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A kind of nanocomposites with good dispersion in water was prepared through noncovalent adsorption of toluidine blue (Tb) on multiwalled carbon nanotubes (MWCNT) for electric communication between horseradish peroxidase (HRP) and electrode. The nanocomposites could be conveniently cast on electrode surface. With the aid of chitosan, HRP was then immobilized on the nanostructure to form a reagentless...
Cachaça samples were studied by means of comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC/TOFMS) during the fermentation process and after ageing in different wood materials. The analyses of the aroma compounds were performed after headspace-solid phase microextraction method (HS-SPME) using an 85μm polyacrylate (PA) fibre. Fingerprint monitoring of the...
Despite that triazene reagents have been widely used for spectrophotometric determinations of cationic surfactants, the mechanism underlying such applications has yet to be studied. We report the synthesis of a new triazene reagent 5-methyl-2-[3-(4-phenylthiazol-2-yl)triazenyl]benzenesulfonic acid (MPTTBSA) and its interaction with N-cetylpyridinium chloride (CPC). The reagent was synthesized by coupling...
A simple and rapid method is described for reliable determination of ultra-trace concentrations of mercury based on a novel combination of a sequential injection (SI) system with cold vapour atomic absorption spectrometry (CVAAS). The SI–CVAAS method achieved a very high sampling frequency of 180h −1 , a detection limit of 0.2–0.3ngmL −1 , a dynamic range of 0–60ngmL −1 and...
Univariate (zero-order), multivariate (first-order) and multiway (second-order) calibrations were assayed for the determination of vinegar acidity using a mechanized procedure based upon vibrational spectroscopy and the emerging multicommutation methodology. The second-order methodology relies on the use of a flow system based on multicommutation and binary sampling. The flow network comprises a set...
A high-performance liquid chromatography–tandem mass spectrometric method (LC/MS/MS) has been developed and validated for the determination of pegylated liposomal doxorubicin and its metabolite doxorubicinol in rat plasma. One hundred microliters plasma samples were treated with Triton X-100 to immediately disperse the liposome. Then the samples were extracted by a single methanol:acetone protein...
A study was undertaken to ascertain the analytical capabilities of combined ICP–OES with ultrasonic nebulization to perform on-line preconcentration and speciation of inorganic V species in urine samples using a micro-column packed with l-methionine immobilized on controlled pore glass (CPG) as solid phase extractant. At pH 5.0, l-methionine is selective only towards V(V) while, total vanadium was...
A method using on-line enrichment and fast high-performance liquid chromatography (HPLC) with fluorescence detection has been developed and validated for the determination of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate samples. The evaporation step for sample preparation can be eliminated since this system allows the injection of 1000μL of sample solution. PAH recoveries were...
Generally speaking, measurement of hydroxylated radical products of salicylic acid requires a fussy separation process. In this study, we describe a simple method to electrochemically detect hydroxyl radicals (OH) using 4-hydroxybenzoic acid (4-HBA) as the OH trap. The OH is generated by the Fenton reaction from iron (II) sulfate and hydrogen peroxide in a phosphate buffer solution. Experimental results...
A procedure is proposed for the direct determination of manganese and iron in wine employing fast sequential flame atomic absorption spectrometry and the reference element technique to correct for matrix effects. Cobalt, silver, nickel and indium have been tested as reference elements. The results demonstrated that cobalt and indium at a concentration of 2 and 10mgL −1 were efficient for quantification...
This work presents the development of an on-line pre-concentration system for simultaneous determination of Cd, Cu, Ni, V, Zn, Co and Pb in aqueous environmental samples and detection by inductively coupled plasma mass spectrometry. The system is based on cationic retention of the analytes onto a mini-column filled with silica gel modified with niobium(V) oxide. The effects of chemicals and flow variables...
Within the framework of an Italian research project aimed at studying organic residues found in archaeological objects from the Roman period, the chemical composition of the contents of several glass vessels recovered from archaeological sites from the Vesuvian area (Naples, Italy) was investigated.In particular, this paper deals with the study of an organic material found in a glass bottle from the...
HPLC studies of the oxidation of substituted hydroquinones show that the corresponding quinones can, in most cases, be produced quantitatively by two electron transfer to hexachloroiridate(IV). As a consequence the chromatographic and spectroscopic properties of substituted quinones that are not readily available can be determined without the necessity of preparation of an isolatable sample. Absorption...
The Lowry method and a capillary electrophoresis method were used to analyse protein residues in the supernatant after solvent deproteination of plasma. Acetonitrile and acetone were much more effective than methanol and ethanol at reducing the levels of proteins in plasma. The ability of different solvents to decrease levels of phospholipids in plasma samples was assessed using electrospray ionisation...
Two different approaches were evaluated and used to estimate the aqueous pK a values of some flavonols sparingly soluble in water (morin, fisetin and quercetin) from their pK a values in methanol/water mixtures obtained by potentiometry. Both approaches lead to similar results, although one of them requires only one pK a value at one unique methanol/water mixture, whereas the...
The volatile extract composition of Lavandula stoechas flowers obtained by hydrodistillation (HD), subcrtical water extraction (SbCWE) and organic solvent extraction under ultrasonic irradiation (USE) were estimated by gas chromatography–mass spectrometry (GC–MS). One hundred and twenty four components were detected in SbCWE extracts while 94 and 65 signals were gained from HD and USE extracts, respectively...
Differential pulse voltammetric method was developed for determination of Silymarin (SMR)/Vitamin E acetate (VEA) mixture in pharmaceuticals. SMR and VE gave well-resolved diffusion-controlled anodic peaks at +756 and +444mV, respectively (versus Ag/AgCl) in Britton–Robinson buffer at pH 2.8. The solution conditions and instrumental parameters were optimized for their quantitative determination. The...
Certain characteristic fragmentations of tryptamines (indoleethylamine) and phenethylamines are described. Based on the GC–EI/MS, LC–ESI/MS and MALDI/TOFMS, the mass fragmentations of 13 standard compounds, including α-methyltryptamine (AMT), N,N-dimethyltryptamine (DMT), 5-methoxy-α-methyltryptamine (5-MeO-AMT), N,N-diethyltryptamine (DET), N,N-dipropyltryptamine (DPT), N,N-dibutyltryptamine (DBT),...
A poly-ABSA/SWNTs composite-modified electrode was fabricated by electropolymerizing aminobenzene sulphonic acid (ABSA) on the surface of glassy carbon electrode (GCE) modified with single-wall carbon nanotubes (SWNTs). SWNTs provide a 3D porous and conductive network for the polymer immobilization. The nanocomposite film was characterized by scanning electron microscope (SEM) and electrochemical...
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