Hydrazone-based ligands for micro-solid phase extraction-high performance liquid chromatographic determination of biogenic amines in orange juice

Eight hydrazone-based ligands were synthesized, trapped in a silica sol-gel matrix, and were subsequently used in the micro-solid phase extraction (μ-SPE) of biogenic amines (BAs). The BAs investigated were tryptamine, phenylethylamine, putrescine, histamine, tyramine and spermidine. Prior to the extraction, dansyl chloride was added to the samples which were heated to 70°C for 10 min. The samples were extracted with μ-SPE, after which analytes were desorbed using acetonitrile via ultrasonication. The extracts were analysed by high performance liquid chromatography (HPLC) with ultraviolet detection. Of the eight ligands investigated as sorbents, benzophenone 2,4-dinitrophenylhydrazone was found to be the most promising. The enhanced π-π interaction between the analytes and the ligand facilitated the adsorption process. Under the most suitable extraction conditions, the method demonstrated good linearity with correlation coefficient of more than 0.985 over a concentration range of 1-50 μg L(-1). Satisfactory repeatability with relative standard deviations of 7.43-11.30% (n=3) were obtained. Detection limits ranged from 3.8 to 31.3 ng L(-1). The μ-SPE method exhibited lower recoveries (71.5-87.4%) when compared to the solid phase extraction technique (79.7-95.0%), but enrichment factors of 94-460 were obtained. The proposed μ-SPE-HPLC method was applied to the determination of BAs in orange juice purchased from local supermarkets, with satisfactory results. The orange juices were characterized by the presence of relatively high levels of putrescine (range, 550-2210 μg L(-1)) but tryptamine and phenylethylamine were not detected in any of the tested samples.     

Environmentally friendly solid‐phase microextraction coupled with gas chromatography and mass spectrometry for the determination of biogenic amines in fish samples

In this work, a facile and environmentally friendly solid‐phase microextraction assay based on on‐fiber derivatization coupled with gas chromatography and mass spectrometry was developed for determining four nonvolatile index biogenic amines (putrescine, cadaverine, histamine, and tyramine) in fish samples. In the assay, the fiber was firstly dipped into a solution with isobutyl chloroformate as derivatization reagent and isooctane as extraction solvent. Thus, a thin organic liquid membrane coating was developed. Then the modified fiber was immersed into sample solution to extract four important bioamines. Afterwards, the fiber was directly inserted into gas chromatography injection port for thermal desorption. 1,7‐Diaminoheptane was employed as internal standard reagent for quantification of the targets. The limits of detection of the method were 2.98–45.3 μg/kg. The proposed method was successfully applied to the detection of bioamines in several fish samples with recoveries ranging 78.9–110%. The organic reagent used for extraction was as few as microliter that can greatly reduce the harm to manipulator and environment. Moreover, the extraction procedures were very simple without concentration and elution procedures, which can greatly simplify the pretreatment process. The assay can be extended to the in situ screening of other pollutant in food safety by changing the derivatization reagent.     

Extraction of biogenic amines and their dansyl derivatives with reverse microemulsions of bis [2-ethylhexyl] sulphosuccinate (AOT) prior to high-performance liquid chromatographic determination

The ability of reverse microemulsions of the surfactant bis [2-ethylhexyl] sulphosuccinate (AOT) in heptane to extract and preconcentrate eight biogenic amines present in aqueous matrices has been explored. The “phase transfer” method, in which the surfactant solution is contacted with an aqueous salt solution containing the analytes, has been used as the analytical methodology. The extraction efficiencies have been compared with those obtained by using the “cloud point” extraction technique with Triton X-114 as surfactant, and with methylene chloride as a typical extracting solvent. In order to improve extraction and detection as compared with the underivatized amines, the fluorescent reagent dansyl chloride has been used to obtain the more hydrophobic and thus, easily extractable dansyl derivatives. Although extraction of most of the biogenic amines is high, extraction of their dansyl derivatives is practically 100%. The procedure was successfully applied to the analysis of commercial fruit juices. The analytical methodology is sensitive, fast, simple and reproducible. The LOD were in the vicinity of 1 and 2 pmol, which is similar or better than other techniques. The micellar phase is compatible with reverse phase HPLC mobile phases, which allow direct injection of the analyte after extraction. This is an advantage over solid phase extraction (SPE), where incomplete recovery can occur. Moreover, AOT showed to be better extracting surfactant for biogenic amines (and their corresponding dansyl derivatives) than Triton X-114 at the same concentration.     

Sensitive determination of biogenic amines by capillary electrophoresis with a new fluorogenic reagent 3-(4-fluorobenzoyl)-2-quinolinecarboxaldehyde

An effective approach was proposed to the derivatization of seven biogenic amines using 3-(4-fluorobenzoyl)-2-quinolinecarboxaldehyde (FBQCA) as a fluorogenic reagent. The sensitive determinations of these derivatives were achieved by micellar electrokinetic capillary chromatography (MEKC) with laser-induced fluorescence (LIF) detection. The derivatization and electrophoretic conditions have been optimized. A running buffer was composed of mixtures of 25 mM pH 9.5 boric acid, 25 mM SDS, and 27% ACN. At 25 °C and 22.5 kV, the baseline separation of the derivatives was accomplished in 13 min. The detection limit (S/N = 3) was found as low as 0.4 nM. The proposed method was validated by the linearity of two orders magnitude and correlation coefficient in the range 0.9969–0.9998. Also, the procedure was successfully applied to the determination of biogenic amines in soy sauce, fish and wine samples.     

Novel (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles from (E)- and (Z)-3-styrylchromones: the unexpected case of (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles

An efficient synthetic method for the preparation of (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles has been developed. The reaction of (E)- and (Z)-3-styrylchromones with hydrazine hydrate afforded the corresponding (E)- and (Z)-4-styrylpyrazoles, respectively, saved 4′-nitro-derivatives where both (E)- and (Z)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations was discussed and the stereochemistry of all products was assigned by NMR experiments.     

Synthesis, characterization and crystal structures of polymeric and dimeric triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls

The triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls (aryls = 4-CH₃, 4-Br, 4-Cl, 4-OCH₃) have been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn-NMR, ESI mass spectrometry, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The crystal structures of a representative carboxylate ligand (aryl = 4-CH₃) and three Sn complexes, viz., polymeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])_n (X = Me (1) and Br (2)) and dimeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])₂ (X = OMe (4)) complexes are reported. The coordination environment in each complex is trigonal bipyramidal trans-Ph₃SnO₂. A single zwitterionic carboxylate ligand bridges adjacent Sn atoms via the carboxylate and phenoxide O atoms.     

Stereoselective synthesis of Z-3-alkoxy-2-[(4′-methoxyphenyl)methylidene]-1(3H)-isobenzofuranones

Photoreorganisation of 2-alkoxy-2-(4′-methoxyphenyl)-1H-indene-1,3(2H)-diones in anhydrous acetone affords exclusively Z-3-alkoxy-3-[(4′-methoxyphenyl)methylidene]-1(3H)-isobenzofuranones. The products were identified by X-ray crystallography of one of them.     

Determination of primary biogenic amines in various food products using isocratic HPLC with 3-(4-chlorobenzoyl)-quinoline-2-carboxaldehyde as a new precolumn fluorogenic reagent

A simple HPLC approach has been successfully established for the sensitive determination of six biogenic amines (BAs) in food samples. The method involves derivatization with 3-(4-chlorobenzoyl)-quinoline-2-carboxaldehyde newly synthesized as a new fluorogenic reagent followed by LC isocratic elution mode. The optimization of both derivatization and separation conditions is carefully studied. Related analyses of the eluted compounds, in the presence of MeOH/THF/H(2)O (78:2.5:19.5 v/v/v) as a mobile phase containing 8 mM, pH 6.0 phosphate buffer solution, have been carried out on a C(18) column. The LOD (S/N = 3) of 2.5 nM, RSD value from 1.0 to 5.1% in peak areas, and good response linearity (R(2) >0.9936) are provided with fluorescence detection at lambda(ex)/lambda(em) = 480/545 nm. Obviously, recovery ranging from 95 to 107% in this method demonstrates its accuracy for determination of histamine, tyramine, 2-phenylethylamine, putrescine, cadaverine, and spermidine in the storage fish sample. Thus, the present method could be developed to monitor BAs in fish, cucumber, and spinach samples.     

Sensitive determination of strongly polar aromatic amines in water samples by stir bar sorptive extraction based on poly(vinylimidazole-divinylbenzene) monolithic material and liquid chromatographic analysis

A simple and sensitive method for the determination of polar aromatic amines (PAAs) was developed using stir bar sorptive extraction (SBSE) coupling to high-performance liquid chromatography. A hydrophilic poly(vinylimidazole-divinylbenzene) (VIDB) monolithic material was prepared and acted as SBSE coating. The influences of polymerization conditions for VIDB on the extraction efficiency were investigated using aniline and 2,4-dinitroaniline as detected solutes. To achieve optimum extraction performance for PAAs, several parameters including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. The results showed that under the optimized experimental conditions, the method showed good sensitivity and excellent recoveries, as well as advantages such as linearity, simplicity, low cost and high feasibility. The extraction performance of present method to the target compounds also compared with commercial SBSE which using polydimethylsiloxane as coating and other SBSE which based on monolithic materials. Finally, the proposed method was successfully applied to the determination of PAAs in lake and sea waters, and excellent recoveries of spiked target compounds in real samples were obtained.     

Preparation, crystal structure, and spectroscopic, chemical, and electrochemical properties of (2E,4E)-4-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-1,3-butadiene compared with those of (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene

Wittig reaction of 3-[4-(dimethylamino)phenyl]propanal (5) with (3-guaiazulenylmethyl)triphenylphosphonium bromide (4) in ethanol containing NaOEt at 25 °C for 24 h under argon gives the title (2E,4E)-1,3-butadiene derivative 6E in 19% isolated yield. Spectroscopic properties, crystal structure, and electrochemical behavior of the obtained new extended π-electron system 6E, compared with those of the previously reported (E)-2-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)ethylene (12), are documented. Furthermore, reaction of 6E with 1,1,2,2-tetracyanoethylene (TCNE) in benzene at 25 °C for 24 h under argon affords a new Diels-Alder adduct 8 in 59% isolated yield. Along with spectroscopic properties of the [π4+π2] cycloaddition product 8, the crystal structure, possessing a cis-3,6-substituted 1,1,2,2-tetracyano-4-cyclohexene unit, is shown. Moreover, reaction of 6E with (E)-1,2-dicyanoethylene (DCNE) under the same reaction conditions as the above gives no product; however, this reaction in p-xylene at reflux temperature (138 °C) for four days under argon affords a new Diels-Alder adduct 9 in 54% isolated yield. Although reaction of 6E with DCNE in toluene at reflux temperature (110 °C) for four days under argon provides 9 very slightly, reaction of 6E with dimethyl acetylenedicarboxylate (DMAD) in toluene at reflux temperature for two days under argon yields a new Diels-Alder adduct 10, in 58% isolated yield, which upon oxidation with MnO₂ in CH₂Cl₂ at 25 °C for 1 h gives 11, converting a (CH₃)₂N-4″ into CH₃NH-4″ group, in 37% isolated yield. The crystal structure of 11 supports the molecular structure 10 possessing a partial structure cis-3,6-substituted 1,2-dimethoxycarbonyl-1,4-cyclohexadiene. The title basic studies on the above are reported in detail.     

A new Cu(II)-5-(4-sulphophenylazo)-8-aminoquinoline complex used for copper determination in presence of gold and silver in water and mineral samples

In this work, a characterization of reagent chromophere 5-(4-sulphophenylazo)-8-aminoquinoline [SPA] by IR and ¹H RMN was carried out and a pK_a value of 3.55 ± 0.03 was found as well. An 1:2 stoichiometry for the Cu(II)-SPA complex was determined at pH 9 by Job and molar ratio methods. A value of 1.4 × 10¹⁴ for the stability constant was also found. Based on the formation of this complex a new method for the copper determination in presence of gold and silver was developed by derivative spectrophotometry using a previous preconcentration on solid phase. In this method, the analytical measures were executed directly in the solid phase containing the complex. The Cu(II) reacts with the reagent chromophere SPA previously retained in the anionic exchange DEAE Sephadex A25. In this determination, the first derivative at 605 nm was used. The quantification range was between (3.2 ± 0.3 × 10⁻¹) × 10⁻⁸ and (94.4 ± 0.9) × 10⁻⁸ mol L⁻¹ (3.2 ± 0.3 × 10⁻¹) × 10⁻⁸ , and (94.4 ± 0.9) × 10⁻⁸ mol L⁻¹. The repeatability expressed as RSD was between 1.1 and 2.0%. The method was applied successfully for the copper determination in mineral residuals and natural water samples. The results were consistent with those provided by ICP-mass spectrometry.     

Improved derivatization technique for gas chromatography-mass spectrometry determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone in drinking water

The quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (Mutagen X or MX) in drinking water is difficult due to the low concentration of MX in drinking water, its high sensitivity to pH change, and matrix effects that interfere with the derivatization and analysis. Typically, the quantification of MX involves derivatization by methylation. We present a one-step derivatization procedure for MX using N-methyl-bis-trifluoroacetamide (MBTFA) and analysis by ion trap GC/MS/MS. The new method resulted in a significant reduction in analysis time, and improved detection limits. The abundant and selective ions in the mass spectrum of the trifluoroacylated MX (trifluoroacetic acid-4-chloro-3-dichloromethyl-5-oxo-2-hydro-furan-2-yl ester) allowed for a clear identification and quantification of the compound, with a method detection limit of 7.7 ng L⁻¹, and a limit of quantitation of 24.4 ng L⁻¹. The trifluoroacylated MX was shown to be stable for 30 days in an excess of the derivatization reagent. The new method was applied for the determination of MX in several drinking water samples, with a concentration range from not-detected to 517 ng L⁻¹; these values are comparable to those obtained in previous studies. The development of this new simplified analytical method for MX is an important step forward in the field of disinfection by-product (DBP) research, particularly in light of the recent scientific recognition of halogenated furanones as emerging drinking water contaminants. Increased analytical ability may well be a decisive factor in the monitoring of these disinfection by-products.     

Facile synthesis of poly(ionic liquid)‐bonded magnetic nanospheres as a high‐performance sorbent for the pretreatment and determination of phenolic compounds in water samples

Poly(ionic liquid)‐bonded magnetic nanospheres were easily synthesized and applied to the pretreatment and determination of phenolic compounds in water samples, which have detrimental effects on water quality and the health of living beings. The high affinity of poly(ionic liquid)s toward the target compounds as well as the magnetic behavior of Fe₃O₄ were combined in this material to provide an efficient and simple magnetic solid‐phase extraction approach. The adsorption behavior of the poly(ionic liquid)‐bonded magnetic nanospheres was examined to optimize the synthesis. Different parameters affecting the magnetic solid‐phase extraction of phenolic compounds were assessed in terms of adsorption and recovery. Under the optimal conditions, the proposed method showed excellent detection sensitivity with limits of detection in the range of 0.3–0.8 ng/mL and precision in the range of 1.2–3.3%. This method was also applied successfully to the analysis of real water samples; good spiked recoveries over the range of 82.5–99.2% were obtained.     

Synthesis of 4-hydroxy-3-[(E)-2-(6-substituted-9H-purin-9-yl)vinyl]coumarins as lipoxygenase inhibitors

The synthesis of 4-hydroxy-3-[(E)-2-(6-substituted-9H-purin-9-yl)vinyl] coumarins has been achieved from the reactions of 4-hydroxycoumarin with 2-(6-substituted-9H-purin-9-yl)acetaldehydes in DMF under heating. The new compounds showed significant lipoxygenase inhibitory activity (e.g., 6a: IC₅₀ = 6.25 μM).     

Grafting of poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide] copolymer onto siliceous support for preconcentration and determination of lead (II) in human plasma and environmental samples

A method is reported for surface grafting of polymer containing a functional monomer for metal chelating, poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide] (poly(AGE/IDA-co-DMAA) onto silica modified by silylation with 3-mercaptopropyltrimethoxysilane. Monomer 1-(N,N-bis-carboxymethyl)amino-3-allylglycerol (AGE/IDA) was synthesized by reaction of allyl glycidyl ether with iminodiacetic acid. The resulting sorbent has been characterized using FT-IR, elemental analysis, thermogravimetric analysis (TGA), FT-Raman and scanning electron microscopy (SEM) and evaluated for the preconcentration and determination of trace Pb(II) in human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 5.5. The sorption capacity of functionalized resin was 15.06 mg g⁻¹. The chelating sorbent can be reused for 15 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 96.2% was obtained for the metal ion with 0.5 M nitric acid as eluting agent. The profile of lead uptake by the sorbent reflects good accessibility of the chelating sites in the poly(AGE/IDA-co-DMAA)-grafted silica gel. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb(II) by modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. On the basis of equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined as 0.70, 1.35 and 2.7, respectively at pH 5.5 and 20 °C. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption.     

Confirmatory development and validation of HPLC-DADmethod for the determination of tetracyclines in gilthead seabream (Sparus aurata) muscle tissue

A confirmatory high-pressure liquid chromatographic method for the determination of nine tetracyclines in Sparus aurata (gilthead seabream) muscle tissue is developed and presented herein. Tetracycline, 4-epi-tetracycline, oxytetracycline, 4-epi-oxytetracycline, chlortetracycline, 4-epi-chlortetracycline, doxycycline, methacycline and demeclocycline were separated on a Kromasil, C18 (250 mm × 4 mm, 5 μm) analytical column by gradient elution with a mobile phase consisting of 0.001 M ethylenediaminetetraacetic acid/sodium salt and acetonitrile at 25°C. Diode array detection with monitoring at 280 nm (for the determination of chlortetracycline, 4-epi-chlortetracycline, methacycline and demeclocycline) and 355 nm (for tetracycline, 4-epi-tetracycline, oxytetracycline, 4-epi-oxytetracycline and demeclocycline) was applied for peak identification and quantification of analytes. Examined antibiotics were isolated from gilthead seabream tissue by leaching using a citrate buffer (pH 4.0) and purified by solid phase extraction using Oasis HLB(200 mg/6 mL) cartridges. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity according to the European Union Decision 2002/657/EC.     

Synthesis,characterization and antimicrobial activity of Ni(II) and Zn(II) complexes with N′,N′-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide. Crystal structures of two highly solvated bimetallic complexes of Ni(II)

The bimetallic [Ni₂(H₂L2)₂](ClO₄)₄ (1), [Ni₂(HL2)(H₂L2)](ClO₄)₃ (2) and [Zn₂(H₂L2)₂](BF₄)₄ (3) complexes (H₂L2 = N′,N′²-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide) were synthesized and characterized. The structure of complexes (1) and (2) was established by X-ray analysis. NMR spectroscopy was used for the characterization of complex (3). The complexes (1) and (2) were obtained from the same synthetic reaction and two crystal types of these complexes have been isolated during the fractional crystallization process.     

(E, E)S, S′-bis(2-benzimidazolylmethyl) dithioglyoxime, synthesis and characterization of heterotrinuclear complexes of and determination of their metal contents by EDXRF analysis

A vicinal dioxime ligand with two 2-benzimidazolylmethyl groups, namely S, S′-bis(2-benzimidazolylmethyl) dithioglyoxine (H₂L) and its axially pyridine and 2,6-dimethyl pyridine bonded Co(III) complexes were prepared according to prior literature [Y. Gök, S.Z. Y?ld?z, Synth. React. Inorg. Met-Org. Chem. 22 (9) (1992) 1327]. BF₂⁺ bridged Co(III) complexes have been synthesized via the hydrogen-bridged Co(III) complexes by using borontrifloride ethyl ether complex. Heterotrinuclear complexes have been prepared by the reaction of these more soluble BF₂-capped Co(III) complexes with stoichiometric amount of CdCl₂ · H₂O and NiCl₂ · 6H₂O salts. Using ¹H, ¹³C NMR, IR and MS spectral data and elemental analysis, the structures of the complexes were identified. Qualitative and quantitative determination of Co, Ni and Cd contents of the heterotrinuclear complexes have been investigated by energy dispersive X-ray fluorescence (EDXRF) method. An annular 50 mCi ²⁴¹Am radioactive source emitting 59.543 keV photons was used for excitation and Si(Li) detector having 157 eV FWHM at 5.9 keV was used for intensity measurements.     

Study on the solid phase extraction and spectrophotometric determination of cobalt with 5-(2-benzothiazolylazo)-8-hydroxyquinolene

A highly sensitive, selective and rapid method for the determination of cobalt based on the rapid reaction of cobalt(II) with 5-(2-benzothiazolylazo)-8-hydroxyquinolene BTAHQ and the solid phase extraction of the Co(II)-BTAHQ complex with C18 membrane disks were developed. In the presence of pH = 6.4 buffer solution and cetylpyridenium chloride (CPC) medium, BTAHQ reacts with cobalt to form a deep violet complex with a molar ratio of 1:1 (cobalt to BTAHQ). This complex was enriched by the solid phase extraction with C18 membrane disks. An enrichment factor of 100 was obtained by elution of the complex from the disks with a minimal amount of isopentyl alcohol. In isopentyl alcohol medium, the molar absorptivity of the complex is 2.42 × 10⁵ L mol⁻¹ cm⁻¹ at 658 nm. Beer’s law is obeyed in the range of 0.01–0.38 μg mL⁻¹ in the measured solution. The relative standard deviation for 11 replicate samples of 0.20 μg mL⁻¹ level is 1.37%. The detection and quantification limits reach 3.1 and 9.7 ng mL⁻¹ in the original samples. This method was applied for the determination of cobalt in biological, water, soil and pharmaceutical preparation samples with good results.     

(E)-3-(meso-Octamethylcalix[4]pyrrol-2-yl)propenal: a versatile precursor for calix[4]pyrrole-based chromogenic anion sensors

The synthesis of (E)-3-(meso-octamethylcalix[4]pyrrol-2-yl)propenal and its use in Knoevenagel reactions are described. The resulting compounds display sharp changes in color in the presence of fluoride, acetate, and dihydrogen phosphate anions.