₄/HNO₃ (3:1) and then functionalized with the peptide. FTIR analysis, Raman measurements, and SEM imaging were used to confirm that CNT functionalization was successful as well as to check the nanostructure of the fiber. To evaluate the functionality of the fiber, it was inserted into a microtube containing a urine sample that included morphine and then sonicated for 5 min at 40 °C. Afterwards, the fiber was washed with methanol 20% (H₂O/methanol) and the resulting sample was analyzed by HPLC. This procedure was repeated for different concentrations of morphine in the urine sample. The computational and experimental results showed that a morphine concentration as low as 0.25 ppb in urine could be adsorbed and detected using the peptide fiber. Therefore, given its semi-selective binding affinity for morphine, this peptide-based fiber can be considered a new approach to the detection of small amounts of morphine in biological samples.

Potential application of amino acids in analytical toxicology

The ability of extraction and preconcentration of small quantities of substances from biological samples is important in analytical sciences, particularly forensic medicine. In the present study, we evaluated the binding potential of amino acids to produce a new solid phase microextraction fiber based on carbon nanotube (CNTs) for extraction and preconcentration of small amount of morphine in urine sample. Raw CNTs were first carboxylated and then functionalized with 3 amino acids including glutamate, arginine, and cysteine. Functionalization was confirmed by FTIR analysis, Raman spectroscopy and SEM imaging. The functionalized CNTs were coated on polypropylene hollow fiber and used for preconcentration. The results of HPLC analysis in isocratic elution mode using acetonitrile-sodium acetate (10:90, v/v; pH 4; 0.01 M) as the mobile phase showed that amino acids are able to adsorb morphine and the prepared fiber could preconcentrate a very low concentration of morphine (0.25 ppb) in urine matrix. In addition, the fiber was successfully used for up to 30 times with no significant loss in the extraction efficiency. Lowest limit of detection (LOD) and limit of quantitation (LOQ) was 0.07 and 0.25, respectively. Also, the lowest and best recovery of the fiber was 87.8% and 139% at LOQ, which belonged to glutamate and arginine, respectively. The fibers based on amino acids can be used for the detection of a small amount of morphine in biological samples, which are not detectable by conventional methods. Simple mechanism of these fibers in preconcentrating morphine makes them a novel candidate for detection of other opiates and drugs of abuses in crime scene investigations and postmortem examinations several days after exposure.