共查询到20条相似文献,搜索用时 31 毫秒
1.
Carmen Moscoso-Pérez Purificación López-Mahía Soledad Muniategui-Lorenzo Esther Fernández-Fernández Darío Prada-Rodríguez 《Analytica chimica acta》2004,526(2):185-192
A highly sensitive and simple method, based on hydride generation and atomic fluorescence detection, has been developed for the determination of As, Bi, Sb, Se(IV) and Te(IV) in aqua regia extracts from atmospheric particulate matter samples. Atmospheric particulates matter was collected on glass fiber filters using a medium volume sampler (PM1 particulate matter). Two-level factorial designs have been used to optimise the hydride generation atomic fluorescence spectrometry (HG-AFS) procedure. The effects of several parameters affecting the hydride generation efficiency (hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations and flow rates) have been evaluated using a Plackett-Burman experimental design. In addition, parameters affecting the hydride measurement (delay, analysis and memory times) have been also investigated. The significant parameters obtained (sodium tetrahydroborate concentration, sodium tetrahydroborate flow rate and analysis time for As; hydrochloric acid concentration and sodium tetrahydroborate flow rate for Se(IV); and sodium tetrahydroborate concentration and sodium tetrahydroborate flow rate for Te(IV)) have been optimized by using 2n + star central composite design. Hydrochloric acid concentration and sodium tetrahydroborate flow rate were the significant parameters obtained for Sb and Bi determination, respectively. Using a univariate approach these parameters were optimized. The accuracy of methods have been verified by using several certified reference materials: SRM 1648 (urban particulate matter) and SRM 1649a (urban dust). Detection limits in the range of 6 × 10−3 to 0.2 ng m−3 have been achieved. The developed methods were applied to several atmospheric particulate matter samples corresponding to A Coruña city (NW Spain). 相似文献
2.
It could be shown that the pre- or double peaks which are frequently observed in the determination of tin by hydride generation atomic-absorption spectrometry are not due to reagent contamination or memory effects. Rather they originate from the silica material used to make the quartz tube atomizer. At elevated temperatures the tin diffuses to the surface and it can be volatilized and atomized only in the presence of hydrogen. The height of the pre-peak depends, among other things, on the time for which the quartz tube atomizer has been at a high temperature without hydrogen. The pre-peaks disappear when argon with 10% (v/v) hydrogen is used as the purge gas. In flow injection the pre-peaks can be separated in time from the analytical signal by using a program in which hydrogen is generated by reaction of sodium tetrahydroborate reluctant solution with the acid carrier prior to the injection of the sample. Also investigated was the influence of the acid and sodium tetrahydroborate concentration on sensitivity and freedom from interferences. Best results were obtained when a saturated boric acid solution containing 0.1M hydrochloric acid was used for standards, samples and carrier solution, and a 0.4% (m/v) sodium tetrahydroborate solution with 0.05% (m/v) sodium hydroxide as the reluctant. Under these conditions tin could be determined accurately in the range 0.008-0.1% in low alloy steel standard reference materials, with matrix-free standard solutions for calibration. 相似文献
3.
Bismuth determination in environmental samples by hydride generation-electrothermal atomic absorption spectrometry 总被引:1,自引:0,他引:1
Moscoso-Pérez C Moreda-Piñeiro J López-Mahı́a P Muniategui-Lorenzo S Fernández-Fernández E Prada-Rodrı́guez D 《Talanta》2003,61(5):633-642
A hydride generation procedure, via flow injection, coupled to electrothermal atomic absorption spectrometry was optimised for Bi determination in sea water and hot-spring water and acid extracts from coal, coal fly ash and slag samples. The effects of several variables such as hydrochloric acid and sodium tetrahydroborate concentrations, hydrochloric acid and sodium tetrahydroborate flow rates, reaction coil length, trapping and atomisation temperatures, trapping time and the Ar flow rate have been investigated by using a 29*3/128 Plackett-Burman design. From these studies, certain variables (sodium tetrahydroborate concentration and trapping time) showed up as significant, and they were optimised by a 22+star central composite design. In addition, a study of the bismuthine trapping and atomisation efficiency from graphite tubes (GTs) permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide and tantalum carbide were investigated. The results obtained were compared with those achieved by iridium and zirconium-treated GTs. The best analytical performances, with characteristic mass of 35 pg and detection limit of 70 ng l−1, were achieved by using U-treated GTs. Accuracy were checked using several reference materials: 1643d (Trace Elements in Water), TM-24 (Reference Water), GBW-07401 (Soil) and 1632c (Trace Elements in Coal). 相似文献
4.
Jianhua Zu Zhiqiang Hu Weitao Wang Jianqiu Zhang E. S. Pino Jianzhong Gu Long Tong 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):479-484
A kind of ion-exchange membrane with strong acid and weak acid groups was prepared by radiation-induced grafting of acrylic
acid (AA) and sodium styrene sulfonate (SSS) onto high-density polyethylene membrane (HDPE). The effect of additives such
as sodium acetate, sodium chloride on grafting yield was studied. It was found that for either pre-irradiation method or simultaneous
radiation method, the weak acid salt of strong alkali sodium acetate had a complex effect on the grafting yield by “pH effect”
and “ion pair effect”, and the neutral salt sodium chloride was helpful to the increase of grafting yield by “ion pair effect”. 相似文献
5.
Rafael B. Rios F. Wilton M. Silva A. Eurico B. Torres Diana C. S. Azevedo Célio L. Cavalcante Jr. 《Adsorption》2009,15(3):271-277
Activated carbon samples from coconut shells (Brazilian coconut species “Coco da Baía”) were prepared by chemical activation
with phosphoric acid as the activating agent. Samples were characterized by nitrogen adsorption isotherms at 77 K. Some samples
were randomly chosen in order to perform methane adsorption experiments under pressures between 1 and 60 bar at 303 K. A close
relationship between surface area, micropore volume and methane adsorption capacity for carbons prepared from the same starting
material was observed. The highest methane storage capacity in the tested samples was found to be 95 v/v at 303 K and 35 bar,
which is comparable to results obtained for commercial samples indicated for this application. A moderate concentration of
phosphoric acid (around 35%) seems to favor high surface areas, micropore volumes and, hence, gas storage capacity. The inclusion
of an acid wash step before carbonization and the use of inert gas flow during carbonization also seem to enhance the development
of porosity. This result suggests that activated carbons prepared from “Coco da Baía” by chemical activation with phosphoric
acid have potential to be used as a storage media for natural gas. 相似文献
6.
E. Ortiz-Islas T. López R. Gomez J. Navarrete 《Journal of Sol-Gel Science and Technology》2006,37(3):165-168
Sol-gel titania was phosphated in two different ways: i) “in situ” phosphation using phosphoric acid as hydrolysis catalyst
in the titanium butoxide gelling system, and ii) gelling with nitric acid and impregnation with ammonium phosphate solution.
In calcined samples at 600°C a positive effect on the specific surface area for the “in situ” phosphated sample was found.
X-ray diffraction patterns showed that the presence of phosphates ions stabilized the anatase phase. FTIR-pyridine adsorption
identified only Lewis acid sites in phosphated samples. In the isopropanol decomposition for “in situ” phosphated titania,
the activity was six times higher than that obtained for titania phosphated by impregnation, showing strong acidity for the
in situ phosphated TiO2 catalyst. 相似文献
7.
Response surface methodology (RSM) was employed for optimization of medium components and cultural parameters in cost effective
cane molasses based medium for attaining high yield of succinic acid. The important factors obtained by “one-variable-at-a-time-approach”
(cane molasses, corn steep liquor, sodium carbonate, and inoculum density) were further optimized by RSM. The optimum values
of the parameters obtained through RSM (cane molasses 12.5%, corn steep liquor 7.5%, and sodium carbonate 25 mM) led to almost
double yield of succinic acid (15.2 g/l in 36 h) as against “one-variable-at-a-time-approach” (7.1 g/l in 36 h) in 500-ml
anaerobic bottles containing 300-ml cane molasses based medium. Subsequently, in 10-l bioreactor succinic acid production
from Escherichia coli was further improved to 26.2 g/l in 30 h under conditions optimized through RSM. This fermentation-derived succinic acid
will definitely help in replacing existing environmentally hazardous and cost-intensive chemical methods for the production
of succinic acid. 相似文献
8.
An improved, automated method for the determination of arsenic and antimony in geological materials is described. After digestion of the material in sulfuric, nitric, hydrofluoric and perchloric acids, a hydrochloric acid solution of the sample is automatically mixed with reducing agents, acidified with additional hydrochloric acid, and treated with a sodium tetrahydroborate solution to form arsine and stibine. The hydrides are decomposed in a heated quartz tube in the optical path of an atomic absorption spectrometer. The absorbance peak height for arsenic or antimony is measured. Interferences that exist are minimized to the point where most geological materials including coals, soils, coal ashes, rocks and sediments can be analyzed directly without use of standard additions. The relative standard deviation of the digestion and the instrumental procedure is less than 2% at the 50 μg l-1 As or Sb level. The reagent-blank detection limit is 0.2 μg l-1 As or Sb. 相似文献
9.
A continuous-flow hydride generator is modified and miniaturized for the determination of picogram amounts of arsenic by atomic absorption spectrometry. A 300-μl sample is dropped into a teflon cup and pumped into an alkaline sodium tetrahydroborate stream, which is acidified in a reaction coil. The evolved hydride is swept with argon through a phase separator into an electrically-heated quartz absorption cell and the absorbance is recorded. To eliminate differences in sensitivity between arsenic(III) and arsenic(V) without prereduction by potassium iodide, it is important that arsenic(V) be mixed with tetrahydroborate prior to mixing with hydrochloric acid. The method has a detection limit of 0.08 ng As ml?1 (24 pg) and the calibrations is linear up to 50 ng As ml?1. The relative standard deviation for 10 replicate measurements is 5.4% for 0.5 ng As ml?1. The addition of potassium iodide and hydroxylamine is confirmed to be effective in minimizing some interferences. The sampling rate is 90 h?1. Results for NBS biological and steel reference materials demonstrate applicability of the technique. 相似文献
10.
Fifty samples of natural surface soils with high but variable organic matter content were analyzed for 13 elements (Na, Al,
K, Sc, V, Cr, Mn, Fe, Co, Zn, Sr, Ba, La) by INAA. The same samples were analyzed for the “total-recoverable” fraction of
these elements by ICP-OES after decomposition with 7M HNO3, and the results are compared. The data are discussed separately for two groups of samples with organic matter contents of
respectively >80% and <70%. In the group with < 70 % organic matter the “total-recoverable” fractions show the following sequence
(% of total): Co (83)>Mn (77)>La (60)>Fe=Zn (53)>V (33)>Cr (29)>Sc (25)>Al=Ba (17)>Sr (13)>K (5)>Na (2). The results are in
good agreement with corresponding literature data for mineral soils in the case of Al, K, Sc, V, Cr, Fe, and La. In the case
of Na, Mn, Co, Zn, Sr, and Ba the present surface soils showed significantly higher “total-recoverable” fractions than the
previously studied subsoils. Possible reasons for these differences are discussed. INAA remains a convenient reference technique
for determination of total concentrations with the rapidly increasing use of strong mineral acids in environmental studies
of elements.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
D. A. Wade C. Mao A. C. Hollenbeck S. A. Tucker 《Analytical and bioanalytical chemistry》2001,369(3-4):378-384
The ability of pyridinium chloride (PC) to selectively quench alternant as opposed to nonalternant polycyclic aromatic hydrocarbons
(PAHs) in organized media is examined. PC was previously shown to be a selective quenching agent of alternant PAHs in neat
polar solvents. Carboxylate-terminated poly(amido) amine (PAMAM-CT) dendrimers and anionic surfactants – sodium dodecanoate
(SD), sodium octanoate (SO), and sodium dodecylsulfate (SDS) – were chosen as the solubilizing media for this study. Selective
quenching of alternant PAHs is observed in the presence of the SDS and SO micelles. However, the extent of PAH quenching in
SO is significantly reduced compared to PAHs dissolved in either water or SDS micelles. In the case of the smaller generation
4.5 (G4.5) PAMAM-CT dendrimers, PC was prevented from quenching both alternant and nonalternant PAHs to any appreciable extent.
The dendrimer is able to “protect” the PAHs from the PC quencher that resides at the dendrimer surface. Both, SD and G5.5
PAMAM-CT precipitated out of solution with the addition of PC. Differences between traditional micelles and “unimolecular
micelle” dendrimers were also examined. These studies further confirm that the PAHs did not reside in the “analogous” palisade
region of the dendrimers as they do in micelles. The PAHs must reside in the outermost branches of the dendrimer, but sufficiently
far enough away from the charged surface groups, where PC associated, to prevent fluorescence quenching. This work further
illustrates the differences between “unimolecular micelle” dendrimers and traditional micelles.
Received: 27 July 2000 / Revised: 25 September 2000 / Accepted: 27 September 2000 相似文献
12.
Yuko Hata Toyoko Suzuki Hideto Minami Masayoshi Okubo 《Colloid and polymer science》2008,286(13):1561-1567
Hollow polymer particles with multiple holes in the shell were prepared by aqueous microsuspension polymerization of micrometer-sized,
monodisperse divinylbenzene/n-hexadecane droplets in the presence of sodium dodecyl sulfate (SDS) at concentrations above 4 mM utilizing the Self-assembling Phase-Separated Polymer (SaPSeP) method developed by the authors. The total surface area of the holes per particle increased with an increase
in the SDS concentration. At [SDS] = 10 mM, “flower-like” non-spherical particles were formed.
Part CCCXV of series “Studies on Suspension and Emulsion” 相似文献
13.
An alternative screening method for haloacetic acids (HAAs) disinfection by-products in drinking water is described. The method is based on the use of piezoelectric quartz crystal microbalance (QCM) transducing system, where the electrode is coated with a trichloacetic acid-molecularly imprinted polymer (TCAA-MIP). This MIP comprises a crosslinked poly(ethyleneglycoldimethacrylate-co-4-vinylpyridine). The coated QCM is able to specifically detect the analytes in water samples in terms of the mass change in relation to acid-base interactions of the analytes with the MIP. The TCAA-MIP coated QCM showed high specificity for the determination of TCAA in aqueous solutions containing inorganic anions, but its sensitivity reduced in water samples containing hydrochloric acid due to a mass loss at the sensor surface. Cross-reactivity studies with HAA analogs (dichloro-, monochloro-, tribromo-, dibromo-, and monobromo-acetic acids) and non-structurally related TCAA molecules (acetic acid and malonic acid) indicated that recognition of the structurally related TCAA compounds by the TCAA-MIP-based QCM is due to a carboxylic acid functional group, and probably involves a combination of both size and shape selectivity. The total response time of sensor is in the order of 10 min. The achieved limits of detection for HAAs (20-50 μg l−1) are at present higher than the actual concentrations found in real-life samples, but below the guidelines for the maximum permissible levels (60 μg l−1 for mixed HAAs). Recovery studies with drinking water samples spiked with TCAA or spiked with mixtures of HAAs revealed the reproducibility and precision of the method. The present work has demonstrated that the proposed assay can be a fast, reliable and inexpensive screening method for HAA contaminants in water samples, but further refinement is required to improve the limits of detection. 相似文献
14.
Elfriede Simon M. G. Weller Reinhard Niessner 《Analytical and bioanalytical chemistry》1998,360(7-8):824-826
The aim of the described method was the characterization of a “atrazine-mercaptopropionic acid” humic acid conjugate, which
was required for the calibration of immunoassays to determine bound residues. In order to estimate the amount of bound triazine,
an oxidative nucleophilic substitution reaction of the covalently linked “atrazine-mercaptopropionic acid” to a new triazine
derivative “atrazine-methoxyethanol” was performed. This cleavage product was quantified by gas chromatography. The conditions
for this cleavage procedure were optimized and applied to the “atrazine-mercaptopropionic acid” humic acid conjugate and to
a humic acid blank. The amount of bound “atrazine-mercaptopropionic acid” was calculated to 16.6 ± 2.5 μmol triazine per gram
humic acid, which is equivalent to 0.39 ± 0.07% atrazine.
Received: 7 August 1997 / Accepted: 12 September 1997 相似文献
15.
Multivariate analysis of HT/GC-(IT)MS chromatographic profiles of triacylglycerol for classification of olive oil varieties 总被引:1,自引:0,他引:1
Cristina Ruiz-Samblás Luis Cuadros-Rodríguez Antonio González-Casado Francisco de Paula Rodríguez García Paulina de la Mata-Espinosa Juan Manuel Bosque-Sendra 《Analytical and bioanalytical chemistry》2011,399(6):2093-2103
The ability of multivariate analysis methods such as hierarchical cluster analysis, principal component analysis and partial
least squares-discriminant analysis (PLS-DA) to achieve olive oil classification based on the olive fruit varieties from their
triacylglycerols profile, have been investigated. The variations in the raw chromatographic data sets of 56 olive oil samples
were studied by high-temperature gas chromatography with (ion trap) mass spectrometry detection. The olive oil samples were
of four different categories (“extra-virgin olive oil”, “virgin olive oil”, “olive oil” and “olive-pomace” oil), and for the
“extra-virgin” category, six different well-identified olive oil varieties (“hojiblanca”, “manzanilla”, “picual”, “cornicabra”,
“arbequina” and “frantoio”) and some blends of unidentified varieties. Moreover, by pre-processing methods of chemometric
(to linearise the response of the variables) such as peak-shifting, baseline (weighted least squares) and mean centering,
it was possible to improve the model and grouping between different varieties of olive oils. By using the first three principal
components, it was possible to account for 79.50% of the information on the original data. The fitted PLS-DA model succeeded
in classifying the samples. Correct classification rates were assessed by cross-validation. 相似文献
16.
L. D. Martinez M. Baucells E. Pelfort M. Roura R. Olsina 《Analytical and bioanalytical chemistry》1997,357(7):850-852
An accurate procedure for the elimination of iron interferences in the determination of selenium in geological materials
by the Hydride Generation – Inductively Coupled Plasma Atomic Emission Spectrometry technique (HG-ICPAES) is proposed. A selective
removal of iron is achieved by on-line incorporation of a microcolumn filled with strongly acidic cation exchange resin (Dowex
50W-X8). The microcolumn manifold used was interfaced with the hydride generation manifold by a flow injection sample injection
valve. After the removal of the iron, a 500 μl sample was injected into a carrier stream of water. This was merged with hydrochloric
acid and sodium tetrahydroborate in order to generate the corresponding selenium hydride. The system was found to have a limit
of detection of 0.4 ng ml-1 and a relative standard deviation of 2% for 20 ng ml-1 selenium. The application of the method on different Geochemical Standard Reference Samples demonstrated that results were
statistically indistinguishable from certified values.
Received: 7 March 1996 / Revised: 30 May 1996 / Accepted: 4 June 1996 相似文献
17.
The efficiency of the extraction of butyltin compounds from sediments and biological matter by acid leaching procedures has been evaluated on real samples using the hydride generation gas chromatography quartz furnace atomic absorption (GC AA) speciation method. The most efficient method uses cold pure acetic acid over a period of four hours. Hydride generation using sodium tetrahydroborate (NaBH4) is dependent on matrix composition and care must be taken to adapt the amount of reactant to the organic content of the sample. 相似文献
18.
Direct determination of Ge in hot spring waters and coal fly ash samples by hydride generation-ETAAS
Moscoso-Pérez C Moreda-Piñeiro J López-Mahía P Muniategui-Lorenzo S Fernández-Fernández E Prada-Rodríguez D 《Talanta》2004,64(2):302-307
A method for Ge determination in hot spring water and acid extracts from coal fly ash samples involving hydride generation, trapping and atomisation of the hydride generated from Ir-treated graphite tubes (GTs) has been developed. Hydride was generated from hydrochloric acid medium using sodium tetrahydroborate. Several factors affecting the hydride generation, transport, trapping and atomisation efficiency were studied by using a Plackett-Burman design. Results obtained from Plackett-Burman designs suggest that trapping and atomisation temperatures are the significant factors involved on the procedure. The accuracy was studied using NIST-1633a (coal fly ash) reference material. The detection limit of the proposed method was 2.4 μg l−1 and the characteristic mass of 233 pg was achieved. The Ge concentrations in fly ash and hot spring samples were between 6.25-132 μg g−1 and 12.84-36.2 μg l−1. 相似文献
19.
《Analytica chimica acta》2002,461(2):261-271
Different procedures of tin hydride generation from aqueous and acidified slurries of marine sediment, soil, coal fly ash and coal samples, coupled to electrothermal atomic absorption spectrometry were optimised by using factorial designs. A batch mode generation system and Ir-treated graphite tubes were used for the hydride generation and atomisation, respectively. Eight variables, affecting the hydride generation and hydride transport efficiency (hydrochloric acid and sodium tetrahydroborate concentrations, particle size, acid volume and argon flow rate), the hydride trapping efficiency (trapping temperature and trapping time) and the atomisation efficiency (atomisation temperature) were studied and optimised. In addition, acid pre-treatment procedures assisted by ultrasonic energy were used for soil and coal matrices, to obtain acidified slurries and acid leachates. The involved variables were hydrochloric and nitric acid concentrations, exposure time to ultrasound, particle size and leaching solution volume. Adequate accuracy (41.5±0.8 and 1.4±0.2 mg kg−1, for PACS-1 (sediment marine) and NIST-1633b (coal fly ash), respectively) were obtained by using aqueous slurry reference materials. In addition, values of 6.2±0.6 and 1.2±0.1 mg kg−1 were assessed by analysing GBW-07401 (soil) and NIST-1632c (coal) certified reference materials. 相似文献
20.
T. Ishikawa M. Hosoda A. Sorimachi S. Tokonami S. Katoh S. Ogashiwa 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):709-713
Nowadays, artificial “radon spa sources” for home baths are commercially available. Although these sources could give a potential
radiation exposure to the users, few studies have been reported on their radiological measurements. In the present study,
five types of radon spa sources were collected and their radiological characterization was investigated. The followings were
estimated for these samples: (1) radon emanation coefficients (dry and water-saturated conditions), (2) surface γ-ray dose
rate, (3) surface count rates for α- and β-rays, (4) activity concentrations of 226Ra, 232Th and 40K, and (5) concentrations of radon and thoron generated from the sources located in an air flow system. The activity concentrations
were very high (except for one sample (named “sample B”), although radon emanation coefficient was low compared with soil.
This leads to high concentrations of radon/thoron generated from the sample. The maximum surface γ-ray dose rate was observed
for sample A (2.7 μGy h−1). If people stay very close to the sample for a long time, the exposure might be significant. 相似文献