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1.
A successful flow-through system was developed for trace analysis of copper using DPASV with a glassy-carbon electrode. Periodical
chemical regeneration of the electrode with a 1 mol/L NaOH solution increased sensitivity and precision. The method was shown
to be applicable with a detection limit of 0.56 μg/L, with a determination time of less than 7 min per measurement (without
deaeration time). The drawback of the system is the 10 min deaeration time. The system gave an accuracy of 0.090±0.005% for
a certified reference material of low alloy steel containing 0.090±0.004% Cu. Applicability to various fresh water samples
with a Cu content between 1.57 and 13.11 μg/L with an RSD<2.36% is illustrated.
Received: 11 March 1996/Revised: 1 July 1996/Accepted: 4 July 1996 相似文献
2.
Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively
coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed
for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range
of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated
by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide
has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard
deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique,
which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level
of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other
methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate
fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore
fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L
level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive
but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short
analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace
bromide and bromate species in water samples.
Received: 5 July 1996/Accepted: 7 August 1996 相似文献
3.
A successful flow-through system was developed for trace analysis of copper using DPASV with a glassy-carbon electrode. Periodical
chemical regeneration of the electrode with a 1 mol/L NaOH solution increased sensitivity and precision. The method was shown
to be applicable with a detection limit of 0.56 μg/L, with a determination time of less than 7 min per measurement (without
deaeration time). The drawback of the system is the 10 min deaeration time. The system gave an accuracy of 0.090±0.005% for
a certified reference material of low alloy steel containing 0.090±0.004% Cu. Applicability to various fresh water samples
with a Cu content between 1.57 and 13.11 μg/L with an RSD<2.36% is illustrated.
Received: 11 March 1996/Revised: 1 July 1996/Accepted: 4 July 1996 相似文献
4.
Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively
coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed
for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range
of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated
by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide
has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard
deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique,
which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level
of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other
methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate
fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore
fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L
level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive
but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short
analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace
bromide and bromate species in water samples.
Received: 5 July 1996/Accepted: 7 August 1996 相似文献
5.
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
6.
Masataka Hiraide Yasushi Mikuni Hiroshi Kawaguchi 《Fresenius' Journal of Analytical Chemistry》1996,354(2):212-215
A silver sample (50–300 mg) was dissolved in 6 mol/l nitric acid and mixed with 6 mol/l hydrochloric acid to form silver
chloride. The solution was evaporated to dryness and the residue was treated ultrasonically in 0.1 mol/l nitric acid for the
extraction of trace impurities from the silver chloride. Traces of iron, copper, lead and bismuth were recovered in greater
than 94% yields, though considerable amounts of cadmium were not extracted due to the strong occlusion in the silver chloride.
The separation factor for the silver was about 10-4; hence the trace heavy metals were immediately determined by graphite-furnace atomic absorption spectrometry without any
interference. The validity of the method was confirmed by the analysis of certified reference material. The proposed method
is simple and allows the detection of as little as 10 ng/g levels in silver samples.
Received: 13 January 1995/Accepted: 29 March 1995 相似文献
7.
A. N. Araújo José A. M. Catita José L. F. C. Lima Elias A. G. Zagatto 《Fresenius' Journal of Analytical Chemistry》1998,360(1):100-103
A monosegmented flow system (MCFA) is proposed to achieve slow enzymatic spectrophotometric determinations, here applied
to the determination of triglycerides in blood serum. The sample (4.5 μL), enzymatic reagent (150 μL) and an air plug (100 μL)
are simultaneously inserted into a carrier stream buffered to pH 7.9 (Tris ⋅ HCl). In order to avoid the cumbersome step of
air removal, a relocating detector was used. This system handles about 60 samples/h, yielding precise results (r.s.d. usually<2.5%).
Sensitivity is 56 mAU ⋅ L/mmol up to 6 mmol/L triglycerides. Accuracy was assessed by running 50 samples already analysed
by a conventional procedure yielding the equation CMCFA(mmol/L)=1.00(±0.04) CRef(mmol/L)−0.03(±0.08); r=0.990.
Received: 22 January 1997/Revised: 12 March 1997/Accepted: 28 March 1997 相似文献
8.
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
9.
P. Bermejo-Barrera Jorge Moreda-Pi?eiro Antonio Moreda-Pi?eiro Adela Bermejo-Barrera 《Fresenius' Journal of Analytical Chemistry》1998,360(2):208-212
Electrothermal atomic absorption spectrometry (ETAAS) applying a Zeeman effect background correction system (ZEBC) and a
tranverse heated atomizer was used to directly determine chromium in sea water. Calcium chloride (at a concentration of 20
mg L–1) was applied as chemical modifier with optimum charring and atomization temperatures of 1600°C and 2000°C, respectively.
The detection limit was 0.2 μg L–1, by injecting 20 μL aliquot of sea water sample. This detection limit could be reduced further to 0.05 μg L–1, using multiple injections (injection of five 20 μL aliquot of sea water). The accuracy of the methods developed were confirmed
by analyses of different certified reference materials. Finally, interferences from major and minor components of sea water
are studied.
Received: 20 February 1997 / Revised: 26 May 1997 / Accepted: 8 June 1997 相似文献
10.
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
11.
6-Mercaptopurine(6-MP) is covalently modified onto a silver electrode to construct a chemically modified electrode (CME).
It exhibits the capability of selectively complexing myoglobin and can be applied as a selective biosensor for this compound.
Myoglobin is accumulated onto the CME at 0.32 V (vs. SCE); after exchanging the medium it is determined by differential pulse
stripping voltammetry. A cathodic stripping peak is obtained at 0.15 V (vs. SCE) by scanning the potential from 0.35 to –0.1
V. The peak currents are linearly proportional to the concentration of myoglobin in the range of 0.2 ∼ 4 μg/mL with a relative
standard deviation of 7.8%. The detection limit is about 0.1 μg/mL. The mechanism of the complexation is also discussed.
Received: 30 January 1997 / Revised: 7 May 1996 / Accepted: 10 May 1996 相似文献
12.
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
13.
D. Bohrer P. C. do Nascimento S. Garcia Pomblum E. Seibert L. Machado de Carvalho 《Fresenius' Journal of Analytical Chemistry》1998,361(8):780-783
A method for the determination of cyanide in blood plasma by differential pulse polarography (DPP) is described without a
drastic acidification of the sample. Cyanide was determined as tetracyanonickelate(II)-anion complex after a microwave-acid
assisted cleanup and a selective complex extraction in a polyethylene methylene blue (PE-MB) impregnated column. The cyano
complex was eluted from the column with water/acetonitrile and determined by pulse-polarography at –380 mV (Ag/AgCl). The
linear range of calibration was obtained from 1.2 to 9.6 μg of cyanide with r = 0.99 and RSD = 9% of 1.2 μg of cyanide. A
detection limit of 40 μg L–1 was calculated and the recoveries of cyanide from spiked samples were about 80%. This method was compared with the classical
pyridine-pyrazolone method.
Received: 3 September 1997 / Revised: 21 January 1998 / Accepted: 24 January 1998 相似文献
14.
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
15.
Amorphous spherical particles of nickel sulfide of 10 nm in diameter were synthesized by the controlled double-jet precipitation
(CDJP) technique using nickel sulfate and sodium sulfide. Cubic crystalline particles of ∼200 nm were obtained by aging dispersions
of amorphous particles at 80 °C for more than a week, as long as the pH was kept between 3 and 3.5. Electrokinetic mobilities
of these particles are reported, as well as color properties of their dispersions in liquids and in poly(vinyl alcohol) films
are described.
Received: 20 January 1997 Accepted: 21 January 1997 相似文献
16.
C. Faller G. Henze N. Stojko S. Saraeva K. Brainina 《Analytical and bioanalytical chemistry》1997,358(6):670-676
The paper describes the determination of tin by ASV using modified thick film electrodes. Three different types of electrodes
were developed: One modified with a mixture of Nafion and mercury(II)acetate, one modified with diethyldithiocarbamate (DDC)
or pyrrolidinedithiocarbamate (PDC) and mercury(II)acetate, and one modified with calomel. The analyte was accumulated on
the electrode surface after special electrochemical pretreatment of the modified electrode. After recording the voltammogram
the electrodes were electrochemically regenerated. By virtue of their lifetime and their measurement reproducibility, we preferred
the DDC and PDC modified electrodes. They can be used for months without changing their chemical characteristics. The linear
range for tin determination with these electrodes is between 1 and 100 μg/L; the detection limit was calculated as 0.9 μg/L.
The electrodes were applied to the direct determination of tin in different canned fruit juices without special sample pretreatment.
Received: 20 December 1996 / Revised: 11 March 1997 / Accepted: 13 March 1997 相似文献
17.
Zhang De-qiang Ni Zhe-ming Sun Han-wen 《Fresenius' Journal of Analytical Chemistry》1997,358(5):641-645
Parts-per-billion levels of germanium can be determined directly by graphite furnace atomic absorption spectrometry (GFAAS)
using palladium plus strontium as a mixed modifier resulting in pyrolysis temperatures up to 1400 °C without loss of germanium.
At this temperature the matrix effect including the most troublesome sulfate interference can be eliminated. Palladium plus
strontium nitrate is advantageous compared to palladium alone or palladium plus magnesium nitrate; an amount of 15 μg of sulfate
does not show any interference on the determination of 1 ng of germanium. The method was successfully applied to the determination
of ng/g levels of germanium in botanical samples and coal fly ash after thermal decomposition of the samples in a mixture
of acids using a pressure bomb. The results were consistent with the reference values given for botanical samples and coal
fly ash with a recovery range of 96.4∼103.4%
Received: 16 September 1996/Revised: 10 December 1996/Accepted: 14 January 1997 相似文献
18.
Stella T. Giroussi Anastasios N. Voulgaropoulos Aristomenis Ayiannidis 《Analytical and bioanalytical chemistry》1997,357(4):429-432
A selective, sensitive and reliable voltammetric method for the simultaneous determination of Cu and Mo is developed. Both
metals form complexes with 8-hydroxyquinoline (oxine). Mo gives two reduction peaks with oxine in acidic chloride media at
−0.52 V and −0.58 V, while copper exhibits only one at −0.14 V. Common heavy metals do not interfere at all. The limit of
detection is 0.29 ng/ml for Mo and 0.14 ng/ml for Cu after preconcentration on the hanging mercury drop electrode for 30 s
at −0.2 V. The R.S.D. at a concentration level of 10 ng/ml is 3.8% for Cu and 5.3% for Mo. The method is applied to different
biological samples.
Received: 15 January 1996/Revised: 11 April 1996/Accepted: 16 April 1996 相似文献
19.
C. Faller G. Henze N. Stojko S. Saraeva K. Brainina 《Fresenius' Journal of Analytical Chemistry》1997,358(6):670-676
The paper describes the determination of tin by ASV using modified thick film electrodes. Three different types of electrodes
were developed: One modified with a mixture of Nafion and mercury(II)acetate, one modified with diethyldithiocarbamate (DDC)
or pyrrolidinedithiocarbamate (PDC) and mercury(II)acetate, and one modified with calomel. The analyte was accumulated on
the electrode surface after special electrochemical pretreatment of the modified electrode. After recording the voltammogram
the electrodes were electrochemically regenerated. By virtue of their lifetime and their measurement reproducibility, we preferred
the DDC and PDC modified electrodes. They can be used for months without changing their chemical characteristics. The linear
range for tin determination with these electrodes is between 1 and 100 μg/L; the detection limit was calculated as 0.9 μg/L.
The electrodes were applied to the direct determination of tin in different canned fruit juices without special sample pretreatment.
Received: 20 December 1996 / Revised: 11 March 1997 / Accepted: 13 March 1997 相似文献
20.
A critical study of the conditions for the direct determination of Cr in urine using GFAAS was carried out. A chemometric
approach showed that the most important parameters that influence the efficiency of atomic Cr cloud formation were the atomization
from the tube wall and the proper implementation of a pyrolysis step. The established procedure does not require any sample
pre-treatment thus minimizing the risk of contamination. The Cr content in urine was determined using a calibration curve
prepared with Cr spiked urine, easily correcting all potential matrix interferences. The heating program proposed took 68
s for a 30 μL urine sample. The procedure was applied for the determination of Cr in urine to investigate the absorption rate
of Cr picolinate. The limit of detection and the characteristic mass for a 30 μL urine sample were 0.18 μg/L and 5.4 pg, respectively.
Received: 22 June 1998 / Revised: 13 January 1999 / Accepted: 18 January 1999 相似文献