共查询到20条相似文献,搜索用时 40 毫秒
1.
J. H. Wang Q. Li M. H. Wu G. Xu Ch. Li B. R. Bao W. F. Zheng H. He Sh. D. Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):249-254
N,N-dimethylhydroxylamine (DMHA) is a novel salt-free reducing reagent used in the separation U from Pu and Np in the reprocessing
of power spent fuel. This paper reports on the radiolysis of aqueous DMHA solution and its radiolytic liquid organics. Results
show that the main organics in irradiated DMHA solution are N-methyl hydroxylamine, formaldehyde and formic acid. The analysis
of DMHA and N-methyl hydroxylamine were performed by gas chromatography, and that of formaldehyde was performed by ultraviolet–visible
spectrophotometry. The analysis of formic acid was performed by ion chromatography. For 0.1–0.5 mol L−1 DMHA irradiated to 5–25 kGy, the residual DMHA concentration is (0.07–0.47) mol L−1, the degradation rate of DMHA at 25 kGy is 10.1–30.1%. The concentrations of N-methylhydroxylamine, formaldehyde and formic acid are (8.25–19.36) × 10−3, (4.20–36.36) × 10−3 and (1.35–10.9) × 10−4 mol L−1, respectively. The residual DMHA concentration decreases with the increasing dose. The concentrations of N-methylhydroxylamine and formaldehyde increase with the dose and initial DMHA concentration, and that of formic acid increases
with the dose, but the relationship between the concentration of formic acid and initial DMHA concentration is not obvious. 相似文献
2.
S. Chinnaesakki Manish Chopra Sanjeev Kumar Vishal Arora S. J. Sartandel S. V. Bara R. M. Tripathi V. D. Puranik B. S. Bajwa 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):885-892
This study presents the high purity germanium (HPGe) gamma spectrometric measurement of natural radioactivity mainly due to
226Ra, 232Th and 40K in soil samples collected in Ferozepur and Faridkot district of Punjab, India. 226Ra activity varied from 28.6 to 51.1 Bq kg−1 with the mean of 39.7 Bq kg−1. The range and mean activity of 232Th were 42.9–73.2 and 58.2 Bq kg−1, respectively. 40K activity was in the range of 470.9–754.9 Bq kg−1 with the mean of 595.2 Bq kg−1. The air kerma rate (AKR) at 1 m height from the ground was also measured using gamma survey meter in all the sampling locations,
which was ranging from 92.1 to 122.8 nGy h−1 with the mean of 110.6 nGy h−1. The radiological parameters such as Raeq and activity index of the soil samples were also evaluated, which are the tools to assess the external radiation hazard due
to building materials. The mean and range of the Raeq values were 168.7 and 132.9–210.4 Bq kg−1, respectively, whereas the activity index varied from 0.5 to 0.8 with the mean value of 0.62. These indices show that the
indoor external dose due to natural radioactivity in the soil used for the construction will not exceed the dose criteria.
The AKR was also evaluated from soil activity concentration and altitude correction of cosmic radiation contribution. The
statistical tests such as Pearson correlation, spearman rank correlation, box and whisker plot, the Wilcoxon/Mann–Whitney
test and chi-square test, were used to compare the measured AKR with evaluated AKR, which indicates good correlation. 相似文献
3.
Liu X Xu J Li Y Dong F Li J Song W Zheng Y 《Analytical and bioanalytical chemistry》2011,399(7):2539-2547
A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil,
water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four
herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected
by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target
compounds was achieved in <2.0 min. The limits of detection were below 1 μg kg−1, while the limits of quantification did not exceed 3 μg kg−1 in different matrices. Quantitation was determined from calibration curves of standards containing 0.05–100 μg L−1 with r
2 > 0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 μg kg−1 for water; 5, 10, and 100 μg kg−1 for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels
ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1–12.5% (n = 5) for all analytes. 相似文献
4.
Y. S. Murillo L. Giraldo J. C. Moreno-Piraján 《Journal of Thermal Analysis and Calorimetry》2011,104(2):555-559
A way to calculate the enthalpic contributions of each component of the mixture of activated carbon and water to the immersion
enthalpy using the concepts of the solution enthalpies is presented. By determining the immersion enthalpies of a microporous
activated carbon in water, with values that are between –18.97 and −27.21 Jg−1, from these and the mass ratio of activated carbon and water, differential enthalpies for the activated carbon,
ΔHDIFacH_{{\rm DIF}_{\rm ac}} and water, ΔHDIFwH_{{\rm DIF}_{\rm w}} are calculated, and values between –15.95 and –26.81 Jg−1 and between –19.14 and –42.45 Jg−1, respectively are obtained. For low ratios of the mixture, the components’ contributions to the immersion enthalpy of activated
carbon and water differ by 3.20 Jg−1. 相似文献
5.
H. Faghihian D. Rahi M. Mostajaboddavati 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(2):711-717
In this study the concentration of natural radionuclides has been investigated in soil and water of Karun river by using a
high resolution (HPGe detector, n-type) γ-spectrometry. The concentrations range in water sample was 47.6 ± 5.6–130.8 ± 6.3,
0.0–23.4 ± 0.5 and 0–6.4 ± 2.0 Bq L−1 for 40K, 232Th and 226Ra respectively. For soil samples the concentration range of 275.7 ± 8.6–458.6 ± 6.8, 19.2 ± 5.35–41.1 ± 3.95 and 29.9 ± 1.53–50 ± 1.54 Bq kg−1 was obtained respectively for 40K, 232Th and 238U. 137Cs was also detected in some part of the region in soil samples. The mean concentration of 137Cs was 5.5 ± 0.6 Bq kg−1. The origin of this activity is unknown. The average absorbed dose rate in outdoor air at a height of 1 m above the ground
was found to be 54.3 ± 3.7 nGy h−1. The results of this study indicate that the area has standard background radiation level. 相似文献
6.
The hydration of mesityl oxide (MOx) was investigated through a sequential quantum mechanics/molecular mechanics approach.
Emphasis was placed on the analysis of the role played by water in the MOx syn–anti equilibrium and the electronic absorption spectrum. Results for the structure of the MOx–water solution, free energy of solvation
and polarization effects are also reported. Our main conclusion was that in gas-phase and in low-polarity solvents, the MOx
exists dominantly in syn-form and in aqueous solution in anti-form. This conclusion was supported by Gibbs free energy calculations in gas phase and in-water by quantum mechanical calculations
with polarizable continuum model and thermodynamic perturbation theory in Monte Carlo simulations using a polarized MOx model.
The consideration of the in-water polarization of the MOx is very important to correctly describe the solute–solvent electrostatic
interaction. Our best estimate for the shift of the π–π* transition energy of MOx, when it changes from gas-phase to water solvent, shows a red-shift of −2,520 ± 90 cm−1, which is only 110 cm−1 (0.014 eV) below the experimental extrapolation of −2,410 ± 90 cm−1. This red-shift of around −2,500 cm−1 can be divided in two distinct and opposite contributions. One contribution is related to the syn → anti conformational change leading to a blue-shift of ~1,700 cm−1. Other contribution is the solvent effect on the electronic structure of the MOx leading to a red-shift of around −4,200 cm−1. Additionally, this red-shift caused by the solvent effect on the electronic structure can by composed by approximately 60 %
due to the electrostatic bulk effect, 10 % due to the explicit inclusion of the hydrogen-bonded water molecules and 30 % due
to the explicit inclusion of the nearest water molecules. 相似文献
7.
Marta Pedrouzo Francesc Borrull Rosa Maria Marcé Eva Pocurull 《Analytical and bioanalytical chemistry》2010,397(7):2833-2839
Stir-bar-sorptive extraction (SBSE) with liquid desorption (LD) and ultra-high-performance liquid chromatography–electrospray
ionization triple-quadrupole tandem mass spectrometry (UHPLC–(ESI)MS–MS) were used for analysis of six personal care products
in environmental water: four UV filters (2,2-dihydroxy-4-methoxybenzophenone, benzophenone-3, octocrylene, and octyldimethyl-p-aminobenzoic acid) and two antimicrobial agents (triclocarban and triclosan). Experimental conditions that affect SBSE-LD
sorption efficiency (extraction time and temperature, sample pH, and ionic strength) and desorption efficiency (solvent, temperature,
and time) were optimized. The method proved to be sensitive—a 50-mL sample was used to determine these compounds in environmental
waters at trace levels. The detection limits of the analytical method were 2.5 ng L−1 for river water and 5–10 ng L−1 for effluent and influent sewage water. In river waters, benzophenone-3 was found at levels from 6 ng L−1 to 28 ng L−1 and triclosan at levels <LOQ. Benzophenone-3 was found between 75 and 127 ng L−1 in influent sewage, whereas concentrations of benzophenone-3 and triclosan were commonly below 25 ng L−1 in effluent sewage. 相似文献
8.
A rapid, sensitive and environmentally friendly method for the analysis of 14 anilines in water samples by dispersive liquid–liquid
microextraction based on solidification of floating organic drop (DLLME-SFO) prior to gas chromatography–mass spectrometry
(GC-MS) was developed and optimized. In the proposed method, cyclohexane was used as the extraction solvent as its toxicity
was much lower than that of the solvent usually used in dispersive liquid–liquid microextraction (DLLME). In the optimized
conditions, the method exhibited good analytical performance. Based on a signal-to-noise ratio of 3, limits of detection for
anilines were in the range of 0.07 to 0.29 μg L−1, and the linear range was 0.5–200 μg L−1 with regression coefficients (r
2) higher than 0.9977. It was efficient for qualitative and quantitative analysis of anilines in water samples. The relative
standard deviations varied from 2.9 to 8.6 % depending on different compounds indicating good precision. Tap water and river
water were selected for evaluating the application to real water samples. The relative recoveries of anilines for the two
real samples spiked with 10 μg L−1 anilines were in the scope of 78.2–114.6 % and 77.3–115.6 %, respectively. 相似文献
9.
A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO2) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic
diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol)
(TX). Under static conditions phenol was quantitatively extracted onto TX-SiO2 in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO2 for phenol is 2.4 mg g−1 with distribution coefficients up to 3.4 × 104 mL g−1; corresponding data for 1-naphthol are 1.5 mg g−1 and 3 × 103 mL g−1. The distribution coefficient does not change significantly for solution volumes of 0.025–0.5 L and adsorbent mass less than
0.03 g; 1–90 μg analyte can be easily eluted by 1–3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol
and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A
540) and phenol concentration (C) in water was found according to the equation A
540 = (6 ± 1) × 10−2 + (0.9 ± 0.1)C (μmol L−1) with a detection range from 1 × 10−8 mol L−1 (0.9 μL g−1) to 2 × 10−7 mol L−1 (19 μL g−1), a limit of quantification of 1 μL g−1 (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric
method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical
analysis. The detection limit of 1-naphthol with this method is 6 μL g−1 while the quantification limit is 20 μL g−1. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one
to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08–3.2 mL g−1. 相似文献
10.
Barbora Drtinová Milan Pospíšil 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(3):631-636
Behavior of cadmium(II) in aqueous solutions irradiated by accelerated electrons was studied. A concentration of 8.8 × 10−4 mol L−1 of cadmium dissolved from Cd(NO3)2 requires dose of 15 kGy to be effectively removed from the system containing 1 × 10−2 mol L−1 of HCOOK as a scavenger of OH radicals. The positive effect of deaeration with N2O or N2 was observed in the range of lower doses. The addition of solid modifiers (bentonite, active carbon, zeolite, Cu2O, NiO, TiO2 and CuO) reduced the effectivity of radiation removal of cadmium. Product of irradiation is CdCO3. On the contrary, in the system with cadmium dissolved from CdCl2 radiation reduction takes place. Systems contained organic complexants (ethylene diamine tetraacetic acid–EDTA, citric acid)
were also studied. The solutions of Cd(NO3)2 containing initial concentration 2.37 × 10−4 mol L−1 of CdII were mixed with 3 × 10−4 mol L−1 EDTA. In this system the efficient degradation proceeds up to 90% at a dose of 45 kGy with addition of 5 × 10−3 mol L−1 carbonate (pH 10.5). The product of irradiation is CdCO3. The presence of 1 × 10−2 mol L−1 of HCOOK in the solution is necessary for radiation removal of cadmium complexed with citric acid (1 × 10−3 mol L−1) at pH 8. With increasing concentration of HCOOK (up to 5 × 10−2 mol L−1) decreases the pH value necessary for the radiation induced precipitation of cadmium. The best result was obtained in the
system containing zeolite as a solid modifier. 相似文献
11.
Minglei Tian Hyung Sang Row Kyung Ho Row 《Monatshefte für Chemie / Chemical Monthly》2010,400(8):285-290
Abstract
The enantioseparation conditions of ligand exchange chromatography were examined using ofloxacin enantiomers. A C18 column was used with the mobile phase consisting of a methanol–water solution (containing different concentrations of l-isoleucine and copper sulfate) at flow rate of 0.5 cm3 min−1. The effect of different kinds and concentrations of ligands, bivalent ligand ions, and organic modifier, and temperature on enantioseparation were evaluated; the results showed that enantioselectivity was strongly affected by the ligand concentration of the mobile phase. Under the optimum conditions (methanol/water 20:80 v/v, containing 2.5 mmol dm−3 l-isoleucine and 0.6 mmol dm−3 Cu2+, room temperature), baseline separation of the two enantiomers was obtained with resolution of 1.32 in less than 30 min. The separation method was used to analyze the ofloxacin enantiomers in different commercial medicines. 相似文献12.
A novel method for the determination of five sulfonylurea herbicides in soil was developed by a dispersive solid-phase extraction
(DSPE) clean-up followed by dispersive liquid–liquid microextraction (DLLME), prior to sweeping micellar electrokinetic chromatography
(MEKC). In the DSPE-DLLME, 10 g of soil sample was first extracted with 10 mL of acetonitrile containing 5% formic acid (pH 3.0).
The extract was then cleaned-up by a DSPE with C18 as sorbent. A 1 mL aliquot of the resulting extract was then added into a centrifuge tube containing 5 mL of water adjusted
to pH 2.0 and 60.0 μL chlorobenzene (as extraction solvent) for DLLME procedure. Then, the organic sample extraction solution
was evaporated to dryness, and reconstituted with 20.0 μL of 1.0 mmol L−1 Na2HPO4 (pH 10.0) for sweeping-MEKC analysis after DLLME. Under optimized conditions, the method provided as high as 3,000- to 5,000-fold
enrichments factors. The linearity of the method was in the range of 3.3–200 ng g−1 for chlorimuron ethyl and bensulfuron methyl, and in the range of 1.7–200 ng g−1 for tribenuron methyl, chlorsulfuron and metsulfuron methyl, with the correlation coefficients (r) ranging from 0.9965 to 0.9983, respectively. The limits of detection (LODs) ranged from 0.5 to 1.0 ng g−1. The intraday relative standard deviations (RSDs, n = 5) were below 5.3% and interday RSDs (n = 15) within 6.8%. The recoveries of the method for the five sulfonylureas from soil samples at spiking levels of 5.0, 20.0,
and 100.0 ng g−1 were 76.0–93.5%, respectively. The developed method has been successfully applied to the analysis of the target sulfonylurea
herbicide residues in soil samples with a satisfactory result. 相似文献
13.
Nitrate ions were used as the oxidant in the cathode chamber of a microbial fuel cell (MFC) to generate electricity from organic
compounds with simultaneous nitrate removal. The MFC using nitrate as oxidant could generate a voltage of 111 mV (1,000 Ω)
with a plain carbon cathode. The maximum power density achieved was 7.2 mW m−2 with a 470 Ω resistor. Nitrate was reduced from an initial concentration of 49 to 25 mg (NO3−−N) L−1 during 42-day operation. The daily removal rate was 0.57 mg (NO3−–N) L−1 day−1 with a voltage generation of 96 mV. In the presence of Pt catalyst dispersed on cathode, the cell voltage was significantly
increased up to 450 mV and the power density was 117.7 mW m−2, which was 16 times higher than the value without Pt catalyst. Significant nitrate removal was also observed with a daily
removal rate of 2 mg (NO3−–N) L−1 day−1, which was 3.5 times higher compared with the operation without catalyst. Nitrate was reduced to nitrite and ammonia in the
liquid phase at a ratio of 0.6% and 51.8% of the total nitrate amount. These results suggest that nitrate can be successfully
used as an oxidant for power generation without aeration and also nitrate removal from water in MFC. However, control of the
process would be needed to reduce nitrate to only nitrogen gas, and avoid further reduction to ammonia. 相似文献
14.
Russo MV Notardonato I Cinelli G Avino P 《Analytical and bioanalytical chemistry》2012,402(3):1373-1381
A solid-phase extraction (SPE) method was developed for extraction and analysis of six phthalate esters in wine samples using
Carbograph 1 sorbent. The SPE procedure allowed efficient recovery of the investigated phthalates ranging between 78% and
105% with a relative standard deviation (RSD) ≤6.5 for an ethanolic phthalic acid ester (PAE) standard solution and between
73–71% and 96–99% with a RSD ≤8.4 for red wine samples spiked with 20 and 50 ng mL−1 of PAE, respectively. The adsorption isotherms and breakthrough curves for Carbograph 1/water solution were reported. Gas
chromatography coupled with an ion-trap mass spectrometer detector (GC/IT-MS) was used for analysis. The instrumental analytical
protocol was found to yield a linear calibration in the range 0.01-10.0 μg mL−1 with R
2 values ≥0.9992. The limits of detection in GC/IT-MS (SIM mode) vary between 0.2 and 14 ng mL−1 (RSD ≤5.6) whereas the limits of quantification range between 0.5 and 25 ng mL−1 (RSD ≤5.9); the intra- and inter-day repeatabilities calculated as RSD for wine samples, were between 0.9–7.8 and 1.0–10.5,
respectively. The analytical method developed was applied to several commercial wine samples. Furthermore, the investigated
methods are simple, reliable, reproducible, and not expensive. 相似文献
15.
Boroujerdi AF Lee PA DiTullio GR Janech MG Vied SB Bearden DW 《Analytical and bioanalytical chemistry》2012,403(3):777-784
In-line solid-phase extraction–capillary electrophoresis coupled with mass spectrometric detection (SPE–CE–MS) has been used
for determination of 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), codeine (COD), hydrocodeine (HCOD), and 6-acetylmorphine
(6AM) in urine. The preconcentration system consists of a small capillary filled with Oasis HLB sorbent and inserted into
the inlet section of the electrophoresis capillary. The SPE–CE–MS experimental conditions were optimized as follows: the sample
(adjusted to pH 6.0) was loaded at 930 mbar for 60 min, elution was performed with methanol at 50 mbar for 35 s, 60 mmol L−1 ammonium acetate at pH 3.8 was used as running buffer, the separation voltage was 30 kV, and the sheath liquid at a flow
rate of 5.0 μL min−1 was isopropanol–water 50:50 (v/v) containing 0.5% acetic acid. Analysis of urine samples spiked with the four drugs and diluted 1:1 (v/v) was studied in the linear range 0.08–10 ng mL−1. Detection limits (LODs) (S/N = 3) were between 0.013 and 0.210 ng mL−1. Repeatability (expressed as relative standard deviation) was below 7.2%. The method developed enables simple and effective
determination of these drugs of abuse in urine samples at the levels encountered in toxicology and doping. 相似文献
16.
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
17.
Zal U’yun Wan Mahmood Che Abd Rahim Mohamed Mei Wo Yii Zaharudin Ahmad Kamaruzzaman Ishak Abdul Kadir Ishak 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):107-113
Inventories and fluxes of 210Pb, 228Ra and 226Ra were determined in sediment cores collected at nine stations covering of the southern South China Sea and Malacca Straits
with the thickness of water column between 42 and 83 m depth. The inventories of 210Pb, 228Ra and 226Ra were calculated range from 0.15–2.55 Bq cm−2, 0.05–0.40 Bq cm−2 and 6.83–83.63 Bq cm−2, meanwhile the fluxes ranged from 0.005–0.079 Bq cm−2 yr−1, 0.009–0.048 Bq cm−2 yr−1 and 0.003–0.037 Bq cm−2 yr−1, respectively. The results show that the highest inventories and fluxes for 210Pb, 228Ra and 226Ra were found at station WC 01 and EC 05. Because there are additional sources of 210Pb, 228Ra and 226Ra, where water transport will brings more dissolved isotopes, influence of the transportation and deposition of suspended
particles, fast rate of regeneration and greater production of those radionuclides and others. 相似文献
18.
Hyoe Takata Tatsuo Aono Keiko Tagami Shigeo Uchida 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):795-799
For safety assessments of geological repositories of nuclear waste, understanding of uranium (U) fate in estuarine areas is
important because U chemical behavior in the areas is expected to be complex. Environmental transfer parameters such as sediment–water
distribution coefficients (K
d) and concentration ratios (CRs) for marine organisms are useful in mathematical models for the assessment. However, due to
its low concentration in estuarine water, K
d and CF data for U are scarce. Thus we studied a rapid method for separation and concentration of U from estuarine water samples
using NOBIAS-CHELATE PA1 resin columns followed by inductively coupled plasma mass spectrometry (ICP-MS) for U measurement.
Chemical recovery was about 100% at pH of 5.7 ± 0.1 from the water samples and alkali and alkaline earth metals were removed.
The method was used to measure U concentrations in estuarine water samples collected at eight Japanese estuarine areas; they
ranged from 0.1 to 3.8 μg L−1. We also measured U concentrations in sediment and marine organism samples by ICP-MS after acid digestion. Using these values,
we observed K
d (range: 39–284 L kg−1) and CRs (0.86–52 L kg−1 for macroalgae, 0.087–15 L kg−1 for crustaceans, and 0.52–93 L kg−1 for molluscs). 相似文献
19.
A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled
carbon nanotubes (MWNTs)–chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized
Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E
θ′) of −22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k
s) in the Chit–MWNTs film was evaluated as 2.58 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive Hb in the Chit–MWNTs film was estimated to be (2.48 ± 0.25) × 10−9 mol cm−2. Meanwhile, the Chit–MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis–Menten constant (K
Mapp) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 × 10−6 to 9.30 × 10−5 mol L−1 with a detection limit of 3.47 × 10−7 mol L−1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility. 相似文献
20.
Thang M. Ngo Nam M. Hoang Tram T. M. Tran 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):287-293
The effects of absorbed doses, initial pH and 1-naphthol concentration onto its radiolysis in aqueous sulphuric and hydrochloric
acids by gamma rays from 60Co were investigated. Under the experimental conditions, 1-naphthol degradation yields increased with increasing the absorbed
doses (0.3–3.0 kGy) and with decreasing the initial 1-naphthol concentration (20–1 ppm). It was found out that the hydrated
electrons did not play any significant roles in 1-naphthol radiolysis, as the degradation yields were higher at pH0 ~ 0.46 compared to those at pH0 ~ 2.0–5.0. The corresponding radiolytic yields G(−1-naphthol) were (6.13 ± 1.00)) × 10−2 and (5.11 ± 0.22) × 10−2 μmol/J in sulphuric acids, (15.61 ± 3.85) × 10−2 and (4.76 ± 0.48) × 10−2 μmol/J in hydrochloric acids. 1-Naphthol degradation rates could be described by the kinetic equations of pseudo-first-order
reactions. An empirical relation between the observed reaction constants k
D and the initial 1-naphthol concentrations was established, enabling to predict the absorbed doses required for a given treatment
efficiency. Three products of 1-naphthol degradation were revealed using an HPLC/UV procedure. 相似文献