Relation between the structure and extracting power of higher tertiary amines

The effect of the composition and structure of higher tertiary amines on their efficiency in extracting nitric acid has been examined. The ionization constants of the amines in methanol have been determined by potentiometric titration. The extraction constants for nitric acid have been determined at constant ionic strength in the aqueous phase (μ=1). The dependence of these constants upon the concentrations and the degree of association of the amine salts in the organic phase has been examined. For the cases in which the role of steric factors is negligible it has been shown that at low amine salt concentrations in the organic phase there are quantitative regularities between the ionization constants of the amines in methanol, their extraction constants for nitric acid and the inductive effects of the substituents on the nitrogen atom.     

In situ derivatization hollow fibre liquid-phase microextraction for the determination of biogenic amines in food samples

Hollow fibre liquid-phase microextraction with in situ derivatization using dansyl chloride has been successfully developed for the high-performance liquid chromatography-ultraviolet (HPLC-UV) determination of the biogenic amines (tryptamine, putrescine, cadaverine, histamine, tyramine, spermidine) in food samples. Parameters affecting the performance of the in situ derivatization process such as type of extraction solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Under the optimized conditions (extraction solvent, dihexyl ether; acceptor phase, 0.1 M HCl; extraction time, 30 min; extraction temperature, 26 °C; without addition of salt), enrichment factors varying from 47 to 456 were achieved. Good linearity of the analytes was obtained over a concentration range of 0.1–5 μg mL⁻¹ (with correlation coefficients of 0.9901–0.9974). The limits of detection and quantification based on a signal-to-noise ratio of 3–10, ranged from 0.0075 to 0.030 μg mL⁻¹ and 0.03 to 0.10 μg mL⁻¹, respectively. The relative standard deviations based on the peak areas for six replicate analysis of water spiked with 0.5 μg mL⁻¹ of each biogenic amine were lower than 7.5%. The method was successfully applied to shrimp sauce and tomato ketchup samples, offering an interesting alternative to liquid–liquid extraction and solid phase extraction for the analysis of biogenic amines in food samples.     

Application of amino‐based chitosan cyclodextrin derivatives for the extraction of catechins in green tea with high‐performance liquid chromatography

Chitosan derivatives have been studied widely, but poor solubility in water restricts their applications. In this study, four types of amine‐based chitosan derivatives were prepared and modified further with beta‐cyclodextrin. The sequential microextraction of catechins ((+)‐catechin and (?)‐epigallocatechin gallate) from green tea powder by an optimized solid‐phase extraction method using these four derivatives was investigated. The optimal conditions for the extraction of catechins were 60°C for a 40 min extraction period. The purity and amount of each catechin were determined by high‐performance liquid chromatography. The different amines strengthened the extraction capacity of chitosan. Among the four types of amines, ethylene diamine grafted chitosan beta‐cyclodextrin had the highest extraction capacity to catechins. Therefore, this material was used in the extraction assay, and the standard curves of (+)‐catechin and (?)‐epigallocatechin gallate were linear over the concentration range, 0.25–500 µg/mL, after assaying five data points in duplicate. Solid‐phase extraction with the amino‐based chitosan beta‐cyclodextrin system is a new application of chitosan, which has potential applications in the extraction of bioactive compounds from plant materials or the removal of different impurities from specific extracts.     

Quantitative evaluations of surface-concentrated amino groups on monolithic-type solid supports prepared by copolymerization method

We have prepared novel monolithic-type highly cross-linked solid supports having surface amino group using a copolymerization method of functional monomers and cross-linking monomer. From the view point of controlled surface functionalities, we have firstly certified and proved quantitative determination methods of the surface amino groups to utilize and evaluate those solid supports prepared as affinity resins. We utilized a typical titration method and ninhydrin method that have been effectively utilized for quantitative determination of primary amine and amino acid. The ninhydrin method was calibrated using octylamine as a standard compound (R ² = 0.998) and proved applicability for the quantitative determination of other primary amines. A commercially available solid support, Affigel, was able to be quantitatively evaluated only by the ninhydrin method, while Toyopearl afforded just compatible amino group density to the value certified by the manufacturer only through titration method. The obtained incompatible results using both determination methods have been unclear at this moment. On the other hand, both determination methods afforded compatible amino group density of the prepared solid support. The obtained value was up to 126 μmol/ml, which was 94% of the calculated theoretical value based on the feed composition. The results suggested surface-concentrated introduction of amino groups. Based on the determination methods, especially ninhydrin method, we prepared the monolithic-type solid supports having various densities of surface amino groups and proved quantitative and surface-concentrated introduction of amino groups. Those amino groups were able to react with a relatively large ligand molecule, methotrexate, quantitatively and also with controlled density. The obtained results strongly suggest that the novel monolithic-type solid supports have possible advantages when we utilize those as affinity resins for target peptide analyses.     

FIA-FAAS system including on-line solid phase extraction for the determination of palladium, platinum and rhodium in alloys and ores

A number of aliphatic mono- and triamines have been investigated as potential reagents for solid phase extraction of Rh, Pd and Pt. Platinum group metals are recovered from hydrochloric acid solutions as ionic associates of their chloride complexes with protonated amines. The recovery of metals depends both on hydrophobic properties of amine and sorbent and on sorption behaviour of amine itself. For on-line solid phase extraction of platinum group metals 4-(n-octyl)diethylenetriamine and hyper cross-linked polystyrene sorbent SSPS have been applied. Quantitative recovery of rhodium and platinum in the form of their hexachloride complexes was achieved under non-equilibrium conditions of on-line dilution. Metals recovered are quantitatively eluted with 1 M hydrochloric acid solution in ethanol. A new FIA-FAAS method for the determination of Rh, Pd and Pt in solutions based on the decomposition of ores and alloys has been proposed. The RSD values are 0.03-0.08 at 50-ppb concentration level. The detection limits are 3-8 ppb for 1 min of preconcentration. The accuracy of the procedure was verified by the analysis of standard reference materials of sulfide ores and alloys.     

气相色谱-质谱法测定蜡笔中的芳香伯胺

建立了固相萃取-气相色谱-质谱(SPE-GC-MS)检测儿童蜡笔中苯胺等9种芳香伯胺的方法。先用正己烷除去蜡笔中的烷烃类物质,再以甲醇为提取剂在室温下超声提取两次,提取液经过浓缩后与还原剂连二亚硫酸钠在70 ℃下反应30 min,将反应后的溶液通过硅藻土固相萃取柱净化收集,然后采用HP-5M色谱柱分离,并用质谱进行检测。采用该方法成功地实现了9种芳香伯胺的分离检测。对于不同的芳香伯胺的定量限为5 mg/kg,实际样品的平均回收率为86.02%～102.43%。实验结果证明,该方法准确、稳定,可以用于蜡笔中芳香伯胺的实际检验。     

Mutual binary separations of cadmium(II), indium(III) and thallium(III) as chlorides by their extraction in high molecular weight amines

The extraction of cadmium(II), indium(III) and thallium(III) with high molecular weight amines have been studied from aqueous hydrochloric acid solutions. Using the data mutual binary separations of these three elements with high separation coefficients are proposed. Various variables like type of amine, amine concentration and organic diluent were explored to propose the best conditions of separations.     

Separation and determination of biogenic amines in fish using MEKC with novel multiphoton excitation fluorescence detection

Biogenic amines are a group of biological molecules derived from the enzymatic decarboxylation of natural amino acids. They can be found in a variety of foods and some of them are involved in essential cellular pathways regulating cellular functions. To address the issues raised by conventional detection methods for biogenic amines, such as laborious sample preparation and limited sensitivity, a new micellar electrokinetic chromatography scheme was developed based on multiphoton excitation fluorescence (MPEF) detection. Six FITC-labeled biogenic amine species were used for the evaluation of this MEKC-MPEF method in comparison to single photon excitation fluorescence detection. The results indicated that MEKC-MPEF had superior resolution with a detection volume as low as aL. Quantitative analysis of varying concentrations of biogenic amine species has also been achieved suggesting a ymole mass detection limit, a linear dynamic range of about two orders of magnitude, and 95-105% recoveries. Furthermore, the biogenic amine profile of decayed oriental crucian carps was successfully determined and quantified using this new method.     

Tailoring D‐Amino Acid Oxidase from the Pig Kidney to R‐Stereoselective Amine Oxidase and its Use in the Deracemization of α‐Methylbenzylamine

The deracemization of racemic amines to yield enantioenriched amines using S‐stereoselective amine oxidases (AOx) has recently been attracting attention. However, R‐stereoselective AOx that are suitable for deracemization have not yet been identified. An R‐stereoselective AOx was now evolved from porcine kidney D ‐amino acid oxidase (pkDAO) and subsequently use for the deracemization of racemic amines. The engineered pkDAO, which was obtained by directed evolution, displayed a markedly changed substrate specificity towards R amines. The mutant enzyme exhibited a high preference towards the substrate α‐methylbenzylamine and was used to synthesize the S amine through deracemization. The findings of this study indicate that further investigations on the structure–activity relationship of AOx are warranted and also provide a new method for biotransformations in organic synthesis.     

Complexation and Separation of Amines, Amino Acids, and Peptides by Functionalized Calix[n]arenes

The ability of calix[n]arenes to form complexes, to act as extractants in liquid–liquid extraction, and run as carriers in transport through liquid membranes of different biological amine compounds (e.g., ammonium ion, amines, amino acids, and peptides) has been the central topics of many reports. These features recommend the calix[n]arenes as competitive candidates for studying the interactions involved in host–guest recognition as well as useful receptors in separation processes. Some specific aspects of their applications in binding and separation of various amine compounds by extraction, and in transport through liquid membranes have therefore been considered. The effect of the factors that might influence the separation of above compounds by extraction, and the transport through liquid membranes using the calix [n]arenes has been presented.     

Complexation and Separation of Amines,Amino Acids,and Peptides by Functionalized Calix[<Emphasis Type="Italic">n</Emphasis>]arenes

The ability of calix[n]arenes to form complexes, to act as extractants in liquid–liquid extraction, and run as carriers in transport through liquid membranes of different biological amine compounds (e.g., ammonium ion, amines, amino acids, and peptides) has been the central topics of many reports. These features recommend the calix[n]arenes as competitive candidates for studying the interactions involved in host–guest recognition as well as useful receptors in separation processes. Some specific aspects of their applications in binding and separation of various amine compounds by extraction, and in transport through liquid membranes have therefore been considered. The effect of the factors that might influence the separation of above compounds by extraction, and the transport through liquid membranes using the calix [n]arenes has been presented.This revised version was published online in July 2005 with a corrected issue number.     

Separation of organic acid compounds from biological samples by zinc oxide nanoparticles–chitosan using genetic algorithm based on response surface methodology and artificial neural network

In this study, zinc oxide nanoparticles–chitosan based on solid phase extraction and high performance liquid chromatography was developed for the separation of organic compounds including citric, tartaric and oxalic acids from biological samples. For simulation and optimization of this method, the hybrids of genetic algorithm with response surface methodology (RSM) and artificial neural network (ANN) have been used. The predictive capability and generalization of both predictive models (RSM and ANN) were compared by unseen data. The results have shown the superiority of ANN compared with RSM. At the optimum conditions, the limits of detections of 2.2–2.9 µg L⁻¹ were obtained for the analytes. The developed procedure was then applied to the extraction and determination of organic acid compounds from biological samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterisation of Tokaj wines based on free amino acids and biogenic amines using ion-exchange chromatography

Summary Tokaj wines (Szamorodni and Aszu wines) of Hungarian origin were investigated on the basis of free amino acids and biogenic amines. The separation and determination of these compounds was performed by an amino acid analyser equipped with an ion-exchange resin column. The total amount of free amino acids and biogenic amines was higher in Aszu wines than in Szamorodni wines. The main amino acids were proline and arginine, while the major biogenic amines were tyramine and putrescine. The free amino acid and biogenic amine content of Aszu wines depended on the vineyards the wines originated from. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Use of complexones for the extraction separation of rare earth and transplutonium elements with amines

The extraction distribution and separation of rare earth elements and americium from the concentrated lithium nitrate solution with solutions of tertiary amines in organic solvents has been studied as a function of the composition and structure of complexones of the polyaminepolyacetic acid series by a radioactive tracer method. It has been found that diethylenetriaminepentaacetic acid is suitable for the separation of REE from americium(III). The apparent stability constants for the lanthanide complexes with EDTA and DTPA in concentrated litium nitrate solutions have been obtained by extraction, pH-metric titration and solubility. Using these constants, the optimum conditions of separation have been found and the separation factors of REE calculated. The calculated and experimental values are in good agreement. The optimum conditions for the separation of americium(III) from REE in a wide range of lanthanide and complexone concentrations (10⁻¹–10⁻⁶ M) have been determined.     

Determination of Enantiomeric Excess in Amine Derivatives with Molecular Self‐Assemblies

We report the first fluorescence‐based assay for the rapid determination of the ee value of amines, amino alcohols, and amino acid esters. The method uses the self‐assembly of 2‐formylphenylboronic acid with a chiral diol and a chiral amine or derivatives (of unknown chirality) to produce two diastereomeric iminoboronates that differ in their fluorescence intensity and polarization. The approach allows for the accurate determination of the ee value of chiral amines with errors of just 1–2 %. We believe that this application of orthogonal dynamic covalent self‐assembly in the determination of the enantioselectivity will lead to the development of high‐throughput procedures for the determination of chirality.     

Solid phase extraction of amines

The objective of this paper is to provide information about solid phase extraction (SPE) as an alternative to liquid-liquid extraction of amines from several matrices. Different sorbents ranging from non-polar phases, such as C₁₈ silica to more polar such as cyanopropylsilica (CN) have been tested for analysis of aliphatic amines as monoamines, diamines and polyamines. Phenylalkylamines such as amphetamine or methamphetamine and heterocyclic amines such as histamine or cephalosporins (which also contain a carboxylic group), have also been studied. The different steps involved in the extraction procedure have been tested (conditioning, retention, pre-concentration, washing and elution) in order to obtain extracts free of interferences and enough sensitivity. C₁₈ silica (100 mg) was selected as optimal phase with recoveries nearly of 100%. The elution of more polar amines was performed in acidic conditions while less polar amines required organic solvents. Cephalosporin retention was performed in acid condition by using disk cartridges EM C_18, which gave better selectivity. The optimised clean-up procedures have been discussed to the quantification of the corresponding amines in real samples (urine, water and beer). The accuracy and precision were outlined.     

Efficient synthesis of tertiary amines from secondary amines

Reliable N-alkylations of secondary amines have been developed. By using DIAD and TPP (or PS-TPP) a variety of secondary amines can be converted to the corresponding tertiary amines in good to excellent yields with diverse alkylhalides; no formation of quaternary amine salts are observed. These protocols are amenable to combinatorial chemistry libraries, and are also useful for the syntheses of secondary amines by an acid lysis of the cleavable tertiary amino resins.     

Determination of selected organics in treated sludges and associated leachates from coal conversion facilities

Methods have been developed for the determination of organic compounds in solid wastes and sludges. The methods involve sequential extraction with acid, base, and organic solvent, as well as dynamic headspace stripping of the volatile components. Methods for assessing the mobility of organic compounds in the environment have been evaluated, including four batch extractions and an upward-flow column extraction. Batch extractions in closed vessels are most effective for the determination of volatile components. The upward-flow column arrangement is shown to be the most aggressive leaching procedure for semi-volatile organic compounds.     

Polymers of tertiary amines

Polymers of tertiary amines and their hydrochlorides of molecular weights in the range 300–2000 have been prepared, starting from trans-1,4-dichlorobutene-2, and primary amines. The polymers present interesting solubility properties. Variation of the reaction conditions leads to crosslinked insoluble polymers. Reaction of the soluble tertiary amine polymers with organic acid dichlorides leads to polymers of tertiary amine–amides, a new type of polymer.     

Determination of less polar heterocyclic amines in meat extracts: fast sample preparation method using solid-phase microextraction prior to high-performance liquid chromatography-fluorescence quantification

A procedure for the determination of less polar heterocyclic amines in meat extracts using solid phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with fluorescence detection is presented. Analytes were first extracted from the samples using methanol/NaOH by an ultrasound-assisted method, and then concentrated on a Carbowax-templated resin (CW-TPR) SPME fiber. The extraction conditions such as extractant mixture composition, extraction time and extractions number, were optimized and the need of an extract freezing step previous to SPME is discussed. The detection limits under optimal conditions are in the range of 0.28-1.1 ng g⁻¹. The method was applied to the determination of less polar heterocyclic amines in four commercial meat extracts. Recovery values obtained are higher than 60% for the majority of amines.