Open Tubular Capillary Research Articles

Chiral hydroxyl-controlled covalent organic framework-modified stationary phase for chromatographic enantioseparation.

Chiral covalent organic frameworks (CCOFs) possess asuperior chiral recognition environment, abundant pore configuration, and favorable physicochemical stability. In the post-synthetic chiral modification of COFs, research usually focused on increasing the density of chiral sites as much as possible, and little attention has been paid to the influence of the density of chiral sites on the spatial structure and chiral separation performance of CCOFs. In this article, 1,3,5-tris(4-aminophenyl) benzene (TPB), 2,5-dihydroxyterephthalaldehyde (DHTP), and 2,5-dimethoxyterephthalaldehyde (DMTP) served as the platform molecules to directly establish hydroxyl-controlled COFs through Schiff base condensation reactions. Then the novel chiral selectors 6-deoxy-6-[1-(2-aminoethyl)-3-(4-(4-isocyanatobenzyl)phenyl)urea]-β-cyclodextrin (UB-β-CD) were pended into the micropore structures of COFs via covalent bond for further construction the [UB-β-CD]x-TPB-DMTP COFs (x represents the density of chiral sites). The chiral sites density on [UB-β-CD]x-TPB-DMTP COFs was regulated by changing the construction proportion of DHTP to obtain a satisfactory CCOFs and significantly improve the ability of chiral separation. [UB-β-CD]x-TPB-DMTP COFs were coated on the inner wall of a capillary via a covalently bonding strategy. The prepared open tubular capillary exhibited strong and broad enantioselectivity toward a variety of chiral analytes, including sixteen racemic amino acids and six model chiral drugs. By comparing the outcomes of chromatographic separation, we observed that the density of chiral sites in CCOFs was not positively correlated with their enantiomeric separation performance. The mechanism of chiral recognition [UB-β-CD]x-TPB-DMTP COFs were further demonstrated by molecular docking simulation. This study not only introduces a new high-efficiency member of the COFs-based CSPs family but also demonstrates the enantioseparation potential of CCOFs constructed with traditional post-synthetic modification (PSM) strategy by utilizing the inherent characteristics of porous organic frameworks.

An innovative detection technique for capillary electrophoresis: Localized terahertz emission-time domain spectroscopy

Terahertz (THz) time-domain spectroscopy (TDS) is a recently emerging analysis method which can provide unique information on molecular vibration and rotation induced by inter/intra-molecular interactions. Although the application of THz-TDS to high-performance microscale separation methods like capillary electrophoresis (CE) has been anticipated, it has been hindered due to the diffraction limit of THz wave (typically, hundreds µm). In order to realize CE-THz-TDS, in this study, we placed a narrow open-tubular capillary on the surface of a GaAs semiconductor substrate as a “localized” THz-emitter. By focusing femtosecond pulsed laser beams at the surface of a gallium arsenide (GaAs) substrate closest to the capillary, THz waves were locally generated to pass through the capillary, so that THz absorbance spectra were obtained from the capillary which has narrower inner diameter than the diffraction limit. As a typical result from acetic acid analysis in the CE-THz-TDS platform, information on the refractive index and extinction coefficient was obtained, which showed non-linear and linear concentration dependence, respectively, similar to conventional THz-TDS using large liquid cells. Finally, CE-THz-TDS analysis of several carboxylic acids was demonstrated. Two acids were successfully separated and detected with THz-TDS, where their electrophoretic mobility values were estimated as close to those obtained with conventional contactless conductivity detection. Our proposed CE-THz-TDS showed the potential for the systematic analysis of inter/intra-molecular weak interactions like hydrogen bonds, which are unable to obtain with conventional detectors.

Columns in analytical-scale supercritical fluid chromatography: From traditional to unconventional chemistries.

Within this review, we thoroughly explored supercritical fluid chromatography (SFC) columns used across>3000 papers published from the first study carried out under SFC conditions in 1962 to the end of 2022. We focused on the open tubular capillary, packed capillary, and packed columns, their chemistries, dimensions, and trends in used stationary phases with correlation to their specific interactions, advantages, drawbacks, used instrumentation, and application field. Since the 1990s, packed columns with liquid chromatography and SFC-dedicated stationary phases for chiral and achiral separation are predominantly used. These stationary phases are based on silica support modified with a wide range of chemical moieties. Moreover, numerous unconventional stationary phases were evaluated, including porous graphitic carbon, titania, zirconia, alumina, liquid crystals, and ionic liquids. The applications of unconventional stationary phases are described in detail as they bring essential findings required for further development of the supercritical fluid chromatography technique.

Chirality-Controlled Mercapto-β-cyclodextrin Covalent Organic Frameworks for Selective Adsorption and Chromatographic Enantioseparation.

Chiral covalent organic frameworks (CCOFs) benefit from superior stability, abundant chiral environment, and homogeneous pore configuration. In its constructive tactics, only the post-modification method allows for the integration of supramolecular chiral selectors into achiral COFs. Here, the finding utilizes 6-deoxy-6-mercapto-β-cyclodextrin (SH-β-CD) as chiral subunits and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (DVA) as the platform molecule to synthesize chiral functional monomers through thiol-ene click reactions and directly establish ternary "pendant-type" SH-β-CD COFs. The chiral site density on SH-β-CD COFs was regulated by changing the proportion of chiral monomers to obtain an optimal construction strategy and remarkably improve the ability of chiral separation. SH-β-CD COFs were coated on the inner wall of the capillary in a covalently bound manner. The prepared open tubular capillary was achieved for the separation of six chiral drugs. By combining the outcomes of selective adsorption and chromatographic separation, we observed the higher density of chiral sites in the CCOFs, and poorer results were achieved. From the perspective of spatial conformational distribution, we interpret the variation in the performance of these chirality-controlled CCOFs for selective adsorption and chiral separation.

Open Tubular Column Immobilized with Covalent Organic Frameworks for Rapid Separation of Small Molecular Compounds by Capillary Electrochromatography

Preparation of a novel TpBD (synthesized from phloroglucinol and benzidine) covalent organic framework (COF) immobilized open-tubular (OT) capillary is described by in situ growth strategy. The stationary phase in the column was characterized by Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD), thermogravimetric analysis (TGA), nitrogen adsorption–desorption isotherms, scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectrum (EDS). Several families of compounds with different properties (alkylbenzenes, parabens, sulfonamides and benzoic acids) were selected to evaluate the performance of the TpBD COF immobilized capillary. The results showed that the stationary phase was uniform with about 6.0 μm thickness under the optimal preparation conditions, and the relative standard deviations (RSDs) were no more than 3.13% of alkylbenzenes on the TpBD COF immobilized capillary for 11 consecutive runs, which exhibited its excellent reproducibility and stability. A rapid baseline separation of each family of the analytes (neutral parabens, amphoteric sulfonamides and acidic benzoic acids) was obtained in less than 6 min with a resolution (Rs) of 2.79~9.30, which sufficiently verified the rapid separation, high resolution and wide application range of the TpBD COF immobilized capillary, and further revealed this strategy of fabricating COF to capillary column to show great promise in capillary electrochromatography.

Development of Novel Analysis and Characterization Methods Utilizing Reaction Dynamics in a Separation Capillary

Electrophoretic migration of an analyte in capillary electrophoresis (CE) reflects reaction dynamics of the analyte in solution. In affinity CE, an analyte of interest interacts with a modifier added in the separation buffer in fast equilibrium, and effective electrophoretic mobility of the analyte is contributed from its equilibrium species. Precise measurement of effective electrophoretic mobility allows analyzing the equilibrium. Analysis of equilibria under CE separation possesses several advantages against traditional analyses in homogeneous solution; coexisting substances including impurities and kinetically generated substances are resolved by CE from the equilibrium species of interest. Characteristics of the CE analysis have been applied to analyses of acid-base equilibria of degradable substances and ion-association equilibria in an aqueous solution. Since CE is operated in an open-tubular capillary, it is also suitable for the characterization of carbon nanoclusters such as graphene and carbon nanotube, and measurement of effective electrophoretic mobility helps characterization of nanoclusters. A novel analysis technique of capillary electrophoresis/dynamic frontal analysis (CE/DFA) has also been proposed for the analysis of such reactions as involving equilibria and kinetic reactions. In CE/DFA, kinetically generated product is continuously resolved from the equilibrium species, and a plateau signal would be detected when the reaction rate is constant. Michaelis-Menten constants have successfully been determined through the plateau height by CE/DFA. In this review, analysis and characterization methods utilizing reaction dynamics in a separation capillary are summarized.

Open tubular capillary ion chromatography with online dilution for small ions determination in drinks

This work aims to develop a more robust, easy-to-use, low-pressure, and cost-effective nonsuppressed open tubular capillary ion chromatography (NS-OTIC) approach with online dialysis for small ions determination in drinks. The fabricated device was applied for two selected columns, including poly(butadiene-maleic acid) on a 50-μm bore and AS18 Latex on 25-µm bore fused silica capillaries, for the separation of mixed cations (Na+, K+, Ca2+, Mg2+) and mixed anions (Cl−, Br−, NO2−, NO3−), respectively. High concentrations of ions (up to 100 mM) level can be directly introduced into the NS-OTIC system without an off-line (manual) dilution step. The linear relationship of the peak area and concentration of model ions can be obtained with a resolution > 1.1. The repeatability of the peak area for both OTIC columns was < 6% RSD. Juice and tea samples were successfully analyzed with % recoveries of 77–112 and 90–119 for cation and anion determinations, respectively.

Establishment of Chiral MIL-53 Based Open Tubular Capillary Electrochromatography for Enantiosepration

Establishment of Chiral MIL-53 Based Open Tubular Capillary Electrochromatography for Enantiosepration

Consecutive Sample Injection Analysis in Tube Radial Distribution Chromatography.

Tube radial distribution chromatography based on the tube radial distribution flow, or annular flow, in an open-tubular capillary has been reported, where the annular flow is created through phase-separation multiphase flow. We have proposed the first-ever procedure for consecutive sample injection analysis using chromatography. In basic terms, a commercially available HPLC system could be used with a sample injector (0.2 μL volume) and a fused-silica capillary tube (250 cm long) as a separation column instead of a normal packed one, while the built-in detection cell was replaced by improved on-capillary detection. A ternary mixed solution of water/acetonitrile/ethyl acetate (3:8:4 volume ratio) was delivered into the capillary tube as an eluent at a flow rate of 2.0 μL min-1. Model sample solutions of 1-naphthol and 2,6-naphthalenedisulfonic acid were consecutively analyzed by the present chromatography with a processing rate of 6 samples per hour. Simple and rapid consecutive analysis could be performed because washing and initialization of the separation tube was no longer necessary. The obtained results provide clues to developing new methodologies which combine features of both chromatography (separation) and the flow injection method (consecutive analysis).

Diffraction-based label-free photothermal detector for separation analyses in a nanocapillary

Miniaturization of column diameter in liquid chromatography is one of the major trends in separation sciences toward single-cell proteomics and metabolomics. Micro/nanoscale open tubular (OT) capillaries are promising tools for efficient separation analyses of the ultra-small volume of samples. However, highly sensitive and label-free on-column detection is still challenging for such ultra-small capillaries. In this study, we developed a photothermal detector using optical diffraction phenomena by a single nanocapillary. Our detection method realized concentration determination of unlabeled sample solutions in a nanocapillary with 460 nm inner diameter. The calculated limit of detection was 0.12 µM, which corresponds to 16 molecules in a detection volume of 0.23 fL. Furthermore, normal-phase chromatography was performed on a 12 cm long nanocapillary, and femtoliter sample injection, efficient separation, and label-free detection of dye molecules were demonstrated. Our photothermal detector will be widely used as a universal tool for chemical/biological analyses using capillaries with micro/nanoscale diameters.

Characterization of a headspace sampling method with a five-component diesel fuel surrogate

PLOT-cryoadsorption concentrates headspace vapors by sweeping them through porous layer open tubular (PLOT) capillaries chilled to 0 °C to promote adsorption onto an alumina layer. Compared to passive headspace concentration employing activated charcoal strips (ACSs) as adsorbents, PLOT-cryoadsorption has several potential advantages for extracting ignitable liquid (IL) residue from fire debris evidence. Capillary vapor traps can be monitored for breakthrough to avoid problematic displacement that occurs when an adsorbent becomes saturated. Capillaries can also be eluted with acetone to avoid highly toxic carbon disulfide. Future adoption of PLOT-cryoadsorption for fire debris analysis requires investigation of sampling parameters including collection volume, flow rate, and temperature. Here we employ a simple five-component surrogate for diesel fuel (that is, a simulated or artificial diesel fuel) to study the effect of flow rate and sample temperature on the composition and spatial distribution of the collected headspace. Flow rates at or below 1.5 scc (standard cubic centimeters)/min yielded the most repeatable results. Across the range 60 °C to 120 °C, we found that high sample temperatures allowed for the collection of more total sample and shifted its composition towards lower-volatility components. Consistent with chromatographic theory, higher-volatility components traveled furthest along the length of the capillary and were more prone to breakthrough. We conclude that the surrogate mixture allowed for effective, quantitative comparisons between sampling conditions that could be translated to real diesel fuel.

Preparation and application of immunoaffinity in-tube solid phase microextraction column with oriented antibody-immobilized porous layer open tubular capillary for high sensitive quantification of serum extracellular domain of human epidermal growth factor receptor 2 levels

Human epidermal growth factor receptor 2 (HER2) gene expresses a transmembrane glycoprotein that is over-expressed in 15–30% breast, 3% lung, and other several digestive cancers. So HER2 is a good biomarker for tumor diagnostic and treatment monitoring. Clinically, detection of HER2 often employs invasive approaches with tissue samples, which at large extent limit its universal application. Shedding of the extracellular domain (ECD) of the HER2 (HER2-ECD) into the circulation has led to the development of a serum test of HER2-ECD as an additional approach to probe the HER2 overexpression. However, few methods were developed due to the high sensitivity required by the serum HER2-ECD determination. In this work, we prepared a novel immunoaffinity in-tube solid phase microextraction (IT-SPME) sorbent for selective enrichment of HER2-ECD. Two clinical available monoclonal antibodies against to HER2, trastuzumab and pertuzumab, were selected as immunoaffinity ligands. Porous layer open tubular capillary with oriented antibody immobilization were fabricated and systematically optimized to afford a higher extraction capacity. The capacity was reached to 120.4 μg/m, which is more than 1000 times higher than that obtained by a common method (directly antibody immobilization on a naked capillary). After sample extraction and enrichment by the IT-SPME, the eluent were determined by a particle-enhanced turbidimetric immunoassay (PETIA). Sensitive quantification of HER2-ECD by the PETIA was thereby accomplished. HER2-ECD concentrations in 82 clinical serum samples were determined by the developed IT-SPME/PETIA method, and the results were well-correlated with that by the clinical used chemiluminescence immunoassay (CLIA). Besides, the IT-SPME/PETIA method was found providing 5 times higher sensitivity than the CLIA, and 500 times higher than the PETIA without IT-SPME. The results indicate that the developed method is suitable for high-sensitive quantification of HER2-ECD in clinical samples.

A Ratiometric Fluorescent Probe for Detection and Quantification of Endogenous Hydrogen Peroxide in Living Cells

We propose a promising capillary immunosensor by combining porous-layer surface modification of an open-tubular capillary and streptavidin-biotin-peroxidase nano-complex signal amplification of chemiluminescence read-out. The immunosensor, namely Porous Layer Open Tubular-Signal Amplification (PLOT-SA) sensor, is successfully applied for ultra-sensitive sensing of procalcitonin (PCT) in human serum samples. The results show the PLOT-SA sensor exhibits essential features for PCT determination, including a wide linear detection range of 0.1 pg/mL-100 ng/mL, an extremely low limit-of-quantitation of 0.01 pg/mL, excellent intra-day and inter-day stability and reproducibility with RSDs less than 4.5%. Our study provides a reliable and robust approach for developing capillary sensors that can be used in analysis of complex biologic samples.

An in-tube aptamer/gold nanoparticles coated capillary solid-phase microextraction for separation of adenosine in serum and urine samples

As an endogenous nucleoside, adenosine was significant for the diagnosis and treatment of some diseases, such as schizophrenia. However, due to the complicated matrix interference, it was difficult to monitor trace or ultra-trace adenosine directly in bio-samples. In this contribution, a novel in-tube SPME technique based on aptamer/Au nanoparticles coated open tubular fused-silica capillary was established to separate and enrich adenosine in bio-samples with high affinity. Therefore, a uniform and dense AuNPs layer was coated on the inner surface of the open tubular capillary, and then adenosine aptamer was immobilized on AuNPs with a high capacity of 2.44 μg per 27-cm capillary. As a result, the capillary shown high selectivity to adenosine with a selectivity factor of 14.4 when compared with the scrambled aptamer/AuNPs coated capillary. Also, the extraction amount of adenosine was 2.8–24.8 times higher than those of its structural analogs and contrast, such as guanosine, uridine, cytidine, thymidine, and toluic acid. After the optimization of extraction conditions, the aptamer/AuNPs coated in-tube SPME-HPLC method was developed for the adenosine assay with the linear range of 0.002–0.100 μg mL−1 and the detection limit of 0.45 ng mL−1. Subsequently, the approach was applied for trace adenosine monitoring in human serum and urine samples. It showed a strong performance of reducing matrix interference and improving sensitivity, and the spiking recoveries of 89.9–92.6% and 91.1–94.5% were achieved respectively.

Ultra-sensitive capillary immunosensor combining porous-layer surface modification and biotin-streptavidin nano-complex signal amplification: Application for sensing of procalcitonin in serum

We propose a promising capillary immunosensor by combining porous-layer surface modification of an open-tubular capillary and streptavidin-biotin-peroxidase nano-complex signal amplification of chemiluminescence read-out. The immunosensor, namely Porous Layer Open Tubular-Signal Amplification (PLOT-SA) sensor, is successfully applied for ultra-sensitive sensing of procalcitonin (PCT) in human serum samples. The results show the PLOT-SA sensor exhibits essential features for PCT determination, including a wide linear detection range of 0.1 pg/mL-100 ng/mL, an extremely low limit-of-quantitation of 0.01 pg/mL, excellent intra-day and inter-day stability and reproducibility with RSDs less than 4.5%. Our study provides a reliable and robust approach for developing capillary sensors that can be used in analysis of complex biologic samples.

Preparation and characterization of micro-bore wall-coated open-tubular capillaries with low phase ratios for fast-gas chromatography–mass spectrometry: Application to ignitable liquids and fire debris

Fast Gas Chromatography (GC) allows for analysis times that are a fraction of those seen in traditional capillary GC. Key modifications in fast GC include using narrow, highly efficient columns that can resolve mixtures using a shorter column length. Hence, a typical fast GC column has an inner diameter of 100–180 μm. However, to maintain phase ratios that are consistent with typical GC columns, the film thickness of fast GC stationary phases are also low (e.g., 0.1–0.18 μm). Unfortunately, decreased film thickness leads to columns with very low sample capacity and asymmetric peaks for analytes that are not sufficiently dilute. This paper describes micro-bore (50 μm i.d.) capillary columns with thick films (1.25 μm), and low phase ratios (10). These columns have greater sample capacity yet also achieve minimum plate heights as low as 110 μm. Hence, separation efficiency is much higher than would be obtained using standard GC columns. The capillary columns were prepared in-house using a simple static-coating procedure and their plate counts were determined under isothermal conditions. The columns were then evaluated using temperature programming for fast GC–MS analysis of ignitable liquids and their residues on fire debris exemplars. Temperature ramps of up to 75 °C min−1 could be used and separations of ignitable liquids such as gasoline, E85 fuel, and lighter fluid (a medium petroleum distillate) were complete within 3 min. Lastly, simulated fire debris consisting of ignitable liquids burned on carpeting were extracted using passive headspace absorption-elution and the residues successfully classified.

Selective capillary electrophoresis separation of mono and divalent cations within a high-surface area-to-volume ratio multi-lumen capillary

In this study, the separation of inorganic mono and divalent cations using multi-lumen silica capillaries (MLCs) of 126 channels, each with either 4 or 8 μm inner diameter, was investigated using capillary electrophoresis and on-capillary capacitively coupled contactless conductivity detection (CE-C4D). MLCs provided sufficiently high surface area-to-volume ratios to generate significant wall ion-exchange interactions for the divalent cations, which significantly affected resultant selectivity, whereas monovalent cations were predominantly separated by simple electrophoresis. The resultant hybrid selectivity was seen for both 4 and 8 μm channel multi-lumen capillaries, without any preconditioning or capillary wall modification. Remarkably, the electrophoretic mobilities for the divalent cations Mg2+ and Ca2+ were reduced 7.5 times compared to those determined using a single channel open tubular capillary of 50 μm i.d., providing much improved selectivity. Apparent electrophoretic mobilities of divalent cations increased as the concentration of BGE increased, while those of monovalent cations decreased parallel to electroosmotic mobility. These results show the electrostatic interaction between the divalent cations and the silica wall. At least, this specific separation of mono- and divalent cations were clearly observed with a mixture standards solution of less than 200 μmol L−1. Using a MLC with 126 × 8 μm i.d. channels and 49.1 cm in length, together with a 20 mmol L−1 MES/His BGE, containing 2 mmol L−1 18-crown-6, monovalent cations (NH4+, K+ Na+ and Li+) and divalent cations (Ca2+ and Mg2+) could be completely separated within 4 min. For monovalent cations, on-capillary detection using C4D provided calibration curve (0–200 μmol L−1) correlation coefficients in the range R2 = 0.995–0.999, and limits of detection of 2.2–6.6 μmol L−1. Relative standard deviations for migration times were less than 0.6%, and recoveries ranged from the 93.8%–105.4%. The new method was applied to the separation and quantitative determination of monovalent and divalent cations in drinking waters and soil extracts.

Molecular dispersion in pre-turbulent and sustained turbulent flow of carbon dioxide

The average dispersion coefficients, Da¯, of two small molecules (acetonitrile and coronene) were measured under laminar, transient, and sustained turbulent flow regimes along fused silica open tubular capillary (OTC) columns (180 μm inner diameter by 20 m length). Carbon dioxide was used as the mobile phase at room temperature (296 K) and at average pressures in the range from 1500 to 2700 psi. The Reynolds number (Re) was increased from 600 to 5000. The measurement of Da¯ is based on the observed plate height of the non-retained analytes as a function of the applied Reynolds number. Da¯ values are directly estimated from the best fit of the general Golay HETP equation to the experimental plate height curves.The experimental data revealed that under a pre-turbulent flow regime (Re < 2000), Da¯ is 2–6 times larger (3.5 × 10−4 cm2/s) than the bulk diffusion coefficients Dm of the analyte (1.6 × 10−4 and 5.8 × 10−5 cm2/s for acetonitrile and coronene, respectively). This result was explained by the random formation of decaying or vanishing turbulent puffs under pre-turbulent flow regime. Yet, the peak width remains controlled exclusively by the slow mass transfer in the mobile phase across the inner diameter (i.d.) of the OTC. Under sustained turbulent flow regime (Re > 2500), Da¯ is about four to five orders of magnitude larger than Dm. The experimental data slightly overestimated the turbulent dispersion coefficients predicted by Flint-Eisenklam model (Da¯=4 cm2/s). The discrepancy is explained by the approximate nature of the general Golay equation, which assumes that Da¯ is strictly uniform across the entire i.d. of the OTC. In fact, both the viscous and buffer wall layers, in which viscous effects dominate inertial effects, cannot be considered as fully developed turbulent regions. Remarkably, the mass transfer mechanism in OTC under sustained turbulent flow regime is not only controlled by longitudinal dispersion but also by a slow mass transfer in the mobile phase across the thick buffer layer and the thin viscous layer. Altogether, these layers occupy as much as 35% of the OTC volume at Re = 4000. From a theoretical viewpoint, the general Golay HETP equation is only an approximate model which should be refined based on the actual profile of the analyte dispersion coefficient across the OTC i.d. In practice, the measured plate height of non-retained analytes under sustained turbulent flow of carbon dioxide are two orders of magnitude smaller than those expected under hypothetical laminar flow regime.

Multiplex immunoassays using surface modification-mediated porous layer open tubular capillary

We proposed an innovative surface modification-mediated porous layer open tubular (PLOT) capillary, which was modified via an in situ biphasic reaction. This capillary comprised three-dimensional homogeneous and porous structures, which could increase the surface-area-to-volume ratio for antibody immobilization. The PLOT capillary was shown as an ideal immunoreaction base to enhance the sensitivity of immunoassays and shorten analysis time. By connecting two separate PLOT capillaries using a suitable sleeve tube, we can perform multiplex targets detection in the same sample. We developed a sensitive, rapid, and multiplex PLOT capillary-mediated immunosensor for the simultaneous identification of alpha fetoprotein (AFP) and carcinoembryonic antigen (CEA) in clinical serum samples with good accuracy. The detection sensitivity of the PLOT immunosensor improved by 10-fold compared with that of bare-capillary sensor, and the whole analysis could be completed within 1 h. This work suggest that suitable surface modification strategy is an effective tool to improve the analytical performance of conventional immunoassay and our study provided a feasible, sensitive, and multi-target assay for the detection of cancer biomarkers, which would be of valuable application in clinical diagnosis.

Synthesis of boronate-decorated polyethyleneimine-grafted porous layer open tubular capillaries for enrichment of polyphenols in fruit juices

A combination between modification with porous layer and grafting of polyethyleneimine (PEI) on the inner face of capillary was for the first time developed for boronate affinity in-tube solid-phase microextraction (SPME) material to enhance the extraction capacity for cis-diol-containing polyphenols. The successful synthesis of boronate-decorated polyethyleneimine-grafted porous layer open tubular (BPPLOT) capillary was confirmed by scanning electron micrograph, Fourier transform-infrared spectra and absorption experiments. The porous layer, PEI and boronate affinity provided high specific surface area, more binding sites for boronate groups and specific selectivity of BPPLOT capillary, respectively. The maximum binding quantity of BPPLOT capillary greatly improved, and ranged from 143 to 170 μg m−1 for cis-diol-containing polyphenols (catechin, chlorogenic acid, caffeic acid and epicatechin). A green method based on boronate affinity in-tube SPME was developed for separation and enrichment polyphenols, and some parameters of in-tube SPME were optimized. After in-tube SPME, HPLC with UV detection was used for quantitative determination of polyphenols. Recoveries of standard spiked cis-diol-containing polyphenols from fruit juice were between 80.9% and 102%, with intra-day and inter-day coefficient of variation ranging from 4.8% to 7.3% and 5.0% to 8.6%, respectively. Conversely, recovery of non-cis-diol-containing ferulic acid was no greater than 3.0%. These results suggested that the BPPLOT capillary could effectively separate and enrich cis-diol-containing polyphenols from real samples.