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1.
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
2.
I. Shimizu H. Okabayashi N. Hattori K. Taga A. Yoshino C. J. O’Connor 《Colloid and polymer science》1997,275(3):293-297
Changes in the 13C and 1H NMR chemical shifts of the silane coupling agent (3-aminopropyltri-ethoxysilane, APTS) in toluene, which were detected as
the concentration of APTS increased, have been interpreted in terms of the formation of micelles and the presence of a critical
micelle concentration (CMC) equal to ca. 0.47 mol 1-1. For the protons of the n-propyl segment, 1H NMR splitting patterns have been analyzed and conformations of the propyl segment have been discussed. Plots of relative
absorbance of the two NH2 stretch IR bands at 3324 and 3384 cm-1 against concentration provided an inflection point (corresponding to the CMC) at a value equal to 0.46 mol 1-1. Thus, consideration of the interaction of APTS with a surface must take into account the presence of both APTS aggregates
as well as APTS monomers.
Received: 16 August 1996 Accepted: 26 September 1996 相似文献
3.
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
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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
11.
A new method for determining the static permittivity (dielectric constant) of extremely thin liquid interlayers is illustrated.
A special condenser, which can be filled with a test liquid, is constructed. Both condenser plates – one planar, the other
spherically curved – are made of vitreous carbon and are supplied with a high-grade politure.
In order to adjust plate separation distances from 10 nm up to about some μm the planar plate can be easily shifted by a piezoelectric
translation stage; the plate separation is monitored by an optical system supported by displacement transducers.
The measuring frequency was kept constant at 1 MHz. Water was chosen as the test liquid. At 19.8 °C thin water layers having
thickness smaller than 0.3 μm exhibit a decrease of the dielectric constant. The experimental data are consistent with a decay
length α-1 of the order of 1 nm which in view of the underlying crude model must be regarded as approximative.
Received: 28 May 1996 Accepted: 30 September 1996 相似文献
12.
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
13.
M. A. Kabil S. E. Ghazy A. A. El-Asmy Y. E. Sherif 《Analytical and bioanalytical chemistry》1997,357(4):401-404
A sensitive and selective flotation procedure for the separation of microamounts of Co(II), Ni(II) and Cu(II) separately
or in admixture is described. The maximum separation rate (∼1) for 0.1 mmol/L of each analyte is achieved using 1 mmol/L of
both oleic acid (HOL) surfactant and 4-phenylthiosemicarbazide (HPTS) as a collector in the pH range 6–7. A method for the
simultaneous separation and microdetermination of the analytes is elaborated, based on adding excess HPTS and floating the
species with HOL at pH ∼6. The filtrate (which is clear brownish-yellow) obtained from the scum is used for the spectrophotometric
determination of Co(II) at 350 nm. The formation constants of 1:1 and 1:2 [Co(II):HPTS] species are 6.9×105 and 1.22×1010 L mol-1, respectively. Beer’s law is obeyed up to 9 μg/mL of Co(II) with a molar absorptivity of 1.15×104 L mol-1 cm-1. The precipitate in the scum layer is quantitatively collected, dissolved in aqua regia and aspirated directly into the flame
for the (AAS) determination of Ni and Cu. The procedure is successfully applied to some natural water samples. A mechanism
for the separation of the analytes is proposed.
Received: 23 January 1996/Revised: 1 April 1996/Accepted: 9 April 1996 相似文献
14.
P. Bermejo-Barrera Antonio Moreda-Piñeiro Jorge Moreda-Piñeiro Adela Bermejo-Barrera 《Analytical and bioanalytical chemistry》1997,358(7-8):844-847
Rapid methods were developed for the direct determination of Ag, Al, Cd and Mn in cocaine and heroin by ETAAS using programmes
omitting the charring step . Sample pretreatment was simple: dissolution in ultrapure water or in 35.0% (v/v) HNO3 for heroin or cocaine, respectively. Optimum drying temperatures were 250 °C for Ag, Al and Mn, and 300 °C for Cd. The run
cycles were 35 and 37 s, for Ag and Al respectively, and 36 s for Cd and Mn. The best results were obtained with Pd, Mg(NO3)2 and (NH4)2HPO4, as chemical modifiers. The limits of detection were 8.6, 55.9, 2.2 and 12.4 μg kg-1 for Ag, Al, Cd and Mn, respectively.
Received: 14 November 1996/Revised: 14 January 1997/Accepted: 18 January 1997 相似文献
15.
A new method for the separation and determination of trace amounts of cadmium and zinc in water as their thenoyltrifluoroacetone
(TTA) complexes with dibenzo-18-crown-6 (DB18C6) in o-dichlorobenzene has been established by means of synergistic extraction
and back-extraction combined with atomic absorption spectrometry. The effect of various factors (synergism with TTA and DB18C6,
shaking time, composition of the extracted species, and mutual separation etc.) on the extraction and back-extraction of cadmium
and zinc has been in- vestigated. When the mixtures were extracted for 4 min at pH 4.9, only zinc was extracted quantitatively,
whereas cadmium remained in the aqueous phase. After the phases were separated, cadmium was again extracted quantitatively
at pH 7.5. Then, the two phases were each shaken with 0.05–0.1 mol/l HCl in order to back-extract cadmium and zinc from the
organic phases; the ions were determined individually by atomic absorption spectrometry. In the process cadmium and zinc TTA
chelates in o-dichlorobenzene form stable adducts with DB18C6 (Cd(TTA)2 ⋅ nDB18C6 and Zn(TTA)2 ⋅ nDB18C6, n=0∼2). The stability constants (βn) of the adducts determined by means of the curve fitting method were log β1=4.62 and log β2=6.74 for cadmium, and log β1=3.48 and log β2=5.18 for zinc.
Received: 8 September 1995/Revised: 22 January 1996/Accepted: 24 January 1996 相似文献
16.
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
17.
The analysis of the interaction of micelles formed by a blockcopolymer is given by means of small-angle X-ray (SAXS) and
small-angle neutron scattering (SANS). The blockcopolymer consists of poly(styrene) and poly(ethylene oxide) (molecular weight
of each block: 1000 g/mol) and forms well-defined micelles (weight-association number: 400, weight-average diameter: 15.4 nm)
in water. The internal structure has been studied previously (Macromolecules 29:4006 (1996)) by SAXS. There it has been shown
that the micelles are spherical objects. The structure factor S(q) as a function of the scattering vector q (q=(4π/λ) sin (θ/2); λ: wavelength of the radiation in the medium; θ: scattering angle) can be extracted from both sets of small-angle
scattering data (SANS: q≤0.4 nm-1; SAXS: q≤0.6 nm-1). It is shown that particle interaction in the present system can be described by assuming soft interaction which is modeled
by a square-step potential.
Received: 12 May 1997 Accepted: 9 July 1997 相似文献
18.
The characteristics of poly(oxyethylene) hydrogenated caster oil ether (HCO-10) vesicles were studied for the standpoints
of encapsulation efficiency, stability, solubilization and permeability or barrier efficiency. The vesicles of 5% HCO-10 had
6.24% of calcein-entrapment efficiency and 240 nm of mean diameter. The stability of HCO-10 vesicle suspensions was dependent
on their concentrations. In the vesicle suspensions of 10% HCO-10 or more, both the size of the vesicles and the fluidity
of the suspensions obviously varied with incubation time, indicating that a flocculation occurred; whereas, the vesicle suspension
of 5% HCO-10 was relatively stable. The solubilization process of HCO-10 vesicles by SDS was similar to that of EggPC liposomes.
The rate constants for permeation of Cl ion and calcein were 2.46×10-3 s-1 and 5.79×10-5 s-1, respectively, suggesting that HCO-10 vesicles possessed some barrier potential for Cl ion and calcein although they were
smaller than those of liposomes. Furthermore, the efflux of the solute such as calcein from HCO-10 vesicles was maximum at
37 °C, where the vesicle membrane was presumably destabilized by dehydration of EOs in HCO-10 molecules.
Received: 7 May 1996 Accepted: 3 September 1996 相似文献
19.
This paper summarizes several key points in applying the microwave preparation technique to the elemental analysis of aquatic
sediments and reports systematic experiments in searching for an optimal microwave preparation procedure for element analysis
in sediment samples. The determination of the elements Cu, Pb and Cd in a standard reference aquatic sediment sample (CRM
280, COMEUR) was achieved by first digesting the samples in a microwave oven equipped with PFA advanced composite vessels,
followed by AAS measurement. The influence of microwave power, digestion time, various dissolution reagents and the HF removing
conditions was studied. It has been shown that for a 0.1 g sediment sample the optimal microwave preparation conditions are:
4–5ml HNO3/HF/H2O2 as solvent, digesting time 30 min with 100% microwave power and evaporating the residual acid within 8 min in an open vessel
at 80 °C. The element recovery rates with AAS measurement can reach up to 92.4–100.6%.
Received: 23 July 1996/Revised: 23 September 1996/Accepted: 25 September 1996 相似文献
20.
Andrea D. Magrí A. L. Magrí Fabrizio Balestrieri Amalia Sacchini D. Marini 《Analytical and bioanalytical chemistry》1997,357(7):985-988
A sensitive spectrophotometric method for the determination of ethanol with potassium dichromate was developed. Chromium(VI),
in 7 mol L-1 perchloric acid, reacts quantitatively with ethanol to form chromium(III) and acetic acid. The reaction is complete in about
15 min at room temperature and the chromium(VI) consumed may be determined by the decrease of the absorbance at 267 nm. The
analytical working parameters (such as acidity and ionic strength of the solution, temperature and time of the reaction, chromium(VI)
concentration, matrix interferences) were optimized. The apparent molar absorptivities of chromium(VI), in the monomer and
dimer form, and the equilibrium quotient for the dimerization reaction were determined in 3 mol L-1 perchloric acid solution. The method was applied to the analysis of micro samples of commercial beverages (beers, wines and
spirits) without the previous distillation of ethanol.
Received: 9 April 1996/Revised: 3 June 1996/Accepted: 11 June 1996 相似文献