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A poly(methacrylic acid-co-ethylene dimethacrylate) polymer(poly(MAA-co-EDMA)) was prepared via in-situ polymerization on the outside surface of vial glass insert and used as stir rod sorptive extraction (SRSE) coating. The extraction performance of the polymer coating toward four sulfonamides (SAs) was investigated. The effects of several parameters to SRSE, such as the pH value, inorganic salt and organic phase concentrations of the sample matrix, were investigated. It demonstrated that the sulfonamides were captured on the poly(MAA-co-EDMA) coating mainly through cation-exchange and hydrophobic interactions. A novel approach is presented for the determination of four sulfonamide antibacterial residues in milk samples by coupling SRSE to liquid chromatography and electrospray ionization mass spectrometry (SRSE/LC-ESI-MS). In this method, the detection limits (S/N = 3) of 0.11-0.52 microg/L and quantification limits (S/N = 10) of 0.35-1.72 microg/L were obtained. The method showed good linearity in the range of 1-500 microg/L. Good method reproducibility was also found by intra- and inter-day precisions, yielding the relative standard deviations (RSDs) less than 11.3%. The results demonstrated that the proposed method is simple, sensitive, low cost and suitable for the determination of sulfonamides in milk samples.

A poly (2-acrylamido-2-methyl-1-propanesulfonic acid-co-ethylene dimethacrylate) (AMPS-co-EDMA) monolith was prepared in a fused-silica capillary (530 microm i.d.) and applied for polymer monolith microextraction (PMME). With the optimal ratio of N, N-dimethyl-formamide (DMF, porogen) and polyethylene glycol (PEG, co-porogen), the resulting monolith exhibited satisfactory permeability, high mechanical strength and good stability in aqueous buffer. The effects of several parameters to PMME were investigated, such as pH value, inorganic salt and organic phase concentration of the sample matrix. It demonstrated that the melamine was captured on the poly (AMPS-co-EDMA) monolith mainly through strong cation-exchange and hydrophobic interactions. A novel approach is presented for the determination of melamine in milk products by coupling PMME to high performance liquid chromatography with ultraviolet detection. Because of the high extraction capacity of the monolith towards melamine, low detection limits (S/N = 3, 0.9 mg/kg) and quantification limits (S/N = 10, 0.3 mg/kg) were obtained. The method showed good linearity ranging from 0.5 to 80 mg/kg. Excellent reproducibility of the method was exhibited by intraday and interday precisions, yielding the relative standard deviations not larger than 7.5%. The proposed method is simple, rapid, sensitive, and low cost.

A novel mimetic biomembrane chromatographic stationary phase of magnesia-zirconia composite matrix was prepared based on the Lewis acid-base interaction between the phosphonate group of phosphatidylcholine residue and the Lewis acid sites of magnesia-zirconia composite. The infrared absorption spectrum and X-ray photoelectron spectrum of the stationary phase illustrated that the magnesia-zirconia composite was successfully modified with phosphatidylcholine. The interactions between the membrane and the drugs were evaluated. It is observed that the log Kmbm values have good relationships with the log Papp, and the linear slope is 1.049, which is near unity. Moreover, on the basis of the thermodynamics derivation, the difference in standard free energies (delta (delta G0)) is introduced to describe the drug-membrane interaction. The results show that the log Kmbm, and delta (delta G0) value provide key information on the transport properties of the drugs. The establishment of this chromatographic model may be a new way for the evaluation of the drug-membrane interactions.

Humic acid-bonded silica was prepared and used as solid-phase extraction material for the pretreatment of Sudan Red dyes in hot chili products, which was followed by high performance liquid chromatographic determination. This sorbent exhibits an excellent adsorption capacity for Sudan Red dyes. A sample was first extracted with n-hexane. Then the extract was cleaned up by humic acid-bonded silica cartridge and eluted with ethanol/dichloromethane (3:7, v/v). Some interferences in hot chili products such as natural pigments and oil were removed by washing step. Good linearities were achieved in the range from 0.05 to 5 mg/L for four Sudan dyes, with linear coefficient r2 values above 0.999. The limits of detection (LOD) in chili powder and chili oil were from 19.8 to 28.8 ng/g and 7.9 to 11.5 ng/g, respectively. Excellent method reproducibility was found by intra- and inter-day precisions (the relative standard deviations less than 9.1% and 8.8%, respectively). Recoveries for them in the real samples were between 82.6% and 94.0%. The proposed method is proved to be simple, rapid, and sensitive in the regular analysis of Sudan Red I, II, III and IV in foods.

This review focuses on the use of monoliths in sample preconcentration, with emphasis on the development and applications of monolith preconcentration coupled to high performance liquid chromatography, capillary electrophoresis, capillary electrochromatography, and on microfluidic chips as well. Novel modes of monolith preconcentration developed in recent years are also presented. Sixty-five references have been cited.

A process impurity (approximately 4%, w/w) was isolated from losartan crude by low-pressure reversed-phase column chromatography. At first the elution portions containing the target compound were collected. After evaporation and recrystallization, the purity of the target compound was found to be over 99% based on high performance liquid chromatography with ultraviolet absorption. The electrospray ionization-mass spectrometry result showed that it was an isomeric compound of losartan, which had same fragmentation pattern with its parent compound. And at last the compound was further characterized by nuclear magnetic resonance. This research demonstrates that the low-pressure reversed-phase column chromatography can raise separation efficiency and recovery comparing with other conventional column chromatography, and the technique can be applied as an effective means for the enrichment and extraction of impurities in pharmaceutical separation.

A new type of organic-inorganic hybrid porous silica-based monolithic columns was developed for reversed-phase capillary electrochromatography (RP-CEC). The monolithic columns were prepared from in situ co-condensation of tetraethoxysilane (TEOS) and phenyltriethoxysilane (PTES) precursors via a two-step catalytic sol-gel procedure in the capillary to create phenyl groups distributed throughout the silica matrix for chromatographic interaction. The functionalized monolithic stationary phase was created without additional surface derivatization. The reaction conditions for the preparation of the monolithic columns were optimized. The structure and pore size distribution of the monolithic columns were characterized by scanning electron microscopy and mercury porosimetry, respectively. The effect of water concentration on the column structure was studied, and the influence of the ratio of two precursors on the pore size distribution was also investigated. The retention behavior of polycyclic aromatic hydrocarbons on the monolithic column is discussed. Seven phenols were also separated with an average efficiency over 100 000 plates/m.

A stationary phase for the separation of C60 and C70 was prepared by modifying zirconia-magnesia composites with 2,4,6-trinitrophenol. The modified composite was characterized by using elemental analysis, diffused reflectance Fourier transform infrared spectroscopy and specific surface area. The effects of the toluene content in toluene-cyclohexane mobile phase and the column temperature on the separation of C60 and C70 were examined. Meanwhile, the separation of fullerenes including 3% high fullerenes was investigated at the temperature of 348 K using pure toluene as the mobile phase. The results showed that the stationary phase of 2,4,6-trinitrophenol-modified zirconia-magnesia composite exhibits advantage in the separation of C60 and C70, and strong temperature dependence. The retention times of C60 and C70 and their separation factor on the stationary phase increase with the increase of the column temperature. The stationary phase is a potential packing material for separation of fullerenes in preparative scale.

The developments of the Lewis base-modified zirconia and mixed-oxide containing zirconia as stationary phases for high performance liquid chromatography (HPLC) are reviewed. Zirconia supports for HPLC based on modification with fluoride, phosphate, phosphonate, carboxylic acid, phenols, and protein, as well as cyclodextrin derivative, are covered. The application of modified-zirconia in capillary electrochromatography (CEC) is also discussed. Fifty-one references are cited.

A new zirconia-based stationary phase (DPZ) was prepared by modifying zirconia with dodecylamine-N,N-dimethylenephosphonic acid (DDPA). DDPA adsorbs on zirconia with only one phosphonic group, and another is free. Besides the hydrophobic interaction provided by non-polar dodecyl, DPZ also has dipolar interaction, ion-exchange and electrostatic repellent interaction provided by the free phosphonic group and amino group at different conditions. Separations of bases on this stationary phase were achieved with satisfaction due to the various retention mechanisms. The influences of methanol content, pH value, ion type and ion strength of mobile phase were studied in detail.

The use of a novel macrocyclic molecule, cucurbit[7] uril (CB[7]), as an additive in capillary electrophoresis (CE) for the separation of several neutral nitrobenzenes is reported. Disodium hydrogen phosphate-hydrochloric acid was used as the buffer solvent with the UV detection at 254 nm. During the running process, CB [7] bore positive charge under the studied pH range (pH 2 - 6.5) and was adsorbed onto the inner wall of fused silica capillary, leading to a reversal of the electroosmotic flow (EOF). The effects of buffer pH and CB [7] concentration on the EOF behavior were investigated. The influences of the CB [7] concentration on electrophoretic behaviors of nitrobenzenes were also studied, and it was found that the selectivity increased with CB[7] concentration. The results showed that CB [7] provided good selectivity for nitrobenzenes and successful separation was obtained under optimum condition (10 mmol/L Na2HPO4 (pH 2.47, adjusted by HCl)-methanol (90 : 10, v/v), containing 5 mmol/L CB[7]). Possible explanation is also proposed.