Search results for "LIMIT"
showing 10 items of 2826 documents
Comparison of different methods for extraction of polycyclic aromatic hydrocarbons (PAHs) from Sicilian (Italy) coastal area sediments.
2012
This paper describes a work aimed at improving the conditions of an extraction method, coupling GC-MS determination, for the analysis without cleanup phase, of polycyclic aromatic hydrocarbons (PAHs) from sediment samples. The automatic Soxhlet extraction in warm mode (using Extraction System B-811 Standard, Buchi) has demonstrated advantages for automation, reduced extraction time, and lower solvent use than for conventional Soxhlet extraction. Under these conditions, the recoveries are very good as they resulted greater than 85 % and, in most of the cases, near 100 %. The repeatability is also satisfactory (relative standard deviation less than 15 %). The detection limits are also accepta…
Improvement of the electrophoretic protein profiles of Leguminosae gums extracts using gamanase and application to the evaluation of carob–guar mixtu…
2004
Abstract A quantitative assay for guar gum in carob gum, based on the extraction of proteins in acetonitrile–water (7:3), separation by capillary electrophoresis and multiple linear regression (MLR) using the areas of nine selected peaks as predictors, was improved by performing the extraction in the presence of gamanase. In the absence of the enzyme, peak migration times and areas depended on the guar content, which complicated peak identification and evaluation. Manual correction of the migration times by comparison with standard electropherograms obtained with pure carob and carob–guar mixtures was required; however, when the proteins were extracted under sonication at 60 °C for 30 min i…
Determination of -Ascorbic Acid in Lycopersicon Fruits by Capillary Zone Electrophoresis
2001
This study shows an improved method for the determination of L-ascorbic acid (l-AA) in fruits of Lycopersicon by capillary zone electrophoresis (CZE). Two backgrounds electrolytes (BGEs) have been tested: (i) 400 mM borate at pH 8.0 and 1 x 10(-2)% hexadimethrine bromide, for the separation of Eulycopersicon subgenus species; and (ii) as in BGE(i) but supplemented with 20% (v/v) acetonitrile, for the separation of species of the Eriopersicon subgenus. The present procedures were compared with two routine methods-enzymatic assay and potentiometric titration with 2,6-dichlorophenol-indophenol. While these routine methods presented some difficulties in quantifying l-AA in several Lycopersicon …
High-frequency electrodeless discharge lamps for atomic absorption analysis
2003
Abstract In this paper we present the results of an investigation of high-frequency electrodeless discharge lamps (HFEDLs), containing Cd, Zn, Hg, As, Te, Se, Pb, Sn, Tl and Bi, developed in our laboratories as light sources for atomic absorption spectrometry (AAS). Important physical processes in the lamps are discussed. Essential characteristics of HFEDLs for AAS, such as intensity, stability and operating life are considered. The intensities and detection limits are compared with the corresponding characteristics of hollow cathode lamps. The temporal behavior of an As HFEDL is compared with that of a commercially available electrodeless discharge lamp. Detection limits in graphite furnac…
Simultaneous determination of hydride and non-hydride forming elements by inductively coupled plasma optical emission spectrometry
2011
e percentagens de recuperacao entre 97 e 103%. A aplicabilidade do sistema foi demonstrada na determinacao simultânea de Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Zn, As, Bi, Sb, Se e Te em amostras certificadas para elementos tracos, NIST 1549 (leite em po desnatado), NIST 1570a (folhas de espinafre), DORM-2 (musculo de cacao) e TORT-2 (hepatopâncreas de lagosta). Os resultados obtidos foram concordantes com os teores certificados. The operating characteristics of a dual nebulization system were studied including instrumental and chemical conditions for the hydride generation and analytical figures of merit for both, hydride and non hydride forming elements. Analytical performance of the neb…
Development of a non-chromatographic method for the speciation analysis of inorganic antimony in mushroom samples by hydride generation atomic fluore…
2009
Abstract A simple and sensitive method has been developed for the direct determination of toxic species of antimony in mushroom samples by hydride generation atomic fluorescence spectrometry (HG AFS). The determination of Sb(III) and Sb(V) was based on the efficiency of hydride generation employing NaBH 4 , with and without a previous KI reduction, using proportional equations corresponding to the two different measurement conditions. The extraction efficiency of total antimony and the stability of Sb(III) and Sb(V) in different extraction media (nitric, sulfuric, hydrochloric, acetic acid, methanol and ethanol) were evaluated. Results demonstrated that, based on the extraction yield and th…
Multicommutation hydride generation atomic fluorescence determination of inorganic tellurium species in milk
2005
Abstract A multicommutated flow system has been developed for hydride generation, atomic fluorescence (HG-AFS) determination of tellurate (Te VI ) and tellurite (Te IV ) in milk samples. After a batch leaching of Te by sonication at room temperature for 10 min with aqua regia, sample slurries in acidic medium were merged with sodium borohydride and HCl to obtain data on Te IV . Another portion of the acidic slurry was mixed with KBr and passed through a reaction coil introduced inside a microwave oven to reduce quantitatively Te VI to Te IV which was analyzed by HG-AFS. The detection limit was 0.57 ng g −1 in the original samples. The linear range obtained was till 4 ng ml −1 and the averag…
Speciation of selenium and tellurium in milk by hydride generation atomic fluorescence spectrometry
2004
A simple, fast and highly sensitive method has been developed for the differentiation of Se and Te into their (IV) and (VI) oxidation states in milk samples by HG-AFS. This procedure involves a previous leaching of milk slurries by sonication with aqua regia for 10 min. Se(IV) and Te(IV) were determined by analysis of the samples without a pre-reduction step; being total Se and Te determined after reduction with KBr. The method provides limit of detection values (LOD) of 0.012 and 0.023 ng ml−1 for Se(IV) and Te(IV) respectively. Average relative standard deviation values of 10.5%, 3.9%, 12% and 12.5% were found for the determination of Se(IV), Se(VI), Te(IV) and Te(VI) in milk samples cont…
Non-chromatographic speciation analysis of arsenic and antimony in milk hydride generation atomic fluorescence spectrometry
2003
Abstract A rapid, high sensitivity method has been developed for the determination of As(III), As(V), Sb(III) and Sb(V) in milk samples by using hydride generation atomic fluorescence spectrometry. The method is based on the leaching of As and Sb from milk through the sonication of samples with aqua regia followed by direct determination of the corresponding hydrides both before and after reduction with KI. It was confirmed by recovery experiments on spiked commercially available samples that neither the reduced nor the oxidized forms of the elements under study or mixtures of the two oxidation states were modified by the room temperature sample treatment with aqua regia. The methodologies …
Antibody-Capped Mesoporous Nanoscopic Materials: Design of a Probe for the Selective Chromo-Fluorogenic Detection of Finasteride
2012
[EN] The synthesis of capped mesoporous silica nanoparticles (MSN) conjugated with an antibody (AB) as a gatekeeper has been carried out in order to obtain a delivery system able to release an entrapped cargo (dye) in the presence of a target molecule (antigen) to which the conjugated antibody binds selectively. In particular, MSN loaded with rhodamine B and functionalized on the external surface with a suitable derivative of N-(t-butyl)- 3-oxo-(5a,17b)-4-aza-androst-1-ene-17-carboxamide (finasteride) have been prepared (S1). The addition of polyclonal antibodies against finasteride induced capping of the pores due to the interaction with the anchored hapten-like finasteride derivative to g…