Benzoin methyl ether

A fluorous porous polymer monolith photo-patterned chromatographic column for the separation of a flourous/fluorescently labeled peptide within a microchip.[Pubmed:24170603]

Electrophoresis. 2014 Feb;35(2-3):441-9.

A fluorous porous polymer stationary phase is photo-patterned within a glass microfluidic chip to conduct CEC. During free radical-initiated polymerization, extraneous polymer forms and contributes to excessive microfluidic channel clogging. Nitrobenzene is explored as free radical quencher to limit clogging by minimizing extraneous polymer formation and a number of initiator to quencher ratios are explored with a 0.5:1 quencher (nitrobenzene): initiator (Benzoin methyl ether) molar ratio shown to be optimal. The microchip patterned with a fluorous monolith was used to carry out the electrochromatographic analysis of a mixture containing fluorescent and fluorous labeling products. The fluorous monolithic column shows fluorous selectivity for compounds labeled with perfluoromethylene tags and a custom peptide is synthesized that possesses functional groups that can be both fluorescently and fluorously labeled. MALDI MS was used to identify the labeled fragments and microchip based electrochromatography was used to analyze the resulting labeling mixture. This is the first report to our knowledge that uses fluorous porous polymer monolith within a microchip to separate analytes using fluorous-fluorous interactions.

New "one-step" method for the simultaneous synthesis and anchoring of organic monolith inside COC microchip channels.[Pubmed:22430301]

Lab Chip. 2012 May 7;12(9):1680-5.

A new method for monolith synthesis and anchoring inside cyclic olefin copolymer (COC) microchannels in a single step is proposed. It is shown that type I photoinitiators, typically used in a polymerization mixture to generate free radicals during monolith synthesis, can simultaneously act as type II photoinitiators and react with the plastic surface through hydrogen abstraction. This mechanism is used to "photograft" poly(ethylene glycol) methacrylate (PEGMA) on COC surfaces. Contact angle measurements were used to observe the changes in surface hydrophilicity when increasing initiator concentration and irradiation duration. The ability of type I photoinitiators to synthesize and anchor a monolith inside COC microchannels in a single step was proved through SEM observations. Different concentrations of photoinitiators were tried. Finally, electrochromatographic separations of polycyclic aromatic hydrocarbons were realized to illustrate the beneficial effect of anchoring on chromatographic performances. The versatility of the method was demonstrated with two widely used photoinitiators: Benzoin methyl ether (BME) and azobisisobutyronitrile (AIBN).

Chiral micellar electrokinetic chromatography-atmospheric pressure photoionization of benzoin derivatives using mixed molecular micelles.[Pubmed:21500208]

Electrophoresis. 2011 May;32(10):1164-75.

In the present work we report, for the first time, the successful on-line coupling of chiral MEKC (CMEKC) to atmospheric pressure photoionization MS (APPI-MS). Four structurally similar neutral test solutes (e.g. benzoin (BNZ) derivatives) were successfully ionized by APPI-MS. The mass spectra in the positive ion mode showed that the protonated molecular ions of BNZs are not the most abundant fragment ions. Simultaneous enantioseparation by CMEKC and on-line APPI-MS detection of four photoinitiators, hydrobenzoin, BNZ, Benzoin methyl ether, benzoin ethyl ether, were achieved using an optimized molar ratio of mixed molecular micelle of two polymeric chiral surfactants (polysodium N-undecenoxy carbonyl-L-leucinate and polysodium N-undecenoyl-L,L-leucylvalinate). The CMEKC conditions, such as voltage, chiral polymeric surfactant concentration, buffer pH, and BGE concentration, were optimized using a multivariate central composite design (CCD). The sheath liquid composition (involving %v/v methanol, dopant concentration, electrolyte additive concentration, and flow rate) and spray chamber parameters (drying gas flow rate, drying gas temperature, and vaporizer temperature) were also optimized with CCD. Models built based on the CCD results and response surface method were used to analyze the interactions between factors and their effects on the responses. The final overall optimum conditions for CMEKC-APPI-MS were also predicted and found in agreement with the experimentally optimized parameters.

Achiral and chiral separations using MEKC, polyelectrolyte multilayer coatings, and mixed mode separation techniques with molecular micelles.[Pubmed:20155738]

Electrophoresis. 2010 Mar;31(6):1036-43.

Mixed mode (MM) separation using a combination of MEKC and polyelectrolyte multilayer (PEM) coatings is herein reported for the separation of achiral and chiral analytes. Many analytes are difficult to separate by MEKC and PEM coatings alone. Therefore, the implementation of a MM separation provides several advantages for overcoming the limitations of these well-established methods. In this study, it was observed that achiral separations using MEKC and PEM coatings individually resulted in partial resolution of eight very similar aryl ketones when the molecular micelle (sodium poly(N-undecanoyl-L-glycinate)) concentration was varied from 0.25 to 1.00% w/v and the bilayer number varied from 2 to 4. However, when MM separation was introduced, baseline resolution was achieved for all eight analytes. In the case of chiral separations, temazepam, aminoglutethimide, benzoin, Benzoin methyl ether, and coumachlor were separated using the three separation techniques. For chiral separations, the chiral molecular micelle, sodium poly(N-undecanoyl-L-leucylvalinate), was employed at concentrations of 0.25-1.50% w/v for both MEKC and PEM coatings. Overall, the results revealed partial separation with MEKC and PEM coatings individually. However, MM separation enabled baseline separation of each chiral mixture. The separation of achiral and chiral compounds from different compound classes demonstrates the versatility of this MM approach.

Preparation of a crosslinked bioimprinted lipase for enrichment of polyunsaturated fatty acids from fish processing waste.[Pubmed:20101527]

Appl Biochem Biotechnol. 2010 Oct;162(3):757-65.

Geotrichum sp. lipase modified with a combined method composed of crosslinking and bioimprinting was employed to selectively hydrolyze waste fish oil for enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in glycerides. Crosslinked polymerization by monomer (polyethylene glycol 400 dimethyl acrylate), crosslinker (trimethylolpropane trimethylacrylate), and photoinitiator (Benzoin methyl ether) coupled to bioimprinting using palmitic acid as imprint molecule, resulted in much more effective enzyme preparation used in aqueous hydrolysis reaction. Since the crosslinked polymerization modification maintained bioimprinted property and gave good dispersion of enzyme in reaction mixture, the crosslinked bioimprinted enzyme exhibited higher hydrolysis temperature, enhanced specific activity, shorter hydrolysis time, and better operational stability compared to free lipase. Crude fish oil was treated at 45 degrees C with this crosslinked bioimprinted lipase for 8 h, and 46% hydrolysis degree resulted in the production of glycerides containing 41% of EPA and DHA (EPA+DHA), achieving 85.7% recovery of initial EPA and DHA. The results suggested that bioimprinted enzymes did not lose their induced property in aqueous environment when prepared according to the described crosslinking-bioimprinting method. It could also be seen that the crosslinked bioimprinted lipase was effective in producing glycerides that contained a higher concentration of polyunsaturated fatty acid with better yield.

Direct photolithographic patterning of electrospun films for defined nanofibrillar microarchitectures.[Pubmed:20092342]

Langmuir. 2010 Feb 16;26(4):2235-9.

In this letter, a method of generating spatially defined electrospun microarchitectures by direct photolithographic patterning of electrospun films is described. A photoinitiator, Benzoin methyl ether, is incorporated into a solid thermoplastic electrospun polyurethane matrix selectively photo-cross-linked by standard photolithographic methods. Subsequent development in an organic solvent yields spatially defined electrospun microstructures on a single substrate. Utilizing a multilayer approach, the method allows for the assembly of complex hierarchical electrospun structures on single substrates using methods analogous to the conventional microfabrication of solid-state devices.

Effect of temperature during photopolymerization of capillary monolithic columns.[Pubmed:19575381]

J Sep Sci. 2009 Aug;32(15-16):2574-81.

Polymeric monolithic capillary columns were synthesized using butyl methacrylate (BMA), ethylene glycol dimethacrylate (EDMA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as monomers and 1,4-butanediol, 1-propanol, and water as a porogen mixture. The synthesis was performed over a wide temperature range from -15 degrees C to +70 degrees C using UV radiation to trigger the polymerization process initiated by Benzoin methyl ether (BME). The columns exhibited different hydrodynamic properties (permeability) as well as efficiency. The most efficient and the most permeable columns were those polymerized at low temperatures (-15 degrees C to +10 degrees C). The columns photopolymerized at higher temperatures (T > or = 30 degrees C) were completely useless because of low permeability or efficiency. The presented results indicate that temperature can be another factor which allows control of porosity during the preparation of monoliths by photopolymerization.

Asymmetric hydrogenation of aromatic ketones catalyzed by the TolBINAP/DMAPEN-ruthenium(II) complex: a significant effect of N-substituents of chiral 1,2-diamine ligands on enantioselectivity.[Pubmed:18925787]

J Org Chem. 2008 Nov 21;73(22):9084-93.

Asymmetric hydrogenation of acetophenone in the presence of Ru(II) catalysts coordinated by TolBINAP and a series of chiral 1,2-diamines was studied. The sense and degree of enantioselectivity were highly dependent on the N-substituents of the diamine ligands. The N-substituent effect was discussed in detail. Among these catalysts, the (S)-TolBINAP/(R)-DMAPEN-Ru(II) complex showed the highest enantioselectivity. The mode of enantioface selection was interpreted by using transition state models based on the X-ray structure of the catalyst precursor. The chiral catalyst effected the hydrogenation of alkyl aryl ketones and arylglyoxal dialkyl acetals to afford the chiral alcohol in >99% ee in the best cases. Hydrogenation of racemic Benzoin methyl ether with the chiral catalyst through dynamic kinetic resolution gave the anti-alcohol (syn:anti = 3:97) in 98% ee, while the reaction of alpha-amidopropiophenones resulted in the syn-alcohols (syn:anti = 96:4 to >99:1) in >98% ee.

Migration behavior and enantioseparation of hydrobenzoin and structurally related compounds in capillary zone electrophoresis with a dual cyclodextrin system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin and beta-cyclodextrin.[Pubmed:16252333]

Electrophoresis. 2005 Nov;26(21):4187-96.

Migration behavior and enantioseparation of racemic hydrobenzoin and structurally related compounds, including benzoin and Benzoin methyl ether, in CZE with a dual CD system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) and beta-CD as chiral selectors in the presence and absence of borate complexation at pH 9.0 were investigated. The results indicate that enantioseparation of hydrobenzoin is mainly governed by CD complexation of hydrobenzoin-borate complexes with SI-S-beta-CD when SI-S-beta-CD concentration is relatively high. Whereas CD complexation of hydrobenzoin-borate complexes with beta-CD plays a significant role in enantioseparation when SI-S-beta-CD concentration is comparatively low. The (S,S)-enantiomer of the hydrobenzoin-borate complex was found to interact more strongly than the corresponding (R,R)-enantiomer with both SI-S-beta-CD and beta-CD. These two types of CD show the same chiral recognition pattern, but they exhibit opposite effects on the mobility of the enantiomers of hydrobenzoin-borate complexes. Enantiomer migration reversal of hydrobenzoin occurred in the presence of borate complexation when varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. Binding constants of the enantiomers of benzoin-related compounds to beta-CD and those of hydrobenzoin-borate complexes to SI-beta-CD were evaluated; the mobility contributions of all complex species to the effective mobility of the enantiomers of hydrobenzoin as a function of beta-CD concentration in a borate buffer were analyzed. In addition, comparative studies on the enantioseparation of benzoin-related compounds with SI-S-beta-CD and with randomly sulfate-substituted beta-CD were made.

Enantioseparations of hydrobenzoin and structurally related compounds in capillary zone electrophoresis using heptakis(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin as chiral selector and enantiomer migration reversal of hydrobenzoin with a dual cyclodextrin system in the presence of borate complexation.[Pubmed:15352010]

Electrophoresis. 2004 Aug;25(16):2786-94.

We investigated the enantioseparations of racemic hydrobenzoin, together with benzoin and Benzoin methyl ether, in capillary electrophoresis (CE) using the single-isomer heptakis(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin (SI-S-beta-CD) as a chiral selector in the presence and absence of borate complexation and enantiomer migration reversal of hydrobenzoin with a dual CD system consisting of SI-S-beta-CD and beta-CD in the presence of borate complexation at pH 9.0 in a borate buffer. The enantioselectivity of hydrobenzoin increased remarkably with increasing SI-S-beta-CD concentration and the enantioseparation depended on CD complexation between hydrobenzoin-borate and SI-S-beta-CD. The (S,S)-enantiomer of hydrobenzoin-borate complexes interacted more strongly than the (R,R)-enantiomer with SI-S-beta-CD. The enantiomers of hydrobenzoin could be baseline-resolved in the presence of SI-S-beta-CD at a concentration as low as 0.1% w/v, whereas the three test analytes were simultaneously enantioseparated with addition of 0.3% w/v SI-S-beta-CD or at concentrations >2.0% w/v in a borate buffer and 0.5% w/v in a phosphate background electrolyte at pH 9.0. Compared with the results obtained previously using randomly sulfated beta-CD (MI-S-beta-CD) in a borate buffer, enantioseparation of these three benzoin compounds is more advantageously aided by SI-S-beta-CD as the chiral selector. The enantioselectivity of hydrobenzoin depended greatly on the degree of substitution of sulfated beta-CD. Moreover, binding constants of the enantiomers of benzoin compounds to SI-S-beta-CD and those of hydrobenzoin-borate complexes to SI-S-beta-CD were evaluated for a better understanding of the role of CD complexation in the enantioseparation and chiral recognition. Enantiomer migration reversal of hydrobenzoin could be observed by varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. SI-S-beta-CD and beta-CD showed the same chiral recognition pattern but they exhibited opposite effects on the mobility of the enantiomers.

Enantioseparation of benzoins and enantiomer migration reversal of hydrobenzoin in capillary zone electrophoresis with dual cyclodextrin systems and borate complexation.[Pubmed:15065800]

J Chromatogr A. 2004 Apr 2;1032(1-2):227-35.

Enantioseparations of racemic hydrobenzoin and structurally related compounds, including benzoin and Benzoin methyl ether, in capillary zone electrophoresis (CZE) with dual cyclodextrin (CD) systems consisting of S-beta-CD (mixed isomers) and a neutral CD, including beta-CD and hydroxypropyl-beta-CD (HP-beta-CD), as chiral selectors in the presence of borate complexation at pH 9.0 were investigated. Effective enantioseparations of hydrobenzoin were achieved with addition of dual CD systems and also with neutral CDs in a borate buffer. The enantioseparation and migration behavior of hydrobenzoin in such an electrophoretic system are primarily governed by the interaction of the borate complex of hydrobenzoin with beta-CDs. The CD complexations of both hydrobenzoin and the borate complexes of hydrobenzoin with beta-CDs increase in the order S-beta-CD < HP-beta-CD < beta-CD. As a result, enantioseparations of hydrobenzoin with the use of dual CD systems consisting of S-beta-CD/beta-CD and S-beta-CD/HP-beta-CD as chiral selectors are more advantageous than that with the use of S-beta-CD alone. With these dual CD systems in the presence of borate complexation, the enantiomer migration reversal was observed for hydrobenzoin. The interactions of hydrobenzoin with neutral CDs and with S-beta-CD exhibit the same chiral recognition pattern, but opposite effect on the mobility of the enantiomers. The (S,S)-enantiomer of hydrobenzoin was found to interact more strongly than the (R,R)-enantiomer with neutral CDs. For comparison, enantioseparation of hydrobenzoin, together with benzoin and Benzoin methyl ether, with dual CD systems in a phosphate background electrolyte at pH 9.0 was also examined. The migration order and enantioselectivity of these three benzoins depend on the degree of CD complexations between benzoins and both S-beta-CD and neutral CD in a phosphate background electrolyte. In addition, effective enantioseparations of hydrobenzoin were also achievable with addition of either beta-CD at concentrations greater than 1.0 mM or HP-beta-CD at concentrations exceeding 2.0 mM in a borate buffer at pH 9.0.

Comparative studies on the enantioseparation of hydrobenzoin and structurally related compounds by capillary zone electrophoresis with sulfated beta-cyclodextrin as the chiral selector in the presence and absence of borate complexation.[Pubmed:15065798]

J Chromatogr A. 2004 Apr 2;1032(1-2):213-8.

Comparative studies on the enantioseparations of racemic hydrobenzoin, together with benzoin and Benzoin methyl ether, in capillary zone electrophoresis using sulfated beta-cyclodextrin (S-beta-CD) as a chiral selector in the presence and absence of borate complexation were investigated. The influences of S-beta-CD concentration on the enantioseparation of benzoins in a borate buffer and a phosphate background electrolyte and the influences of the concentration and the pH of borate buffer containing S-beta-CD on the enantioseparation of hydrobenzoin were examined. The results indicate that, depending on the degree of strong borate complexation and comparatively weak CD complexation, the selectivity of the enantiomers of hydrobenzoin can be greatly reduced in a buffer system containing borate ions. Enantioseparation of hydrobenzoin is mainly governed by the interaction between hydrobenzoin-borate complexes and S-beta-CD in a borate buffer, whereas enantioseparation of benzoins is primarily determined by CD complexation in a phosphate background electrolyte. Effective enantioseparations of benzoins were simultaneously achieved with addition of S-beta-CD at a concentration greater than 3.0% (w/v) in a borate buffer and at a concentration greater than 2.5% (w/v) in a phosphate background electrolyte at pH 9.0.

Synthesis and evaluation of polymer-based zwitterionic stationary phases for separation of ionic species.[Pubmed:11354481]

Anal Chem. 2001 May 1;73(9):1993-2003.

Three different zwitterionic functional stationary phases for chromatography were synthesized on the basis of 2-hydroxyethyl methacrylate (HEMA) polymeric particles. Two synthesis routes, producing materials designated S300-ECH-DMA-PS or S300-TC-DMA-PS, involved activation of the hydroxyl groups of the HEMA material with epichlorohydrin or thionyl chloride, respectively, followed by dimethylamination and quaternizing 3-sulfopropylation with 1,3-propane sultone. The third route was accomplished by attaching methacrylate moieties to the HEMA through a reaction with methacrylic anhydride, followed by graft photopolymerization of the zwitterionic monomer 3-[N,N-dimethyl-N-(methacryloyloxyethyl)ammonium] propanesulfonate, initiated by Benzoin methyl ether under 365-nm light. According to elemental analyses, both the S300-ECH-DMA-PS and S300-TC-DMA-PS materials appeared to have overall charge stoichometries close to unity, whereas the grafted material, S300-MAA-SPE, seemed to carry an excess of anion exchange sites in addition to the zwitterionic groups. Yet all three zwitterionic stationary phases were capable of separating inorganic anions and cations simultaneously and independently using aqueous solutions of perchloric acid or perchlorate salts as eluent, albeit with markedly different selectivities. On the S300-TC-DMA-PS and S300-MAA-SPE materials, the retention times increased for cations and decreased for anions with increasing eluent concentration, whereas with the S300-ECH-DMA-PS material, the retention times of both anions and cations decreased with increasing eluent concentration. These results demonstrate the importance of choosing appropriate synthesis conditions in order to prepare covalently bonded zwitterionic separation materials with an acceptable charge balance.