共查询到20条相似文献,搜索用时 15 毫秒
1.
The separation of carnitine, acetylcarnitine and palmitoylcarnitine as ADAM (9-anthryldiazo-methane) derivatives was performed
using capillary electrophoresis. A buffer system with 90% methanol and various amounts of phosphoric acid and micelle forming
SDS was optimized with respect to the best resolution of the carnitine derivatives. A detection limit of 10 μmol/l or 32 ng
carnitine was determined by laser induced fluorescence detection. Under optimized conditions low carnitine contents in acylcarnitine
standards have been determined.
Received: 30 May 1996/Accepted: 17 June 1996 相似文献
2.
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
3.
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
4.
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
5.
Jin-Lin Shen Christian Hummert B. Luckas 《Analytical and bioanalytical chemistry》1997,357(1):101-104
Extracts containing the diarrhetic shellfish poisoning (DSP) toxins okadaic acid (OA), dinophysistoxin-2 (DTX2), and dinophysistoxin-1 (DTX1) were purified on a silica gel cartridge and derivatized with 4-bromomethyl-7 methoxycoumarin (BrMmc). After pre-column derivatization
the BrMmc derivatives of the DSP toxins were directly injected into an HPLC system, isocratically eluted, and quantified by
fluorescence detection. The signals of the esters showed good linearity in the fluorescence detector within the examined contamination
range of 0.03 mg DSP/kg to 2.5 mg DSP/kg. The detection limits for the DSP toxins as 7-Mmc esters were 0.04 ng (corresponding
to 0.05 mg DSP/kg). The chromatographic conditions allow to couple the HPLC device with mass spectrometry. The method was
tested with various mussel tissue samples.
Received: 14 December 1995/Revised: 26 January 1996/Accepted: 30 January 1996 相似文献
6.
Jin-Lin Shen Christian Hummert B. Luckas 《Fresenius' Journal of Analytical Chemistry》1997,357(1):101-104
Extracts containing the diarrhetic shellfish poisoning (DSP) toxins okadaic acid (OA), dinophysistoxin-2 (DTX2), and dinophysistoxin-1 (DTX1) were purified on a silica gel cartridge and derivatized with 4-bromomethyl-7 methoxycoumarin (BrMmc). After pre-column derivatization
the BrMmc derivatives of the DSP toxins were directly injected into an HPLC system, isocratically eluted, and quantified by
fluorescence detection. The signals of the esters showed good linearity in the fluorescence detector within the examined contamination
range of 0.03 mg DSP/kg to 2.5 mg DSP/kg. The detection limits for the DSP toxins as 7-Mmc esters were 0.04 ng (corresponding
to 0.05 mg DSP/kg). The chromatographic conditions allow to couple the HPLC device with mass spectrometry. The method was
tested with various mussel tissue samples.
Received: 14 December 1995/Revised: 26 January 1996/Accepted: 30 January 1996 相似文献
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
13.
Determination of lead traces in water and liqueurs by derivative atom trapping flame atomic absorption spectrometry 总被引:3,自引:0,他引:3
H. Sun Li-li Yang De-qiang Zhang Wei-Xiao Wang Jian-min Sun 《Fresenius' Journal of Analytical Chemistry》1997,358(5):646-651
A new method for the direct determination of lead traces using derivative atom trapping flame atomic absorption spectrometry
(DAT-FAAS) with an improved water-cooled stainless steel trapping equipment in an air-acetylene flame was investigated. The
optimum conditions concerning the sensitivity were studied. For a 1 min collection, the characteristic concentration (given
as derivative absorbance of 0.0044) and the detection limit (3s) were 1.4 ng/mL and 0.27 ng/mL, respectively. This is 361
and 74-fold better than those of the conventional flame atomic absorption spectrometry (FAAS) and comparable to those of graphite
furnace atomic absorption spectrometry (GFAAS). The detection limit and sensitivity of DAT-FAAS for a 3 min collection time
were 2 and 3 orders of magnitude higher than those of conventional FAAS. The present method was applied to the determination
of lead in water and liqueur samples with a recovery range of 94–108% and a relative standard deviation of 3.5–5.6%.
Received: 10 January 1996/Revised: 9 December 1996/Accepted: 20 December 1996 相似文献
14.
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
15.
Seven rain and 2 snow samples collected in October and November 1993 were analyzed by GFAAS. Manganese concentrations ranging
from 0.3 to 11.3 μg/L were found. pH-values (4.04–4.89, mean 4.52) and redox potentials (528–665 mV, mean 581 mV) were additionally
determined. This is important with respect to a qualified specification of Mn in atmospheric samples. A 0.45 μm-filtration
of the samples prior to GFAAS-analysis showed the same manganese concentrations in the filtrate as in the unfiltered samples.
Hence, the amount of solid Mn species in the investigated samples is negligible. For an examination of the oxidation state
of Mn some investigations concerning the stability of Mn(III) were carried out. They indicated that Mn(III) is unstable under
atmospheric conditions. For checking whether all the manganese in rainwater exists as Mn(II), a sensitive IC method for the
detection of Mn(II) was developed. By adapting a photometric procedure based on the oxidation of Leucomalachite Green (LMG)
to Malachite Green (MG) by permanganate (MnO-
4) to the IC-flow-through-system, a limit of determination of 1 μg/L Mn(II) could be achieved. A comparison of the IC measurements
with GFAAS-results of the filtered samples showed agreeing results. Thus, manganese in rainwater and snow exists entirely
as soluble Mn(II).
Received: 24 May 1996/Revised: 7 July 1996/Accepted: 14 July 1996 相似文献
16.
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
17.
Seven rain and 2 snow samples collected in October and November 1993 were analyzed by GFAAS. Manganese concentrations ranging
from 0.3 to 11.3 μg/L were found. pH-values (4.04–4.89, mean 4.52) and redox potentials (528–665 mV, mean 581 mV) were additionally
determined. This is important with respect to a qualified specification of Mn in atmospheric samples. A 0.45 μm-filtration
of the samples prior to GFAAS-analysis showed the same manganese concentrations in the filtrate as in the unfiltered samples.
Hence, the amount of solid Mn species in the investigated samples is negligible. For an examination of the oxidation state
of Mn some investigations concerning the stability of Mn(III) were carried out. They indicated that Mn(III) is unstable under
atmospheric conditions. For checking whether all the manganese in rainwater exists as Mn(II), a sensitive IC method for the
detection of Mn(II) was developed. By adapting a photometric procedure based on the oxidation of Leucomalachite Green (LMG)
to Malachite Green (MG) by permanganate (MnO-
4) to the IC-flow-through-system, a limit of determination of 1 μg/L Mn(II) could be achieved. A comparison of the IC measurements
with GFAAS-results of the filtered samples showed agreeing results. Thus, manganese in rainwater and snow exists entirely
as soluble Mn(II).
Received: 24 May 1996/Revised: 7 July 1996/Accepted: 14 July 1996 相似文献
18.
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
19.
Optimised conditions have been found for the separation of 3-carboxy-4-hydroxy-6-acetylaminoazo-benzene derivatives substituted
in the position 4′ (4′-R-CHAAB, where R=–H, –CH3, –OCH3, –Cl, –COCH3, –NO2 and –NHCOCH3) using reversed phase HPLC with a C18 chemically bonded stationary phase. Suitable mobile phases are mixtures of 0.01 mol/L
NaH2PO4 at pH 4 with methanol (1+1), 0.01 mol/L NaH2PO4 at pH 2 with acetonitrile (1+1) or 1% aqueous acetic acid with methanol (4+6). UV photometry is the most universal detection
technique and yields limits of detection around 10-6 mol/L. Direct anodic voltammetry on a glassy carbon fibre array detector yields lower limits of detection for –COCH3 derivatives and higher limits of detection for –NO2 and –NHCOCH3 derivatives. When the analytes are chemically reduced using zinc powder in acetic acid, the voltammetric detection has limits
of detection one order of magnitude lower than those obtained UV photometrically.
Received: 27 June 1996/Revised: 25 October 1996/Accepted: 3 November 1996 相似文献
20.
C. Brunori M. B. de la Calle-Gunti?as R. Morabito 《Fresenius' Journal of Analytical Chemistry》1998,360(1):26-30
Parameters for the reduction of Se(VI) to Se(IV) in HCl medium by heating in a microwave oven have been optimized. The reduction
resulted to be quantitative applying 100% power, corresponding to 600 W heating for 2 min in 6 mol/L or for 3 min in 4 mol/L
HCl. The behavior of selenomethionine and selenocystine under the optimized reduction conditions was studied in order to evaluate
a possible interference of these selenium species in the determination of Se(VI). The final determination of Se(IV), and Se(VI)
were done by hydride generation-atomic absorption spectrometry. The analytical merits of the method are reported. The method
was applied to the selective determination of Se(IV), and Se(VI) in spiked river and lake water.
Received: 6 December 1996/Revised: 1 April 1997/Accepted: 3 April 1997 相似文献