Zhi-Guo Shi

Wuhan University, Wu-han-shih, Hubei, China

Are you Zhi-Guo Shi?

Claim your profile

Publications (59)199.1 Total impact

  • Jian Li, Li Xu, Zhi-guo Shi, Min Hu
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, a novel two-dimensional liquid chromatographic (2D-LC) system was developed for simultaneous separation and toxicity prediction of pharmaceutical and its related substances. A conventional ODS column was used on the 1st-D to separate the sample; while, bio-partitioning micellar chromatography served as the 2nd-D to predict toxicity of the components. The established system was tested for the toxicity of ibuprofen and its impurities with known toxicity. With only one injection, ibuprofen and its impurities were separated on the 1st-D; and LC50 values of individual impurity were obtained based on the quantitative retention-activity relationships, which agreed well with the reported data. Furthermore, LC50 values of photolysis transformation products (TPs) of carprofen, ketoprofen and diclofenac acid (as unknown compounds) were screened in this 2D-LC system, which could be an indicator of the toxicity of these TPs and was meaningful for the environmental monitoring and drinking water treatment. The established 2D-LC system was cost-effective, time-saving and reliable, and was promising for fast online screening of toxicity of known and unknown analytes in the complex sample in a single step. It may find applications in environment, pharmaceutical and food, etc. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of hazardous materials 08/2015; 293. DOI:10.1016/j.jhazmat.2015.03.035 · 4.33 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study described the preparation and application of zwitterionic stationary phases (ACS) with controllable ratio of positively charged tertiary amine groups and negatively charged carboxyl groups. Various parameters, including water content, pH values and ionic strength of the mobile phase, were investigated to study the chromatographic characteristics of ACS columns. The prepared ACS columns demonstrated a mix-mode retention mechanism composed of surface adsorption, partitioning and electrostatic interactions. The elemental analysis of different batches of the ACS phases demonstrated good reproducibility of the preparation strategy. Additionally, various categories of compounds, including nucleosides, water-soluble vitamins, benzoic acid derivatives and basic compounds were successively employed to evaluate the separation selectivity of the prepared ACS stationary phases. These ACS phases exhibited entirely different selectivity and retention behavior from each other for various polar analytes, demonstrating the excellent application potential in the analysis of polar compounds in HILIC. Copyright © 2015 Elsevier B.V. All rights reserved.
    Talanta 08/2015; 141:8-14. DOI:10.1016/j.talanta.2015.03.058 · 3.51 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The zirconia-coated silica (ZrO2/SiO2) material was obtained by coupling layer-by-layer (LbL) self-assembly method and sol-gel technology, to take dual advantages of the suitable porous structure of SiO2 and basic resistance of ZrO2. Adenosine 5′-monophosphate (5′-AMP) was then self-assembled onto ZrO2/SiO2 via Lewis acid-base interaction, generating 5′-AMP-ZrO2/SiO2. The chromatographic properties of 5′-AMP-ZrO2/SiO2 were systemically studied by evaluating the effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the 5′-AMP-ZrO2/SiO2 possessed hydrophilic interaction chromatographic (HILIC) property comprising hydrophilic, hydrogen-bonding, electrostatic and ion-exchange interactions. For basic analytes, the column efficiency of ZrO2/SiO2 and 5′-AMP-ZrO2/SiO2 was superior to the bare ZrO2, and different selectivity was obtained after the introduction of 5′-AMP. For acidic analytes, good resolution was obtained on 5′-AMP-ZrO2/SiO2 while the analysis failed on the bare ZrO2 column owing to strong adsorption. Hence, the proposed 5′-AMP-ZrO2/SiO2 had great potential in analyzing acidic compounds in HILIC mode. It was an extended application of ZrO2 based SP.
    Journal of Chromatography A 01/2015; 1383. DOI:10.1016/j.chroma.2015.01.017 · 4.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A hydrophilic stationary phase (SP) was prepared through grafting N-methylene phosphonic acid chitosan on magnesia-zirconia particles (P-CTS-MgO-ZrO2) via Lewis acid-base interaction. The resulting material was characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope and nitrogen adsorption analysis. The chromatographic performance of P-CTS-MgO-ZrO2 was systemically evaluated by studying effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the novel SP provided hydrophilic, electrostatic-repulsion and ion-exchange interactions. Compared to the bare MgO-ZrO2, P-CTS-MgO-ZrO2 exhibited superior peak shape, reasonable resolution and reduced analysis time in separation of basic analytes. Besides, remarkable resolving power of acids, i.e. six non-steroidal anti-inflammatory drugs which failed to be eluted from the bare MgO-ZrO2, was obtained with the theoretical plate number (N/m) of 4653-31313, asymmetry factor <1.21 and the resolution of 1.6-3.4. Finally, P-CTS-MgO-ZrO2 SP was applied to separate monosaccharides, phospholipids and peptides. P-CTS-MgO-ZrO2 was a promising hydrophilic SP for wide applications. Copyright © 2014 Elsevier B.V. All rights reserved.
    Analytica Chimica Acta 01/2015; 854C:191-201. DOI:10.1016/j.aca.2014.11.022 · 4.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A simple dispersive liquid–liquid microextraction (DLLME) method, based on retrieval of the extraction solvent by magnetic particles and followed by HPLC–UV analysis, was proposed for the determination of UV filters in environmental water samples. The new method uses vortex agitation in the DLLME process to achieve rapid equilibrium. Another feature of the proposed method is that the retrieval of the extraction solvent is accomplished by functionalized magnetic particles rather than by special designed vessels or refrigeration and thawing process associated with DLLME when low-density extraction solvent was used. The parameters that may influence the extraction, including vortex time, volume of extraction solvent, weight of the magnetic particles, volume of desorption solvent, pH, and ionic concentration of the sample solution, were investigated in detail. Under the optimized conditions, the limits of detection for the target UV filters were in range of 0.7–12.3 ng mL−1. The results also demonstrated good linearity and precision, with the regression coefficients above 0.9989 and the RSDs below 4.4%, respectively.
    Journal of Liquid Chromatography &amp Related Technologies 01/2015; 38(1). DOI:10.1080/10826076.2014.883538 · 0.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present study, magnetic nanoparticles (MNPs) with phenyl functionalized core and a hydrophilic methylcellulose coating were synthesized. The functionalized MNPs showed excellent dispersibility in aqueous solution and they were applied to magnetic solid phase extraction (MSPE) of sildenafil and its metabolite, desmethyl sildenafil, from human urine and plasma samples followed by high performance liquid chromatographic analysis. The factors that may influence the extraction, including the amount of MNPs, pH and salt concentration of sample solution, extraction and desorption time, and the volume of desorption solvent, were investigated in detail. Under the optimum MSPE conditions, the developed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 8.2% and low limits of detection of 0.41-0.96ngmL(-1) from urine and plasma samples. The proposed material possessed good water compatibility and demonstrated excellent applicability for biological samples.
    Talanta 12/2014; 130C:427-432. DOI:10.1016/j.talanta.2014.07.006 · 3.51 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the current study, zirconia (ZrO2) and its composite, magnesia-zirconia (MgO-ZrO2), were prepared as the hydrophilic interaction chromatographic (HILIC) stationary phases (SPs). Different experimental variables including water content, pH and buffer concentration in the mobile phase (MP) as well as column temperature were systematically studied to permit an in-depth understanding of the chromatographic properties of the mentioned SPs and to explore the retention mechanism further on. The results were compared with a native SiO2 column. Adsorption was demonstrated as the main retention mechanism on the two ZrO2-based SPs. The transferring of the analytes from the MP to the ZrO2-based SPs was endothermic and high column temperature would facilitate the retention. In addition, the MgO-ZrO2 SP exhibited superior resolution, column efficiency as well as stronger retention in comparison to the bare ZrO2 SP, which demonstrated that the introduction of MgO could improve the structure and properties of the material. In conclusion, MgO-ZrO2 was a promising material for HILIC applications.
    Talanta 11/2014; 129C:438-447. DOI:10.1016/j.talanta.2014.06.016 · 3.51 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hybrid thiol-silica spheres constructed by interlacing arrays of submicrometer-sized blocks and large macropores were fabricated by a one-pot approach and were successfully used for the fast capture of heavy metal ions with a total capture time of less than 2 min.
    Materials Letters 08/2014; 128:140–143. DOI:10.1016/j.matlet.2014.04.103 · 2.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, a tandem reversible addition fragmentation chain transfer (RAFT)/click chemistry method was developed to prepare amide-polystyrene-silica (NHCO-Psty-silica) stationary phase. Styrene was immobilized on amino-silica surface via an azide functionalized RAFT agent in a one-pot procedure. The resultant NHCO-Psty-silica column demonstrates better performance for shielding of residue silanols than traditional ODS column, which was ascertained by Engelhardt test (E test), Tanaka test (T test), Galushko test (G test), and Walters test (W test). Our results showed lower values of silanol activity calculated according to the formula in these standard tests for NHCO-Psty-silica column compared to the ODS column we tested. As a result, the NHCO-Psty-silica is suitable for the separation of basic compounds. The hydrophobic, anion exchanging and π-π interaction of the column toward analytes were also evaluated. Moreover, the NHCO-Psty-silica column also showed excellent stability with pure water as mobile phase.
    Journal of Chromatography A 05/2014; DOI:10.1016/j.chroma.2014.05.054 · 4.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Exposed heavy metal ions have led to serious pollution and significant health problems to human beings. To eliminate these ions from the environment, in this study, a remediation method based on recycling magnetic nanoparticles is proposed. Long alkyl chain derivatized magnetic nanoparticles were fabricated, and then dodecyl mercaptan was assembled onto the functional nanoparticles via hydrophobic interaction. Since mercapto moieties can form molecular complex with many heavy metal ions via chelation, the proposed material was used to retrieve these ions from water samples. It is noteworthy that, as dodecyl mercaptan was attached onto the magnetic particles via hydrophobic interaction, it can be easily removed by washing with methanol. As a result, the nanoparticles can be recovered for recycling usage, which would be economical for environmental remediation. The material was characterized by scanning electron microscopy, nitrogen sorption, infrared/Raman spectrometry and elemental analysis. Ag+and Pb2+were used as model analytes to evaluate the effectiveness of the material. It is found that, the maximum adsorption capacities of the particles for Ag+and Pb2+reach 43.6 and 38.2mg/g, respectively.
    Materials and Manufacturing Processes 12/2013; 29(1). DOI:10.1080/10426914.2013.852209 · 1.49 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Penetrable silica possesses hierarchical pores, mesopores and penetrable macropores, offering fast mass transfer, satisfactory mechanical strength as well as low column pressure. In the present study, penetrable octadecyl-bonded silica (ODS) was for the first time used as biopartitioning micellar chromatography (BMC) stationary phase to profile ecotoxicity and skin permeability of benzophenone UV-filters. Mobile phase (MP) pH and concentration of polyoxyethylene(23)lauryl ether in the MP were systematically studied. Quantitative retention-activity relationships (QRARs) model was established to correlate retention factors (k) on BMC with bioconcentration factor (BCF) and transdermal rate (TR) of UV-filters. Coefficient of determination (r(2)) of the QRARs model between log BCF and logk were 0.9398-0.9753, while r(2) between TR and logk were 0.7569-0.8434, which demonstrated satisfactory predictive ability of the methodology. It was a powerful tool for fast screening by combining penetrable ODS with BMC, and avoiding column blockage often occurring in BMC.
    Analytica chimica acta 12/2013; 804C:321-327. DOI:10.1016/j.aca.2013.10.040 · 4.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cytokinins (CKs), a vital family of phytohormones, play important roles in the regulation of shoot and root development. However, the quantification of CKs in plant samples is frequently affected by the complex plant matrix. In the current study, we developed a simple, rapid and efficient hydrophilic interaction chromatography-solid phase extraction (HILIC-SPE) method for CKs purification. CKs were extracted by acetonitrile (ACN) followed by HILIC-SPE (silica as sorbents) purification. The extraction solution of plant samples could be directly applied to HILIC-SPE without solvent evaporation step, which simplified the analysis process. Moreover, with HILIC chromatographic retention mechanism, the hydrophobic co-extracted impurities were efficiently removed. Subsequently, CKs were separated by RPLC, orthogonal to the HILIC pretreatment process, and detected by tandem mass spectrometry. The method exhibits high specificity and recovery yield (>77.0%). Good linearities were obtained for all eight CKs ranging from 0.002 to 100ngmL(-1) with correlation coefficients (r) higher than 0.9927. The limits of detection (LODs, signal/noise=5) for the CKs were between 1.0 and 12.4pgmL(-1). Reproducibility of the method was evaluated by intra-day and inter-day measurements and the results showed that relative standard deviations (RSDs) were less than 10.5%. Employing this method, we successfully quantified six CKs in 20mg Oryza sativa leaves and the method was also successfully applied to Brassica napus (flower and leaves).
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 10/2013; 942-943C:31-36. DOI:10.1016/j.jchromb.2013.10.024 · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: SiO2-TiO2 composite fibers, prepared by electrospinning, were successfully applied to the rapid enrichment of phosphopeptides using a lab-in-syringe approach for the first time. Because of their large surface area, mesoporous structure, extraordinary length and appropriate Lewis acidity, the as-prepared SiO2-TiO2 composite fibers exhibited high selectivity and capacity in the enrichment of phosphopeptides from the digestion mixture of β-casein and bovine serum albumin (BSA), as well as human blood serum and nonfat milk. The targeted phosphopeptides could be easily enriched and detected even when the total amount of β-casein was decreased to only 10 fmol, indicating the high detection sensitivity of this method. In addition, the whole enrichment extraction procedure can be finished in less than 3 min, which can avoid or decrease the degradation of endogenous phosphoproteins by proteases released ex vivo during time-consuming treatments. The developed method is rapid, cost-effective, selective, sensitive, operationally simple, and does not require any harsh conditions and intricate equipment, providing an ideal candidate for the enrichment of phosphopeptides from complex biological samples either in the lab or in the field.
    The Analyst 07/2013; 138(18). DOI:10.1039/c3an01091k · 3.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In pharmaceutical science, construction of drug delivery system based on various carriers is a great challenge. Here we proposed a new silica carrier for drug delivery. The carrier is characterized by penetrable macropores and large pore volume, which renders it an ideal carrier for drug loading especially for macromolecular drugs. Bovine serum albumin (BSA) and oxaprozin were used as models to investigate its delivery behavior. From the results, it demonstrates that the drug loading capacity is very high (for BSA, it reaches 212.2 wt% [drug/carrier]). It is also found that an ultra-fast release for oxaprozin was achieved on this carrier, indicating the material is suitable for constructing enhanced delivery platform for specific drugs to improve the bioavailability.
    Materials and Manufacturing Processes 05/2013; 28(6). DOI:10.1080/10426914.2013.773014 · 1.49 Impact Factor
  • Yi Luan, Ying-Wen Xue, Zhi-Guo Shi
    [Show abstract] [Hide abstract]
    ABSTRACT: A porous carbon sphere (PCS), which exhibits hierarchical macro/meso/microporosity, is fabricated by nanocasting. The macropores within the PCS are penetrable, fully open and well interconnected, which is admirable for fast mass transfer applications. The carbon has been attempted as a novel electrode material for a fast rechargeable electrochemical double layer capacitor (EDLC). Though the total surface area is only 826 (±2) m2 g−1 and a large quantity of micropores exist, the capacitance of the EDLC can reach 172 (± 3) F g−1 regardless of the cyclic voltammetry scan rate. The macropores within the PCS acted as ion-buffering reservoirs in-situ, which facilitates the accessibility of the mesopores as well as the micropores within the PCS. As a result, unlike traditional microporous carbon material, the micropores in the PCS show no obvious negative effect to the performance of the EDLC. The PCS material is a promising candidate in fast mass transfer applications.
    Materials Letters 12/2012; 88:30–32. DOI:10.1016/j.matlet.2012.08.046 · 2.27 Impact Factor
  • Lei Ye, Qing Wang, Jinping Xu, Zhi-Guo Shi, Li Xu
    [Show abstract] [Hide abstract]
    ABSTRACT: Restricted-access materials based on non-ionic surfactant-coated dodecyl-functionalized magnetic nanoparticles were prepared and applied to extract steroid hormones from environmental and biological samples. The magnetic nanoparticles were synthesized by co-precipitation, and were functionalized with dodecyltriethoxysilane, giving dodecyl-grafted magnetic nanoparticles (C₁₂-Fe₃O₄). They were further modified with different non-ionic surfactants by self-assembly adsorption. Several types of non-ionic surfactants, Tween-20, 40, 60 and 85, and Span-40, 60 and 80, were investigated as the coatings. Tween surfactants coated C₁₂-Fe₃O₄, named as TW-20 (40, 60, 85)-C₁₂, exhibited good dispersibility in aqueous solution, which was a preferred character in extraction; besides, TW-20-C₁₂ and TW-40-C₁₂ showed good anti-interference ability and satisfactory reproducibility when they were used as magnetic solid-phase extraction (MSPE) sorbents. The factors that may influence the extraction, including the amount of magnetic nanoparticles, extraction and desorption time, the amount of salt addition, the type and volume of desorption solvent, the volume of methanol addition and pH of sample solution, were investigated in detail. High performance liquid chromatography-UV detection was employed for analysis of target analytes (steroid hormone compounds). The developed method was successfully used for the determination of the target analytes in environmental and urine samples. Both tested materials afforded good recovery, satisfactory reproducibility and low limits of detection for environmental samples, which indicates that the materials possessed anti-interference ability. However, compared to TW-40-C₁₂, TW-20-C₁₂ nanoparticles provided better recovery in relatively complex biological samples, which may indicate that the latter one is more appreciated in complex samples.
    Journal of Chromatography A 05/2012; 1244:46-54. DOI:10.1016/j.chroma.2012.04.075 · 4.26 Impact Factor
  • Cong Zhang, Jian Li, Li Xu, Zhi-Guo Shi
    [Show abstract] [Hide abstract]
    ABSTRACT: In the present study, an immobilized liposome chromatography (ILC) stationary phase based on penetrable silica microspheres was prepared. The silica possessed mesopores and penetrable macropores, which afforded sufficient surface area and fast mass transfer, respectively. Compared with the ILC column based on common porous silica gels, the penetrable silica had larger capacity for liposomes' immobilization, lower backpressure and higher separation efficiency. Twenty-two kinds of drugs were used as tested analytes and their retention behaviors on newly prepared ILC column were investigated in detail. Column temperature and pH of mobile phase were both key factors affecting the retention of solutes. The retention of these drugs on ILC column reflected their permeability in vivo. Furthermore, the methanolic aqueous extracts of three traditional Chinese medicines (TCMs), Radix Liquiritiae, Scutellaria Baicalensis and Flos Sophorae, were screened on this novel ILC column. Effects of column temperature and eluent pH on chromatographic behaviors of components of the TCM methanolic extracts were also studied. Several permeable components can be found, indicating that they are potentially active components in the TCMs. It is also found that the as-prepared ILC column remained stable in at least 1 month and the relative standard deviations of adjusted retention times for solutes were lower than 9.0%. The proposed ILC based on the penetrable silica microspheres is promising for the fast and low-pressure separation, especially for fast screening of permeable compounds and modeling the drug-membrane interaction in vitro. It would be a useful approach to predict the permeability of potential active drugs.
    Journal of Chromatography A 02/2012; 1233:78-84. DOI:10.1016/j.chroma.2012.02.013 · 4.26 Impact Factor
  • Ping-Ping Zhang, Zhi-Guo Shi, Yu-Qi Feng
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, a two-step liquid-phase microextraction (LPME) method was presented for the extraction of phenols in environmental water samples. Firstly, the polar phenol in water samples (donor phase) was transferred to 1-octanol (extraction mesophase) by magnetic stirring-assisted LPME. Subsequently, target analytes in the 1-octanol was back extracted into 0.1 mol/L sodium hydroxide solution (acceptor phase) by vortex-assisted LPME. By combination of the two-step LPME, the enrichment factors were multiplied. The main features of this two-step LPME for phenols lie in the following aspects. Firstly, the extraction can be accomplished within relatively short time (ca. 20 min). Secondly, it was compatible with HPLC analysis, avoiding derivatization step that is generally necessary for GC analysis. Thirdly, high enrichment factors (296-954 fold) could be obtained for these analytes. Under the optimized conditions, the linearities were 10-1000, 1-500, 1-500, 5-500 and 1-500 ng/mL for different phenols with all regression coefficients higher than 0.9985. The limits of detection were in the range from 0.3 to 3.0 ng/mL for these analytes. Intra-and inter-day relative standard deviations were below 7.6%, indicating a good precision of the proposed method.
    Talanta 10/2011; 85(5):2581-6. DOI:10.1016/j.talanta.2011.08.021 · 3.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, a novel method for the fabrication of magnetic carbon nanotubes based on 'aggregation wrap' was proposed. When carbon nanotubes and magnetic nanoparticles were vortically mixed in a solvent, the magnetic nanoparticles were wrapped into the carbon nanotube bundles that formed during the aggregation process, leading to the formation of magnetic carbon nanotubes. Thus, the resultant material can be separated from the solvent rapidly and conveniently by a magnet. Our investigation demonstrated that the 'aggregation wrap' mechanism for the preparation of magnetic composite is also applicable to other self-aggregated micro/nanomaterials, including graphene, graphite, C(60), etc. To testify the feasibility of the magnetic composites in sample preparation, the resultant magnetic carbon nanotubes were applied as sorbents for magnetic solid-phase extraction (MSPE) of estrogens in milk samples. Under optimized conditions, a rapid, convenient and efficient method for the determination of estrogens in milk samples was established by the combination of MSPE with high-performance liquid chromatography with fluorescence detector. The linearity range of the proposed method was 5-2000 μg/L with correlation coefficients (R) of 0.9983-0.9994. The limit of detection (LOD) for three estrogens ranged from 1.21 to 2.35 μg/L. The intra- and inter-day relative standard deviations (RSDs) were <9.3%. The reproducibility of the MSPE with different batches of magnetic carbon nanotubes was acceptable with RSD values <3.6%.
    Journal of Separation Science 09/2011; 34(18):2498-504. DOI:10.1002/jssc.201100323 · 2.59 Impact Factor
  • Source
    Xi-Tian Peng, Zhi-Guo Shi, Yu-Qi Feng
    [Show abstract] [Hide abstract]
    ABSTRACT: A rapid and high-throughput method for monitoring melamine (MEL) in milk products and eggs was presented. This method was based on a full automatic platform that was composed of on-line polymer monolith microextraction and high-performance liquid chromatography with ultraviolet detection. A poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-ethylene dimethacrylate) monolith was selected as the sorbent for purification and enrichment of MEL in milk products and eggs. A novel mixed-mode chromatographic column packed with octyl and sulfonic acid co-bonded silica was employed for quantitative determination of MEL in real samples. Several factors affecting extraction performance were investigated. Under the optimal conditions, the recoveries of MEL in milk products and eggs spiked at three levels of 0.5, 5.0, and 20.0mg/Kg, ranged from 87.0% to 95.5%, with RSDs less than 6.4%. The limits of detection were 0.024 and 0.018mg/Kg for MEL in the milk products and eggs, respectively. KeywordsMelamine–Polymer monolith microextraction–Mixed-mode separation–Milk products–Eggs
    Food Analytical Methods 09/2011; 4(3):381-388. DOI:10.1007/s12161-010-9181-1 · 1.80 Impact Factor