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1.
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
2.
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
3.
The extraction behavior of tervalent rare-earth metals (Ln) using a heptane solution containing bis(2-ethylhexyl)phosphinic
acid (PIA-8, HR) from 0.1 mol/dm3 sodium perchlorate media was studied. The pH0.5 values and separation factors obtained were compared among the metals. The stoichiometry of the extracted species and the
extraction constants for the present aqueous/heptane system were determined by slope analysis. It is demonstrated that the
rare-earth metals were extracted as monomers LnR3⋅mHR (m=3, 4, 5 or 6), and the extracted species could be stripped into a relatively low concentrated hydrochloric acid. PIA-8
was found to be the most selective extractant for the mutual separation of rare-earth metals among the other phosphinic acids
reported.
Received: 27 February 1996/Revised: 13 May 1996/Accepted: 21 May 1996 相似文献
4.
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
5.
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
6.
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
7.
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
8.
Adsorptive accumulation of the Pd(II) complex with dimethylglyoxime was evaluated for stripping voltammetry with respect
to different parameters. The sensitivity of the method and the linearity between the peak current and the concentration of
Pd(II) depends on the ionic strength, the electrode area, the preconcentration time, the transport rate to the electrode,
and the potential scan rate. The most appropriate medium was 0.1 mol/L acetate buffer between pH 3.5 and 4. Using 2 min of
preconcentration at a 2.6 mm2 electrode and the differential pulse mode, a detection limit of 0.05 μg/L Pd was achieved for liquid samples and 50 ng/g
for solid samples. Different aqueous and solid samples were analysed and the recovery from biological and inorganic materials
investigated.
Received: 29 February 1996/Revised: 29 July 1996/Accepted: 1 August 1996 相似文献
9.
Anne-Marie Wifladt Grethe Wibetoe W. Lund 《Fresenius' Journal of Analytical Chemistry》1997,357(1):92-96
A method was developed for the determination of Sb in wine by electrothermal atomic absorption spectrometry, based on preconcentration
by hydride generation with collection directly in the graphite furnace. Thiourea was added for prereduction of Sb(V) to Sb(III).
The hydride was directly generated from diluted wine. Palladium was used as modifier in the collection step; the overall efficiency
of the hydride/trapping system was found to be 67%. Sb was determined in several samples of red wine; the concentrations found
were in the range 0.6 to 5.7 μg/L Sb. The detection limit of the method was 39 pg Sb, corresponding to 0.13 μg/L Sb in wine
when 0.3 mL wine was analyzed.
Received: 3 November 1995/Revised: 22 February 1996/Accepted: 24 February 1996 相似文献
10.
A method was developed for the determination of Sb in wine by electrothermal atomic absorption spectrometry, based on preconcentration
by hydride generation with collection directly in the graphite furnace. Thiourea was added for prereduction of Sb(V) to Sb(III).
The hydride was directly generated from diluted wine. Palladium was used as modifier in the collection step; the overall efficiency
of the hydride/trapping system was found to be 67%. Sb was determined in several samples of red wine; the concentrations found
were in the range 0.6 to 5.7 μg/L Sb. The detection limit of the method was 39 pg Sb, corresponding to 0.13 μg/L Sb in wine
when 0.3 mL wine was analyzed.
Received: 3 November 1995/Revised: 22 February 1996/Accepted: 24 February 1996 相似文献
11.
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
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.
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
14.
L. D. Martinez M. Baucells E. Pelfort M. Roura R. Olsina 《Analytical and bioanalytical chemistry》1997,357(7):850-852
An accurate procedure for the elimination of iron interferences in the determination of selenium in geological materials
by the Hydride Generation – Inductively Coupled Plasma Atomic Emission Spectrometry technique (HG-ICPAES) is proposed. A selective
removal of iron is achieved by on-line incorporation of a microcolumn filled with strongly acidic cation exchange resin (Dowex
50W-X8). The microcolumn manifold used was interfaced with the hydride generation manifold by a flow injection sample injection
valve. After the removal of the iron, a 500 μl sample was injected into a carrier stream of water. This was merged with hydrochloric
acid and sodium tetrahydroborate in order to generate the corresponding selenium hydride. The system was found to have a limit
of detection of 0.4 ng ml-1 and a relative standard deviation of 2% for 20 ng ml-1 selenium. The application of the method on different Geochemical Standard Reference Samples demonstrated that results were
statistically indistinguishable from certified values.
Received: 7 March 1996 / Revised: 30 May 1996 / Accepted: 4 June 1996 相似文献
15.
Anionic cartridge preconcentrators for inorganic arsenic, monomethylarsonate and dimethylarsinate determination by on-line HPLC-HG-AAS 总被引:1,自引:0,他引:1
M. Gómez C. Cámara M. A. Palacios A. López-Gonzálvez 《Analytical and bioanalytical chemistry》1997,357(7):844-849
Preconcentration anionic cartridges in combination with hyphenated FI-HG-AAS and HPLC-HG-AAS have been evaluated for the
preconcentration and quantification of total toxic arsenic and of inorganic arsenic, monomethylarsonate and dimethylarsinate
species, respectively. Optimum retention and elution parameters of the species on the anionic cartridges are evaluated and
the quality parameters of the analysis are reported. The detection limits for the arsenic species under study range from 0.1 μg L-1 to 0.6 μg L-1. The proposed method was successfully applied to the determination of arsenic species in spiked fresh water.
Received: 2 April 1996/Revised: 22 July 1996/Accepted: 25 July 1996 相似文献
16.
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
17.
Pilar Bermejo-Barrera Carmen Barciela-Alonso Consuelo González-Sixto Adela Bermejo-Barrera 《Analytical and bioanalytical chemistry》1997,357(3):274-278
A method was optimized for the determination of tin in slurries of marine sediment samples using palladium-magnesium nitrate
as chemical modifier and Triton X-100 (0.1%) surfactant as stabilizer. To obtain a complete pyrolysis of the slurry sample,
two charring steps were used, the first at 480 °C and the second at 1300 °C. The precision and accuracy of the method were
studied using the Reference Material PACS-1 (marine sediment) from National Research Council Canada. The detection limit (LOD)
was 57.6 μg kg-1. The method was applied to the determination of tin in marine sediment samples from the Galicia coast.
Received: 16 February 1996/Revised: 26 March 1996/Accepted: 12 April 1996 相似文献
18.
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
19.
Chunshan Zhou Xingan Xiong Mingjian Wu G. Schwedt 《Analytical and bioanalytical chemistry》1997,357(7):894-896
A reversed-phase HPLC-method for the separation of mixtures of collectors for the flotation of heavy metal minerals is described.
It is based on a Nucleosil 5C18 column, isocratic elution and UV-detection at 238 nm. The mobile phase is methanol-water-5%
phosphoric acid (40:60:4, v/v). The method is applied to the determination of six collectors in aqueous solutions from flotation
processes. The relative standard deviations are 1.6–3.2% in the concentration range 2–10 mg/L. The detection limits are 1 μg/L
for 8-hydroxyquinoline, dimethylglyoxime and salicylic acid, 2 μg/L for salicylhydroxamic acid and 5 μg/L for benzenetriazol
and salicylaldoxime, respectively.
Received: 19 April 1996/Revised: 14 August 1996/Accepted: 23 August 1996 相似文献
20.
A flow-through optosensor for tryptophan with C18 silica gel as a substrate is proposed. It has been developed in conjunction
with a flow-injection analysis system and is based on the retention of tryptophan on the C18 column and the enhancement of
its fluorescence. The detection limit is 25 ng mL-1 with a relative standard deviation of 2.9% for 7 determinations of 10 μg mL-1 of tryptophan. Most of the common species do not interfere. The method has been successfully applied to a pharmaceutical
preparation.
Received: 8 July 1996/Revised: 26 September 1996/Accepted: 30 September 1996 相似文献