Chromophore formation in resorcinarene solutions and the visual detection of mono- and oligosaccharides

The colorimetric properties of resorcinarene solutions had not been investigated since Baeyer's initial synthesis. We recently reported that solutions containing resorcinarene macrocycles develop color upon heating or standing. In the presence of saccharides, these solutions exhibit significant color changes which are easily seen. We herein present strong evidence that the solution color is due to macrocycle ring opening and oxidation. The optical responses to saccharides are due to complexation of the sugar with the acyclic chromophores. We apply these mechanistic insights toward the challenging problem of the visual detection of neutral oligosaccharides by simple chromogens. In addition, we also report the first single-crystal X-ray crystal structure determination of a rarely observed "diamond" resorcinarene stereoisomer.     

Highly sensitive chemosensor for detection of PPi with improved detection limit

We have developed a new chemosensor 1·2Zn for the detection of PPi in an aqueous solution by photo-induced electron transfer. Two coumarin units were introduced to enhance the fluorescent signals. Consequently, this chemosensor showed an improved detection limit as compared to the previously reported chemosensor 2·2Zn.     

Postcolumn reactor using a laser-drilled capillary for light-emitting diode-induced fluorescence detection in CE

This study investigated a novel postcolumn reactor for fluorescence detection in CE. A laser-drilled capillary, with an aperture made by laser ablation, was used for mixing derivatization reagents with the analytes separated by CZE. The derivatization reagents, o-phthaldialdehyde (OPA), and 2-mercaptoethanol, were introduced into the capillary through the aperture and reacted with the analytes after CZE separation. High voltages were applied to both the inlet reservoir and the reservoir filled with the derivatization reagents. Thus, the flow rate of the derivatization reagents was controlled by the electric potential that was applied to the reservoir of the derivatization reagents. A UV light-emitting diode was used as an excitation light source for the fluorescence detection of OPA derivatives. A commercially available tee connector was compared with the laser-drilled capillary. The results implied that the dead volume of the laser-drilled capillary was less than that of the tee connector, since the laser-drilled capillary suppressed band broadening more efficiently. The LODs for amino acids were determined to be approximately 5 microM. The method was applied to the determination of amino acids in a Japanese beverage.     

Selective oxidative debenzylation of mono- and oligosaccharides in the presence of azides

When using benzyl ethers as permanent protecting groups in oligosaccharide synthesis selective oxidative debenzylation with NaBrO(3) + Na(2)S(2)O(4) under biphasic conditions is efficient and compatible with anomeric azides and many other functions.     

Trifluoroacetyl-chlorin as a new chemosensor for alcohol/amine detection

Chlorophyll derivative possessing a trifluoroacetyl group at the 3-position was synthesized as a new chemosensor for alcohols and amines. Intense Q_y peak of the trifluoroacetyl-chlorin (701 nm in CHCl₃) showed blue shifts to 667 nm in MeOH and 665 nm in n-BuNH₂ due to the formation of the corresponding hemiacetal and hemiaminal with visible color changes. Thermodynamic parameters for the complexation between trifluoroacetyl-chlorin and n-BuNH₂ in CDCl₃ were determined to be ΔH = −48 kJ mol⁻¹ and ΔS = −147 J K⁻¹ mol⁻¹. Ratiometric fluorescence sensing of n-BuNH₂ in THF was also demonstrated.     

Unmodified fluorescein as a fluorescent chemosensor for fluoride ion detection

Unmodified fluorescein (1) behaves as a fluorescent chemosensor for F⁻ detection, where the F⁻-induced fluorescence enhancement is driven by a transfer of the phenolic OH protons to F⁻.     

Optimization of the capillary gas chromatographic analysis of mono- and oligosaccharides in honeys

Summary A capillary gas chromatographic method has been developed for simultaneous determination of at least 18 sugars (2 monosaccharides, 11 disaccharides and 5 trisaccharides) in honey, as their oxime-trimethylsilyl ethers. The chromatographic conditions have been systematically and thoroughly optimized, to eliminate the peak overlap commonly reported for this and other methods, especially for disaccharides. Complete analytical details are reported.     

Study of the nmr spectra of mono- and oligosaccharides in the region of a strong magnetic field

Conclusions An investigation of the NMR spectra of mono- and oligosaccharides in the region of a strong magnetic field permits a judgment of the conformational and configurational changes in the structure of monosaccharides, as well as the order and conformation of the bonds between monosaceharide residues in oligosaccharides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1854–1856, August, 1969.     

Fluorescent oligomer as a chemosensor for the label-free detection of Fe and dopamine with selectivity and sensitivity

In this article, a sensitive and selective turn-off fluorescence chemosensor, Tyloxapol (one kind of water soluble oligomer), was developed for the label-free detection of Fe³⁺ ions in aqueous solution. Fluorescence (FL) experiments demonstrated that Tyloxapol was a sensitive and selective fluorescence sensor for the detection of Fe³⁺ directly in water over a wide range of metal cations including Na⁺, K⁺, Ag⁺, Hg²⁺, Cd²⁺, Co²⁺, Cu²⁺, Cr³⁺, Mn²⁺, Ba²⁺, Zn²⁺, Ni²⁺, Mg²⁺, Ca²⁺, and Pb²⁺. Moreover, the fluorescence intensity of Tyloxapol has shown a linear response to Fe³⁺ in the concentration range of 0–100 μmol L⁻¹ with a detection limit of 2.2 μmol L⁻¹ in aqueous solution. Next, based on a competition mechanism, another turn-on sensing application of the Tyloxapol/Fe³⁺ platform to probe dopamine (DA) against various other biological molecules such as other neurotransmitters or amino acids (norepinephrine bitartrate, acetylcholine chloride, alanine, valine, phenylalanine, tyrosine, leucine, glycine, histidine) were also investigated. It is expected that our strategy may offer a new approach for developing simple, cost-effective, rapid and sensitive sensors in biological and environmental applications.     

Fluorescent detection of phosphate anion by a highly selective chemosensor in water

A macrocyclic dinuclear copper complex, [Cu₂^II(1)Br₄]·2H₂O has been synthesized and characterized by X-ray crystallography, in which each metal ion is pentacoordinated in a square pyramidal environment and the macrocycle is folded to form a boat-shaped empty cavity. As studied by an indicator displacement assay, the dinuclear complex shows strong selectivity for phosphate over sulfate, nitrate, perchlorate and halides in water at physiological pH.     

Postcolumn derivatization liquid chromatography/mass spectrometry for detection of chemical-weapons-related compounds

Postcolumn derivatization for liquid chromatography/mass spectrometry (LC/MS) analysis was characterized for detection of some compounds related to chemical-weapons (CW) agents using an Atmospheric Pressure Chemical Ionization (APCI) source. The derivatizing reagents were added directly to the LC eluent flow, and the derivatization reactions occurred in the APCI source under typical operating conditions. The compound S-[2-(diisopropylamino)ethyl] methylphosphonothioic acid was methylated using the derivatizing reagent trimethylphenyl ammonium hydroxide (TMPAH). Methylphosphonic acid was doubly derivatized to form dimethyl methylphosphonate, although the signal for the derivatization product was very sensitive to the amount of TMPAH. Arsenic compounds related to the CW agent lewisite, including chlorovinyl arsonous acid and arsenic (III) oxide, were derivatized using 2-mercaptopyridine. The thiol group reacted readily with the arsenic (III) center and provided a significant improvement in sensitivity relative to the underivatized signal using APCI or electrospray ionization. Triethanolamine and ethyl diethanolamine were derivatized with benzoyl chloride, a commonly used LC derivatizing reagent for alcohols, to modify their mass spectra. Postcolumn derivatization using an APCI source gives an alternative for detecting some difficult-to-ionize compounds. It has the limitations that sensitivity was not always improved even though the major mass spectral peaks can be shifted; it is necessary to carefully select the reagent; and some reagents introduced strong interference peaks at specific masses in the spectrum and may suppress the ionization of some derivatized analyte ions. The reagent also produced contamination in the source, which had to be cleaned daily.     

Application of Iodine-Azide Reaction as Postcolumn Reaction in HPLC for Determination of 2-Thiobarbituric Acid

The reaction between iodine and azide ion induced by 2-thiobarbituric acid (TBA) has been utilized as a postcolumn reaction for chromatographic determination of this sulphur compound. The method is based on the separation of thiobarbituric acid on an Nova-Pak® CN HP column with an acetonitrile–aqueous solution of sodium azide mobile phase. The separation stage is followed by spectrophotometric measurement of the residual iodine (λ=350 nm) from the postcolumn iodine-azide reaction induced by thiobarbituric acid after mixing iodine solution containing iodide with the column effluent containing azide ions and the inductor. Chromatograms obtained for thiobarbituric acid showed negative peaks as a result of the decrease in absorbance of background. The detection limit (defined as S/N=3) was 0.16 pmol (22.9 pg) for thiobarbituric acid. Calibration graphs, plotted as peak heights or peak area vs. concentrations, were linear up to 1 nM.     

Determination of mono- and disaccharides by capillary electrophoresis with contactless conductivity detection

The separation and detection of common mono- and disaccharides by capillary electrophoresis (CE) with contactless conductivity detection (CCD) is presented. At high values of pH, the sugars are converted to anionic species that can be separated by CE and indirectly detected by CCD. The main anionic species present in the running electrolytes are hydroxide and phosphate, which have greater mobility than the ionized sugars, and, thus, the indirect detection is possible. The method was applied to analysis of glucose, fructose, and sucrose in soft drinks, isotonic beverages, fruit juice, and sugarcane spirits. Galactose was used as internal standard in all cases. Plate numbers range from ca. 70,700 to 168,200 and the limits of detection from 13 to 31 microM.     

Oligosaccharide profiling: the facile detection of mono-, di- and oligosaccharides by electrospray orthogonal time-of-flight mass spectrometry using 3-aminophenylboronic acid derivatization

Monosaccharides, disaccharides and larger carbohydrates can be derivatized using 3-aminophenylboronic acid (3-APBA). This procedure is carried out at low pH (2.7-3.0) and allows the use of positive ion mode electrospray orthogonal time-of-flight mass spectrometry (ES-OTOFMS) to analyze the resulting boronate complexes. A carbohydrate profile map of a complex carbohydrate mixture, honey, was prepared which displayed superior sensitivity when compared with lithium ion cationization. Complexes formed using simple mono- and disaccharides show that facile in situ derivatization leads to an equilibrium mixture; which is reproducible for a specific set of electrospray conditions. D-Glucose could be detected at 5 microM concentration using the standard instrument spray interface. Lower detection levels of approximately 500 nM could be achieved using a nanospray device. The 3-APBA complexes are observed on instruments employing a low temperature interface (140-150 degrees C) which allows formation of the boronate species while still promoting efficient desolvation of the ions. The spectral identification of 3-APBA complexed carbohydrates in complex mixtures is facilitated by the easily observed 1 mass unit separated peak pair bearing the 1:4 ratio resulting from the natural isotopic abundance of (10)B and (11)B.     

Direct detection method of oligosaccharides by high-performance liquid chromatography with charged aerosol detection

A simple and rapid detection method of oligosaccharides using high-performance liquid chromatography with a charged aerosol detection (HPLC-CAD) was studied. The direct detection of a sialylglycopeptide (SGP) derived from egg yolk was accomplished by HPLC-CAD using an amido-silica column, and its limit of detection was 0.40 pmol [signal-to-noise ratio (S/N) = 3]. The sensitivity of this method was lower than that of the fluorescence detection; however, the method showed approximately 5 times higher sensitivity than that using the conventional UV absorbance detection. Furthermore, this method was used for the analysis of the acid hydrolysis products of SGP. Monosialo- and asialo-oligosaccharides as well as free sialic acid were detected without using fluorescent derivatization. These results indicate that the present method is a new tool for the analysis of oligosaccharides.     

HPLC with electrode array detection

Summary A fast method for the determination of amitrole in drinking and ground water is described. Amitrole is separated from other substances by HPLC. For the determination a highly sensitive coulometric electrode array detector is applied. Tap and well water with concentrations down to 0.1 g amitrole/L can be determined without any enrichment steps. The detection limit of amitrole added to Viennese tap water is 0.05 g/L.     

New colorimetric and fluorometric chemosensor based on a cationic polythiophene derivative for iodide-specific detection

Electrostatic interactions between anions and a new water-soluble, cationic, affinitychromic poly(3-alkoxy-4-methylthiophene) derivative provide a new tool for a selective optical detection method (colorimetric or fluorometric) for iodide ions.     

Investigations on inulin-type oligosaccharides with regard to HPLC analysis and prospective food applicability

Abstract  

Relevance of research on prebiotic food components is recently largely enhanced as consumption of health-promoting functional foodstuffs displays a definite increase. Since there is a direct correlation between oligomer distribution of inulin and its prebiotic effect, it is of crucial importance to be capable to characterize its actual composition in thermally treated food samples. A newly developed high performance liquid chromatography method is applied for the examination of plant inulin samples using evaporative light scattering detection. The procedure contains a direct detection procedure of native inulin/fructo-oligosaccharide components after dissolving the samples in water at room temperature and by detecting the chain-distribution with HPLC coupled with evaporative light scattering detection. The method is accurate, simple, and without interferences from the detectable signals of mono- and disaccharides as thermal decomposition products of inulin. The analytical procedure eliminates the need to use artificial chemical hydrolysis of the macromolecule. The fructo-oligosaccharide components have been investigated by mass spectrometric detection with APCI ionization. The composition of several industrial samples and the thermal properties of inulin have also been investigated in order to reveal exact composition of inulin comprising bakery products exposed to thermal treatment. The thermal degradation leads to increase of the prebiotic feature as well.