Polymer Monolith Research Articles

Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) Monolith with Dual Porosity for Size Exclusion Chromatography.

The use of polymeric monoliths as stationary phases for liquid chromatography has been limited, despite their ability to enhance the convection flow of the mobile phase with respect to particulate-based columns. This is due to a poor balance between the volume of flow through pores and the number of active sites within polymeric monoliths. In this paper, we present the obtainment of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (P(GMA-co-EDMA)) monoliths with dual pore size distributions (with pore sizes of 60 and 550 nm). Hierarchical pore size distributions were achieved by performing the monolith synthesis by reversible addition-fragmentation chain transfer (RAFT) polymerization as well as using ternary porogen mixtures (containing PEG, dodecanol, and dioxane). While the controlled polymerization mechanism promoted mesopores in the monolith, ternary porogen mixtures allowed the formation of macropores. The monoliths obtained were used as stationary phases for size exclusion chromatography (SEC) for the separation of poly(methyl methacrylate) standards with molar masses between 2.50 × 103 and 3.06 × 106 g/mol, allowing selectivities that were comparable with commercially available SEC columns packed with porous particles. We believe the approach presented in this work could be the first step toward the obtainment of stationary phases for SEC with enhanced accessibility of exclusion pores. Monolithic columns with accessible porous structures can be beneficial for size-based separations of ultrahigh molar mass analytes with low diffusion coefficients.

An Innovative Biphasic Reaction System for Highly Selective Benzene Hydroxylation based on Photocatalytic Polymer Composites

AbstractThe hydroxylation of benzene to phenol in presence of hydrogen peroxide was performed using a new biphasic system consisting of a solid phase, a photocatalytically active monolithic polymer composite, immersed in an aqueous phase in which H2O2 is dissolved. In detail, ZnO photocatalytic particles were embedded into the hydrophobic syndiotactic polystyrene (sPS) polymer. Zinc oxide nanostructures (ZnO NSs) were synthesized by an electrochemical procedure. The surface morphology and structure of ZnO nanoparticles and ZnO‐sPS monolithic aerogel composite (ZnO/sPS) were investigated by scanning electron microscopy, X‐ray diffraction and X‐ray photoelectron spectroscopy analysis. Photocatalytic results evidenced that, under UV irradiation, both ZnO NSs and biphasic system water‐photocatalytic composites had a high benzene oxidative property but with very low phenol yield (<2 %) at pH=7. To enhance the phenol selective formation, the pH of the aqueous solution surrounding the photocatalytic polymer composite was modified. A phenol yield of about 94 % and benzene conversion higher than 99 % was obtained in alkaline conditions (pH=11).

L-Cysteine-Bonded Polymeric Monolithic Stationary Phase for Enantioseparation of Dansyl Amino Acids in Capillary Liquid Chromatography.

A chiral monolith stationary phase was fabricated by modifying the monolith surface using L-cysteine through a thiol-epoxy click reaction. L-cysteine-bonded polymer monolith was characterized by scanning electron microscopy/energy-dispersive X-ray and attenuated total reflectance Fourier-transformed infrared. The monomer content and modification temperature were carefully optimized to create a polymer monolith with excellent mechanical stability and permeability. Our findings revealed that the column morphology depended significantly on the porogen concentration and modification temperature for its morphology and efficiency. Adequate pores and binding sites were formed with the optimal porogen content, while a higher modification temperature improved the modification yield, enhancing peak shapes and increasing separation efficiency. The column demonstrated its capability for enantioseparation of dansyl glutamic acid, dansyl aspartic acid, dansyl methionine, and dansyl phenylalanine using a 60mM ammonium acetate buffer solution and acetonitrile in a 20:80 v/v ratio. It maintained good mechanical stability and repeatability with no relative standard deviation exceeding 7%. These results indicated that the L-cysteine-bonded polymer monolith has excellent potential as a chiral stationary phase.

Preparation and chromatographic properties of ordered macroporous polymer monoliths by colloidal crystal templating method

Preparation and chromatographic properties of ordered macroporous polymer monoliths by colloidal crystal templating method

Effect of binary porogen mixtures on polymer monoliths prepared by gamma-radiation initiated polymerization

Gamma-radiation initiated polymerization is an easy-to-use and simple technique for the preparation of porous polymer monoliths widely used as active materials in separation columns. Herein, binary porogen mixtures of ethyl acetate/acetone/acetonitrile with methanol were used to synthesize diethylene glycol dimethacrylate monoliths with this technique. Systematic studies have been performed to determine the effect of the composition of the solvent mixture on the morphology and the reaction kinetics, including the growth mechanism and the growth rate. The irradiation dose-dependent conversion profiles showed that with binary solvents the polymerization is much faster than with the same compounds used as single solvents. Depending on the type and the composition of the solvent one-, two- and three-dimensional, and fractal growth mechanisms were identified.

Assessing PET composite prosthetic solutions: A step towards inclusive healthcare

The demand for affordable prostheses is particularly high in Low Middle-Income Countries (LMICs). Currently, sockets are predominantly manufactured using monolithic thermoplastic polymers, which lack durability and strength, or consumptive thermoset resin reinforcing with expensive composite fillers like carbon, glass, or Kevlar fibers. However, there exist unmet and demanding needs among amputees for procuring low-cost, high-strength, and faster socket manufacturing methods. We evaluate a socket made from a novel manufacturing technique utilizing an affordable and sustainable composite material called commingled PET (polyethylene terephthalate) yarn, along with a reusable vacuum bag, to produce custom-made sockets in a purpose-built curing oven. Our innovative fabrication methodology enables the production of complex-shaped patient sockets in under 4 h. To evaluate the efficacy and performance of the PET sockets, we conducted trials with both unilateral and bilateral amputees over a six-month period, in collaboration with Bhagwan Mahaveer Viklang Sahayata Samiti (BMVSS) in India. Utilizing a 6-min walking test, we measured various gait parameters, including ground reaction forces and flexion angle, for both unilateral and bilateral amputees.The gait analysis conducted on amputees using our PET-based sockets demonstrated their ability to engage in daily activities without interruptions, reaffirming the functional efficacy of our approach. By combining self-reinforced PET with our novel fabrication technique, we offer a unique and accessible solution that benefits clinicians and patients alike. This study represents significant progress towards achieving affordable and personalized prostheses that cater to the needs of LMICs.

Preparation of Hierarchical Porous Monoliths With High Surface Areas by a Solvent Knitting Strategy.

Hierarchical porous hypercrosslinked monoliths (PolyHIPE-HCP) with ultrahigh specific surface areas are prepared via a solvent knitting strategy. Compared to previous work, the solvent knitting strategy is carried out in a relatively low air-controlled atmosphere with gradient heating starting from low temperature while using DCM (Dichloromethane) as both a solvent and a cross-linker, allowing for a slow and controlled cross-linking process, thereby achieving a BET surface area ranging from 514 to 728m2g-1. Scanning electron microscopy (SEM) shows that the knitting process does not affect the presence of macroporous structure in the PolyHIPE. With the introduction of mesopores and micropores, these hierarchical porous monoliths exhibit significant potential for applications in gas adsorption and water treatment. Hence, a universal, simple and low-cost method to synthesize polymeric monoliths with hierarchically porous structure and higher surface area is proposed, which has fascinating prospects in industrialization.

Fabrication and application of gold nanoparticles functionalized polymer monolith in spin column for the determination of S-nitrosoglutathione in meat

S-nitrosoglutathione (GSNO) is the most important S-nitrosothiol in vivo, which could affect the quality of meat by participating in calcium release, glucose metabolism, proteolysis and apoptosis, therefore may potentially serve as a marker for meat freshness. In this work, a solid-phase extraction (SPE) monolithic spin column modified with gold nanoparticles was prepared for GSNO extraction. The optimized SPE-LC-MS/MS method for GSNO quantification displays low limit of detection (0.01 nM), good precision (RSD < 15 %) and acceptable recovery (> 77.7 %). Furthermore, this approach has been applied to monitor GSNO levels in beef and pork stored at −20 °C for different days, showing that endogenous GSNO level increases during prolonged storage and could be employed as a marker to evaluate the freshness of ice stored meat. Additionally, the monolithic spin column remains in good quality after a half-year storage, which is promising to develop into commercial enrichment kit for endogenous GSNO analysis.

Chromoionophoric probe decorated porous polymer monolithic scaffold as solid-state colorimetric sensor and concentrator for target specific capturing of ultra-trace copper and cobalt ions

The present work reports on the development of an affordable aqueous-compatible two-in-one solid-state sensor engineered through the systematic suffusion of a chromoionophoric probe onto the porous poly(BTM-co-EGD) monolithic scaffolds for the selective colorimetric sensing of ultra-trace Cu2+ and Co2+ that are of industrial importance and environmental nuisance. The structurally regulated dual pore poly(BTM-co-EGD) template offers a high surface area for voluminous/homogenous imbuement of the probe molecules in a frozen geometrical alignment. The intriguing properties such as surface morphology, pore dimensions, structural network, phase identification, purity/elemental composition and thermal stability of the polymer monolith and probe-inoculated sensor were studied using XPS, BET/BJH, HR-TEM-SAED, FE-SEM-EDAX, XRD, FT-IR and DTG analysis. The ion recognition efficacy of the sensor material is evaluated through naked-eye color transformations and UV-Vis-DRS-based analysis. The sensor imposes a vibrant color transitional from pale yellow (blank) to intense olive brown and dark reddish brown for Cu2+ and Co2+, respectively, due to stable ligand-to-metal charge transfer complex formation. The sensor imposes high sensitivity with a response linear range of 0–200 and 0–150 ppb, with a detection limit of 0.13 and 0.16 ppb for Cu2+ and Co2+, respectively. The sensor exhibits impressive workability in the pH range of 7.0–8.0, with 0.05 mmol/g probe coating onto the poly(BTM-co-EGD) template, with an enriched response of ≤50 s, using 4 mg of the sensor material. Upon practical testing with natural/synthetic samples, the sensor executes stable characteristics with reliable and reproducible data (RSD ≤1.98 %). The proposed sensing methodology is simple, cost-effective and can be reused over eight sensing trails for the ultra-trace detection of Cu2+ and Co2+. The portable sensor has the potential for commercialization based on its effortlessness in real-time utility.

Adsorption Study of Cu2+ by Using CO2/Electric Potential-Responsive Polymeric Monoliths Prepared by Medium Internal Phase Emulsion

Adsorption Study of Cu²⁺ by Using CO₂/Electric Potential-Responsive Polymeric Monoliths Prepared by Medium Internal Phase Emulsion

Hybrid organic monolithic column containing MIL-68(Al) for the separation of small molecules by capillary HPLC

A hybrid organic monolithic column made of poly(lauryl methacrylate-co-1,6-hexanediol dimethacrylate) and the metal-organic framework MIL-68(Al) was prepared for the first time. The column was used in capillary liquid chromatography, both in isocratic and gradient elution modes. Separation performance towards small molecules of different chemical nature (polycyclic aromatic hydrocarbons, alkylbenzenes, phenols, etc.) was studied. Monte Carlo simulations were made to both select the proper precursors to obtain empty metal-organic framework micropores in the monolithic polymer and also, to analyze the potential free access of the studied analytes into the micropores (necessary to improve mass transfer and column efficiency). The hereby synthesized metal-organic framework microcrystals allowed obtaining homogeneous hybrid monolithic columns. Adding of MIL-68(Al) (1030 m2 g-1 BET specific surface area) increased the surface area from 3.9 m2 g-1 for the parent monolith to 18.2 m2 g-1 for the hybrid column containing 8 mg mL-1 of the microcrystals. Chromatographic performance of this new column was evaluated by studying retention factors, resolution, and plate counts at room temperature. Different compounds, not completely resolved in the parent monolith, were partially or completely separated after metal-organic framework addition. Using the monolithic column with only 2 mg mL-1 of MIL-68(Al), five alkylbenzenes were completely separated with very symmetrical peak shapes, resolution factors up to 3.60 and plate counts of 4300 plates m-1 for n-hexylbenzene. This value is higher than those obtained by other authors who used organic monolithic columns with embedded metal-organic frameworks to perform separations at room temperature. Additionally, nine polycyclic aromatic hydrocarbons were partially or completely resolved in gradient elution mode. The hybrid monolithic columns exhibited very good intra-day (%RSD=1.9), inter-day (%RSD=2.6), and column-to-column (%RSD=4.3) reproducibility values. Easy and fast column preparation, and versatility to efficiently separate several compounds of different chemical nature in isocratic and gradient mode, makes this new hybrid column a very good option for the analysis of small molecules in capillary (or nano) HPLC.

Electropolymerization of Various Aromatic Monomers Using Streaming Potentials

Bipolar electrodes, i.e., wireless electrodes driven by an external electric field, have been paying more and more attention1. Electrolysis using bipolar electrodes is an eco-friendly electrolysis system because they work with a low concentration of supporting electrolytes, which become waste after reactions. Indeed, we achieved the electrochemical fluorination on the bipolar electrodes, reducing the amount of supporting electrolyte to 1/100 compared to a conventional electrolysis2. However, in bipolar electrolysis, driving electrodes are necessary to generate an external electric field, which creates concern regarding the side reaction occurring on the driving electrode. Streaming potentials can be promising candidates to solve this problem. Streaming potentials are the potential differences between an inlet and an outlet of a narrow channel, which is generated when low-concentrated electrolytes are fed into the channel3. In the previous work, we developed a bipolar electrode system using the streaming potential4. The streaming potential was successfully generated by filling the cotton into a narrow channel to conduct the electropolymerization of pyrrole and 3,4-ethylenedioxythiophene. Yet, a large pressure drop of about 10 MPa is needed in this case. Moreover, the value of streaming potential is still low and the monomer scope was limited to pyrrole and 3,4-ethylenedioxythiophene.In this study, we aimed to investigate the condition with a low-pressure drop and a high-streaming potential, which enabled to expand the scope of electropolymerization. The screening of the filling declared that a polymer monolith, a porous material having continuous pores, was the best filling material for electrolysis. Then, the electropolymerization of thiophene and the ruthenium monomer, which could not be polymerized with the cotton-filled channel because of a low-streaming potential, was successfully carried out to obtain the corresponding polymers. The details of the streaming potential measurement and electropolymerization will be presented in the talk.References N. Shida, Y. Zhou, S. Inagi, Acc. Chem. Res., 2019,52, 2598–2608.K. Miyamoto, H. Nishiyama, I. Tomita, S. Inagi, ChemElectroChem, 2019, 6, 97–100.A. V. Delgado, F. González-Caballero, R. J. Hunter, L. K. Koopal, J. Lyklema, J. Colloid Interface. Sci., 2007, 309, 194–224.S. Iwai, T. Suzuki, H. Sakagami, K. Miyamoto, Z. Chen, M. Konishi, E. Villani, N. Shida, I. Tomita, S. Inagi, Commun. Chem., 2022, 5, 66. Figure 1

Morphological Control and Mechanical Properties of Porous Phenolic Resins Derived from Poly(4‐Vinylphenol): Effects of Molecular Weight and Polydispersity of Prepolymer

Improvement of mechanical stability for porous polymer monoliths is one of the prime concerns as represented by the long‐standing research efforts on resorcinol‐formaldehyde (RF) aerogels. To this end, it is imperative not only to tailor mechanically robust porous morphology but also to design macromolecular structure of polymer scaffolds. Previously, we have developed porous RF gels showing a unique mechanical feature combining high mechanical strength and outstanding flexibility against uniaxial compression. Comparison of mechanical properties between the porous gels with varied morphologies has elucidated the influence of porous structure, whereas effects of macromolecular structure still remain elusive. Herein, we have fabricated a series of macroporous phenolic resins from three types of linear prepolymers with phenol pendant groups, poly(4‐vinylphenol) or poly(4‐hydroxystyrene), which differ in molecular‐weight properties, by the sol–gel process in conjunction with spinodal decomposition. The difference in gelation and phase separation behaviors observed for the discrete systems indicates the dissimilar cross‐linked networks developed in the respective gels, which consequently influence the mechanical strength and flexibility against uniaxial compression. This study also demonstrates the improvement of mechanical features by thermal treatment for the porous monoliths derived from the high‐molecular‐weight prepolymer with a view to the application in mechanical energy absorption.

Hybrid NiCo2O4-BiOCOOH heterostructure nanocomposite impregnated porous polymer monolith as high-performance visible light photocatalyst for the decontamination of antimicrobial pollutants

We report a first-of-its-kind preparation of a NiCo2O4-BiOCOOH heterostructure as visible light-responsive nanocomposites (NCs) for the fast decontamination of moxifloxacin drug molecules, with longer persistence and non-biodegradability nature that could promote gene-resistance bacteria in aqueous medium. Further, a reusable/recoverable photocatalyst is fabricated through the uniform decoration of NiCo2O4(15 %)-BiOCOOH(85 %), i.e., NB-15 NCs across a tailor-made poly(EGDMA) monolith (PEM) that serves as the host template for the photoactive NCs. The electron microscopy, optical spectroscopy, diffraction, and surface analysis techniques confirm the photocatalyst's superior structural morphology, surface topography, and porosity features that assist in high-performance photocatalysis. The inorganic-organic hybrid photocatalyst exhibits a narrow energy bandgap that promotes ample generation of reactive oxygen species upon visible light irradiation, as confirmed by the electrochemical and spectroscopic analysis. The BET/BJH plot for the photocatalyst reveals a large surface area of 345 m2/g, with voluminous pore distributions (2–80 nm), indicating the coexistence of mesopores-infused macroporous framework that offers better contact/equilibration of the pollutant molecules with the abundantly dispersed photoactive sites. The optimized parameters reveal ≥99.2 % drug dissipation in ≤0.33 h and drug mineralization in ≤2.0 h, using a mere 50 mg of photocatalyst irradiated with a 150 W/cm2 tungsten lamp. The synthesized photocatalyst has a simple/cost-saving procedure that can transform into scalable, cheaper, and eco-friendly products for the real-time monitoring of toxic pollutants. Besides, the photocatalyst exhibits excellent stability and reusability characteristics for efficiently decontaminating organic pollutants, thus highlighting an innovative approach for fabricating high-performance photocatalysts.

Effect of crosslinker/porogen ratio on sponge-nested polymer monoliths for solid-phase extraction

Polymer monoliths can be polymerised within different molds, but limited options are available for the preparation of free-standing polymer monoliths for analytical sample preparation, and in particular, solid-phase extraction (SPE). Commercial melamine-formaldehyde sponges can be used as supports for the preparation of polymer monoliths, due its flexibility, giving various shapes to monoliths. Herein, the crosslinker/porogen ratio of highly porous sponge-nested divinylbenzene (DVB) polymer monoliths has been evaluated. Monoliths prepared using different crosslinker/porogen ratios were applied to the extraction of bisphenol F, bisphenol A, bisphenol AF, and bisphenol B. Monoliths containing 50 wt % DVB and 50 wt % porogens presented the highest recovery of bisphenols. Under the optimised conditions, the developed method showed a linear range between 2.5 µg L−1 and 150 µg L−1 for BPA and BPAF, and between 5 µg L−1 and 150 µg L−1 for BPB and BPF. The limits of detection (LOD, S/N = 3) and limits of quantification (LOQ, S/N = 10) ranged from 0.36 µg L−1 to 1.09 µg L−1, and from 1.20 µg L−1 to 3.65 µg L−1, respectively. The recoveries for spiked bisphenols (10 µg L−1) in tap water and water contained in a polycarbonate containers were between 82 % and 114 %.

A novel halloysite nanotubes-based hybrid monolith for in-tube solid-phase microextraction of polar cationic pesticides

The accurate determination of polar cationic pesticides in food poses a challenge due to their high polarity and trace levels in complex matrices. This study hypothesized that the use of halloysite nanotubes (HNTs) can significantly enhance the extraction efficiency and sensitivity of these analytes because of their rich hydroxyl groups and cation exchange sites. Therefore, we chemically incorporated HNTs with organic polymer monoliths for in-tube solid-phase microextraction (SPME). This novel hybrid monolith extended service life, improved adsorption capacity, and exhibited excellent extraction performance for polar cationic pesticides. Based on these advancements, a robust and sensitive in-tube SPME-HILIC-MS/MS method was constructed to determine trace levels of polar cationic pesticides in complex food matrices. The method achieved limits of detection of 1.9, 2.1, and 0.1 μg/kg for maleic hydrazide, amitrole, and cyromazine, respectively. The spiked recoveries in five food samples ranged from 80.2 to 100.8%, with relative standard deviations below 10.7%.

Development of an organic polymer monolith column for the nano liquid chromatography fast analysis of monoclonal antibody in infusion bags prepared in a hospital pharmacy.

Poly(butyl methacrylate-co-ethylene dimethacrylate) monolith was in situ prepared in a liquid chromatography capillary column with a 75 μm internal diameter. This monolith offered high permeability (5.3 ± 10-14m2) and good peak capacity (140 for a 15 cm column length at 300 nl/min with a 20 min gradient time). This is exemplified by its separation ability in reversed mode for subunit analysis of monoclonal antibodies after IdeS digestion (middle-up analysis). The potential of this column was also illustrated for the fast analytical control of therapeutic monoclonal antibodies in standardized infusion bags prepared in advance in a pharmacy department. Linearity analysis revealed the column's capability for accurate quantification analysis of the different dose bandings (in mg) of monoclonal antibodies in <2min. In addition, lifetime analysis data indicated that the column can be highly reproducible and has a long lifetime with stable and low back pressure. The variations observed on the peak shape and area between unstressed (intact) and stressed monoclonal antibodies indicated that our nano liquid chromatographic method was stability indicating. In addition, using a gradient elution mode, the presence of minor components in the infusion bags was visualized.

Influence of the Polymerization Parameters on the Porosity and Thermal Stability of Polymeric Monoliths.

Rigid porous polymeric monoliths are robust, highly efficient, versatile stationary phases. They offer simple preparation and convenient modification provided by a whole range of synthesis factors, e.g., starting monomers, cross-linkers, initiators, porogens, polymerization techniques, and temperature. The main aim of this study was to synthesize polymeric monoliths and determine the correlation between polymerization parameters and the porosity and thermal stability of the obtained materials. Polymeric monoliths were synthesized directly in HPLC columns using N-vinyl-2-pyrrolidone (NVP) and 4-vinylpiridine (4VP) as functional monomers, with trimethylolpropane trimethacrylate (TRIM) serving as the cross-linking monomer. During copolymerization a mixture of cyclohexanol/decane-1-ol was used as the pore-forming diluent. Polymerization was carried out at two different temperatures: 55 and 75 °C. As a result, monoliths with highly developed internal structure were synthesized. The value of their specific surface area was in the range of 92 m2/g to 598 m2/g, depending on the monomer composition and polymerization temperature. Thermal properties of the obtained materials were investigated by means of thermogravimetry (TG). Significant differences in thermal behavior were noticed between monoliths synthesized at 55 and 75 °C. Additionally, the poly(NVP-co-TRIM) monolith was successfully applied in GC analyses.

The role of unit cell topology in modulating the compaction response of additively manufactured cellular materials using simulations and validation experiments

Additive manufacturing has enabled a transformational ability to create cellular structures (or foams) with tailored topology. Compared to their monolithic polymer counterparts, cellular structures are potentially suitable for systems requiring materials with high specific energy-absorbing capability to provide enhanced damping. In this work, we demonstrate the utility of controlling unit-cell topology with the intent of obtaining a desired stress–strain response and energy density. Using mesoscale simulations that resolve the unit-cell sub-structures, we validate the role of unit-cell topology in selectively activating a buckling mode and thereby modulating the characteristic stress–strain response. Simulations incorporate a linear viscoelastic constitutive model and a hyperelastic model for simulating large deformation of the polymer under both tension and compression. Simulated results for nine different cellular structures are compared with experimental data to gain insights into three different modes of buckling and the corresponding stress–strain response.

A new approach towards highly sensitive detection of endogenous N-acetylaspartic acid, N-acetylglutamic acid, and N-acetylaspartylglutamic acid in brain tissues based on strong anion exchange monolith microextraction coupled with UHPLC-MS/MS.

Anovel in-tube solid-phase microextraction coupled withan ultra-high performance liquid chromatography-mass spectrometry method has been established for simultaneous quantification of three crucial brain biomarkers N-acetylaspartic acid (NAA), N-acetylglutamic acid (NAG), and N-acetylaspartylglutamic acid (NAAG). A polymer monolith with quaternary ammonium as the functional group was designed and exhibited efficient enrichment of target analytes through strong anion exchange interaction. Under the optimized conditions, the proposed method displayed wide linear ranges (0.1-80 nM for NAA and NAG, 0.2-160 nM for NAAG) with good precision (RSDs were lower than 15%) and low limits of detection (0.019-0.052 nM), which is by far the most sensitive approach for NAA, NAG, and NAAG determination. Furthermore, this approach has been applied to measure the target analytes in mouse brain samples, and endogenous NAA, NAG, and NAAG were successfully detected and quantified from only around 5mg of cerebral cortex, cerebellum, and hippocampus. Compared with existing methods, the newly developed method in the current study provides highest sensitivity and lowest sample consumption for NAA, NAG, and NAAG measurements, which would potentially be utilized in determining and tracking these meaningful brain biomarkers in diseases or treatment processes, benefiting the investigations of pathophysiology and treatment of brain disorders.