Facile liquid-phase deposition synthesis of titania-coated magnetic sporopollenin for the selective capture of phosphopeptides.

Titania-grafted magnetic sporopollenin is synthesized by the liquid-phase deposition (LPD) technique, characterized by SEM, EDX, and nitrogen adsorption porosimetry, and used for the selective enrichment of phosphorylated peptides. The material is low cost because of easier availability of pollens and has rich surface chemistry which enables strong attachment of titania onto magnetic sporopollenin. The material shows higher selectivity of 1:1000 with ß-casein spiked in BSA. Higher sensitivity of 10 fmol is recorded for phosphopeptides from standard ß-casein digest. Twenty phosphorylated peptides are enriched from milk digest and four endogenous phosphopeptides from diluted human serum. The magnetic property of titania-coated magnetic sporopollenin facilitates the fast and effective isolation of phosphopeptides from complex mixtures through external magnet. The material is finally applied to tryptic digest of rat brain cell lysate for phosphopeptide enrichment where 2718 phosphopeptides are identified by using LC-MS/MS with C18 column. Titania-coated magnetic sporopollenin captures both mono-phosphorylated (2489) and multi-phosphorylated peptides (229) due to strong affinity of TiO2 with phosphates. TiO2-coated magnetic material also shows better enrichment efficiency in comparison to commercial TiO2. Graphical abstract.

Black phosphorus-assisted laser desorption ionization mass spectrometry for the determination of low-molecular-weight compounds in biofluids.

Quantitative analysis of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been a challenging task due to matrix-derived interferences in low m/z region and poor reproducibility of MS signal response. In this study, we developed an approach by applying black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix for the quantitative analysis of small molecules for the first time. Black phosphorus-assisted laser desorption/ionization mass spectrometry (BP/ALDI-MS) showed clear background and exhibited superior detection sensitivity toward quaternary ammonium compounds compared to carbon-based materials. By combining stable isotope labeling (SIL) strategy with BP/ALDI-MS (SIL-BP/ALDI-MS), a variety of analytes labeled with quaternary ammonium group were sensitively detected. Moreover, the isotope-labeled forms of analytes also served as internal standards, which broadened the analyte coverage of BP/ALDI-MS and improved the reproducibility of MS signals. Based on these advantages, a reliable method for quantitative analysis of aldehydes from complex biological samples (saliva, urine, and serum) was successfully established. Good linearities were obtained for five aldehydes in the range of 0.1-20.0 µM with correlation coefficients (R (2)) larger than 0.9928. The LODs were found to be 20 to 100 nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations (RSDs) less than 10.4 %, and the recoveries in saliva samples ranged from 91.4 to 117.1 %. Taken together, the proposed SIL-BP/ALDI-MS strategy has proved to be a reliable tool for quantitative analysis of aldehydes from complex samples. Graphical Abstract An approach for the determination of small molecules was developed by using black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix.

Preparation of a hyper-cross-linked polymer monolithic column and its application to the sensitive determination of genomic DNA methylation.

A hyper-cross-linked polymer monolithic column, poly(methacrylatoethyl trimethyl ammonium-co-vinylbenzene chloride-co-divinylbenzene) (MATE-co-VBC-co-DVB) with phenyl and quaternary ammonium groups was successfully prepared in the current study. The prepared monolith possesses large specific surface area, narrow mesopore size distribution and high column efficiency. The poly(MATE-co-VBC-co-DVB) monolithic column was demonstrated to have strong anion exchange/reversed-phase (SAX/RP) mixed-mode retention for analytes on capillary liquid chromatography (cLC). By using this monolithic column, we developed a rapid and sensitive method for the detection of DNA methylation. Our results showed that six nucleobases (adenine, guanine, cytosine, thymine, uracil, and 5-methylcytosine (5-mC)) can be baseline separated within 15 min by electrostatic repulsion and hydrophobic interactions between nucleobases and the monolithic stationary phase. The limit of detection (LOD, signal/noise = 3) of 5-mC is 0.014 pmol and endogenous 5-mC can be distinctly detected by using only 10 ng genomic DNA, which is comparable to that obtained by mass spectrometry analysis. Furthermore, by using the method developed here, we found that DNA methylation inhibitor 5-azacytidine (5-aza-C) and 5-aza-2'-deoxycytidine (5-aza-CdR) could induce a significant decrease of genome-wide DNA methylation in human lung carcinoma cells (A549) and cervical carcinoma cells (HeLa).

Dispersive microextraction based on magnetic polypyrrole nanowires for the fast determination of pesticide residues in beverage and environmental water samples.

In this study, magnetic polypyrrole nanowires (mPPYs) were fabricated via a simple co-mixing method based on an "aggregation-wrap" mechanism. The polypyrrole (PPy) nanowires were synthesized by in situ chemical oxidative polymerization using cetyltrimethylammonium bromide as the "soft template" and the magnetic nanoparticles (MNPs) prepared using solvothermal methods. Typically, when these two nanomaterials were vortically mixed in a solvent, the MNPs were wrapped into the PPy nanowire networks that formed during the aggregation process, leading to the formation of mPPYs which can be separated from the solvent rapidly and conveniently by a magnet. Due to the better permeability, good adsorption ability, and magnetic separability of the resultant material, mPPYs were applied for the enrichment of 11 pesticides including organophosphorus, organochlorine, and pyrethroid using magnetic solid phase extraction (MSPE) to test their feasibility in sample preparation. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of pesticide residues was established by coupling with gas chromatography/mass spectrometry (GC/MS) analysis. The whole pretreatment process was rapid and can be accomplished within 15 min. The linearity range of the proposed method was 0.2-10 µg/L, with correlation coefficients (R) of 0.995-0.999; the limits of quantification for the target compounds were in the range of 0.09-0.29 µg/L. In addition, an acceptable reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations of less than 14 and 16 %, respectively. Finally, the established MSPE-GC/MS method was successfully applied for the determination of pesticide residues in beverage teas, juices, and environmental water samples.

Preparation of a novel carboxyl stationary phase by "thiol-ene" click chemistry for hydrophilic interaction chromatography.

A novel carboxyl-bonded silica stationary phase was prepared by "thiol-ene" click chemistry. The resultant Thiol-Click-COOH phase was evaluated under hydrophilic interaction liquid chromatography (HILIC) mobile phase conditions. A comparison of the chromatographic performance of Thiol-Click-COOH and pure silica columns was performed according to the retention behaviors of analytes and the charged state of the stationary phases. The results indicated that the newly developed Thiol-Click-COOH column has a higher surface charge and stronger hydrophilicity than the pure silica column. Furthermore, the chromatographic behaviors of five nucleosides on the Thiol-Click-COOH phase were investigated in detail. Finally, a good separation of 13 nucleosides and bases, and four water-soluble vitamins was achieved.

Determination of eight illegal drugs in human urine by combination of magnetic solid-phase extraction with capillary zone electrophoresis.

Using magnetite/silica/poly(methacrylic acid-co-ethylene glycol dimethacrylate) (Fe(3)O(4)/SiO(2)/poly(MAA-co-EDMA)) magnetic microspheres, a rapid and high-throughput magnetic solid-phase extraction coupled with capillary zone electrophoresis (MSPE-CZE) method was developed for the determination of illegal drugs (ketamine, amphetamines, opiates, and metabolites). The MSPE of target analytes could be completed within 2 min, and the eight target analytes could be baseline separated within 15 min by CZE with 30 mM phosphate buffer solution (PBS, pH 2.0) containing 15% v/v ACN as background electrolyte. Furthermore, hydrodynamic injection with field-amplified sample stacking (FASS) was employed to enhance the sensitivity of this MSPE-CZE method. Under such optimal conditions, the limits of detection for the eight target analytes ranged from 0.015 to 0.105 µg/mL. The application feasibility of MSPE-CZE in illegal drugs monitoring was demonstrated by analyzing urine samples, and the recoveries of target drugs for the spiked sample ranging from 85.4 to 110.1%. The method reproducibility was tested by evaluating the intra- and interday precisions, and relative standard deviations of <10.3 and 12.4%, respectively, were obtained. To increase throughput of the analysis, a home-made MSPE array that has potential application to the treatment of 96 samples simultaneously was used.

Porous monoliths: sorbents for miniaturized extraction in biological analysis.

In this review the focus is on application of porous monoliths to miniaturized extraction of biological analysis, with emphasis on porous monolithic materials and different miniaturized extraction formats. The general approaches used to synthesize organic polymer and silica monolithic materials are highlighted, and their properties and applicability are described and compared. Several extraction formats, including in-tube microextraction, chip-based microextraction, tip-based microextraction, among others, are reviewed in depth.

Grafting of silica with a hydrophilic triol acrylamide polymer via surface-initiated "grafting from" method for hydrophilic-interaction chromatography.

A novel hydrophilic polymer-coated silica sorbent has been prepared using the radical "grafting from" polymerization method through surface-bound azo initiators for hydrophilic-interaction chromatography (HILIC). The azo groups were introduced to the surface of silica gel through the reaction with amino groups on the surface of silica gel with 4,4'-azobis(4-cyanopentanoic acid chloride) (ACVC). The resultant azo-immobilized silica gel served as surface initiator to polymerize hydrophilic triol acrylamide monomer N-acryloyltris(hydroxymethyl) aminomethane (NA) in methanol to get hydrophilic polymer-coated silica sorbent. The obtained poly(NA)-coated silica (pNA-sil) was characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), and nitrogen sorption porosimetry (NSP). Then the pNA-sil was packed into the stainless-steel column and evaluated in high-performance liquid chromatography (HPLC). Good chromatographic performance for the separation of peptides and nucleosides was obtained under HILIC mode. The results indicated that the pNA-sil stationary phase behaved as mixed-mode retention mechanisms of hydrophilic and ionic interactions. Furthermore, the pNA-sil phase was used to separate tryptic digest of ß-casein and our results showed that more than 12 peptides peaks were resolved and well distributed within the elution window. Finally, the pNA-sil stationary phase was demonstrated to possess remarkable reproducibility and stability. Taken together, the pNA-sil stationary phase prepared in the current study offers a potential application in proteomics study.

Magnetic solid-phase extraction using magnetic hypercrosslinked polymer for rapid determination of illegal drugs in urine.

A novel magnetic material Fe(3)O(4)/SiO(2)/P(MAA-co-VBC-co-DVB) was prepared via the hypercrosslinking of its precursor which was produced via precipitation polymerization of methacrylic acid (MAA), vinylbenzyl chloride (VBC), and divinylbenzene (DVB) in the presence of Fe(3)O(4)/SiO(2) submicrospheres with the surface containing abundant reactive double bonds. The resultant sorbent was characterized by scan electron microscopy, N(2) adsorption, and Fourier transform infrared spectroscopy. It was found that this material had remarkable features such as large surface area (500 m(2)/g) and pore volume (0.32 cm(3)/g), as well as desirable chemical composition (including hydrophobic and ion-exchange moieties). Taking advantages of the Fe(3)O(4)/SiO(2)/P(MAA-co-VBC-co-DVB), a magnetic SPE (MSPE) coupled with capillary electrophoresis (CE) method was developed for the determination of illegal drugs in urine samples. The extraction time could be clearly shortened up to 3 min. The recoveries of these drug compounds were in the range of 84.0-123% with relative standard deviations ranging between 1.7 and 10.5%; the limit of detection was in the range of 4.0-6.0 µg/L. The proposed method is simple, effective, and low-cost, and provides an accurate and sensitive detection platform for abused drug analysis.

Boronate affinity monolith for highly selective enrichment of glycopeptides and glycoproteins.

A novel boronate affinity monolith, poly(3-acrylamidophenylboronic acid-co-ethylene dimethacrylate) (AAPBA-co-EDMA), was prepared in 530 microm capillaries by a one-step in situ polymerization procedure using a pre-polymerization mixture consisting of functional monomer 3-acrylamidophenylboronic acid, cross-linker ethylene dimethacrylate, porogenic solvent methanol with added poly(ethylene glycol) 20,000 (PEG 20,000) and initiator azobisisobutyronitrile (AIBN). The preparation of the monolith was optimized by investigating the ratio of functional monomer to cross-linker and the effect of poly(ethylene glycol) molecular weight. The resulting boronate monolith was used as a sorbent for polymer monolith microextraction (PMME). Using nucleosides as the testing analyte, the extraction performance of this boronate monolith towards glycol-containing compounds was examined. Finally, the boronate monolith was applied for selective enrichment of glycopeptides and glycoproteins.

Preparation of a poly(N-isopropylacrylamide-co-ethylene dimethacrylate) monolithic capillary and its application for in-tube solid-phase microextraction coupled to high-performance liquid chromatography.

A poly(N-isopropylacrylamide-co-ethylene dimethacrylate) (poly(NIPAAm-co-EDMA)) monolith was in situ prepared in the capillary and was investigated for in-tube solid-phase microextraction (SPME). NIPAAm, an acrylamide monomer with isopropyl group, was crosslinked with EDMA. PEG of 400-20,000 Da molecular weight and methanol were selected as the binary porogens. The porous structures of the resulting monoliths have been assessed by SEM, nitrogen adsorption-desorption, and pressure drop measurements. To investigate the extraction mechanism, several groups of model analytes (including neutral, acidic, and basic) were examined. The result showed that this monolithic material exhibited high extraction efficiencies for compounds under highly acidic and basic conditions, which was due to the hydrophobic interactions and excellent pH stability of the monolith. The equilibrium extraction time profiles were also monitored for model compounds to evaluate the extraction capacity of monolithic capillary. Finally, the developed monolith in-tube SPME-HPLC method was applied to the determination of three tricyclic antidepressants from urine samples.

Preparation of pH-responsive stationary phase for reversed-phase liquid chromatography and hydrophilic interaction chromatography.

Novel pH-responsive polymer-grafted silica was successfully synthesized through the radical "grafting from" polymerization on azo initiator-immobilized silica. The immobilization of azo initiator onto the silica surface was achieved by the reaction of surface amino groups with 4,4'-azobis(4-cyanovaleric acid chloride). The polymer-grafted silica was prepared by stirring suspension of the azo initiator-immobilized silica in anhydrous dioxane containing acrylic acid (AAc) and butyl acrylate (BA). The resulting polymer-grafted silica was demonstrated to be pH responsive to hydrophobic/hydrophilic property by reversed-phase liquid chromatography (RPLC) and hydrophilic interaction chromatography (HILIC). In RPLC mode, the retention of aromatic compounds decreased with the increase in the pH of mobile phase. However, the opposite result was obtained in HILIC mode; the retention of soybean isoflavones was stronger with the mobile phase at higher pH. Finally, the separations of sulfonamides and soybean isoflavones were carried out in RPLC mode and the separation of some nucleotides was achieved in HILIC mode.

Preparation of polymer monolithic column functionalized by arsonic acid groups for mixed-mode capillary liquid chromatography.

A mixed-mode polymer monolithic column functionalized by arsonic acid groups was prepared by single-step in situ copolymerization of monomers p-methacryloylaminophenylarsonic acid (p-MAPHA) and pentaerythritol triacrylate (PETA). The prepared poly(p-MAPHA-co-PETA) monolithic column has a homogeneous monolithic structure with good permeability and mechanical stability. Zeta potential measurements reveal that the monolithic stationary phase holds a negative surface charge when the mobile phase resides in the pH range of 3.0-8.0. The retention mechanisms of prepared monolithic column are explored by the separation of selected polycyclic aromatic hydrocarbons (PAHs), nucleosides, and three basic compounds. The results indicate that the column functions in three different separation modes associated with reversed-phase chromatography based on hydrophobic interaction, hydrophilic interaction chromatography, and cation-exchange chromatography. The column efficiency of prepared monolithic column is estimated to be 70,000 and 76,000 theoretical plates/m for thiourea and naphthalene, respectively, at a linear flow velocity of 0.85 mm/s using acetonitrile/H2O (85/15, v/v) as the mobile phase. Furthermore, an analysis of the retention factors obtained for the PAHs indicates that the prepared monolithic column exhibits good reproducibility with relative standard deviations of 2.9%, 4.0%, and 4.7% based on run-to-run injections, column-to-column preparation, and batch-to-batch preparation, respectively. Finally, we investigate the separation performance of the proposed monolithic column for select phenols, sulfonamides, nucleobases and nucleosides.

Polymer monolith microextraction with in situ derivatization and its application to high-performance liquid chromatography determination of hexanal and heptanal in plasma.

A simple, rapid and sensitive method for the determination of hexanal and heptanal in plasma by high-performance liquid chromatography (HPLC) has been developed, which is based on polymer monolith microextraction (PMME) with in situ derivatization. 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing reagent was first adsorbed on a poly (methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith, and then microextraction was performed simultaneously with derivatization on the monolith. The several parameters affecting the in situ derivatization simultaneously with PMME were investigated, including the flow rate, pH, buffer concentration, and temperature. The whole pretreatment process can be accomplished within 8 min. The limits of detection for hexanal and heptanal were found to be 2.4 and 3.6 nmol/L, respectively. The recoveries in plasma sample were in the range of 83-87% with the inter- and intra-day precisions less than 6.8%. This method was successfully applied to the analysis of hexanal and heptanal in plasma samples from different cancer patients.

Graft modification of cotton with phosphate group and its application to the enrichment of phosphopeptides.

Grafting copolymerization, especially "grafting from" approach, has attracted a great attention for the preparation of cellulose-based materials with various functionalities. In this study, a novel phosphate group-containing cotton fiber-based material, CF-NH2-AZO-p(VPA-x), was successfully synthesized by a "grafting from" radical polymerization approach using vinyl phosphonic acid (VPA) as monomer. The phosphate group content of CF-NH2-AZO-p(VPA-x) could be easily regulated by adjusting the concentration of VPA monomer. Subsequently, titanium ions immobilized CF-NH2-AZO-p(VPA-x) (CF-NH2-AZO-p(VPA-x)-Ti4+) was prepared and used as an immobilized metal affinity chromatography (IMAC) adsorbent for the selective enrichment of phosphopeptides from various biological samples. The relationship between enrichment efficiency and phosphate group content of CF-NH2-AZO-p(VPA-x)-Ti4+ was investigated. The optimized CF-NH2-AZO-p(VPA-2)-Ti4+ (x=2) exhibited high selectivity and extraction capacity in phosphopeptides enrichment from standard peptides mixture, non-fat milk digests and protein-rich human serum. In addition, CF-NH2-AZO-p(VPA-2)-Ti4+ was further applied for the specific capture of phosphopeptides from tryptic digests of rat brain lysate, and 3241 unique phosphopeptides were identified from 0.5mg of rat brain by combining CF-NH2-AZO-p(VPA-2)-Ti4+ pretreatment with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. We expect the proposed method can promote the development of "grafting from" approach in the preparation of cellulose-based adsorbents and broaden the application of cellulose-based adsorbents for biological analysis.

Analysis of estrogens in environmental waters using polymer monolith in-polyether ether ketone tube solid-phase microextraction combined with high-performance liquid chromatography.

A simple, rapid and sensitive on-line method for simultaneous determination of four endocrine disruptors (17beta-estradiol, estriol, bisphenol A and 17alpha-ethinylestradiol) in environmental waters was developed by coupling in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). A poly(acrylamide-vinylpyridine-N,N'-methylene bisacrylamide) monolith, synthesized inside a polyether ether ketone (PEEK) tube, was selected as the extraction medium. To achieve optimum extraction performance, several parameters were investigated, including extraction flow-rate, extraction time, and pH value, inorganic salt and organic solvent content of the sample matrix. By simply filtered with nylon membrane filter and adjusting the pH of samples to 6.0 with phosphoric acid, the sample solution then could be directly injected into the device for extraction. Low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method were achieved in the range of 0.006-0.10 ng/mL and 0.02-0.35 ng/mL from spiked lake waters, respectively. The calibration curves of four endocrine disruptors showed good linearity ranging from quantification limits to 50 ng/mL with a linear coefficient R(2) value above 0.9913. Good method reproducibility was also found by intra- and inter-day precisions, yielding the RSDs less than 12 and 9.8%, respectively. Finally, the proposed method was successfully applied to the determination of these compounds in several environmental waters.

Determination of endogenous brassinosteroids using sequential magnetic solid phase extraction followed by in situ derivatization/desorption method coupled with liquid chromatography-tandem mass spectrometry.

In this study, a sequential magnetic solid phase extraction followed by in situ derivatization/desorption method was proposed for the fast, selective and sensitive determination of brassinosteroids (BRs) in plant tissues. Magnetic sorbent for quick, easy, cheap, effective, rugged and safe method (mQuEChERS) and polymer(4-vinylphenylboronic acid-co-ethylene glycol dimethacrylate) coated Fe3O4@SiO2 (p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2) were prepared and characterized. Using them as sorbents, pigments and hydrophilic interferents were firstly removed from plant extract by mQuEChERS, and then endogenous BRs were selectively enriched by p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 through boronate affinity interaction. After loading BRs on p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2, instead of directly eluting free BRs, the adsorbed BRs were released by adding 4-(N,N-dimethyamino)phenylboronic acid (4-DMAPBA) solution for in situ derivatizaiton/desorption of BRs based on a transesterification reaction between the boronate moieties of p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 and 4-DMAPBA, finally the resultant solution was submitted to LC-MS/MS for quantification. The whole procedure of the sequential MSPE could be accomplished within 1h, and the matrix effect to MS signal after the sample pretreatment was estimated to be in the range of 93.0-97.4%. The established method provided broad linear dynamics ranges (1.0-100.0pg/mL) with correlation coefficients (R) >0.9978, substantial sensitivity (limits of detection ranged from 0.27 to 1.29pg/mL), high reproducibility (intra-day and inter-day relative standard deviations (RSDs) less than 14.8%) and satisfactory accuracy (recoveries ranged from 74.0%-116.6%). Furthermore, endogenous BRs were successfully detected in one flower of Brassica napus L. (22.5-542.7pg/g fresh weight) and other plant tissues (13.7-289.8pg/g fresh weight).

Electrospun fibrous thin film microextraction coupled with desorption corona beam ionization-mass spectrometry for rapid analysis of antidepressants in human plasma.

Appropriate sample preparations prior to analysis can significantly enhance the sensitivity of ambient ionization techniques, especially during the enrichment or purification of analytes in the presence of complex biological matrix. Here in, we developed a rapid analysis method by the combination of thin film microextraction (TFME) and desorption corona beam ionization (DCBI) for the determination of antidepressants in human plasma. Thin films used for extraction consisted of sub-micron sized highly ordered mesoporous silica-carbon composite fibers (OMSCFs), simply prepared by electrospinning and subsequent carbonization. Typically, OMSCFs thin film was immersed into the diluted plasma for extraction of target analytes and then directly subjected to the DCBI-MS for detection. Size-exclusion effect of mesopores contributed to avoid of the protein precipitation step prior to extraction. Mass transfer was benefited from high surface-to-volume ratio which is attributed to macroporous network and ordered mesostructures. Moreover, the OMSCFs provided mixed-mode hydrophobic/ion-exchange interactions towards target analytes. Thus, the detection sensitivity was greatly improved due to effective enrichment of the target analytes and elimination of matrix interferences. After optimization of several parameters related to extraction performance, the proposed method was eventually applied for the determination of three antidepressants in human plasma. The calibration curves were plotted in the range of 5-1000 ng/mL with acceptable linearity (R(2) >0.983). The limits of detection (S/N=3) of three antidepressants were in ranges of 0.3-1 ng/mL. Reproducibility was achieved with RSD less than 17.6% and the relative recoveries were in ranges of 83.6-116.9%. Taken together, TFME-DCBI-MS method offers a powerful capacity for rapid analysis to achieve much-improved sensitivity.

Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid phase microextraction coupled to high performance liquid chromatography and analysis of amphetamines in urine samples.

In-tube solid-phase microextraction (SPME) based on a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column was investigated for the extraction of amphetamine, methamphetamine and their methylenedioxy derivatives. The monolithic capillary column showed high extraction efficiency towards target analytes, which could be attributed to its larger loading amount of extraction phase than conventional open-tubular extraction capillaries and the convective mass transfer procedure provided by its monolithic structure. The extraction mechanism was studied, and the results indicated that the extraction process of the target analytes was involved with hydrophobic interaction and ion-exchange interaction. The polymer monolith in-tube SPME-HPLC system with UV detection was successfully applied to the determination of amphetamine, methamphetamine and their methylenedioxy derivatives in urine samples, yielding the detection limits of 1.4 - 4.0 ng/mL. Excellent method reproducibility (RSD < 2.9%) was found over a linear range of 0.05-5 microg/mL, and the time for the whole analysis was only approximately 25 min. The monolithic capillary column was reusable in coping with the complicated urine samples.

Magnesia-zirconia based mimetic biomembrane chromatography for predicting human drug absorption.

In this paper, a novel mimetic biomembrane chromatography stationary phase of magnesia-zirconia composite matrix were prepared with the Lewis acid-base interaction between phosphatidylcholine's residue phosphonate group and Lewis acid sites of magnesia-zirconia composite; the retention factors of a chemically diverse set of drugs on the new stationary phase were determined; the drugs logK(mbm) values were correlationed with the absorbed fraction of drugs orally administered in humans (%F(a)) and a hyperbolic relationship was obtained. Meanwhile, the relationship between the logK(mbm) values and hydrophobic parameters (logP(oct) and logD(oct)) were discussed. The usefulness of the new column for predicting oral drug absorption in humans is demonstrated by comparing this model with IAM, ILC and BMC models. Results show that the logK(mbm) values have good relationship with logK(W)(IAM), logK(BMC) and have moderate to fair relationship with logK(s) determined on four different ILC column (EPL, PC, PC-PE, PC-PS). Therefore, the logK(mbm) values can provide key information about the transport properties of drugs and this chromatographic model may be applicable for prediction of drug uptake through epithelial cell membranes during the drug discovery process.