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1.
The integration of an urease reactor into a gas diffusion flow injection system was investigated for the determination of
urease inhibitors. The enzyme was immobilized by entrapping in polyacrylamide gel. Besides copper and silver ions mercury
ions inhibit the conversion of urea to carbon dioxide and ammonia catalysed by urease. The pH change of the carrier solution
caused by the ammonia released was measured potentiometrically with a pH electrode. The inhibition behaviour of Hg(II) ions
was investigated. A linear range from 2 to 20 μg L-1 Hg(II) was obtained after a 90 s inhibition, with a correlation coefficient of r=0.9997. The relative standard deviation
was 1.4% for five measurements of 2 μg L-1Hg(II). A sample frequency of 7 h-1 was achieved. The inhibited enzyme can be reactivated. The method was applied to the determination of Hg(II) in two drinking
water samples.
Received: 16 April 1996/Revised: 3 June 1996/Accepted: 11 June 1996 相似文献
2.
Traces of uranium and thorium in barium(II), strontium(II) titanate ((Ba, Sr)TiO3) ferroelectric materials were determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were completely
dissolved by a mixture of 1.4% H2O2 and 1.0 mol⋅l-1 HNO3. For a complete separation of the analytes from the matrix elements, a two step separation technique involving leaching and
anion-exchange was applied. By the leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-exchange step
was carried out on a BIO⋅RAD AG1-X8 column with a mixture of 1.0 mol⋅l-1 HF and 0.5 mol⋅l-1 HNO3 as eluent. The content of uranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were
0.043 ng g-1 and 0.035 ng g-1 for U and Th, respectively. The reproducibility was satisfactory with a relative standard deviation of less than 3% (at the
1 ng g-1 level, n=5). The matrix concentrations in the final solution were reduced to the sub-μg ml-1 level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy).
The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the analytes at levels of 1, 5 and 10 ng g-1 and three (Ba, Sr)TiO3 ferroelectric samples containing sub-ng g-1 levels of the analytes.
Received: 26 February 1996/Revised: 28 May 1996/Accepted: 5 June 1996 相似文献
3.
Solid-phase spectrophotometric microdetermination of iron with ascorbic acid and ferrozine 总被引:1,自引:0,他引:1
M. L. Fernández-de Córdova A. Ruíz-Medina A. Molina-Díaz 《Analytical and bioanalytical chemistry》1997,357(1):44-49
A very sensitive and selective method for the determination of trace amounts of iron has been developed, based on the reduction
of Fe(III) to Fe(II) by ascorbic acid, followed by chromogenic chelation of Fe(II) with ferrozine. The complex Fe(II)-ferrozine
is easily sorbed on a dextran-type anion-exchange gel packed in a 1 mm cell, and the absorbance of the gel is measured directly
at 569 and 800 nm. The extended linear range of the determination is 0.5–10 ng ml-1 of iron (apparent molar absorptivity=4.4×107 l mol-1 cm-1) and the precision (RSD) 1.3% for a concentration of 5 ng ml-1 of iron (n=10). The detection limit for a sample volume of 1000 ml, using 0.040 g of anion-exchanger, corresponds to 0.12 ng ml-1. The method has been successfully applied to the determination of iron in natural and waste waters, wine, soil extract and
previously digested vegetal tissues, drugs and human hair.
Received: 20 November 1995/Revised: 23 January 1996/Accepted: 26 January 1996 相似文献
4.
Traces of uranium and thorium in barium(II), strontium(II) titanate ((Ba, Sr)TiO3) ferroelectric materials were determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were completely
dissolved by a mixture of 1.4% H2O2 and 1.0 mol⋅l-1 HNO3. For a complete separation of the analytes from the matrix elements, a two step separation technique involving leaching and
anion-exchange was applied. By the leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-exchange step
was carried out on a BIO⋅RAD AG1-X8 column with a mixture of 1.0 mol⋅l-1 HF and 0.5 mol⋅l-1 HNO3 as eluent. The content of uranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were
0.043 ng g-1 and 0.035 ng g-1 for U and Th, respectively. The reproducibility was satisfactory with a relative standard deviation of less than 3% (at the
1 ng g-1 level, n=5). The matrix concentrations in the final solution were reduced to the sub-μg ml-1 level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy).
The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the analytes at levels of 1, 5 and 10 ng g-1 and three (Ba, Sr)TiO3 ferroelectric samples containing sub-ng g-1 levels of the analytes.
Received: 26 February 1996/Revised: 28 May 1996/Accepted: 5 June 1996 相似文献
5.
Determination of trace elements in AR grade alkali salts after preconcentration by column solid-phase extraction on TiO2 (anatase) 总被引:1,自引:0,他引:1
Column solid-phase extraction using TiO2 (anatase) as a solid sorbent was applied to preconcentrate traces of Cd, Co, Cu, Fe, Mn, Ni and Pb from AR grade alkali salts
prior to their measurements by atomic absorption spectrometry (AAS). Multi-element preconcentration was achieved from NaCl, KCl,
KNO3, NaNO3, CH3COONa, NaHCO3 and Na2CO3 solutions, whereas the sorption of trace elements from phosphates and sulfates is not quantitative. Optimal conditions (recoveries
of the analytes >95%) for solid-phase co-extraction of the most common heavy metal ions are proposed. The conditions for quantitative
and reproducible elution and subsequent AAS are established. A method of determination of trace elements in different salts
is proposed. It is characterized by precision, reproducibility and a high preconcentration factor. The solid-phase extraction
by TiO2, combined with ETAAS allows the determination of 0.1 ng g-1 Cd, 2 ng g-1 Co, 1 ng g-1 Cu and Ni, 0.5 ng g-1 Mn and 0.4 ng g-1 Pb.
Received: 1 April 1996/Revised: 24 June 1996/Accepted: 9 July 1996 相似文献
6.
A column preconcentration method has been established for the spectrophotometric determination of traces of nitrite using
diazotization and coupling on an naphthalene-tetradecyldimethylbenzylammonium (TDBA)-iodide (I) adsorbent. Nitrite ion reacts
with sulfanilic acid (SA) in the pH range 1.8–3.0 for the SA-1-naphthol system and in the pH range 2.3–3.2 for the SA-1-naphthylamine-4-sulfonate
system (SA-NAS system) in hydrochloric acid medium to form water-soluble colourless diazonium cations. These cations were
coupled with 1-naphthol in the pH range 1.6–4.6 and with NAS in the pH range 2.6–5.0 to be retained on naphthalene-TDBA-I
packed in a column. The solid mass was dissolved from the column with 5 mL of dimethylformamide (DMF) and the absorbance measured
at 418 nm for the SA-1-naphthol system and at 485 nm for the SA-NAS system. The calibration curve was linear over the concentration
range 0.02–0.87 mg/L for SA-1-naphthol and 0.02–0.80 mg/L in the sample for SA-NAS. The molar absorptivity was calculated
to be 1.70×104 L mol-1 cm-1 for SA-1-naphthol and 1.66×104 L mol-1 cm-1 for SA-NAS. The detection limits were found to be 0.014 and 0.016 mg/L for SA-1-naphthol and SA-NAS, respectively. The preconcentration
factors were 8 and 6 for SA-1-naphthol and SA-NAS, respectively. Replicate determinations of seven sample solutions containing
6.6 μg of nitrite for SA-1-naphthol and 5.3 μg of nitrite for SA-NAS gave mean absorbances of 0.486 and 0.382 with relative
standard deviations of 0.49 and 0.58%, respectively. Interferences due to various foreign ions have been studied and the method
has been applied to the determination of 27–65 μg/L levels of nitrite in natural waters. The recovery and relative standard
deviation for water samples were 98–102% and 0.49–0.58% for both systems.
Received: 1 December 1995/Revised: 22 April 1996/Accepted: 22 April 1996 相似文献
7.
3]2+. Whereas the initial method is carried out in an aqueous solution, the improved one employs an aqueous micellar medium formed
by the cationic surfactant cetylpyridinium bromide (CPBR). The λmax in both methods is the same, i.e. 510 nm. The mean apparent
molar absorptivity (ɛ) and Sandell’s sensitivity (Ss) were calculated as ɛ=2.10×104 Lmol-1 cm-1 and Ss=8.37 ng cm-2 for the initial procedure, and ɛ=2.62×104 Lmol-1 cm-1 and Ss=6.72 ng cm-2 for the improved one. The regression line equation for the improved method was: A=1.487×10-1C −1.415×10-2 (r=0.9998). The accuracy and the precision of the improved method were investigated and the conclusions were satisfactory.
The results obtained for ASCA by both the described method and an official one, were statistically compared by means of the
Student’s t-test and by the variance ratio F-test; and no significant difference was observed.
Received: 15 January 1996/Revised: 7 March 1996/Accepted: 13 March 1996 相似文献
8.
Vibha Saxena Vinay Shirodkar Rajiv Prakash 《Journal of Solid State Electrochemistry》2000,4(4):234-236
A device has been developed for the measurement of copper(II) ions (Cu2+) in aqueous medium. The device reported here is an electrochemical transistor which consists of two platinum electrodes separated
by 100 μm spacing and bridged with an anodically grown film of polycarbazole. Polycarbazole film (undoped form) is observed
to be highly selective for the Cu(II) ions. In a completed device, the conductivity of the polycarbazole film changes on addition
of Cu(II) ions. The change in conductivity is attributed to the conformational changes in the polymer phase on occupation
of the Cu(II) ions, without affecting electron/proton transfer. The device turns on by adding 2.5 × 10−6 M Cu(II) ions and reaches a saturation region beyond 10−4 M Cu(II) ion concentrations. In the above concentration range, the device response [I
D vs. log Cu(II) ion concentration] is linear. The selectivity of the device for other metal ions such as Cu(I), Ni(II), Co(II),
Fe(II), Fe(III), Zn(II) and Pb(II) is also studied.
Received: 6 April 1999 / Accepted: 20 August 1999 相似文献
9.
A flow injection method for the sequential determination of iron(II) and iron(III) was developed. It is based on the differential
reaction kinetics of iron(II) and iron(III) with Tiron in a double-injection FI system. The proposed method employs the accelerating
action of copper(II) for the oxidation of iron(II) in the presence of Tiron. A linear calibration graph is obtained for iron
(II) and iron(III) in the concentration range 1.8 × 10–5– 1.8 × 10–4 mol/L; the throughput of samples is 30 injections/h.
Received: 22 October 1996 / Revised: 4 December 1996 / Accepted: 10 December 1996 相似文献
10.
Pyrene-tetramethylpiperidinyl (Pyr-Tempo) as a spin label fluorescent probe for iron(II) was synthesized. It exhibited weak
fluorescence (λexc/λem = 346/399 nm) in aqueous solution due to an intramolecular quenching pathway. A method for determination of iron(II) was
proposed based on the fluorescence enhancement of the probe in the presence of iron(II) in acidic medium. Under optimum conditions,
the fluorescence enhancement of Pyr-Tempo is linearly proportional to the iron(II) concentration range of 6.0 × 10−8 to 9.6 × 10−6 mol L−1 with a detection limit of 8.0 × 10−9 mol L−1. The relative standard deviation (RSD) of six replicate measurements is 1.95% for 3.0 × 10−7 mol L−1 iron(II). The developed spin label fluorescence probe is found to be rapidly and sensitively responsive to iron(II) with
high selectivity compared to existing fluorescence methods. The proposed method was successfully applied to iron(II) detection
in five real samples with satisfactory results obtained by manual UV/Vis spectrophotometry (standard method) with 1,10-phenanthroline. 相似文献
11.
Francisco Laborda María V. Vicente José M. Mir J. R. Castillo 《Analytical and bioanalytical chemistry》1997,357(7):837-843
Chromatographic effluents were on-line analyzed by Zeeman-ETAAS, using a flow-through cell placed in a graphite furnace autosampler
as interface. To obtain high sampling rates, the use of fast graphite furnace programmes was studied. Conventional programmes
of 96 s were reduced to 18 s by using hot injection (120 °C) and reducing the charring step to 2 s. The increase of the injection
volume from 20 to 60 μl lengthened the programme to 46 s. Nickel had to be added to get a comparable response for both inorganic
and organic selenium species (selenite and selenomethionine) and to reduce the interferent effect produced in presence of
the chromatographic eluent (TRIS 0.01 mol l-1, NH4NO3 0.1 mol l-1, pH 7). The optimized conditions were applied to the speciation of selenium in human erythrocyte lysates by size exclusion
LC-ETAAS. Using a high performance size exclusion column selenium could be assigned to proteins of 100 and 35 kDa. Detection
limits in the range of 1 ng (2 μg l-1 for 500 μl injection volume) were obtained for the combined technique.
Received: 9 October 1996/Revised: 8 July 1996/Accepted: 14 July 1996 相似文献
12.
5,10,15,20-tetrakis(phenoxy acetic acid) porphyrin (PAAP) was covalently linked to Merrifield chloromethylated resin. Characterization
of PAAP and the modified polymeric matrix were performed by 1H NMR, FTIR and elemental analysis. The sorbent was used for the separation and enrichment of the d-electron metals (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) at pH 6–8 and of the f-electron metals U(VI) and Th(IV) at pH 4–5. The metals ions were preconcentrated with a concentration factor range of 115–215
and then determined by flame atomic absorption spectrometry or visible spectrophotometry using Arsenazo(III). The retained
metals were eluted with 2.0 mol L−1 HNO3 in the case of the d-electron metals and 0.1/0.25 mol L−1 HCl in the case of the f-electron metals. The procedure was validated by analyzing the NIST standard reference material 2709 (San Joaquin Soil).
Correspondence: Melek Merdivan, Chemistry Department, Faculty of Arts and Sciences, Dokuz Eylul University, 35160 Buca, Izmir,
Turkey 相似文献
13.
Elena A. Reshetnyak Nataliia V. Ivchenko Nataliya A. Nikitina 《Central European Journal of Chemistry》2012,10(5):1617-1623
Photometric determination of aqueous Co(II), Cu(II), Ni(II) and Fe(III) was performed using indicator films prepared by immobilization
of 1-nitroso-2-naphthol-3,6-disulfonic acid disodium salt (NRS) into hardened photographic film. Immobilization was based
on electrostatic interaction of reagent and metal complexes with the gelatin. The isoelectric point pH of hardened gelatin
(4.46±0.04) was evaluated by viscometry. Co(II), Fe(III), Ni(II) form 1:3 complexes with NRS in gelatin at pH 2 and Cu(II)
forms 1:2 complexes. Their log β′ values were: Co-6.7, Fe-8.6, Cu-8.0, and Ni-6.4. The absorption maxima were: 370nm for NRS,
and 430nm, 470nm, 495nm and 720nm for complexes of Co(II), Ni(II), Cu(II) and Fe(III). An algorithm for their simultaneous
determination using the indicator films was developed. The detection limits were: clim(Co2+) = 0.45×10−5 M, clim(Fe3+) = 0.50×10−5 M, clim(Cu2+) = 0.67×10−5 M, clim(Ni2+) = 0.75×10−5 M,; and their sum clim(ΣMn+) = 0.82×10−5 M.
相似文献
14.
Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3-methylglutarates were prepared as solids with general formula MC6 H8 O4 ×n H2 O, where n =0–8. Their solubilities in water at 293 K were determined (7.0×10−2 −4.2×10−3 mol dm−3 ). The IR spectra were recorded and thermal decomposition in air was investigated. The IR spectra suggest that the carboxylate
groups are mono- or bidentate. During heating the hydrated complexes lose some water molecules in one (Mn, Co, Ni, Cu) or
two steps (Cd) and then mono- (Cu) or dihydrates (Mn, Co, Ni) decompose to oxides directly (Mn, Cu, Co) or with intermediate
formation of free metals (Co, Ni). Anhydrous Zn(II) complex decomposes directly to the oxide ZnO.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Waxes were separated from needles by chloroform washing, drying and dissolving the residue in tetrahydrofuran (THF). Both
a THF solution of the wax and an aqueous solution of the Pd-Mg matrix modifier were sampled directly into the graphite tube.
The reaction conditions were optimised for the wax concentration of 45 mg ml-1 in THF and the Pd:Mg ratio of 1:1 in the matrix modifier. The atomisation and charring temperatures for As, Cd and Pb were
the same as those recommended for analysis of aqueous solutions except the charring temperature of Cd takes 200 °C lower.
The characteristic masses for As (26 pg), Cd (0.5 pg) and pb (9 pg) are also comparable to published data. The parameters
of calibration curves were identical for all three elements dissolved either in clear THF or in the wax solution. Elemental
concentrations were found to range from 0.1 to 1.0 mg g-1, increasing with needle age for As, Pb but not Cd.
Received: 20 September 1996 / Revised: 14 November 1996 / Accepted: 13 December 1996 相似文献
16.
The polarographic reduction of Co(II) in the presence of moxifloxacin (1-cyclopropyl-7-[(S,S)-2.8-diazabicyclo[4.3.0]non-8-yl]-6-fluoro-8-methoxy-1.4-dihydro-4-oxo-3-quinolinecarboxylic
acid) gives rise to an additional adsorption peak corresponding to the reduction of Co(II)-moxifloxacin complex on the mercury
drop electrode at −1.17 V. This new peak is applicable to Co(II) determination with the linearity proportional to the Co(II)
concentration in the range of 4.93 × 10−7−6.90 × 10−5 M and can be attributed to an adsorption-controlled process with an irreversible reduction. Without using moxifloxacin, the
polarographic determination of 2.50 × 10−6 M Co(II) is impossible under the given conditions due to very poor sensitivity at −1.38 V. The proposed method showed good
precision and accuracy with a relative standard deviation of 3.01% and relative error of +6.40% for the determination of 2.50
× 10−6 M Co(II) next to 5.0 × 10−6 M of Zn(II), Ni(II), and Cd(II). The accuracy of the method was also checked by the determination of Co(II) spiked with tap
water and certified sea water, and the percentage recoveries were 97.5 and 96.7%, respectively (n = 4 at 95% confidence interval).
The text was submitted by the authors in English. 相似文献
17.
Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless
copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and
pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.)
filled with an ethylenediamine sulfate electrolyte (20 mol L−1 ethylendiamine, pH7.0 with H2SO4; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s
hydrodynamic injection were 5×10−6 mol L−1 for Cu(II) and 1×10−6 mol L−1 for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively,
with five consecutive injections of standard solution containing 5×10−5 mol L−1 of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples
is also demonstrated. 相似文献
18.
A flow-through optosensor for quinine is described. It has been developed in conjunction with a flow-injection analysis system
and uses immobilized β-cyclodextrin as the sensing agent. The detection limit for quinine was 0.20 ng ml-1 with a relative standard deviation of 2.1% for the determination of 0.05 μg ml-1 (n=7) of quinine. The method has been successfully tested for the determination of quinine in some pharmaceutical preparations.
Received: 4 June 1996 / Revised: 23 August 1996 / Accepted: 24 August 1996 相似文献
19.
A flow-through optosensor for quinine is described. It has been developed in conjunction with a flow-injection analysis system
and uses immobilized β-cyclodextrin as the sensing agent. The detection limit for quinine was 0.20 ng ml-1 with a relative standard deviation of 2.1% for the determination of 0.05 μg ml-1 (n=7) of quinine. The method has been successfully tested for the determination of quinine in some pharmaceutical preparations.
Received: 4 June 1996 / Revised: 23 August 1996 / Accepted: 24 August 1996 相似文献
20.
A. Merko?i A. Sastre J. L. Cortina C. Maccà 《Fresenius' Journal of Analytical Chemistry》1997,358(4):489-492
The acidity constant of di(2-ethylhexyl) thiophosphoric acid (DEHTPA) was investigated using potentiometric measurements
with a pH glass electrode. Owing to the low solubility of DEHTPA in pure water, its concentration and acidity constants were
determined by linearised pH-metric titration in 16.7% ethanol. A Ka value of (2.39±0.08)×10-4 was obtained. Quantitative determination of DEHTPA was performed by capillary zone electrophoresis (CZE) with carbonate buffer
(pH 11.0) as a background electrolyte, operating at −20 kV with direct UV detection at 210 nm. The migration time was 8.97 min
and the detection limit was 5 ppm.
Received: 2 September 1996/Revised: 19 November 1996/Accepted: 21 November 1996 相似文献