Ion-exchange preconcentration and group separation of ionic and neutral organic compounds

In many cases sample pretreatment continues to be the most time-consuming and costly step in the analytical process. In the present work it is shown that macroporous ion-exchange resins of low exchange capacity can be used both to preconcentrate organic solutes from aqueous samples and to separate these solutes into groups. Thus, neutral and basic organic compounds are both taken up from aqueous solution by a very short column packed with a special cation-exchange resin. The neutral group of compounds is subsequently eluted with an organic solvent. The bases are then eluted 2 M methylamine in methanol. In a similar manner organic acids are concentrated on a special anion-exchange column. Extensive data are shown to demonstrate the efficiency of the preconcentration and group separation of neutral and basic compounds.     

Synthesis of analogs of pyridoxal 5′-phosphate and pyridoxamine 5′-phosphate

The following analogs of pyridoxamine 5′-phosphate (PAMP) have been synthesized by the direct phosphorylation of the corresponding amines: 2-nor-PAMP, 6-methyl-2-nor-PAMP, and 6-methyl-PAMP. A method for the synthesis of analogs of pyridoxal 5′-phosphate (PLP) by the phosphorylation of the Schiff's bases of the corresponding aldehydes with p-phenetidine and subsequent hydrolysis on a sulfonated resin has been worked out. 2-Nor-PLP, 6-methyl-2-nor-PLP, and 6-methyl-PLP have been obtained with yields of 53–73%. The spectral properties of the compounds obtained have been investigated.     

固定化有机改进剂RP－HPLC固定相的研究

通过在ＲＰＨＰＬＣ固定相Ｃ１８表面键合氨基硅烷，引入氨基基团，将有机改进剂固定至硅胶键合相表面，克服了固定相表面硅羟基对含氮有机化合物的不可逆吸附。以最简单的ＣＨ３ＯＨ－Ｈ２Ｏ洗脱体系即能获得含氮有机物的最佳分离，从而可简化分离操作，提高柱寿命，降低分离成本。     

固定化有机改进剂RP－HPLC固定相的研究

通过在ＲＰＨＰＬＣ固定相Ｃ１８表面键合氨基硅烷，引入氨基基团，将有机改进剂固定至硅胶键合相表面，克服了固定相表面硅羟基对含氮有机化合物的不可逆吸附。以最简单的ＣＨ３ＯＨ－Ｈ２Ｏ洗脱体系即能获得含氮有机和的最佳分离，从而可简化分离操作，提高柱寿命，降低分离成本。     

Determination of trace metal complexes by natural organic and inorganic ligands in coastal seawater.

It is well-documented that organic compounds form strong complexes with most metals in aquatic systems, and that seawater is a complex medium which contains a large variety of organic and inorganic ligands, including colloidal matter. We suggest that most trace metals are complexed in seawater and that some inorganic metals complexes are either labile or not stable. In contrast, metal-organic complexes are often stable and need various and specific treatments to be dissociated. In this paper we try to illustrate a good tendency of some trace metals to be complexed by organic ligands in seawater. A solid-phase extraction method was applied using a C18 column as a resin that is able to separate metals complexed by neutral organic ligands, and the chelamine resin to separate metal species that are present as labile inorganic complexes. The determination of total dissolved metal concentrations was achieved by formatting a metal-8-hydroxyquinoline complex, followed by adsorption on C18 columns and ICP-AES analysis.     

Basicity of some organic superbases in acetonitrile

[structure: see text] It is shown that the pK(a) values of strong neutral organic (super)bases in acetonitrile are well described by the density functional theory (DFT) employing the isodensity polarization continuum model (IPCM) for treating solvent-solute interactions. High pK(a) values are predicted for two model compounds, and their synthesis is strongly recommended.     

Identification and determination of phenols and chloro-phenols in very dilute aqueous solutions by gas-liquid chromatography,paper chromatography and spectrophotometry

After concentration of the organic substances from water samples of 700 to 20,000 l by adsorption on active carbon and desorption with chloroform in a large Soxhlet apparatus, tlie organic compounds were separated by extraction into 5 different groups: acids, phenols, bases, neutral and amphoteric substances. The phenol group was investigated by gas and paper chromatography, ultraviolet difference spectrophotometry and infrared spectroscopy. Phenol, 2,4,6-trichlorophcnol, 2- and 3-cresol, 2,4-xylenol and 2,4-dichlorophenol were identified in samples of raw and treated water. Quantitative measurements proved to be possible with gas chromatography. The conditions for quantitative desorption and separation were studied.     

Surface-enhanced Raman spectroscopic-encoded beads for multiplex immunoassay

A new type of encoded bead, which uses surface-enhanced Raman scattering (SERS), is described for multiplex immunoassays. Silver nanoparticles were embedded in sulfonated polystyrene (PS) beads via a polyol method, and they were used as SERS-active substrates. Raman-label organic compounds such as 4-methylbenzenethiol (4-MT), 2-naphthalenethiol (2-NT), and benzenethiol (BT) were then adsorbed onto the silver nanoparticles in the sulfonated PS bead. Although only three kinds of encoding have been demonstrated here, various combinations of these Raman-label organic compounds have the potential to give a large number of tags. The Raman-label-incorporated particles were then coated with a silica shell using tetraethoxyorthosilicate (TEOS) for chemical stability and biocompatibility. The resulting beads showed unique and intense Raman signals for the labeled organic compounds. We demonstrated that SERS-encoded beads could be used for multiplex detection with a model using streptavidin and p53. In our system, the binding event of target molecules and the type of ligand can be simultaneously recognized by Raman spectroscopy using a single laser-line excitation (514.5 nm).     

反相液相色谱中离子抑制剂的有机调节剂作用

系统地研究了在反相液相色谱（RPLC）流动相中作为离子抑制剂的酸、碱及缓冲溶液对中性化合物保留行为的影响,着重探讨了有机酸、有机碱离子抑制剂的有机调节剂作用,定量地考察了甲醇和乙腈、甲醇和乙酸、甲醇和三乙胺、乙腈和乙酸、乙腈和三乙胺在十八烷基硅烷键合相上洗脱强度之间的关系,为RPLC中有机调节剂的洗脱强度排序提供一种评判方法．另外,讨论了乙酸和三乙胺作为有机调节剂时不同的作用机理．本实验结果对于RPLC分离方法的快速建立和准确优化都具有一定的借鉴意义．     

Generalization of ionic partition diagrams to lipophilic compounds and to biphasic systems with variable phase volume ratios.

The ionic partition diagram methodology has been generalized to address both hydrophilic and lipophilic compounds and to consider biphasic systems with variable phase volume ratios. With this generalized approach electrochemical measurements of ion transfer potentials afford the determination of the standard partition coefficients of all forms of ionizable molecules, including the neutral form, as well as the evaluation of the dissociation constant of monoprotic substances. An interesting consequence of this approach is the definition of an extraction pK(a,ext) which is the apparent pK(a) of neutral acids and bases when dissolved in the organic phase.     

Use of Sulfonated Cation-Exchange Resin Based on Hypercrosslinked Polystyrene for the Separation of Organic Acids

The use of sulfonated cation-exchange resins based on hypercrosslinked polystyrene (HCPS) and highly cross-linked polystyrene–divinylbenzene (80% divinylbenzene) for the separation of organic acids was studied. The influence of the concentration of the eluent, temperature of the chromatographic column, and concentration of acetonitrile in the eluent on the retention of aliphatic carboxylic acids in ion-exclusion chromatography was examined. The optimal separation of organic acids on the HCPS sorbent is attained at 65°C with the use of 10 mM H₂SO₄with or without acetonitrile addition as the eluent. The sorbent based on HCPS in combination with spectrophotometric detection is promising for the determination of organic acids and other weakly ionized and neutral compounds with low molecular mass in samples of complex composition (juices and beer).     

Investigation on Pyrolysis of Casein

First casein was processed by pyrolysis and investigated under optimal thermal treatment condition to obtain a good quality adsorbent with high developed porosity structure and liquid product as a complex raw material for different kind of organic compounds with interesting properties and structures. The yields of hard residue, pitch, pyrolysis water and gases were determined and compared with the yields of pyrolysis products of other investigated different kind of organic materials. The chemical composition of pitch was determined as following: free carbons - 4.52%, organic acids - 0.64%, organic bases -38.00%, phenols - 7.75%, asphaltenes - 0.97%, paraffin's - 1.30%, neutral oils - 16.20% and preasphaltanes - 30.10%. The pitch was fractionated by air distillation into 3 liquid fractions with different boiling range and a bitumen like residue with a lower softening temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sulfonated silica‐based electrolyte nanocomposite membranes

New functionalized particles were prepared by attaching sulfonated aromatic bishydroxy compounds onto fumed silica surface. First, a bromophenyl group was introduced onto the silica surface by reaction of bromophenyltrimethoxysilane with fumed silica. Then, sulfonated bishydroxy aromatic compounds were chemically attached to the silica surface by nucleophilic substitution reactions. The structure of the modified silica was characterized by elemental analysis: ¹³C‐NMR, ²⁹Si‐NMR, and FTIR. Afterward, novel inorganic–organic electrolyte composite membranes based on sulfonated poly(ether ether ketone) have been developed using the sulfonated aromatic bishydroxy compounds chemically attached onto the fumed silica surface. The composite membrane prepared using silica with sulfonated hydroxytelechelic, containing 1,3,4‐oxadiazole units, has higher proton conductivity values in all range of temperatures (40–140 °C) than the membrane containing only the plain electrolyte polymer, while the methanol permeability determined by pervaporation experiment was unchanged. A proton conductivity up to 59 mS cm^?1 at 140 °C was obtained. The combination of these effects may lead to significant improvement in fuel cells (fed with hydrogen or methanol) at temperatures above 100 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2278–2298, 2006     

Neutral and Anionic Diboron Compounds Bearing Electron-Precise B−B Bond

Electron-precise B−B bonded compounds are valuable reagents in organic syntheses, which can be used as key starting material for the synthesis of functionalized organoboranes. Bis(pinacolato)diborane(4) B₂pin₂ and its derivatives are among the most studied diboron species. However, their B−B bonds usually need to be activated by transition metal catalysts or bases for further transformations. Recently, many well-designed/reactive electron-precise B−B bonded compounds have been developed, which could facilitate direct reactions with small molecules, unsaturated substrates, and electrophiles. This review highlights the synthesis, structure, and reactivity of neutral and anionic B−B bonded compounds.     

Novel imidazolium stationary phase for high-performance liquid chromatography

A new imidazolium anion-exchange phase immobilized on silica is synthesized. HPLC separations of common inorganic anions (IO3-, Cl-, NO2-, Br-, NO3-, I-, SCN-) have been performed using a HPLC column (200 mm x 4.6 mm I.D.) packed with this stationary phase, with a phosphate buffer solution as the mobile phase and UV detection at 200 nm. The effects of pH and concentration of eluent on the separation of anions have been studied. Chromatographic parameters are calculated and the results show that the new stationary phase is of significant potential for the analysis of these anions. Successful separations of some ordinary organic anions have also been achieved with the said stationary phase. Meaningfully, organic and inorganic anions can be determined simultaneously and satisfactorily with several neutral compounds using the column. The separation of some organic compounds including hydroxybenzenes, bases and amines by this stationary phase with only water as the eluent has been investigated.     

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants

Liquid chromatography–mass spectrometry using atmospheric pressure ionization (LC–API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC–MS application to transformation products.     

GC-MS analysis of penta- and tetra-cyclic triterpenes from resins of Pistacia species. Part I. Pistacia lentiscus var. Chia

Pistacia species contain oleoresins with bioactive triterpenes. In this study triterpenes, including minor components, were identified and quantified in both neutral and acidic fraction of Pistacia lentiscus var. Chia resin, grown exclusively in Chios island (Greece), collected traditionally, as well as by the use of stimulating agents (liquid collection). It was proved that these two resin samples were composed of several different minor triterpenes. In the traditional collection of the resin, 36 triterpenes were identified, 23 of which are new minor compounds (five in the acidic and eighteen in the neutral fraction). In the liquid collection resin eight compounds were identified in the acidic and 11 in the neutral fraction, while seven compounds were not contained in resin traditionally collected. The main triterpenes in both resin samples collected traditionally and by use of stimulating agents were in the following order: isomasticadienonic acid (24 and 22.5% w/w of triterpenic fraction respectively), masticadienonic acid (9.3 and 14.7% w/w of triterpenic fraction) and 28-norolean-17-en-3-one (19 and 36% w/w of triterpenic fraction respectively). The aim of this study was to compare the qualitative and quantitative composition of triterpenes in the resin samples collected using the traditional and new liquid techniques, and examine whether the collection technique influences the contained triterpenes in P. lentiscus var. Chia resin samples. Finally, since there is confusion on interpreting mass spectra of triterpenes we present an analytical review on the base peaks, main fragments and fragmentation mechanism/pattern of several skeleton penta- and tetra- cyclic triterpenes reported in P. lentiscus resin. Also, a biosynthetic route for triterpene skeletons contained in P. lentiscus resin was approached.     

Amberlyst A21: A reusable solid catalyst for green synthesis of pyran annulated heterocycles at room temperature

Amberlyst A21, a neutral ion-exchange resin and a solid base, can catalyze the three-component reaction of aldehyde and malononitrile with various active methylene compounds at room temperature to synthesize a range of pharmaceutically important pyran annulated heterocycles. Use of the solid base could generate a highly green protocol by eliminating chromatographic purification that involves hazardous organic solvents, and facilitate easy recovery and reusability of the catalyst.     

Use of mercuric resins for selective abstraction of mercaptans in capillary gas chromatography

A small amount of mercuric non-porous resin placed in the liner of the injection splitter of a gas chromatograph retains mercaptans but allows other organic sulfur and non-sulfur compounds to be chromatographed normally: mercaptans in the gaseous state are retained by the mercuric resin. The method works well at 200°C but an increasing number of impurity peaks are observed as the temperature is increased to 250°C.     

Chromatographic hydrophobicity index: pH profile for polyprotic compounds

The Chromatographic Hydrophobicity Index (CHI) has been measured for several diprotic compounds. In order to model the variation of CHI with pH, a general equation for polyprotic compounds which allows the calculation of CHI for each one of the species has been proposed. Different types of diprotic solutes have been selected: neutral acids, neutral bases, and amphiprotic compounds (non-zwitterionic and zwitterionic). The applicability of the model to these complex polyprotic compounds, its advantages and limitations, as well as the information provided by the fits is discussed. In general, the model fits the experimental behaviour of all kind of solutes very well, obtaining the higher hydrophobicity values for the neutral form of the compounds, except for the zwitterionic phenylalanine. The equation and parameters obtained allow an easy calculation of CHI of the compound at any pH value.