FTIR and Raman studies on benzimidazole

The FTIR and laser Raman spectra of benzimidazole have been recorded. The observed frequencies were assigned to various modes of vibrations on the basis of normal coordinate calculations, assuming C_s point group symmetry. The potential energy distribution associated with normal modes is also reported here. The assignment of fundamental vibrations agrees well with the calculated frequencies.     

Chromatographic behavior of benzimidazole derivatives on hypercrosslinked polystyrene by reverse-phase HPLC

Abstract

An important part in the research of separation of various compound classes is the study of relationship between structure and property by describing the effect of structure on compounds’ chromatographic retention. The aim of this work was to study the chromatographic retention of the firstly synthesized benzimidazoles from water-acetonitrile and water-methanol solutions on hypercrosslinked polystyrene (HCP) by high-performance liquid chromatography (HPLC). The effect of water-methanol and water-acetonitrile solutions’ composition on the benzimidazole derivative retention factors on HCP was studied. The thermodynamic characteristics of sorption of benzimidazoles’ transition from water-organic solutions onto the surface of HCP phase were obtained. The thermodynamic compensation effects were studied. It has been shown that the benzimidazole nitro derivative realizes additional specific interactions with the aromatic network of HCP. The slope ratio of the Soczewiński–Wachtmeister equation was calculated. It was shown that 1-hydroxymethylbenzimidazole and 2-aminobenzimidazole characterized by small volumes and containing hydrophilic substituents do not subordinate Soczewiński–Wachtmeister model under ranging from 75 to 85% concentrations of acetonitrile.     

Analysis of Non-volatile Constituents in Dracocephalum Species by HPLC and GC-MS

In this paper we identify/determine the composition of the extracts of Dracocephalum moldavica L. and D. ruyschiana L. with special emphasis on their flavonoids, aliphatic, aromatic carboxylic acids and sugars. The plant materials were extracted using methanol-acetone 1:1 (v/v) acidified with HCl (0.05%). Composition of extract's most red fractions was identified by HPLC, while the constituents of the entire extract were identified and quantified as their trimethylsilyl-(oxime) ether/ester derivatives by GC-MS. On the basis of HPLC analyses - (performed on Phenomenex Luna 5 µm C18 column, 250× 4.6 mm I.D.; eluent: acetonitrile - trifluoroacetic acid (0.1 %); isocratic/gradient conditions) - delphinidin, cyanidin and pelargonidin (in traces) were identified by spectral analysis and on the basis of authentic standard's addition. GC-MS analyses were carried out immediately with extracts, as well as subsequently to extract's hydrolysis (trifluoroacetic acid: 2M, 2h, 4h). Constituents were identified and quantified as their trimethylsilyl-(oxime) ether/ester derivatives, from a single run, on the basis of their total (TIC) and selective fragment ion (SIM) responses. Calculations were related to the dry matter content of extracts. As main constituents monosaccharides, sugar alcohols di- and trisaccharides, aliphatic (phosphoric, succinic, levulinic, malic, tartaric, fatty acids) and aromatic (quinic, chlorogenic, caffeic, ferulic, 3,4-dihydroxyphenyllactic, rosmarinic) carboxylic acids and their corresponding esters; apigenin, luteolin flavon aglycons and tocopherol, in total 33 constituents were quantitated partly by their TIC, partly by their SIM responses. Identification/quantification proved to be in total of 35–69% (expressed in the dry matter content of extracts).     

Evaluation of polycyclic aromatic hydrocarbons in gasoline by HPLC and GC-MS

Summary In this paper the evaluation of polycyclic aromatic hydrocarbons (PAHs) in gasoline is described. A procedure involving a double extraction of samples with N-methylpirrolidone-water-phosphoric acid and with cyclohexane has been used followed by HPLC-DAD and GC-MS. The results obtained show that all gasoline samples contain PAHs with two to six rings and no substantial difference was noticed between leaded and unleaded gasoline. The benzo(a)-pyrene content ranged between 1.0–2.0 mg L⁻¹, a comparatively high concentration for a dangerous compound.     

GC-MS与HPLC/DAD联用对纺织品中4-氨基偶氮苯的测定

从化学反应条件的控制及气相色谱-质谱(GC-MS)和高效液相色谱/二极管阵列检测器(HPLC/DAD)联用方面,探讨了4-氨基偶氮苯的检测方法。实验表明,在样品中加入氢氧化钠,样品中的4-氨基偶氮苯和新鲜配制的连二亚硫酸钠发生反应,使4-氨基偶氮苯的碳碳双键断裂。释放的4-氨基偶氮苯在氯化钠存在的混合物中与叔丁基甲醚进行液液萃取。取叔丁基甲醚层进行分析,通过GC-MS的保留时间及特征离子碎片并结合HPLC/DAD紫外法对4-氨基偶氮苯进行定性和定量分析。4-氨基偶氮苯在2.5~30 mg/kg范围内呈良好的线性关系,其线性方程为:y=91.23x+5.272,相关系数r=1.000,检出限为3.20 mg/kg,平均回收率不低于90%。     

Kinetics and mechanism of amitraz hydrolysis in aqueous media by HPLC and GC-MS

Degradation processes of amitraz in aqueous media have been studied by spectrophotometry, HPLC and GC-MS. Amitraz undergoes hydrolysis reactions at any pH, but towards the acidic pH range hydrolysis proceeds at a faster rate. Depending on the pH value, different products of the hydrolysis have been identified. The main degradation products are 2,4-dimethylaniline at very acidic pH values (pH<3), N-(2,4-dimethylphenyl)-N'-methylformamidine and 2,4-dimethylphenylformamide at less acidic media (pH 3-6) and 2,4-dimethylphenylformamide at basic pH. The mechanisms of the different hydrolysis processes have been elucidated.     

Analysis of fossil-fuel fractions by on-line coupled microcolumn HPLC capillary column GC-MS

A multidimensional LC-GC-MS system was developed and used to analyze complex fossil-fuel samples. The electron-acceptor stationary phase, 5 μm 2,4-dinitrophenylmercaptopropylsilica, was packed into a 0.32-mm × 350-mm microcapillary liquid chromatography (μLC) column. Aromatic fractions eluted from the μLC system at 12 μL/min and were diverted to the gas chromatograph mass spectrometer (GC-MS) by a ten-port switching valve with 50 and 7.6-μL loops. Concurrent cosolvent evaporation occurred in a 0.32-mm × 3-m precolumn ahead of a 0.25-mm × 30-m DB-5 analytical column. Solvent vapors exited through an open-split interface. The utility of the μLC-GC-MS system was demonstrated through the analyses of solvent refined coal, kerosene, and crude oil.     

pH-metric studies on ternary metal complexes of some amino acids and benzimidazole

The stability constants of binary and ternary complexes of copper(II) and nickel(II) with some amino acids (d-histidine, dl-serine, lysine) as primary ligands and benzimidazole as a secondary ligand were determined pH-metrically. The study was conducted in 10% (v/v) ethanol-H(2)O medium and at an ionic strength of 0.1 mol dm(-3) NaNO(3) at 20 +/- 1 degrees C, Values of Delta log K were discussed on the basis of statistical considerations and the nature of the species formed. The stability of the binary and mixed ligand complexes are discussed in terms of the molecular structure of benzimidazole and the amino acids as well as the nature of the metal ion.     

Gravimetric and thermogravimetric studies of zinc and mercury with benzimidazole

Summary Methods are proposed for the gravimetric determination of zinc and mercury with benzimidazole at pH ranges of 8.4–10.0 and 9.0–10.0, respectively. Using suitable masking agents zinc has been separated from a large number of diverse ions. Thermograms of the zinc and mercury complexes reveal that they are extraordinarily stable up to 520° and 340°C.

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Zusammenfassung Zur gravimetrischen Bestimmung von Zink oder Quecksilber wird die Fällung mit Benzimidazol bei pH 8,4–10,0 bzw. 9,0–10,0 empfohlen. Zink kann bei Verwendung geeigneter Maskierungsmittel mit guter Genauigkeit von zahlreichen Fremdionen abgetrennt werden. Durch thermogravimetrische Untersuchungen wurde festgestellt, daß die Zn-bzw. Hg-Komplexe bis zu 520 bzw. 340° C beständig sind.

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The work was carried out at Chemistry Department, Jadavpur University, Calcutta-32, India.     

Determination of metabolites in Uncaria sinensis by HPLC and GC-MS after green solvent microwave-assisted extraction

Uncaria sinensis (Oliv.) Havil (Rubiaceae) has been used as an important Traditional Chinese Medicine (TCM) herb for the treatment of fevers and various nervous disorders. The major bioactive secondary metabolites from different classes of chemical compounds, i.e. organic acid, flavonoid and alkaloid, present in this TCM herb, namely catechin, caffeic acid, epicatechin and rhynchophylline, were extracted by microwave-assisted extraction (MAE) method with ultra-pure water as the extraction solvent. The optimal extraction conditions for this green solvent MAE method were found to be 100 °C for 20 min. The recoveries of the compounds were found to be comparable to that of heating under reflux using ultra-pure water for 60 min. The method precision (RSD, n = 6) was found to vary from 0.19% to 5.60% for the proposed method on different days for the secondary metabolites. Simultaneously, the key primary metabolites such as sucrose and phenylalanine for the biosynthesis of bioactive secondary metabolites were successfully characterized by GC-MS. Furthermore, an approach using the combination of primary and secondary metabolite profiling based on their chemical fingerprints with Principal Component Analysis (PCA) was successfully developed to evaluate the quality of U. sinensis obtained from different sources. This approach was shown to be feasible in discriminating U. sinensis from different origins and thus a potential application for the quality control of other medicinal herbs.     

Determination of airborne carbonyls via pentafluorophenylhydrazine derivatisation by GC-MS and its comparison with HPLC method

The classical analytical method for gaseous carbonyl measurements based on solid sorbent coated with 2,4-dinitrophenylhydrazine (DNPH) and analysis by HPLC/UV suffers from limited resolution of carbonyls with similar molecular structures and high molecular weights. In this paper, we report the development of a sensitive and reliable analytical method for simultaneous determination of 21 airborne carbonyls within the C₁-C₉ range. Carbonyls were collected on a sampling tube filled with 100 mg Tenax TA (60-80 mesh) sorbent coated with 1 μmol pentafluorophenyl hydrazine (PFPH), followed by solvent desorption and analysis by gas chromatography (GC)/mass spectrometry (MS). Common carbonyl gases including formaldehyde, acetaldehyde, butyraldehyde, hexaldehyde and benzaldehyde at ppbv levels were collected with efficiency greater than 90% onto sampling tubes at a flow rate of 100 mL min⁻¹. The limits of detection (LODs, signal/noise = 3) of the tested carbonyls were in the range of 0.08-0.20 ppbv for a sampled volume of 24.0 L. These limits are less than or comparable with those that can be obtained using the DNPH-HPLC method. The method has been field-tested both in ambient air of York and in diluted cigarette smoke. Comparing field tests with the classical DNPH-HPLC method, good agreement was displayed between the two methods for the same carbonyls, but with more carbonyl species detected by the PFPH-GC/MS method. The PFPH-GC/MS method provides better molecular separation for carbonyls with similar structures, is highly sensitivity and gives confirmation of identification by structures when detected using MS.     

Separation and analysis of nitroarenes from airborne particulate organic matter by HPLC and capillary GC-MS methods

Normal-phase HPLC has been applied to the separation of nitroarenes from dichloromethane extracts from airborne particulate matter samples collected in urban regions of Upper Silesia. GC-MS and capillary gas chromatography with NP detector analysis of the nitroarene fraction made it possible to identify and determine quantitatively those compounds which dominate in the organic matter emitted to the atmosphere in highly industrialized regions (2-nitrofluorene, isomeric nitroarenes of MW = 247, i.e. nitropyrene/nitrofluoranthene/nitroacephenanthrylene).     

Preparation of stir cake sorptive extraction based on polymeric ionic liquid for the enrichment of benzimidazole anthelmintics in water,honey and milk samples

In this work, a new stir cake sorptive extraction (SCSE) using polymeric ionic liquid monolith as sorbent was prepared. The sorbent was obtained by in situ copolymerization of an ionic liquid, 1-allyl-3-methylimidazolium bis[(trifluoro methyl)sulfonyl]imide (AMII) and divinylbenzene (DB) in the presence of N,N-dimethylformamide. The influence of the content of ionic liquid and the porogen in the polymerization mixture on extraction performance was studied thoroughly. The physicochemical properties of the polymeric ionic liquid were characterized by infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry. The usefulness of SCSE–AMIIDB was demonstrated by the enrichment of trace benzimidazole anthelmintics. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of trace benzimidazoles residues in water, milk and honey samples was established by coupling SCSE–AMIIDB with high performance liquid chromatography/diode array detection (SCSE–AMIIDB–HPLC/DAD). Results indicated that the limits of detection (S/N = 3) for target compounds were 0.020–0.072 μg L⁻¹, 0.035–0.10 μg L⁻¹ and 0.026–0.076 μg L⁻¹ in water, milk and honey samples, respectively. In addition, an acceptable reproducibility was achieved by evaluating the repeatability and intermediate precision with relative standard deviations (RSD) of less than 9% and 11%, respectively. Finally, the established AMII–SCSE–HPLC/DAD method was successfully applied for the determination of benzimidazoles residues in milk, honey and environmental water samples. Recoveries obtained for the determination of benzimidazole anthelmintics in spiking samples ranged from 70.2% to 117.6%, with RSD below 12% in all cases.     

Determination of thermodynamic pKa values of benzimidazole and benzimidazole derivatives by capillary electrophoresis

Thermodynamic pK_a values for benzimidazole and several substituted benzimidazoles were determined by CE. Electrophoretic mobilities of benzimidazoles were determined by CE at different pH levels and ionic strengths. The dependence of electrophoretic mobilities on pH was used to obtain pK_a values at different ionic strengths. Extrapolations to zero ionic strength were used to determine the thermodynamic pK_a values. Using this method the thermodynamic pK_a values of 15 benzimidazoles were determined and found to range from 4.48 to 7.38. Results from the CE measurements were compared with spectrophotometric measurements which were evaluated at wavelengths where the highest absorbance difference for varying pH was recorded. The two analytical techniques were in good agreement.     

GC-MS and HPLC analyses of lignin degradation products in biomass hydrolyzates

Summary The gas-chromatographic separation of lignin degradation products of hydrolytically degraded biomass (e. g. poplar wood) and their mass spectrometric identification are described. For routine analysis of lignin degradation products of biomass hydrolyzates, a time saving HPLC gradient method using a UV-detection system (280 nm), is described. In addition to reference samples, solutions of hydrothermally degraded biomass were analyzed.

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GC-MS- und HPLC-Analytik von Ligninabbauprodukten in Biomassehydrolysaten

Zusammenfassung Die gas-chromatographische Trennung von Ligninabbauprodukten nach hydrolytischer Spaltung von Biomasse (z.B. Pappelholz) sowie die massenspektrometrische Identifizierung werden beschrieben. Für eine routinemäßige Analytik der Ligninabbauprodukte in Biomassehydrolysaten wird weiterhin die Trennung mittels einer Gradienten-HPLC-Methode aufgezeigt. Die Detektion erfolgte bei 280 nm. Neben Referenzproben wurden hydrothermale Abbaulösungen untersucht.

     

Synthesis and interaction studies of benzimidazole derivative with human serum albumin

A benzimidazole derivative, 1-(2-picolyl)-3-(2-picolyl) benzimidazole iodide (PPB), was synthesized. Fourier transform infrared spectroscopy (FT-IR), UV–visible, three-dimensional (3D) fluorescence, synchronous fluorescence (SF) and fluorescence spectroscopic methods were used to determine the PPB binding mode and the effects of PPB on protein stability and secondary structure. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of PPB to human serum albumin (HSA). The binding constants between PPB and HSA were obtained according to Scatchard equation. The number of binding sites, the binding constants and the thermodynamic parameters were measured. The results showed a spontaneous binding of PPB to HSA through hydrogen bonds and van der Waals forces. In addition, the distance between PPB and the Trp 214 was estimated via employing the Förster's non-radiative energy transfer theory, and was found to be 3.49 nm, which indicated that PPB can bind to HSA with high probability. Site marker competitive experiments indicated that the binding of PPB to HSA primarily took place in subdomain IIA.     

Comparative study of sample preparation methods; supported liquid membrane and solid phase extraction in the determination of benzimidazole anthelmintics in biological matrices by liquid chromatography-electrospray-mass spectrometry

Supported liquid membrane (SLM) and solid phase extraction (SPE) have been applied as clean-up and/or enrichment techniques for a mixture of five benzimidazole anthelmintics compounds, namely albendazole, fenbendazole, mebendazole, oxibendazole, and thiabendazole. Two biological matrices, mainly urine and milk, and ultra high purity (UHP) water were spiked with a mixture of these five compounds. Waters Oasis^® MCX and International Sorbent Technology (IST) HCX SPE sorbents were used. The liquid membrane used for clean-up and/or enrichment of these compounds was 5% tri-n-octylphosphine oxide (TOPO) dissolved in n-undecane/di-n-hexyl ether (1:1). The SLM extraction efficiencies and SPE percentage recoveries ranged between 60 and 100%. The detection limits (DLs) for different benzimidazole compounds by SPE/LC-ES-MS for thiabendazole, oxibendazole, and albendazole was 0.1 ng/L, for fenbendazole and mebendazole was 1 and 10 ng/L, respectively. Similarly, the detection limits of SLM/LC-ES-MS for thiabendazole, oxibendazole, and albendazole was 0.1 ng/L and for fenbendazole and mebendazole was 1 ng/L. The results of optimization of various parameters of the SLM method are reported.