共查询到20条相似文献,搜索用时 234 毫秒
1.
Kang Chen Yuanjin Xu Hong Zhang Lihua Nie Shouzhuo Yao 《Fresenius' Journal of Analytical Chemistry》1997,357(4):379-383
A novel surface acoustic wave-interdigitated array electrode (SAW-IDA) ammonia gas sensor is proposed. A gas-permeable membrane
is employed to separate the buffer solution in the inner cell of the gas-sensing probe from the sample solution in the detection
cell. The response of the IDA conductive electrodes is based on the impedance change of the buffer solution during ammonia
adsorption. Therefore, this gas sensor overcomes the influence of water vapour in the conventional film-coated SAW gas sensor
and can be used for the detection of gases in aqueous solutions. The ammonia sensor exhibits a favourable frequency response
to 5 × 10−7−1 × 10−3 mol/1 ammonia. The optimal buffer composition and probe parameters have been determined. Dynamic range, response time, selectivity,
and temperature drift are discussed. The ammonia sensor was also applied to the determination of serum ammonia. Results were
in good agreement with those from the conventional enzymatic-spectro-photometric method. 相似文献
2.
Mieczysław Korolczuk 《Analytical and bioanalytical chemistry》1997,357(4):389-391
A selective and sensitive method is proposed for the determination of mercury by anodic stripping voltammetry after its preconcentration
from the gas phase. Mercury from the sample solution is reduced to elemental Hg by SnCl2 and volatilized by the bubbles of a carrier gas. The gas containing mercury vapour is dried and passed through a capillary
onto a gold coated graphite electrode. An anodic stripping voltammogram is recorded from 0.1 mol/l HClO4+3×10-3 mol/l HCl solution. The calibration curve is linear from 1×10-9 to 4×10-8 mol/l Hg(NO3)2. The absolute detection limit is 0.46 ng Hg. The relative standard deviations for 4×10-9 mol/l and 2×10-8 mol/l Hg(NO3)2 are 9.8% and 6.1%, respectively (n=5).
Received: 18 December 1995/Revised: 16 April 1996/Accepted: 20 April 1996 相似文献
3.
Takashi Masadome T. Imato Satoshi Itoh Yasukazu Asano 《Analytical and bioanalytical chemistry》1997,357(7):901-903
A potentiometric flow injection method for the determination of anionic polyelectrolytes utilizing a flow-through type surfactant-selective
electrode detector is described. The method is based on the detection of the concentration increase of anionic surfactant
liberated from a reagent stream containing an ion associate between cationic polyelectrolyte, poly(diallyldimethylammonium
chloride) and anionic surfactant, dodecylbenzenesulfonate, which is caused by the formation of a polyion complex between cationic
and anionic polyelectrolytes. The response of the electrode detector as a peak-shaped signal was obtained for injected anionic
polyelectrolyte samples. A linear relationship was found to exist between peak height and the logarithmic concentration of
potassium poly (vinyl sulfate) (PVSK) with a slope of 30 mV decade-1 in a concentration range of 1.0×10-4 to 1.0×10-3 mol/L. Identical relationships were obtained for sodium alginate and carageenan (also anionic polyelectrolytes) as for PVSK
but with a lower sensitivity. The detection limit for PVSK was 2.5×10-5 mol/L. The relative standard deviation for 5 injections of a 2.5×10-4 mol/L PVSK solution was 1.3% and the sampling rate was ca. 10 samples h-1.
Received: 9 April 1996/Revised: 8 July 1996/Accepted: 14 July 1996 相似文献
4.
M. R. Ganjali Tahereh Poursaberi Fatemeh Basiripour Masoud Salavati-Niassari Mohammad Yousefi Mojtaba Shamsipur 《Analytical and bioanalytical chemistry》2001,370(8):1091-1095
A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity
sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10–6 to 1.0 × 10–1 mol L–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10–7 mol L–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor
has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.
Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001 相似文献
5.
Irena Grabec vegl Mitja Kolar Boidar Ogorevc Boris Pihlar 《Fresenius' Journal of Analytical Chemistry》1998,361(4):358-362
A vermiculite modified carbon paste electrode (VMCPE) was employed for the in situ preconcentration of traces of Hg(II)
and Ag(I) via an ion-exchange route. Heavy metal ions were accumulated in Britton-Robinson (BR) buffer pH 7 for Hg(II) and
pH 6 for Ag(I), and afterwards reduced at –0.7 V vs. Ag/AgCl in the separate measurement solution (BR buffer pH 5 + 0.05 mol/L
NaNO3) prior to the anodic stripping square-wave voltammetric (ASSWV) detection. For Hg(II) ions, at 15 min accumulation, a linear
range from 1.0 × 10–7 to 8.0 × 10–6 mol/L was obtained, with a 5.7 × 10–8 mol/L limit of detection. The VMCPE response was linear for Ag(I) ions in the concentration range from 2.0 × 10–7 to 8.0 × 10–6 mol/L, at 10 min accumulation with a corresponding limit of detection of 6.3 × 10–8 mol/L. The relative standard deviation of the analytical procedure including accumulation from a 5 × 10–7 mol/L solution of Hg (15 min) or Ag(I) (10 min), electrolysis, ASSWV detection, regeneration and activation of the VMCPE,
was 4% (n = 6). The optimisation of the parameters for the application of the VMCPE in combination with ASSWV detection is presented
and discussed.
Received: 10 July 1997 / Revised: 31 October 1997 / Accepted: 3 November 1997 相似文献
6.
M. H. Pournaghi-Azar F. Ahour M. S. Hejazi 《Analytical and bioanalytical chemistry》2010,397(8):3581-3587
Development of an electrochemical DNA biosensor for the direct detection and discrimination of double-stranded oligonucleotide
(dsDNA) corresponding to hepatitis C virus genotype 3a, without its denaturation, using a gold electrode is described. The
electrochemical DNA sensor relies on the modification of the gold electrode with 6-mercapto-1-hexanol and a self-assembled
monolayer of 14-mer peptide nucleic acid probe, related to the hepatitis C virus genotype 3a core/E1 region. The increase
of differential pulse voltammetric responses of methylene blue, upon hybridization of the self-assembled probe with the target
ds-DNA to form a triplex is the principle behind the detection and discrimination. Some hybridization experiments with non-complementary
oligonucleotides were carried out to assess whether the developed DNA sensor responds selectively to the ds-DNA target. Diagnostic
performance of the biosensor is described and the detection limit was found to be 1.8 × 10−12 M in phosphate buffer solution, pH 7.0. The relative standard deviation of measurements of 100 pM of target ds-DNA performed
with three independent probe-modified electrodes was 3.1%, indicating a remarkable reproducibility of the detection method. 相似文献
7.
Ying Wang Wanhui Liu Kemin Wang Guoli Shen R. Yu 《Fresenius' Journal of Analytical Chemistry》1998,360(6):702-706
A new optical fiber sensor was prepared for the determination of berberine in aqueous solution using a micrometer-sized flow-cell
and a bifurcated optical fiber. The sensing is based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO)
in the PVC membrane. This process is accompanied by non-fluorescent ground-state complex formation. With this sensor, berberine
can be determined in sample solutions from 2.42 × 10–5 mol L–1 to 6.04 × 10–7 mol L–1. Satisfactory reproducibility, reversibility, and short response times of less than 1 min are realized. The sensor also shows
good selectivity over some common pharmaceutical species and alkali and alkali-earth metal salts, and can be used for the
direct assay of berberine in commercial tablets. The results are in correspondence with those obtained by the pharmacopoeia
method.
Received: 4 April 1997 / Revised: 8 August 1997 / Accepted: 12 August 1997 相似文献
8.
Optical fiber sensor for berberine based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole 总被引:1,自引:0,他引:1
Ying Wang Wanhui Liu Kemin Wang Guoli Shen R. Yu 《Analytical and bioanalytical chemistry》1998,360(6):702-706
A new optical fiber sensor was prepared for the determination of berberine in aqueous solution using a micrometer-sized flow-cell
and a bifurcated optical fiber. The sensing is based on fluorescence quenching of 2-(4-diphenylyl)-6-phenylbenzoxazole (PBBO)
in the PVC membrane. This process is accompanied by non-fluorescent ground-state complex formation. With this sensor, berberine
can be determined in sample solutions from 2.42 × 10–5 mol L–1 to 6.04 × 10–7 mol L–1. Satisfactory reproducibility, reversibility, and short response times of less than 1 min are realized. The sensor also shows
good selectivity over some common pharmaceutical species and alkali and alkali-earth metal salts, and can be used for the
direct assay of berberine in commercial tablets. The results are in correspondence with those obtained by the pharmacopoeia
method.
Received: 4 April 1997 / Revised: 8 August 1997 / Accepted: 12 August 1997 相似文献
9.
C. Sanchez-Pedreño M. S. García J. A. Ortuño M. I. Albero E. Ballester 《Analytical and bioanalytical chemistry》2001,369(7-8):680-683
A flow-through bulk optode based on the use of 1-(2-pyridylazo)-2-naphthol (PAN) immobilized in a plasticized poly(vinyl
chloride) membrane entrapped in a cellulose support, in conjuntion with the flow injection analysis technique, is proposed
for the determination of manganese(II). The calibration graph obtained at 570 nm was linear in the range 0.27–27.5 mg L–1 (5 × 10–6– 5 × 10–4 M) Mn(II) with a detection limit of 0.18 mg L–1. The coefficients of variation of the sensor response for 5.5 mg L–1 of Mn(II) were ±0.22% for consecutive measurements (n = 10), ±0.48% between days (n = 5) and ±0.38% between different membranes
(n = 6). The sensor was readily regenerated with the carrier acetic acid/acetate buffer of pH 4.5. The method was applied
to the determination of manganese in steels, waters and lemon tree leaves.
Received: 13 December 2000 / Revised: 25 January 2001 / Accepted: 26 January 2001 相似文献
10.
An optical sensor membrane is described for the determination of lanthanum(III) ions based on the immobilization of 4-hydroxysalophen
on a hydrolyzed triacetylcellulose membrane. 4-Hydroxysalophen is covalently bonded to a transparent hydrolyzed triacetylcellulose
film. The sensing membrane in contact with lanthanum ions at pH 4.0 changes color from white-yellow to orange (323 to 433
nm). Under the optimum conditions, the proposed membrane displayed a linear range from 1.0 × 10−6 to 1.0 × 10−2 M La(III) with a limit of detection of 1 × 10−7 M. The response time of the membrane was within 5–6 min depending on the concentration of La(III) ions. The selectivity of
the probe towards lanthanum ions was found to be excellent. The sensor was successfully applied to the determination of La(III)
in water, industrial waste water, and in NIST-615 (glass matrix) and NIST-3127a (lanthanum solution) samples with satisfactory
results. 相似文献
11.
Fang Yan Chuanmin Ruan Xiaohong Chen J. Deng Jilie Kong 《Fresenius' Journal of Analytical Chemistry》1999,363(1):83-87
An irreversible reduction peak of oxymyoglobin (MbO2) was observed on the bare glassy carbon electrode (GCE) in acetate buffer solution under atmospheric conditions. It is the
reduction of bonded oxygen in Mb, but not the heme Fe(III)/Fe(II) redox couple that underwent electrochemical reaction on
the electrode. The peak current achieved a maximum value in acetate buffer solution of pH 4.0. The peak potential was pH dependent,
suggesting that the proton was involved in the electrochemical reaction. Furthermore, the peak current was linearly related
to the concentration of myoglobin in the range of 2.5 × 10–8∼ 1.0 × 10–6 mol · L–1 with a detection limit of 5 × 10–9 mol · L–1.
Received: 20 March 1998 / Revised: 24 June 1998 / Accepted: 1 July 1998 相似文献
12.
A novel ion-selective sensor for procaine hydrochloride has been proposed and applied successfully to analysis of pharmaceutical
preparations. The sensor is based on modification of the Ag-electrode of an AT-cut piezoelectric quartz crystal with a PVC
membrane containing procaine tetraphenylborate. A linear relation between the logarithm of the response frequency and the
logarithm of the procaine hydrochloride concentration was found experimentally and could be explained by combination of a
modified Sauerbrey equation and the Freundlich isotherm. The detection range was from 8.3 × 10−8 to 5.0 × 10−3 M with a detection limit of 8.3 × 10−8 M. The selectivity of the sensor and the influence of experimental parameters such as solution pH and detection time were
investigated.
Received February 10, 1999. Revision October 10, 1999. 相似文献
13.
A fiber-optic sensor for carbon dioxide gas is constructed, without an inner buffer solution, by using a dispersion of fluorescein in poly(ethylene glycol) deposited on the distal end of an optical fiber. Evaporation of the solvent is thus negligible. The response range is 0–28% (v/v) for carbon dioxide, with a detection limit of 0.1%. The response time achieved is 10 s. The membrane (ca. 10 μm thick) is composed of poly(ethylene glycol)s with molecular weights of 200 and 1540 dalton in a 20:80% (w/w) ratio. The best concentration of fluorescein is 5 × 10?7 mol g?1 of poly(ethylene glycol). The response mechanism of the sensor is discussed. 相似文献
14.
H. Karimi-Maleh A. A. Ensafi A. R. Allafchian 《Journal of Solid State Electrochemistry》2010,14(1):9-15
A ferrocenedicarboxylic acid modified carbon paste electrode was constructed and used as a fast and sensitive tool for the
determination of captopril at trace level. It has been shown by direct current cyclic voltammetry and double step chronoamperometry
that ferrocenedicarboxylic acid can catalyze the oxidation of captopril in aqueous buffer solution and produces a sharp oxidation
peak current at about +0.49 vs. Ag/AgCl reference electrode. The square wave voltammetric peak currents of the electrode increased
linearly with the corresponding captopril concentration in the range of 3.0 × 10−7–1.4 × 10−4M with a detection limit of 9.1 × 10−8 M. The influence of pH and potential interfering substances on the determination of captopril were studied. Electrochemical
impedance spectroscopy was used to study the charge transfer properties at the electrode–solution interface. Finally, the
sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of captopril in real
samples, such as drug and urine, with satisfactory results. 相似文献
15.
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
16.
M. Trinkel W. Trettnak F. Reininger R. Beneš P. O Leary O. S. Wolfbeis 《International journal of environmental analytical chemistry》2013,93(1-4):237-251
Abstract An optical sensor for the determination of ammonia in water based on ion pairing has been investigated. A pH-sensitive dye is immobilized as an ion pair in a silicone matrix. The colour of the dye changes from yellow to blue depending on the concentration of ammonia in the sample solution. This change is reversible. The concentration of ammonia can be determined by measuring the transmittance at a given wavelength. All measurements were performed with a dual-beam optical meter. The measurement range was from 5.9 × 10?7 to 1 × 10?3 M (0.01 to 17 mg/l) in 0.1 M phosphate buffer of pH 8. The detection limit was 10 μg/l. The response times at a flow rate of 2.5 ml/min were 4 min for t90 and 10 min for t100 at a change from 41.9 to 82.5 μM ammonia and 12 min for t90 and 48 min for t100 at a change from 160 to 0 μM ammonia. The operational lifetime of the ammonia sensor was limited to a period of a few days only. A continuous decrease in baseline signal and relative signal change was observed over the whole measurement. The storage stability was more than 10 months (dry). With respect to possible application of the ammonia sensor to environmental analysis, the influence of pH, typical interferences, such as amines and various detergents on the sensor response was investigated. No interference due to pH was observed in the range from pH 5 to pH 9. With methyl- and ethylamine the response was not completely reversible. The sensor was affected by cationic detergents, but not by anionic or neutral detergents. 相似文献
17.
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
18.
A new simple and inexpensive optical chemical sensor for cadmium(II) ions is presented. The cadmium sensing system was prepared
by incorporating 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA) on a triacetylcellulose membrane. The absorption spectra of the optical sensor membrane in Cd(II) solution showed a maximum
peak at 430 nm. The proportionality in intensity of the membrane color on the optode to varying amounts of Cd(II) suggests
its potential applications for screening Cd(II) in aqueous samples by visual colorimetry. The sensor provided a wide concentration
range of 3.0 × 10−6–3.4 × 10−4 M of Cd(II) ions with a detection limit of 1.0 × 10−6 M (0.2 μg/mL). The relative standard deviations for eight replicate measurements of 8.0 × 10−6 and 5.0 × 10−5 M Cd(II) were 2.7 and 2.3%, respectively. The response time of the optode was 6 min. The influence of interfering ions on
the determination of 1.0 × 10−5 M Cd(II) was studied and the main interferences were removed by extraction method. The sensor was applied to the determination
of Cd(II) in water samples. 相似文献
19.
S. Pozdniakova R. Ragauskas A. Dikius A. Padarauskas 《Fresenius' Journal of Analytical Chemistry》1999,363(1):124-125
A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior
to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm
× 75 μm I.D.) filled with a borate buffer (50 mmol L–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved
is 2 × 10–6 mol L–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions.
Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998 相似文献
20.
S. Pozdniakova R. Ragauskas A. Dikčius A. Padarauskas 《Analytical and bioanalytical chemistry》1999,363(1):124-125
A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior
to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm
× 75 μm I.D.) filled with a borate buffer (50 mmol L–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved
is 2 × 10–6 mol L–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions.
Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998 相似文献