共查询到20条相似文献,搜索用时 46 毫秒
1.
Zenovia Moldovan 《Chemical Papers》2009,63(4):385-390
A simple, selective and sensitive kinetic method for the determination of nitrite in water was developed. The method is based
on the catalytic effect of nitrite on the oxidation of methylene blue (MB) with bromate in a sulfuric acid medium. During
the oxidation process, absorbance of the reaction mixture decreases with the increasing time, inversely proportional to the
nitrite concentration. The reaction rate was monitored spectrophotometrically at λ = 666 nm within 30 s of mixing. Linear
calibration graph was obtained in the range of 0.005–0.5 μg mL−1 with a relative standard deviation of 2.09 % for six measurements at 0.5 μg mL−1. The detection limit was found to be 0.0015 μg mL−1. The effect of different factors such as acidity, time, bromate concentration, MB concentration, ionic strength, and order
of reactants additions is reported. Interference of the most common foreign ions was also investigated. The optimum experimental
conditions were: 0.38 mol L−1 H2SO4, 5 × 10.4 mol L−1 KBrO3, 1.25 × 10.5 mol L−1 MB, 0.3 mol L−1 sodium nitrate, and 25°C. The proposed method was conveniently applied for the determination of nitrite in spiked drinking
water samples. 相似文献
2.
Lopes IC De Souza D Machado SA Tanaka AA 《Analytical and bioanalytical chemistry》2007,388(8):1907-1914
This work describes the application of an ordinary pyrolitic graphite electrode modified by metallophthalocyanine allied to
square wave voltammetry for the study of the electrochemical behavior of the herbicide paraquat and the development of a method
for its analytical determination in natural water samples. Preliminary experiments indicated that the best responses, considering
the intensities of the current and voltammetric profile for the paraquat reduction process, were obtained when the electrode
modified by cobalt phthalocyanine was employed, which had a better catalytic activity as a result of this modification compared
with that for an unmodified electrode and electrodes modified by iron, manganese and the acid form of the phthalocyanines.
Studies of the concentration of cobalt phthalocyanine and the adsorption time showed that 1.0 × 10−4 mol L−1 cobalt phthalocyanine with an adsorption time of 10 min was sufficient to obtain reliability and stability of modification
for employment in the development of the electroanalytical procedure for paraquat determination in natural water samples.
The variation in pH of a 0.10 mol L−1 Britton–Robinson buffer solution and the square wave parameters indicated that the best conditions to reduce paraquat were
pH 7.0, a frequency of 100 s−1, a scan increment of 2 mV and a square wave amplitude of 50 mV. Under such conditions, the variation of paraquat concentrations
from 5.00 × 10−7 to 2.91 × 10−5 mol L−1 showed a linear relation, with detection and quantification limits of 26.53 and 88.23 μg L−1; those values were lower than the maximum limits for drinking water permitted by the Brazilian Environmental Council (100 μg
L−1), indicating that the method could be employed to analyze paraquat in drinking water samples. 相似文献
3.
The effect of the concentration of water on the rate of reduction of molecular nitrogen to hydrazine by niobium(iii) hydroxide in alkaline H2O−MeOH and D2O−MeOD mixtures was studied. In both cases, the reaction rate is maximum when [H2O]=4 mol L−1, and the inverse isotopic effect (K
D/k
H>1) is observed when [H2O]<20 mol L−1. Similar regularity was observed for the reaction of hydrogen elimination. It was found that HD is formed in the H2O−MeOH system in the presence of D2. The conclusion was made that the ratedetermining stage in hydrazine formation is the transfer of a hydride ion to the dinitrogen
molecule coordinated to the binuclear NbIII center. A kinetic scheme satisfactorily explaining the effect of the concentration of water ([H2O]=1.5−49.0 mol L−1) on the reaction rate constant was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1600–1604, September, 1997. 相似文献
4.
A combined method involving electrochemical oxidation of iodide to iodate at a platinum electrode followed by extraction in
CCl4 of ionic associates of iodine-iodide complexes with brilliant green, formed in excess of iodide, was developed for the spectrophotometric
quantification of iodide. The slope of the calibration curve yields a molar extinction coefficient of ɛ = 3·105 L mol−1cm−1. This method can be used for the quantification of iodide in the concentration range of 3·10−7 − 3·10−6 mol L−1 with a detection limit of 5·10−8 mol L−1. The interfering effect of other ions on the determination of the iodide concentration was also investigated. The method
was successfully applied for the determination of iodide in real samples of NaCl and spring water. Relative standard deviation
is 1–2%. 相似文献
5.
It has been found that gold nanoparticles (nano-Au) enhance the chemiluminescence (CL) of the luminol–hydrogen peroxide system
and that estrogens inhibit these CL signals in alkaline solution. CL spectra, UV–visible spectra, X-ray photoelectron spectra
(XPS), and transmission electron microscopy (TEM) were used to investigate the mechanism of the CL enhancement. On the basis
of the inhibition, a flow-injection CL method has been established for determination of three natural estrogens. Under the
optimized conditions, the linear range for determination of the estrogens was 0.07 to 7.0 μmol L−1 for estrone, 0.04 to 10 μmol L−1 for estradiol, and 0.1 to 10 μmol L−1 for estriol. The detection limits were 3.2 nmol L−1 for estrone, 7.7 nmol L−1 for estradiol, and 49 nmol L−1 for estriol, with RSD of 2.9, 2.6, and 1.8%, respectively. This method has been used for analysis of estrogens in commercial
tablets and in urine samples from pregnant women. 相似文献
6.
Dora Melucci Simona Montalbani Clinio Locatelli 《Central European Journal of Chemistry》2012,10(1):267-276
The present work reports the critical comparison about the employment of three different supporting electrolytes (0.1 mol
L−1 HClO4, 0.01 mol L−1 EDTA-Na2 + 0.06 mol L−1 NaCl + 2.0 mol L−1 HClO4 and 0.1 mol L−1 KSCN + 0.001 mol L−1 HClO4) and their instrumental and chemical optimisation for the simultaneous voltammetric determination of total mercury(II) and
copper(II) in sediments and sea water at gold electrode, especially discussing the reciprocal interference problems. 相似文献
7.
A survey of contamination of surface and drinking waters around Lake Maggiore in Northern Italy with polar anthropogenic environmental
pollutants has been conducted. The target analytes were polar herbicides, pharmaceuticals (including antibiotics), steroid
estrogens, perfluorooctanesulfonate (PFOS), perfluoroalkyl carboxylates (including perfluorooctanoate PFOA), nonylphenol and
its carboxylates and ethoxylates (NPEO surfactants), and triclosan, a bactericide used in personal-care products. Analysis
of water samples was performed by solid-phase extraction (SPE) then liquid chromatography–triple-quadrupole (tandem) mass
spectrometry (LC–MS–MS). By extraction of 1-L water samples and concentration of the extract to 100 μL, method detection limits
(MDLs) as low as 0.05–0.1 ng L−1 were achieved for most compounds. Lake-water samples from seven different locations in the Southern part of Lake Maggiore
and eleven samples from different tributary rivers and creeks were investigated. Rain water was also analyzed to investigate
atmospheric input of the contaminants. Compounds regularly detected at very low concentrations in the lake water included:
caffeine (max. concentration 124 ng L−1), the herbicides terbutylazine (7 ng L−1), atrazine (5 ng L−1), simazine (16 ng L−1), diuron (11 ng L−1), and atrazine-desethyl (11 ng L−1), the pharmaceuticals carbamazepine (9 ng L−1), sulfamethoxazole (10 ng L−1), gemfibrozil (1.7 ng L−1), and benzafibrate (1.2 ng L−1), the surfactant metabolite nonylphenol (15 ng L−1), its carboxylates (NPE1C 120 ng L−1, NPE2C 7 ng L−1, NPE3C 15 ng L−1) and ethoxylates (NPE
n
Os, n = 3-17; 300 ng L−1), perfluorinated surfactants (PFOS 9 ng L−1, PFOA 3 ng L−1), and estrone (0.4 ng L−1). Levels of these compounds in drinking water produced from Lake Maggiore were almost identical with those found in the lake
itself, revealing the poor performance of sand filtration and chlorination applied by the local waterworks. 相似文献
8.
Jinzhang Gao Dongyu Lv Wu Yang Xiaoxia Wei Jie Qu Hua Chen Hongxia Dai Jie Ren 《Central European Journal of Chemistry》2007,5(2):581-589
A convenient and sensitive method for determination of sulfanilamide (SNA) was described based on the Mn(II)-catalyzed oscillating
chemical reaction. Under optimum conditions, a linear relationship existed between the changes of oscillating period or amplitude
and the negative of logarithm of SNA concentration in the range of 4.27 × 10−8 mol ·L−1 ∼ 7.41 × 10−6 mol ·L−1 (RSD, 0.85%) and 9.33 × 10−8 mol ·L−1 ∼ 3.02 × 10−6 mol ·L−1 (RSD, 1.08%), respectively. The lower limit of detection was found to be 2.69 × 10−8 mol ·L−1 and 6.03 × 10−8 mol ·L−1, respectively.
相似文献
9.
Nagwa Burham Sami A. Azeem Mohamed F. El-Shahat 《Central European Journal of Chemistry》2009,7(4):945-954
A new solid — phase extraction sorbent was developed based on stepwise anchoring of two ligand molecules for the determination
of copper, zinc, lead and cadmium in drinking water by flame AAS. Amberlite XAD-2 functionalized with 4′-(2-hydroxyphenylazo)-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one
(HPAPyr) was utilized for preconcentration/separation of these elements. The sorbent was prepared by two successive azo coupling
reactions. First, 2-aminophenol was anchored to the amino groups in the resin resulted from nitration followed by reduction.
Then, the resulted 2-aminophenol functionalized resin was further diazotized and coupled to the pyrazolone compound and the
final product HPAPyr-XAD-2 was characterized by IR and elemental analysis. The optimum pH range for sorption, shaking time,
exchange capacity, sample flow rate, preconcentration factor and interference from co-existing ions were investigated. All
metal ions were quantitatively desorbed from the resin by 4.5 mol L−1 nitric acid solution. The sorbent provides limit of detection within the range 0.9–3.3 μg L−1 and concentration factor up to 250. The procedure was validated by analysis of certified material NIST-SRM 1577b. Application
to drinking water showed satisfactory results with relative standard deviation RSD ≤ 8.5%.
相似文献
10.
Popp M Hann S Mentler A Fuerhacker M Stingeder G Koellensperger G 《Analytical and bioanalytical chemistry》2008,391(2):695-699
A novel method employing high-performance cation chromatography in combination with inductively coupled plasma dynamic reaction
cell mass spectrometry (ICP–DRC–MS) for the simultaneous determination of the herbicide glyphosate (N-phosphonomethylglycine) and its main metabolite aminomethyl phosphonic acid (AMPA) is presented. P was measured as 31P16O+ using oxygen as reaction gas. For monitoring the stringent target value of 0.1 μg L−1 for glyphosate, applicable for drinking and surface water within the EU, a two-step enrichment procedure employing Chelex
100 and AG1-X8 resins was applied prior to HPIC–ICP–MS analysis. The presented approach was validated for surface water, revealing
concentrations of 0.67 μg L−1 glyphosate and 2.8 μg L−1 AMPA in selected Austrian river water samples. Moreover, investigations at three waste water-treatment plants showed that
elimination of the compounds at the present concentration levels was not straightforward. On the contrary, all investigated
plant effluents showed significant amounts of both compounds. Concentration levels ranged from 0.5–2 μg L−1 and 4–14 μg L−1 for glyphosate and AMPA, respectively. 相似文献
11.
A method was developed for determining selenium with a self-made ion-selective electrode was developed. This electrode was
made by using Ag2Se as electroactive material. Optimal working conditions and interferences were investigated. The electrode exhibits good
potentiometric response for Se2− ions over the concentration range from 6 × 10−7 mol · L−1 to 1 × 10−4 mol · L−1 with a Nernstian slope of 28 ± 1 mV per decade and a detection limit of about 4.5 × 10−7 mol · L−1. It was used over six months and exhibits good selectivity and sensitivity towards Se2−. The method was applied to determine selenium in biological materials. The recovery ranges between 92% and 105.5%, and the
relative standard derivation is less than 3.6% (n = 6). 相似文献
12.
A Pt wire coated with a bentonite–carbon composite in a poly(vinyl chloride) membrane was used for detection of lead. The
sensor has a Nernstian slope of 29.42±0.50 mV per decade over a wide range of concentration, 1.0×10−7 to 1.0×10−3 mol L−1 Pb(NO3)2. The detection limit is 5.0×10−8 mol L−1 Pb(NO3)2 and the electrode is applicable in the pH range 3.0–6.7. It has a response time of approximately 10 s and can be used at
least for three months. The electrode has good selectivity relative to nineteen other metal ions. The practical analytical
utility of the electrode is demonstrated by measurement of Pb(II) in industrial waste and river water samples. 相似文献
13.
Carboxyl group-functionalized single-walled carbon nanotubes (SWNTs) and 2,6-pyridinedicarboxylic acid (PDC) were electropolymerized
by cyclic voltammetry on a glassy-carbon electrode (GCE) surface to form composite films (SWNTs/PDC). Zirconia was then electrodeposited
on the SWNTs/PDC/GCE from an aqueous electrolyte containing ZrOCl2 and KCl by cycling the potential between −1.1 V and +0.7 V at a scan rate of 20 mV s−1. DNA probes with a phosphate group at the 5′ end were easily immobilized on the zirconia thin films, because of the strong
affinity between zirconia and phosphate groups. The sensors were characterized by cyclic voltammetry (CV) and electrochemical
impedance spectroscopy (EIS). EIS was used for label-free detection of the target DNA by measuring the increase of the electron
transfer resistance (R
et) of the electrode surface after the hybridization of the probe DNA with the target DNA. The PAT gene fragment and polymerase
chain reaction (PCR) amplification of the NOS gene from transgenically modified beans were satisfactorily detected by use
of this DNA electrochemical sensor. The dynamic range of detection of the sensor for the PAT gene fragment was from 1.0 × 10−11 to 1.0 × 10−6 mol L−1 and the detection limit was 1.38 × 10−12 mol L−1. 相似文献
14.
A new Schiff-base ligand [N, N′, N″-Tri- (2,4-dihydroxyacetophenone) – triaminotriethylamine (TDATA)] with a tripodal structure
was synthesized. Its fluorescence intensity with the europium(III) complex was increased about 178-fold in the presence of
sodium acetate (NaAc) and about 126-fold in the presence of sodium phosphate (Na3PO4) solution. After adding the organic solvent dimethylsulfoxide (DMSO) to the above system, which leads to Eu3+ the fluorescence was further enhanced about 12-fold. Spectrofluorimetric determination of trace amounts of Eu3+ based on the phenomenon was performed. The excitation and emission wavelength is 365 nm and 615 nm, respectively. Under optimum
conditions, the fluorescence intensities vary linearly with the concentration of Eu3+ in the range of 4.9 × 10−12–3.2 × 10−6 mol · L−1 with a detection limit of 4.5 × 10−12 mol · L−1 (for the TDATA-NaAc-DMSO system) or 6.2 × 10−11–8.6 × 10−6 mol · L−1 with a detection limit of 6.0 × 10−11 mol · L−1 (for the TDATA-Na3PO4-DMSO system). Interferences of some rare earth metals and other inorganic ions are described. The method is a selective,
sensitive, rapid and simple analytical procedure for the determination of europium(III) in a high purity yttrium oxide and
synthetic sample. The mechanism for the fluorescence enhancement is also discussed. 相似文献
15.
Gao J Dai H Yang W Chen H Lv D Ren J Wang L 《Analytical and bioanalytical chemistry》2006,384(6):1438-1443
A rapid and convenient method for the determination of furfural is presented that is based upon sequential perturbation of
the Mn(II)-catalyzed B-Z oscillating system with different amounts of furfural using a continuous-flow stirred tank reactor
(CSTR). When the sample was injected, the change in the amplitude and/or period was linearly proportional to the logarithm
of the concentration of furfural over the range 3×10−8∼1×10−5 mol L−1. This method gave a detection limit of 3×10−9 mol L−1 under optimum conditions. Finally, the possible mechanism of furfural perturbation in the oscillating reaction is discussed.
When the furfural was injected into the Mn(II)-catalyzed B-Z oscillating system, the change in the amplitude and/or period
was linearly proportional to the logarithm of the concentration of furfural over the range 3×10−8~1×10−5 mol L−1, with a detection limit of 3×10−9 mol L−1 under optimum conditions.
相似文献
16.
de la Escosura-Muñiz A González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,384(3):742-750
A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon
electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was
bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological
reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I)
bound to the anti-HSA was electrodeposited in 0.1 mol L−1 HCl at −1.00 V for 5 min then oxidised in 0.1 mol L−1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were
then performed in aqueous 1.0 mol L−1 NH3–2.0×10−4 mol L−1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10−10 to 1.0×10−8 mol L−1 and 1.0×10−10 to 1.0×10−9 mol L−1 HSA, respectively, with estimated detection limits of 1.5×10−10 mol L−1 (10 ng mL−1) and 1.0×10−10 mol L−1 (7 ng mL−1), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay
formats. 相似文献
17.
Cecylia Wardak 《Central European Journal of Chemistry》2008,6(4):607-612
A new all plastic sensor for Co2+ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits
a low detection limit of 1.5 × 10−6 mol L−1 and almost theoretical Nernstian slope in the activity range 4.0 × 10−6–1 × 10−1 mol L−1 of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any
measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions.
The electrode was successfully applied for determination of Co2+ in real samples and as an indicator electrode in potentiometric titration of Co2+ ions with EDTA.
相似文献
18.
Zhao RS Cheng CG Yuan JP Jiang T Wang X Lin JM 《Analytical and bioanalytical chemistry》2007,387(2):687-694
A novel purge-and-trap method coupled with gas chromatography-mass spectrometry (GC-MS) is developed for the analysis of trace
and ultratrace phenols based on their derivatization with acetic anhydride. Parameters affecting the extraction efficiency,
such as purge temperature, concentration of sodium chloride, purge time, and volume of derivatization reagent, were investigated.
The optimized conditions were addition of 150 μL acetic anhydride, purge time of 25 min at the purge temperature of 60 °C
with 30% NaCl. The linear range was 0.2–100 μg L−1 for phenols. The limits of detection (LODs) ranged from 0.08 to 0.15 μg L−1 and the relative standard deviations (RSDs) for most of the phenols at the 10 μg L−1level were below 10%. Natural water samples collected from a pool were successfully analyzed using the proposed method. The
recovery of spiked water samples was 72.9–84.2%. 相似文献
19.
R. Rahnama Kozani Y. Assadi F. Shemirani M. R. Milani Hosseini M. R. Jamali 《Chromatographia》2007,66(1-2):81-86
Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking
water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL
acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation
by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture
detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume
of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment
factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L−1. The linear range was 0.01–50 μg L−1 (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L−1 THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that
total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L−1. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L−1 were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple
and rapid (less than 2 min) method which requires a small volume of sample (5 mL). 相似文献
20.
Jinzhang Gao Jing Liu Jie Ren Xiuli Niu Yingying Zhang Wu Yang 《Central European Journal of Chemistry》2009,7(3):298-302
This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn2+-KBrO3-H2SO4. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed
a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L−1 tartrate, 4.0 mL 0.7 mol L−1 H2SO4, 1.5 mL 1.5×10−4 mol L−1 MnSO4, 4.0 mL 0.4 mol L−1 acetone and 7.0 mL 0.05 mol L−1 KBrO3 was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative
logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10−7∼3.75×10−5 mol L−1 with a lower detection limit of 2.50×10−8 mol L−1.
相似文献