Cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase for the enantioseparation of drugs in supercritical fluid chromatography: comparison with HPLC.

A cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase was studied as a tool for the enantioselective separation of 21 selected analytes with different pharmaceutical and physicochemical properties. The enantioseparations were performed using supercritical fluid chromatography. The effect of the mobile phase composition was studied. Four different additives (diethylamine, triethylamine, isopropylamine, and trifluoroacetic acid) and isopropylamine combined with trifluoroacetic acid were tested and their influence on enantioseparation was compared. The influence of two different mobile phase co-solvents (methanol and propan-2-ol) combined with all the additives was also evaluated. The best mobile phase compositions for the separation of the majority of enantiomers were CO2 /methanol/isopropylamine 80:20:0.1 v/v/v or CO2 /propan-2-ol/isopropylamine/trifluoroacetic acid 80:20:0.05:0.05 v/v/v/v. The best results were obtained from the group of basic ß-blockers. A high-performance liquid chromatography separation system composed of the same stationary phase and mobile phase of similar properties prepared as a mixture of hexane/propan-2-ol/additive 80:20:0.1 v/v/v was considered for comparison. Supercritical fluid chromatography was found to yield better results, i.e. better enantioresolution for shorter analysis times than high-performance liquid chromatography. However, examples of enantiomers better resolved under the optimized conditions in high-performance liquid chromatography were also found.

Synthetic analogs of stryphnusin isolated from the marine sponge Stryphnus fortis inhibit acetylcholinesterase with no effect on muscle function or neuromuscular transmission.

The marine secondary metabolite stryphnusin (1) was isolated from the boreal sponge Stryphnus fortis, collected off the Norwegian coast. Given its resemblance to other natural acetylcholinesterase antagonists, it was evaluated against electric eel acetylcholinesterase and displayed inhibitory activity. A library of twelve synthetic phenethylamine analogs, 2a-7a and 2b-7b, containing tertiary and quaternary amines respectively were synthesized to investigate the individual structural contributions to the activity. Compound 7b was the strongest competitive inhibitor of both acetylcholinesterase and butyrylcholinesterase with IC50 values of 57 and 20 µM, respectively. This inhibitory activity is one order of magnitude higher than the positive control physostigmine, and is comparable with several other marine acetylcholinesterase inhibitors. The physiological effect of compound 7b on muscle function and neuromuscular transmission was studied and revealed a selective mode of action at the investigated concentration. This data is of importance as the interference of therapeutic acetylcholinesterase inhibitors with neuromuscular transmission can be problematic and lead to unwanted side effects. The current findings also provide additional insights into the structure-activity relationship of both natural and synthetic acetylcholinesterase inhibitors.

Spectrophotometric determination of some histamine H1-antagonists drugs in their pharmaceutical preparations.

Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of three histamine H1-antagonists drugs, e.g., chlorphenoxamine hydrochloride (CPX), diphenhydramine hydrochloride (DPH) and clemastine (CMT) in bulk and in their pharmaceutical formulations. The first method depend upon the reaction of molybdenum(V) thiocyanate ions (Method A) with the cited drugs to form stable ion-pair complexes which extractable with methylene chloride, the orange red color complex was determined colorimetrically at lambda(max) 470nm. The second method is based on the formation of an ion-association complex with alizarin red S as chromogenic reagents in acidic medium (Method B), which is extracted into chloroform. The complexes have a maximum absorbance at 425 and 426nm for (DPH or CMT) and CPX, respectively. Regression analysis of Beer-Lambert plots showed a good correlation in the concentration ranges of 5.0-40 and 5-70microgmL(-1) for molybdenum(V) thiocyanate (Method A) and alizarin red S (Method B), respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. Applications of the procedure to the analysis of various pharmaceutical preparations gave reproducible and accurate results. Further, the validity of the procedure was confirmed by applying the standard addition technique and the results obtained in good agreement well with those obtained by the official method.

6-TIPS-ß-Cyclodextrin-Modified Fe3 O4 for Facile Enantioseparation of 1-(1-Naphthyl)ethylamine.

A new type of chiral magnetic nanoparticle was prepared from covalently linked magnetic nanoparticles (Fe3 O4 ) and heptakis-(6-O-triisopropylsilyl)-ß-cyclodextrin (6-TIPS-ß-CD). The resulting selectors (TIPS-ß-CD-MNPs) combined the good magnetic properties Fe3 O4 and efficient chiral recognition ability of 6-TIPS-ß-CD. The enantioselectivity of TIPS-ß-CD-MNPs towards 1-(1-naphthyl)ethylamine was six times higher than that of the parent ß-CD modified Fe3 O4 particles.

Enantiomeric separation of 1-phenylethylamine and 1-cyclohexylethylamine in capillary electrophoresis with contactless conductivity detection.

Contactless conductivity detection was employed for the detection of the enantiomers of 1-phenylethylamine and 1-cyclohexylethylamine which were separated in capillary electrophoresis with unprecedented high resolutions R(s) of 2.3 and 3.3, respectively, by using a combination of dimethyl-beta-cyclodextrin and the chiral crown ether 18C6H4 as chiral selectors in a citric acid buffer of pH 2.4. The conductivity measurement enabled the direct detection, i.e. without having to derivatize or resort to indirect methods, of all species including the non-UV-absorbing enantiomers of cyclohexylamine. Detection limits of 0.5 microM were achieved and the determination of enantiomeric ratios of up to 99:1 was found possible.

Novel cation-exchange column for the separation of hydrophobic and/or polyvalent amines.

The term amines encompasses a wide variety of compounds: monovalent or polyvalent amines, hydrophobic or hydrophilic amines, and combinations of all of these. Due to their charge, polyvalent amines such as the biogenic amines have very strong cation-exchange interaction with the cation-exchange groups in the stationary phase. Very high acid concentrations are required to elute them effectively from a high-capacity, carboxylated cation-exchange column. The eluent must contain a divalent ion to elute them from a sulfonated cation-exchange column due to its selectivity. Chromatography for these amines with a new "tailored" amine column of moderate capacity using a simple acidic eluent is described. The hydrophobic nature of other amines, such as long-carbon-chained amines, results in partitioning into the polymeric substrate of previous carboxylated stationary phases, so that organic solvent is required to elute them effectively. The substrate resin of this new "tailored" amine column is first coated so that, when it is functionalized in a subsequent step, this type of interaction is minimized. Examples are given. Methods that require eluent gradients and/or step changes of eluent concentration are especially well suited to this column because the background conductivity remains almost unchanged under gradient conditions.

Discovered triethylamine as impurity in synthetic DNAs for and by electrochemiluminescence techniques.

The purity of the synthetic oligonucleotides is very important because it is crucial for the accuracy of the established biological assays. Herein, it was discovered that one impurity in synthetic DNAs might affect the experiment results of electrochemiluminescence (ECL) detection techniques, which was never reported before. According to a series of experiments using ECL detection methods combined with capillary electrophoresis (CE) (CE-ECL), the impurity was identified as triethylamine (TEA), which came from incomplete removal after HPLC purification of synthetic DNAs. Moreover, CE-ECL technique was for the first time to be proposed for discovering, identifying and sensitive determining the possible impurity such as TEA in various DNA samples, which was usually neglected by other detection techniques for purification quality control of synthetic oligonucleotides. A detection range from 5.00×10(-10) to 2.00×10(-5) M with a detection limit as low as 50 nM (S/N=3) was reached for TEA. Through further designed ECL methods and data analysis, situations which would be really affected by the impurity of TEA were studied. To avoid or eliminate the impact of the TEA impurity on ECL applications, judgment basis for choosing purification ways was discussed according to individual requirements.

Ultrasound-assisted low-density solvent dispersive liquid-liquid extraction for the determination of alkanolamines and alkylamines in cosmetics with ion chromatography.

A new one-step sample preparation technique termed ultrasound-assisted low-density solvent dispersive liquid-liquid extraction (UA-LDS-DLLE) coupled with ion chromatography (IC) was developed for the determination of three alkanolamines and two alkylamines in complex samples. Sample matrices were rapidly dissolved and dispersed to form cloudy solutions by using two solvents, where target analytes were transferred into acid solutions, while liposoluble substances were dissolved in cyclohexane. The obtained extracts could be used directly for injection analysis without any additional purification because the potential matrix interferences had been effectively eliminated in extraction process. The extraction efficiency could be markedly enhanced and the extraction could be quickly accomplished within 13 min under the synergistic effects of ultrasound radiation, vibration and heating. Various parameters influencing extraction efficiency were evaluated using orthogonal array experimental design. The extraction performance of the approach was demonstrated for the determination of target analytes in 15 commercial cosmetics covering very different matrices. Linearity ranges of 0.3-50 mg L(-1) and limits of detection varying from 0.072 to 0.12 mg L(-1) were achieved. The recoveries ranged from 86.9-108.5% with the relative standard deviations (RSDs) of 1.2-6.2%. The method was proved to be a simple and effective extraction technique that provided an attractive alternative to the analysis of trace amounts of target analytes in large numbers of cosmetics.

Gas phase bio-filter for the removal of triethylamine (TEA) from air: microbial diversity analysis with reference to design parameters.

Biotic (packed bio-filter; PBF) and abiotic (packed filter; PF) studies were carried out on two similar 2L gas phase filters for the removal of triethylamine (TEA) at inlet concentration in the range of 250-280 ppmV. Removal efficiency (RE) of PBF remained in the range of 90-99% during the stable period of operation (170 days) whereas RE of PF dropped gradually to 10% in a span of 90 days. Five different bacterial species viz; Aeromonas sp., Alcaligenes sp., Arthrobacter sp., Klebsiella sp., and Pseudomonas sp., were identified in PBF. It was observed that diethyl amine, ethylamine and nitrate were formed as metabolites during the degradation pathway. Empty bed residence time of 20s, mass loading rate of 202.26 g/m(3)/h, space velocity of 178.82 m(3)/m(3)/h and elimination capacity of 201.52 g/m(3)/h were found to be optimum design parameters for PBF to get RE in the range of 90-99%.

Ion chromatographic separation and quantitation of alkyl methylamines and ethylamines in atmospheric gas and particulate matter using preconcentration and suppressed conductivity detection.

Two methods based on ion chromatography (IC) were developed for the detection of methyl and ethyl alkyl amines (methylamine (MA), ethylamine (EA), dimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA) and triethylamine (TEA)) and NH(3)/NH(4)(+) in online atmospheric gas-particle and size-resolved particulate samples. The two IC methods were developed to analyze samples collected with an ambient ion monitor (AIM), an online gas-particle collection system, or with a Micro Orifice Uniform Deposit Impactor (MOUDI) for size-resolved particle samples. These methods enable selective and (semi-) quantitative detection of alkyl amines at ambient atmospheric concentrations (pptv and pgm(-3)) in samples where significant interferences can be expected from Na(+) and NH(4)(+), for example marine and rural air masses. Sample pre-concentration using a trace cation column enabled instrumental detection limits on the order of pmol (sub-ng) levels per sample, an improvement of up to 10(2) over current IC methods. Separation was achieved using a methanesulfonic acid gradient elution on Dionex CS12A and CS17 columns. The relative standard deviations in retention times during 3 weeks continuous (hourly) sampling campaigns ranged from 0.1 to 0.5% and 0.2 to 5% for the CS12A and CS17 across a wide dynamic range of atmospheric concentrations. Resolution of inorganic and organic cations is limited to 25min for online samples. Mass-dependent coelution of NH(4)(+)/MA/EA occurred on the CS12A column and DEA/TMA coeluted on both columns. Calibrations of ammonium show a non-linear response across the entire calibration range while all other analytes exhibit high linearity (R(2)=0.984-0.999), except for EA and TEA on the CS12A (R(2)=0.960 and 0.941, respectively). Both methods have high analytical accuracy for the nitrogenous bases ranging from 9.5 to 20% for NH(3) and <5-15% for the amines. Hourly observations of amines at Egbert, ON in October 2010 showed gaseous DMA and TMA+DEA at 1-10pptv in air, while particulate DMA and TMA+DEA were present at 0.5-4ng m(-3). A size-resolved particulate sample collected over 23h was found to contain DMA, TMA+DEA and MEA at 1.78, 8.15 and 0.03ngm(-3) mass loadings, with the amine mass enhanced in particle sizes between 100 and 1000nm. These results highlight a need for very sensitive and selective detection of methyl and ethyl amines in addition to NH(3) in continuous online monitoring strategies.

Two novel phenethylamine alkaloids from streptomyces sp. YIM10049.

Two novel phenethylamine alkaloids were isolated from Streptomyces sp. YIM 10049. On the basis of spectral data, their structures were determined as (S)-N-(cu-phenylethyl)-2 -hydroxyl-acrylimine (1) and (S)-N-nitroso-1-amino-p-hydroxy phenylethanol (2). Three known compounds, indole-3-carboxylic acid (3), cyclo(L-Ala-L-Tyr)(4), and bis(2-ethylhexyl) phthalate (5), were also isolated and characterized. Compound 1 is a rare enol tautomer, and compound 2 an unusual phenethylamine alkaloid with a N-NO group.

Isolation and structure characterization of related impurities in 10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H) bulk drug and quantitation by a validated RP-LC.

10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H), a novel active derivative of ginkgolide B, is a platelet-activating factor antagonist which is being under clinical trial. Two unknown related impurities were observed in analysis of XQ-1H bulk drug. A scaling up preparative liquid chromatography (Prep LC) was used for isolation of the two impurities. Based on LC-MS/MS and nuclear magnetic resonance (NMR) spectra, they were characterized as 10-O-(N,N-dimethylaminoethyl)-11,12-seco-ginkgolide B (imp-1) and 10-O-(N,N-dimethylaminoethyl)-11,12,2,15-diseco-3,14-dehydroginkgolide B (imp-2), respectively. A reversed-phase liquid chromatography (RP-LC) was developed for simultaneous determination of XQ-1H as well as imp-1 and imp-2. Main variables that significantly influence the chromatographic procedure were optimized and efficient chromatographic separation was achieved on a CN column with mobile phase consisting of 5mM dipotassium hydrogen phosphate (pH 7.5) and methanol delivered in a gradient mode at the flow rate of 1.0mLmin(-1). The method was validated and found to be suitable to check the quality of bulk samples of XQ-1H at test concentration of 5.0mgmL(-1) for a 20microL injection volume.

Alkaloids and aromatics of Cyathobasis fruticulosa (Bunge) Aellen.

A beta-carboline-, a tryptamine-, and two phenylethylamine-derived alkaloids and three known aromatic compounds were isolated from the aerial parts and roots of Cyathobasis fruticulosa (Bunge) Aellen, and their structures were elucidated by spectroscopic techniques. The one new alkaloid, N-methyl-N-formyl-4-hydroxy-beta-phenylethylamine (1), showed marginal antifungal activity.

Gas chromatographic analysis of bacterial amines as their free bases.

Columns of Chromosorb 103, Tenax-GC, Amine 220 plus potassium hydroxide on Chromosorb W, and Carbowax 20M plus potassium hydroxide on Chromosorb W were compared for their ability to separate bacterial amines as their free bases in aqueous solution. A 1.52 m X 0.6 cm O.D. column of Chromosorb 103 separated eleven amines when operated isothermally at 185 degrees C. A further four high-boiling amines could be separated at 240 degrees C. The other packings separated only eight amines isothermally, except for Tenax-GC which separated seven of the free bases. Chromosorb 103 performed less well than Carbowax 20 M plus potassium hydroxide with respect to number of plates or peak resolution. The maximum number of amines separated, thirteen, required Chromosorb 103 programmed from 170 degrees C to 230 degrees C at 3 degrees C min-1 after an initial holding time of 20 min. It was possible tentatively to identify amines in culture supernatant fluid of Proteus mirabilis, viz. ethylamine, isobutylamine and isoamylamine, after direct injection of culture supernatant fluid.

Varacin and three new marine antimicrobial polysulfides from the far-eastern ascidian Polycitor sp.

Varacin [1] and three new antimicrobial marine polysulfides, varacins A-C [3-5], have been isolated from the Far Eastern ascidian Polycitor sp. Their structures have been elucidated by spectroscopic methods and by chemical transformations.