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1.
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
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.
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
4.
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
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.
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
8.
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
9.
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
10.
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
11.
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
12.
The effectiveness of a new polymer based solid phase extraction cartridge (SDB 1) to recover phenolic compounds from aqueous
samples has been evaluated by comparison of performance against conventional silica based cartridges. The polymer based material
is found to be much more retentive, requiring a larger volume of solvent to achieve maximum recovery. Recovery efficiency
is enhanced if the recovery solvent (methanol) is acidified to 0.1% with trifluoroacetic acid. The optimised extraction procedure
has been applied to surface water samples and yields quantitative recovery at the 10 ng ml-1 level of all nine phenols studied.
Received: 26 November 1996/Revised: 21 March 1997/Accepted: 30 March 1997 相似文献
13.
Sérgio L. C. Ferreira Marcus L. S. F. Bandeira Valfredo A. Lemos Hilda C. dos Santos A. C. Spinola Costa Djane S. de Jesus 《Analytical and bioanalytical chemistry》1997,357(8):1174-1178
A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic
acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP).
The iron(II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 × 105 l mole–1cm–1 and 5.69 × 104 l mole–1cm–1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 μg ml–1, a calibration sensitivity of 0.744 ml μg–1 at 560 nm and 0.323 ml μg–1 at 748 nm, and a detection limit of 15 ng ml–1 and 44 ng ml–1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations.
The results demonstrated a good precision (R.S.D. < 1%) and are in agreement with those obtained with others methods. The
Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system.
Received: 7 May 1996 / Revised: 1 July 1996 / Accepted: 8 August 1996 相似文献
14.
Sérgio L. C. Ferreira Marcus L. S. F. Bandeira Valfredo A. Lemos Hilda C. dos Santos A. C. Spinola Costa Djane S. de Jesus 《Fresenius' Journal of Analytical Chemistry》1997,357(8):1174-1178
A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic
acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP).
The iron(II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 × 105 l mole–1cm–1 and 5.69 × 104 l mole–1cm–1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 μg ml–1, a calibration sensitivity of 0.744 ml μg–1 at 560 nm and 0.323 ml μg–1 at 748 nm, and a detection limit of 15 ng ml–1 and 44 ng ml–1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations.
The results demonstrated a good precision (R.S.D. < 1%) and are in agreement with those obtained with others methods. The
Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system.
Received: 7 May 1996 / Revised: 1 July 1996 / Accepted: 8 August 1996 相似文献
15.
A novel catalytic procedure for zirconium was proposed based on Zr(IV) catalyzed oxidation of gallocyanine by hydrogen peroxide
in hexamethylene tetramine-hydrochloric acid buffer medium. The calibration graph is linear for 0–110 ngċml−1, and the detection limit is 0.4 ngċml−1 Zr(IV). Most foreign ions do not interfere with the determination, except for Cu2+, Fe3+ and Cr(VI). The interferences of Cu2+ and Fe3+ could be eliminated by masking with EDTA and mannitol, and that of Cr(VI) by reducing to Cr(III) with ascorbic acid. The
typical features of this procedure are that it is sensitive for zirconium, and the determination could be carried out at room
temperature. It had been used to the determination of zirconium in zirconium bronze, simulated samples and a certified reference
material. The recoveries were 98.6 ∼ 102%, and relative standard deviations (R.S.D.) were 0.9 ∼ 1.5%, respectively.
Received September 12, 1999. Revision April 10, 2000. 相似文献
16.
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
17.
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
18.
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
19.
New titrimetric and spectrophotometric methods for the fast determination of chlorhexidine digluconate (CHG) are described.
The titrimetric determination is based on the precipitation of CHG as a 1 : 1 complex with Cu2+-ions and EDTA back-titration of the non-bonded Cu2+-ions without separating the precipitate. The spectrophotometric determination is based on the formation of a soluble CHG
associate with dodecylsulphate (DDS) in a mixed medium of DDS-H2SO4-propanol. Both methods are applied to tooth pastes. When analysing a series of identical samples, the coefficient K (absorption
of 1 g of the matrix) could be determined. Standard tooth pastes and corresponding placebo-compositions (containing all components
except CHG) were specially prepared for the investigations and for estimating the accuracy of the methods.
Received: 8 January 1996 / Revised: 2 August 1996 / Accepted: 7 August 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