Monolithic Capillary Research Articles

Cd (II) imprinted polymer modified silica monolithic capillary microextraction combined with inductively coupled plasma mass spectrometry for the determination of trace Cd (II) in biological samples

Using surface imprinting technique, Cd (II) imprinted polymer surface modified silica monolithic capillary (shortened as Cd(II) imprinted monolithic capillary (Cd(II)-IMC)) was prepared for extraction of Cd (II). Based on it, a method of monolithic capillary microextraction - inductively coupled plasma mass spectrometry was developed for trace analysis of Cd (II) in human serum and urine samples. Taking Mn (II), Cu (II) and Zn (II) as competing ions, the extraction efficiency, distribution ratio and selectivity of the Cd(II)-IMC was investigated. It was found that the relative selectivity coefficients of the prepared Cd(II)-IMC towards Mn (II), Cu (II) and Zn (II) were 3.8, 2.2 and 2.2 respectively. Compared with non-imprinted monolithic capillary, the Cd(II)-IMC presented larger dynamic sorption capacity (6 μg m−1 over 4.2 μg m−1). Under the optimized extraction conditions, the limit of detection for Cd (II) was 3.5 ng L−1, with the relative standard deviation of 4.9% (c = 0.1 μg L−1, n = 7). The enrichment factor was 20-fold. The accuracy of the method was evaluated by measurement of the certified reference material (GBW 07601a, human hair). The proposed method was applied to determine Cd in human serum and urine samples with only consumption of 1 mL samples. The recoveries for the spiked human serum and urine samples were in the range of 86–110%. Compared with other reported methods, the proposed method is featured with easy to remove the template Cd (II), high selectivity, good interference resistance, low sample consumption and easy regeneration. Therefore, this method is suitable for the separation and enrichment of trace Cd (II) in micro-samples with complex matrix.

In-tube solid-phase microextraction with a dummy molecularly imprinted monolithic capillary coupled to ultra-performance liquid chromatography-tandem mass spectrometry to determine cannabinoids in plasma samples

A selective and sensitive method that uses automated in-tube solid-phase microextraction coupled to ultra-performance liquid chromatography–tandem mass spectrometry (in-tube SPME/UHPLC–MS/MS) was developed to determine cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) in plasma samples. A new dummy molecularly imprinted monolithic capillary (MIP monolith) for in-tube SPME was prepared by in situ polymerization in a fused silica capillary; hydrogenated cannabidiol was employed as dummy template. Fourier Transform Infrared Spectroscopy (FTIR) confirmed that the synthesis reagents were incorporated into the polymer chain. On the basis of the microscopy images (scanning electron microscopy – SEM and transmission electron microscopy – TEM), the MIP monolithic phase presented larger pores than the non-imprinted monolithic phase (NIP monolith), as well as a skeleton comprising clusters consisting of microspheres. By optimizing the polymerization conditions, the MIP monolith specifically recognized CBD and Δ9-THC. The MIP monolith had CBD and Δ9-THC sorption capacity of 148.05 and 44.49 ng cm−3, respectively. The capillary was reused over fifty times without significant changes in its extraction efficiency. For both CBD and Δ9-THC, in-tube SPME/UHPLC–MS/MS presented linear range from 10 to 300 ng mL−1, precision with coefficient of variation (CV) values ranging from 0.2% to 19.1% (LLOQ), and accuracy with relative standard deviation (RSD) values spanning from −9.3% to 19.6% (LLOQ). The developed method was successfully applied to determine cannabinoid levels in plasma samples from volunteer patients in treatment with CBD.

A monolithic copolymer prepared from N-(4-vinyl)-benzyl iminodiacetic acid, divinylbenzene and N,N′-methylene bisacrylamide for preconcentration of cadmium(II) and cobalt(II) from biological samples prior to their determination by ICP-MS

A capillary monolith consisting of poly[N-(4-vinyl)-benzyl iminodiacetic acid-co-divinylbenzene-co-N,N'-methylene bisacrylamide), referred to as poly(VBIDA-DVB-Bis), has been prepared. It is shown to be an efficient sorbent for the enrichment of Co(II) and Cd(II). The two ions are completely retained by the monolith in the pH range from 4.0 to 9.0. The breakthrough curve tests were adopted to evaluate the adsorption performance of the monolith towards Co(II) and Cd(II). A dose-response model was used to describe the breakthrough curves of the two ions at different initial concentrations. The adsorption capacities for Co(II) and Cd(II) are 1.54 and 1.73mg·m-1 at a concentration level of 2.5mg·L-1, respectively. The enrichment factor is 100, and the required sample volume is 5mL. Following elution of the two ions with 0.5M HNO3, they were quantified by ICP-MS. The limits of detection in a 1mL sample are 0.35ng·L-1 for Co(II) and 0.44ng·L-1 for Cd(II). The method was applied to the determination of Co(II) and Cd(II) in spiked rice, human urine and seawater samples. Graphical abstract Schematic representation of a monolithic copolymer prepared from N-(4-vinyl)-benzyl iminodiacetic acid (VBIDA), divinylbenzene (DVB) and N,N'-methylene bisacrylamide (Bis) and its application for selective capturing of cadmium(II) and cobalt(II) from complex sample matrices prior to their determination by ICP-MS.

A Dual Ligand Sol⁻Gel Organic-Silica Hybrid Monolithic Capillary for In-Tube SPME-MS/MS to Determine Amino Acids in Plasma Samples.

This work describes the direct coupling of the in-tube solid-phase microextraction (in-tube SPME) technique to a tandem mass spectrometry system (MS/MS) to determine amino acids (AA) and neurotransmitters (NT) (alanine, serine, isoleucine, leucine, aspartic acid, glutamic acid, lysine, methionine, tyrosine, and tryptophan) in plasma samples from schizophrenic patients. An innovative organic-silica hybrid monolithic capillary with bifunctional groups (amino and cyano) was developed and evaluated as an extraction device for in-tube SPME. The morphological and structural aspects of the monolithic phase were evaluated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nitrogen sorption experiments, X-ray diffraction (XRD) analyses, and adsorption experiments. In-tube SPME-MS/MS conditions were established to remove matrix, enrich analytes (monolithic capillary) and improve the sensitivity of the MS/MS system. The proposed method was linear from 45 to 360 ng mL−1 for alanine, from 15 to 300 ng mL−1 for leucine and isoleucine, from 12 to 102 ng mL−1 for methionine, from 10 to 102 ng mL−1 for tyrosine, from 9 to 96 ng mL−1 for tryptophan, from 12 to 210 ng mL−1 for serine, from 12 to 90 ng mL−1 for glutamic acid, from 12 to 102 ng mL−1 for lysine, and from 6 to 36 ng mL−1 for aspartic acid. The precision of intra-assays and inter-assays presented CV values ranged from 1.6% to 14.0%. The accuracy of intra-assays and inter-assays presented RSE values from −11.0% to 13.8%, with the exception of the lower limit of quantification (LLOQ) values. The in-tube SPME-MS/MS method was successfully applied to determine the target AA and NT in plasma samples from schizophrenic patients.

Colistin Sulfate Chiral Stationary Phase for the Enantioselective Separation of Pharmaceuticals Using Organic Polymer Monolithic Capillary Chromatography.

A new functionalized polymer monolithic capillary with a macrocyclic antibiotic, namely colistin sulfate, as chiral selector was prepared via the copolymerization of binary monomer mixtures consisting of glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) in porogenic solvents namely 1-propanol and 1,4-butanediol, in the presence of azobisiso-butyronitrile (AIBN) as initiator and colistin sulfate. The prepared capillaries were investigated for the enantioselective nano-LC separation of a group of racemic pharmaceuticals, namely, α- and β-blockers, anti-inflammatory drugs, antifungal drugs, norepinephrine-dopamine reuptake inhibitors, catecholamines, sedative hypnotics, antihistaminics, anticancer drugs, and antiarrhythmic drugs. Acceptable separation was achieved for many drugs using reversed phase chromatographic conditions with no separation achieved under normal phase conditions. Colistin sulfate appears to be useful addition to the available macrocyclic antibiotic chiral phases used in liquid chromatography.

In-situ photopolymerized C4-functionalized organosilicon monoliths for reversed-phase protein separation in nano-liquid chromatography

In this study, polyhedral oligomeric silsesquioxane (POSS)-based capillary monoliths with short alkyl chain ligand in the form of butyl (C4) were synthesized via two different polymerization routes, namely UV-initiated free radical copolymerization of methacrylate-derivatized POSS (POSS-MA) with butylmethacrylate (BMA) and UV-initiated thiol-methacrylate copolymerization of POSS-MA with butanethiol (BT). An organosilicon monolith with a pore size distribution lying on both mesoporous and macroporous scales, a lower mean pore size and a higher specific surface area was obtained with UV-initiated thiol-methacrylate polymerization. Both monoliths were then comparatively evaluated for gradient separation of proteins under reversed phase conditions in nano-liquid chromatography. The chromatographic performance was defined in terms of peak-resolution and peak capacity. Four carbon (C4) functionalized-poly(POSS-MA) monolith produced by UV-initiated thiol-methacrylate polymerization exhibited better separation performance with higher peak resolutions and peak capacities. Both, the morphological characterization of monoliths and the results of gradient separation of proteins showed that thiol-methacrylate polymerization was more suitable for the synthesis of C4 functionalized organosilicon based stationary phases for reversed-phase protein separation. The monolith prepared by thiol-methacrylate polymerization was also successfully applied for impurity analysis of two important hormones, namely insulin and genotropin. A comparison with a commercial poly(styrene-co-divinylbenzene) monolith documented the good chromatographic performance of the new BT-attached poly(POSS-MA) monolith.

Ti (IV) attached-phosphonic acid functionalized capillary monolith as a stationary phase for in-syringe-type fast and robust enrichment of phosphopeptides.

In this study, poly(vinylphosphonic acid-co-ethylene dimethacrylate), poly(VPA-co-EDMA) capillary monolith was synthesized as a starting material for obtaining a stationary phase for microscale enrichment of phosphopeptides. The chelation of active phosphonate groups with Ti (IV) ions gave a macroporous monolithic column with a mean pore size of 5.4 μm. The phosphopeptides from different sources were enriched on Ti (IV)-attached poly(VPA-co-EDMA) monolith using a syringe-pump. The monolithic capillary columns exhibited highly sensitive/selective enrichment performance with phosphoprotein concentrations as low as 1.0 fmol/mL. Six different phosphopeptides were detected with high intensity by the treatment of β-casein digest with the concentration of 1.0 fmol/mL, using Ti (IV)@poly(VPA-co-EDMA) monolith. Highly selective enrichment of phosphopeptides was also successfully carried out even at trace amounts, in a complex mixture of digested proteins (molar ratio of β-casein to bovine serum albumin, 1:1500) and three phosphopeptides were successfully detected. Four highly intense signals of phosphopeptides in human serum were also observed with high signal-to-noise ratio and a clear background after enrichment with Ti (IV)@poly(VPA-co-EDMA) monolith. It was concluded that the capillary microextraction system enabled fast, efficient and robust enrichment of phosphopeptides from microscale complex samples. The whole enrichment process was completed within 20 min, which was shorter than in the previously reported studies.

Butyl Methacrylate-Co-Ethylene Glycol Dimethacrylate Monolith for Online in-Tube SPME-UHPLC-MS/MS to Determine Chlopromazine, Clozapine, Quetiapine, Olanzapine, and Their Metabolites in Plasma Samples.

This manuscript describes a sensitive, selective, and online in-tube solid-phase microextraction coupled with an ultrahigh performance liquid chromatography-tandem mass spectrometry (in-tube SPME-UHPLC-MS/MS) method to determine chlopromazine, clozapine, quetiapine, olanzapine, and their metabolites in plasma samples from schizophrenic patients. Organic poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith was synthesized on the internal surface of a fused silica capillary (covalent bonds) for in-tube SPME. Analyte extraction and analysis was conducted by connecting the monolithic capillary to an UHPLC-MS/MS system. The monolith was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The developed method presented adequate linearity for all the target antipsychotics: R2 was higher than 0.9975, lack-of-fit ranged from 0.115 to 0.955, precision had variation coefficients lower than 14.2%, and accuracy had relative standard error values ranging from −13.5% to 14.6%, with the exception of the lower limit of quantification (LLOQ). The LLOQ values in plasma samples were 10 ng mL−1 for all analytes. The developed method was successfully applied to determine antipsychotics and their metabolites in plasma samples from schizophrenic patients.

On-line trapping/capillary hydrophilic-interaction liquid chromatography/mass spectrometry for sensitive determination of RNA modifications from human blood

RNA modification has recently been proposed to play important roles in biological regulation. The detection and quantification of RNA modifications generally are challenging tasks since most of the modifications exist in low abundance in vivo. Here we developed an on-line trapping/capillary hydrophilic-interaction liquid chromatography/electrospray ionization-mass spectrometry (on-line trapping/cHILIC/MS) method for sensitive and simultaneous quantification of RNA modifications of N6-methyladenosine (m6A) and 5-methylcytosine (5-mC) from human blood. The hydrophilic organic-silica hybrid monolith was prepared using sol-gel combined with “thiol-ene” click reaction for the separation of nucleosides. A poly(MAA-co-EGDMA) monolithic capillary was used as the on-line trapping column. With the developed on-line trapping/cHILIC/MS analytical platform, the detection limits of m6A and 5-mC can reach to 0.06 fmol and 0.10 fmol. We then investigated the contents of m6A and 5-mC in human blood RNA from healthy persons at the age of 6–14 and 60–68 years. Our results showed that both m6A and 5-mC contents were significantly decreased in elder persons, suggesting the RNA modifications of m6A and 5-mC are correlated to aging.

Improving affinity of boronate capillary monolithic column for microextraction of glycoproteins with hydrophilic macromonomer

A novel boronate affinity monolithic capillary was prepared by in-situ polymerization and successfully applied to microextraction (PMME) of glycoproteins. Using functional monomer 3-(acrylamido)phenylboronic acid (AAPBA) and hydrophilic macromonomer oligo (ethylene glycol) methyl ether methacrylate (OEG), crosslinking monomer ethylene glycol dimethacrylate (EDMA) and binary porogens of n-propanol and 1,4-butanediol, poly(AAPBA-co-OEG-co-EDMA) monolith was made with uniform structure and good column permeability. Systematic optimization of preparation conditions were performed, including AAPBA content, the molar ratio of AAPBA to OEG, crosslinking monomer content, n-propanol content in binary porogens. The optimized OEG boronic monolithic column was characterized with infrared absorption spectroscopy, field emission scanning electron microscopy and N2 adsorption experiment. In this study, extraction performance was tested by PMME of horseradish peroxidase (HRP) and ovalbumin (OVA). Compared with the corresponding OEG-free boronate monolith, the recovery of HRP and OVA was significantly improved to 97.51% and 93.97% (RSDs < 5.0%), respectively, which increased by 30.0%. Moreover, the newly developed monolith was further applied for extraction of HRP and OVA from the egg white samples with the recovery of 96.10% and 92.24% (RSDs < 7.5%), respectively. The results suggested that the introduction of hydrophilic macromonomer into boronic material is an effective method to improve the affinity of boronate affinity chromatography to glycoproteins.

"Single-pot" approach towards the preparation of alkyl and polyfluoroalkyl organo-silica monolithic capillaries for reversed-phase liquid chromatography.

Organo-silica monolithic capillary columns were prepared using thermally initiated polymerization of mixtures containing 3-(methacryloyloxy)propyltrimethoxysilane as the silicon-containing monomer, an aqueous acid catalyst, ethylene dimethacrylate as the cross-linker, a functional monomer selected from the group comprising octadecyl methacrylate, trifluoroethyl methacrylate, pentafluoropropyl methacrylate, and heptadecafluorodecyl methacrylate, toluene as the porogen, and 2,2'-azobisisobutyronitrile as the initiator. The permeability of the monoliths was controlled by varying the composition of the polymerization mixture. Chromatographic properties of resulting monolithic 100μm i.d. capillaries were evaluated utilizing four sets of probe compounds under isocratic elution conditions in the reversed-phase mode. Baseline separation of alkylbenzenes and the best steric selectivity were achieved using the octadecyl methacrylate monolithic column verifying that its surface was the most hydrophobic. In contrast, separation of a mixture containing polar compounds was observed using columns prepared in the absence of the functional monomer due to the presence of residual surface silanols at the pore surface. Polyfluoroalkyl stationary phases, especially those with a high number of fluorine atoms, exhibited the highest selectivity towards fluorine-containing analytes.

A novel one-pot strategy to prepare β-cyclodextrin functionalized capillary monoliths for enantioseparation of basic drugs

With native β-cyclodextrin (β-CD) added into the polymerization mixture directly, a novel, convenient and low-cost one-pot strategy was developed to prepare the β-CD functionalized organic polymer monolithic capillary column. Diazabicyclo[5.4.0]undec-7-ene (DBU) as a basic catalyst for the ring opening reaction between β-CD and glycidyl methacrylate (GMA) was introduced into the polymerization system for the first time. Thereby, two consecutive reactions namely the in situ methacrylation of β-CD and copolymerization reaction can be achieved in one pot. The preparation conditions including the type and composition of porogens，the ratio of functional monomer to crosslinker and amount of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) were optimized. The specific surface area and morphology of the prepared monolith were characterized using scanning electron microscopy (SEM) and nitrogen adsorption analysis, respectively. Raman spectroscopy and nuclear magnetic resonance (NMR) spectroscopy confirmed that β-CD was covalently bonded onto the monolith successfully. Then, the monolithic column was applied to enantioseparation of six basic drugs in capillary electrochromatography (CEC). Under the optimal conditions, tropicamide, homatropine, homatropine methylbromide, brompheniramine, chlorpheniramine and clorprenaline were all totally separated with the resolution (Rs) values of 2.84, 4.70, 4.61, 3.01, 2.57 and 2.33, respectively. Furthermore, the column demonstrated satisfactory stability and repeatability of retention time and enantioselectivity using homatropine as model analyte.

Online screening of acetylcholinesterase inhibitors in natural products using monolith-based immobilized capillary enzyme reactors combined with liquid chromatography-mass spectrometry

In order to develop a direct and reliable method for discovering lead compounds from traditional Chinese medicines (TCMs), a comparative online ligand fishing platform was developed using immobilized capillary enzyme reactors (ICERs) in combination with liquid chromatography-mass spectrometry (LC–MS). Methacrylate-based monolithic capillaries (400 μm I.D. × 10 cm) containing epoxy reactive groups were used as support to immobilize the target enzyme acetylcholinesterase (AChE). The activity and kinetic parameters of the AChE-ICER were investigated using micro-LC-UV. Subsequently, ligand fishing and identification from mixtures was carried out using the complete AChE-ICER-LC–MS platform. For efficient distinction of true actives from false positives, highly automated comparative analyses were run alternatingly using AChE-ICERs and negative control-ICERs, both online installed in the system. After washing unbound compounds to the waste, bound ligands were eluted from the AChE-ICER to a trapping loop using a denaturing solution. The trapped ligands were further separated and identified using LC–MS. Non-specific binding to the monolith support or non-functional sites of the immobilized enzyme was investigated by exposing analytes to the negative control-ICER. The specificity of the proposed approach was verified by analyzing a known AChE inhibitor in the presence of an inactive compound. The platform was applied to screen for AChE inhibitors in extracts of Corydalis yanhusuo. Eight compounds (columbamine, jatrorrhizine, coptisine, palmatine, berberine, dehydrocorydaline, tetrahydropalmatine and corydaline) with AChE binding affinity were detected and identified, and their AChE inhibitory activities were further verified by an in vitro enzymatic inhibition assay. Experimental results show that the proposed comparative online ligand fishing platform is suitable for rapid screening and mass-selective detection of AChE inhibitors in complex mixtures.

Molecularly Imprinted Porous Monolithic Materials from Melamine-Formaldehyde for Selective Trapping of Phosphopeptides.

Thirty-five melamine-formaldehyde (MF) monolithic materials with bimodal pore distributions were synthesized in fused silica capillaries by catalyst-free polycondensation, starting with an aqueous MF precondensate, using acetonitrile as the macroporogen and a variety of aliphatic polyethers and triblock copolymeric surfactants as porogens and mesoporogens, respectively. By varying the prepolymer composition and the type and molecular weight of the polymeric porogen components, a library of porous monolithic materials was produced, covering a range of meso- and macroporous properties. A multivariate evaluation revealed that the amount of surfactant was the strongest contributor to specific surface area and pore volume and to the inversely related mesopore size, whereas the macropore dimensions were controlled mainly by the amount of aliphatic polyether porogen. One of these capillary monoliths, chosen based on the combination of meso- and macropores providing optimal percolative flow and accessible surface area, was synthesized in the presence of N-Fmoc and O-Et protected phosphoserine and phosphotyrosine to prepare molecularly imprinted monoliths with surface layers selective for phosphopeptides. These imprinted monoliths were characterized alongside nonimprinted monoliths by a variety of techniques and finally evaluated by liquid chromatography-mass spectrometry in the capillary format to assess their abilities to trap and release phosphorylated amino acids and peptides from partly aqueous media. Selective enrichment of phosphorylated targets was demonstrated, suggesting that these materials could be useful as trapping media in affinity-based phosphoproteomics.

Development of a metal/chelate polyhydroxyethylmethacrylate monolith capillary for selective depletion of immunoglobulin G from human plasma for proteomics

In this study, we report the development of a new poly HEMA (HEMA-co-DEGDA-co-DATD) monolith capillary functionalized with “IDA-Cu (II) complex”. Of the two tested crosslinkers (methylene bisacrylamide (MBAAm) and diethylene glycol diacrylate (DEGDA)), presence of DEGDA has enhanced the monolith rigidity. Structural assembly of these monoliths are organized with highly interconnected large globule like structures and dominated by macropore region. Iminodiacetic acid (IDA) immobilization was performed using two chemical approaches (i. aldehyde − secondary amine reaction and ii. epoxy − sec. amine reaction). FT-IR analysis confirmed successful IDA immobilization in both cases. For the first time, a reaction of sec. amine ligand with aldehyde functional material was successfully reported. Overall, the Cu (II)-IDA monolith capillary showed good permeability (3.05×10 −13m2), high IgG adsorption capacity and reusablilty even after 5 consecutive adsorption-desorption cycles. The amount of protein (IgG/HSA) adsorbed on Cu (II)-IDA monolith prepared via the two chemistries is almost similar. Using this affinity monolith capillary, we selectively depleted ∼95% of IgG from human plasma (dilution of 1:16).

Metal–organic framework incorporated monolithic capillary for selective enrichment of phosphopeptides

Protein phosphorylation is a major post-translational modification, which plays a central role in the cellular signaling of numerous biological processes.

Gold nanoparticles-supported histamine-grafted monolithic capillaries as efficient microreactors for flow-through reduction of nitro-containing compounds

Hybrid microreactors consisting in 5, 20, 100 nm-sized gold nanoparticles immobilized on histamine grafted polymeric monoliths were successfully prepared, finely characterized and further applied to the catalytic reduction of nitro-derivatives.

Cationic pTyr/pSer imprinted polymers based on a bis-imidazolium host monomer: phosphopeptide recognition in aqueous buffers demonstrated by μ-liquid chromatography and monolithic columns.

We report on the design and characterization of imprinted cationic host polymers for selective trapping of phosphoserine and phosphotyrosine peptides. A series of imidazolium host monomers were synthesized and characterized with respect to binding affinity and stoichiometry of interaction with salts of phenylphosphonic acid. The strongest binders were subsequently used for the preparation of imprinted polymers in the form of crushed monoliths, using Fmoc-phosphotyrosine-ethyl ester or Fmoc-phosphoserine-ethyl ester as templates in combination with a hydrophilic crosslinking monomer. The polymers were compared with respect to binding and its dependence on solvent, and whether charged or uncharged host monomers were used. The recipes were subsequently implemented in the capillary monolith format for evaluation by micro-liquid chromatography in both buffered and organic media. Results from both tested formats reveal that the cationic host polymers displayed enhanced recognition in polar and buffered media, in contrast to neutral urea-based hosts which showed best results in acetonitrile rich mobile phases.

Size-Based Analysis of Au NPs by Online Monolithic Capillary Microextraction-ICPMS.

An online hydrophilic polymer monolithic capillary microextraction (CME)-inductively coupled plasma mass spectrometry (ICPMS) analytical system was developed for the size-based analysis of Au NPs in the range of 3-40 nm. Au NPs with different particle sizes retained on the poly(acrylamide-vinylpyridine-methylene bis(acrylamide)) (poly(AA-VP-Bis)) monolithic capillary showed different elution behavior when cysteamine was used as the eluent, and the napierian logarithm of the critical eluent concentration (Ln C (cysteamine)) was linearly dependent on the particle size of Au NPs. This means that the unknown particle size of Au NPs can be deduced based on their critical eluent concentrations. The developed method was successfully used for the baseline separation of 3 and 20 nm Au NPs, as well as 10 and 30 nm Au NPs. Compared with chromatographic-based methods for the size analysis of Au NPs, the developed online poly(AA-VP-Bis) monolithic CME-ICPMS method is featured with simultaneous separation and enrichment of Au NPs, simple operation, low cost, high analytical speed, and high adsorption capacity.

Gold nanoparticles as intermediate ligands for polymer monolithic capillary microextraction of trace rare earth elements followed by inductively coupled plasma mass spectrometry detection

In this work, a novel method of Au nanoparticles (NPs) modified polymer monolithic capillary microextraction (CME) on-line coupling with inductively coupled plasma-mass spectrometry (ICP-MS) was developed for the determination of trace rare earth elements (REEs) in environmental and biological samples. The poly(glycidyl methacrylate-ethylene dimethacrylate) monolithic capillary was prepared, functionalized with thiol ligands for the attaching of Au NPs, and then modified with mercaptosuccinic acid to provide massive carboxyl groups which have high affinity to REEs. With the modification of Au NPs, the adsorption capacity of the monolith towards target REEs has been improved by 3 to 6.5 times. Under the optimized conditions, the limits of detection of the developed method for REEs were in the range of 0.16 (Tb)–0.85 (Gd) ngL−1. The enrichment factor was 25-fold with the sample throughput of 10h−1. And the relative standard deviations were between 2.7 (Lu) and 9.8% (Dy) (c=10ngL−1, n=9). The accuracy of the method was validated by the analysis of a standard stock solution of GSB04-1789-2004 and a Certified Reference Material of GBW07301a stream sediment. The proposed method was applied for the analysis of trace REEs in seawater samples as well as human whole blood with good recoveries. The prepared monolith is featured with strong anti-interference ability, superior adsorption capacity as well as long lifespan, and the developed monolithic CME-ICP-MS is sensitive, simple and rapid for the analysis of trace/ultra-trace REEs in environmental and biological samples with complex matrix.