An etched polyether ether ketone tube covered with immobilized graphene oxide for online solid phase microextraction of quaternary alkaloids prior to their quantitation by HPLC-MS/MS

Synthesis of Magnetic Attapulgite Nanoparticles Via a Novel Surface Covalent Reaction Method and its Application in the Magnetic Solid Phase Extraction

In this study, the attapulgite nanoparticle was immobilized on the surface of magnetic nanoparticle Fe3O4 via a novel surface covalent reaction method for the magnetic solid phase extraction (MSPE) for the first time. The surface covalent reaction method has the advantages of controllable steps, and can make the magnetic attapulgite nanoparticle (MANP) have good homogeneity and high stability. Field emission scanning electron microscopy, equipped with an energy dispersive spectrometer, Nitrogen adsorption BET, X-ray diffraction and Fourier transform infrared spectroscopy were applied to characterize the prepared MANP, confirming that the attapulgite nanoparticle could be effectively immobilized on the surface of magnetic nanoparticle Fe3O4 via covalent reactions. Under optimal conditions of the MSPE experiment based on the MANP, the limits of detection were found to be 10 ng/mL for melamine and 3 ng/mL for cyromazine with a relative standard deviation < 10% by a high-performance liquid chromatography system. Meanwhile, 0.1 mg/mL melamine in milk and 0.1 mg/mL cyromazine in cucumber can also be detected according to our MSPE procedure. More importantly, the MANP still has good magnetism and enrichment efficiency after several decades of use. These results showed that the MANP prepared by our method is a kind of promising material for the MSPE.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Surface area expansion by flower-like nanoscale layered double hydroxides for high efficient stir bar sorptive extraction

Enhancing the surface area of stationary phase is essential in chromatographic science. In this work, nanoscale NiAl-layered double hydroxides (NiAl-LDHs) with flower-like structure was used as a platform for supporting the stationary phase. Then strong hydrophobic p-naphtholbenzein molecule was immobilized onto the LDHs layer as sorbent for stir bar sorptive extraction (SBSE). The flower-like LDHs layer significantly increased the extraction efficiency through increasing the specific surface area and immobilized amounts of stationary phase. In addition, the LDHs can also provide anion exchange ability, which expanded the application of this stir bar for analysis of not only hydrophobic but also anionic analytes. For improving the workability, a poly(ether ether ketone) (PEEK) jacket stir bar with detachable dumbbell-shaped structure was employed. The PEEK jacket with high mechanical strength and dumbbell-shaped structure improved the durability of stir bar and the detectable design allowed elution to be realized with less solvent that enhanced the enrichment factor. The proposed stir bar showed good performance for the extraction of multiple analytes including flavonoids, non-steroid anti-inflammatory drugs and chlorophenoxy acids. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), the SBSE-HPLC-UV method was applied for the extraction of three active components including bavachin, isobavachalcone and bavachinin in Psoralea corylifolia L. herb with low limit detection of 0.01-0.02 ng/mL.

Bioanalytical HPLC Applications of In-Tube Solid Phase Microextraction: A Two-Decade Overview

In-tube solid phase microextraction is a cutting-edge sample treatment technique offering significant advantages in terms of miniaturization, green character, automation, and preconcentration prior to analysis. During the past years, there has been a considerable increase in the reported publications, as well as in the research groups focusing their activities on this technique. In the present review article, HPLC bioanalytical applications of in-tube SPME are discussed, covering a wide time frame of twenty years of research reports. Instrumental aspects towards the coupling of in-tube SPME and HPLC are also discussed, and detailed information on materials/coatings and applications in biological samples are provided.

Online Sol-gel Capillary Microextraction-Mass Spectrometry (CME-MS) Analysis of Illicit Drugs

Providing rapid and sensitive sample cleanup, sol-gel capillary microextraction (CME) is a form of solid phase microextraction (SPME). The capillary format of CME couples easily with mass spectrometry (MS) by employing sol-gel sorbent coatings in inexpensive fused silica capillaries. By leveraging the syringe pump and six-port valve readily available on the commercial MS, we can obviate the need for chromatography for samples as complex as urine in quantitative assays. Two different sol-gel materials were studied as microextraction sorbents: one with a single ligand of octadecyl (C₁₈) and the other with a dual-ligand combination of C₁₈ and phenyl (Phe) groups. The CME-MS method was optimized for flow rate and solvent desorption and studied for overall microextraction performance between the two sorbents studied. We extract illicit drugs including cocaine, heroin, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, and oxycodone, proving good run-to-run reproducibility (RSD% < 10%) and low detection limits (< 10 ng mL^-1). The dual-ligand sorbent demonstrated superior performance due to typical hydrophobic properties of C₁₈ as well as potential π-π interactions of the Phe functionality and the aromatic moiety common to many drugs. This study demonstrates the advantage of fine-tuning sol-gel sorbents for application-specific CME-MS. We apply our method to the analysis of various drugs in synthetic and human urine samples and show low carryover effect (~ 5%) and low matrix effect in the presence of the urine matrix. Thus, the sol-gel CME-MS technique described herein stands to be an attractive alternative to other SPME-MS techniques.

Applications of three-dimensional graphenes for preconcentration, extraction, and sorption of chemical species: a review

This review (with 115 refs) summarizes applications of 3-dimensional graphene (3DGs) and its derivatives in the fields of preconcentration, extraction, and sorption. Following an introduction into the field (including a definition of the materials treated here), the properties and synthetic strategies for 3DGs are described. The next section covers applications of 3DG-based adsorbents in solid phase extraction of organic species including drugs, phthalate esters, chlorophenols, aflatoxins, insecticides, and pesticides. Another section treats applications of 3DGs in solid phase microextraction of species such as polycyclic aromatic hydrocarbons, alcohols, and pesticides. We also describe how the efficiency of assays may be improved by using these materials as a sorbent. A final section covers conclusions and perspectives. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.Tiff file of graphical abstract was attached. Schematic presentation of synthesis of three-dimensional graphene (3DG) from two-dimensional graphene (2DG) with self-assembly, template-assisted and direct deposition methods. Application of 3DG-based nanoadsorbents in direct immersion-solid phase microextraction (DI-SPME), headspace-SPME (HS-SPME), magnetic-solid phase extraction (Magnetic-SPE), dispersive-SPE, and magnetic sheet-SPE.

Recent advances in mixed-mode chromatographic stationary phases

Mixed-mode phases have become very popular in the last decade, and the number of new mixed/multi-mode sorbents is growing fast. Unlike single-mode stationary phases, perfectly suited for the separation of the analytes possessing similar physicochemical properties, for instance reversed-phase chromatography for hydrophobic solutes, mixed-mode sorbents providing multimodal interactions can render better separation selectivity for complex mixtures of solutes differing significantly in their physicochemical characteristics. The most frequent modern mixed-mode stationary phases are di/tri-mode sorbents embracing the following interactions, hydrophobic, electrostatic (coulombic), and hydrophilic. According to their structures, it is possible to distinguish silica-based, polymer-based, hybrid, and monolithic mixed-mode stationary phases. Herewith, newly synthesized mixed-mode sorbents developed within the last two and half years are categorized, discussed, and summarized. The main attention is devoted to the description of the synthetic routes and characterization methods applied for the new stationary phases.

Development of on-line monolith-based in-tube solid phase microextraction for the sensitive determination of triazoles in environmental waters

In this work, a convenient and sensitive method for the determination of triazoles in environmental waters was developed by on-line combining in-tube solid phase microextraction (IT-SPME) and high performance liquid chromatography with diode array detector (HPLC-DAD). To extract triazoles effectively, poly (4-vinyl pyridine-co-ethylene dimethacrylate) monolith was in-situ fabricated and utilized as the extraction phase of IT-SPME. A series of key extraction parameters including desorption solvent, sample volume, adsorption and desorption flow rate, pH value and ionic strength in sample matrix were optimized thoroughly. Under the most favorable conditions (volume of sample, 6.0 mL; adsorption flow rate, 0.2 mL/min; desorption solvent, 80.0 µL mixture of ACN/water (70/30, v/v); desorption flow rate, 50.0 µL/min; sample pH value, 8.0; ionic strength did not be adjusted), the developed monolith-based IT-SPME could extract target analytes effectively and expected analytical merits were achieved. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were in the ranges of 0.014-0.031 µg/L and 0.11-0.074 µg/L, respectively. Satisfactory method reproducibility was obtained by intra-day and inter-day precisions, with relative standard deviations (RSDs) lower than 10%. The optimized IT-SPME-HPLC-DAD method was then applied to detect triadimenol, triazolone and hexaconazole in water samples including lake, river and sewage waters. The spiked recoveries were 78.9-106% and the RSDs were in the range of 0.2-7.2%. The results well evidence that the proposed method is convenient, accurate, sensitive, practical and environmentally friendly for the determination of triazoles in environmental waters.

Analysis of six active components in Radix tinosporae by nonaqueous capillary electrophoresis with mass spectrometry

Nonaqueous capillary electrophoresis with mass spectrometry has advantages for the analysis of active components in herbs. Here, a rapid nonaqueous capillary electrophoresis with mass spectrometry method was developed to separate, identify, and quantify palmatin, columbin, cepharanthine, menisperine, magnoflorine, and 20-hydroxyecdysone in Radix tinosporae. Electrospray ionization MS^1-3 spectra of the six components were collected and possible cleavage pathways of main fragment ions were elucidated. The conditions that could affect separation, such as the composition of running buffer and applied voltage, were studied, and the conditions that could affect the mass spectrometry detection, such as the composition and flow rate of sheath liquid, the pressure of nitrogen gas, and the temperature and flow rate of the dry gas, were also optimized. Under the optimized conditions, the correlation coefficient was >0.99. The relative standard deviations of migration time and peak areas were <10%. The recoveries were calculated to be 99.31-107.80% in real samples. It has been demonstrated that the proposed method has good potential to be applied to determine the six bioactive components in Radix tinosporae.