共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Horvat L. Liang S. Azemard V. Mandi J.-P. Villeneuve M. Coquery 《Fresenius' Journal of Analytical Chemistry》1997,358(3):411-418
Due to the increased demand for new reference materials certified for total and methylmercury (MeHg) a sample of mussel homogenate
(IAEA-142) has been prepared. Thirteen experienced laboratories reported results for total Hg of which 9 laboratories also
reported results for MeHg content. Laboratories reporting MeHg results used various isolation techniques (solvent extraction,
saponification, acid leaching, ion-exchange separation, and distillation) and detection systems (cold vapour atomic absorption
spectrometry (CV AAS), cold vapour atomic fluorescence spectrometry (CV AFS), gas chromatography with electron capture detector
(GC/ECD) and HPLC with CV AAS detector). In the case of total Hg, most of the laboratories used acid digestion, only two used
alkaline dissolution, followed either by CV AAS or CV AFS. One laboratory used neutron activation analyses with radiochemical
separation. The data received were in good agreement. The value for total Hg was certified to be 126 ng/g, with a 95% confidence
interval from 119 to 132 ng/g. For MeHg the certified value of 47 ng/g expressed as Hg was assigned, with a 95% confidence
interval from 43 to 51 ng/g. Stability testing has shown that both total and MeHg are stable if samples are stored in a dry
and dark place at room temperature. The sample is now available as a certified reference material and is, in particular, useful
for quality control measurements of Hg and MeHg in mussel samples at low concentration levels.
Received: 24 September 1996 / Revised: 20 November 1996 / Accepted: 8 December 1996 相似文献
2.
For the determination of 16 PAHs in soils and sediment samples by GC/FID and GC/MS, the dynamic off-line supercritical fluid
extraction with both pure and modified carbon dioxide has been evaluated. The optimisation of extraction parameters was performed
for four individual groups of PAHs according to their number of aromatic rings (2–3 rings, 4 rings, 5 rings and 6 rings) by
varying pressure (200–510 bar), temperature (50–150 °C), extraction fluid volume (10–50 ml), and the methanol modifier concentration
(0–10%). Using a five level spherical factorial experimental design the number of experiments required for optimisation was
45. In spiked soil samples extraction efficiencies of 80–100% were achieved for the individual groups of PAHs. At the optimal
set of conditions 10–30% lower recoveries of PAHs were obtained for the standard reference material NIST SRM 1941a (marine
sediment). The largest differences between extraction recoveries of native and spiked PAHs occurred at high molecular weight
PAHs. Using SFE efficiency data for the standard reference material, cluster analysis proved that dividing the 16 PAHs into
four groups according to their number of aromatic rings was appropriate and correct.
Received: 2 February 1996/Revised: 26 November 1996/Accepted: 30 November 1996 相似文献
3.
R. Becker Matthias Koch Sigrid Wachholz Tin Win 《Accreditation and quality assurance》2002,7(7):286-289
Due to the utilisation of 1,1,2-trichlorotrifluoroethane (CFE) as extraction solvent the IR-spectrometric determination of
total petrol hydrocarbon (TPH) in soil according to ISO/TR 11046 has been replaced by gas chromatography/flame ionisation
detection (GC/FID) after extraction with a halogen-free solvent according to ISO/DIS 16703:2001. The results obtained with
both methods by field laboratories in three proficiency testing (PT) rounds are compared. The consensus means obtained with
GC/FID are typically 10%–20% (ranging between 0% and 25%) higher than those found with IR-spectroscopy. On the contrary, coefficients
of variation (CV) are roughly double in case of GC/FID and are briefly discussed against the background of the Horwitz equation.
Received: 19 November 2001 Accepted: 17 March 2002 相似文献
4.
I. Papadakis P. D. P. Taylor P. D. Bièvre 《Analytical and bioanalytical chemistry》1997,357(8):1020-1023
The certification measurement for the cadmium concentration in the samples as performed by Isotope Dilution (ID) using Inductively
Coupled Plasma Mass Spectrometry (ICP-MS) is described in framework of the International Measurement Evaluation Programme
(IMEP). By using a primary method of measurement (ID), making up a full uncertainty budget and using a sensitive technique
(ICP-MS), reference values traceable to SI can be obtained for this material.
The uncertainty budget is performed in accordance with the ISO and EURACHEM guides on uncertainty. A comparison is made with
certification results of other experienced laboratories also using primary methods where possible.
Received: 8 July 1996/Revised 26 August 1996/Accepted: 1 September 1996 相似文献
5.
I. Papadakis P. D. P. Taylor P. D. Bièvre 《Fresenius' Journal of Analytical Chemistry》1997,357(8):1020-1023
The certification measurement for the cadmium concentration in the samples as performed by Isotope Dilution (ID) using Inductively
Coupled Plasma Mass Spectrometry (ICP-MS) is described in framework of the International Measurement Evaluation Programme
(IMEP). By using a primary method of measurement (ID), making up a full uncertainty budget and using a sensitive technique
(ICP-MS), reference values traceable to SI can be obtained for this material.
The uncertainty budget is performed in accordance with the ISO and EURACHEM guides on uncertainty. A comparison is made with
certification results of other experienced laboratories also using primary methods where possible.
Received: 8 July 1996/Revised 26 August 1996/Accepted: 1 September 1996 相似文献
6.
André Henrion 《Accreditation and quality assurance》1998,3(3):127-130
Repeated subsampling or a hierarchical design of experiments combined with an analysis of variance (ANOVA) is demonstrated
to be a useful tool in the determination of uncertainty components in amount-of-substance measurements. With the reference
material of human serum as investigated here for total cholesterol, besides several in-laboratory sources of uncertainty,
a vial-to-vial effect which can be regarded as an off-laboratory source was found to be significant. This knowledge might
be essential when the material is used for calibration and for the self-assessment of a laboratory.
Received: 29 October 1997 · Accepted: 26 November 1997 相似文献
7.
Jose′ L. F. C. Lima Antoacutenio O. S. S. Rangel M. Renata S. Souto 《Fresenius' Journal of Analytical Chemistry》1997,358(5):657-662
A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 相似文献
8.
Flow injection system with gas diffusion for the sequential determination of total nitrogen and phosphorus in vegetables 总被引:1,自引:0,他引:1
Jose´ L. F. C. Lima Antoacutenio O. S. S. Rangel M. Renata S. Souto 《Analytical and bioanalytical chemistry》1997,358(5):657-662
A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 相似文献
9.
To characterize the real stoichiometry of ceramic high-temperature superconductors of the Y-Ba-Cu-O type and the Bi(Pb)-Ca-Sr-Cu-O
type complex, chemical methods including digestion, separation and subsequent titrimetric determination of the elemental components
were investigated. Using optimized automatic titration procedures with photometric, potentiometric or voltametric equivalence
point detection, a high accuracy of the analytical results could be achieved. The random as well as the systematic errors
are less than 0.5%. The exact stoichiometric coefficients of the components and thereby the phase compositions or the single
phase character of the materials were determined and compared with the results of X-ray diffraction measurements.
Received : 27 November 1995/Revised: 5 February 1996/Accepted: 10 February 1996 相似文献
10.
To characterize the real stoichiometry of ceramic high-temperature superconductors of the Y-Ba-Cu-O type and the Bi(Pb)-Ca-Sr-Cu-O
type complex, chemical methods including digestion, separation and subsequent titrimetric determination of the elemental components
were investigated. Using optimized automatic titration procedures with photometric, potentiometric or voltametric equivalence
point detection, a high accuracy of the analytical results could be achieved. The random as well as the systematic errors
are less than 0.5%. The exact stoichiometric coefficients of the components and thereby the phase compositions or the single
phase character of the materials were determined and compared with the results of X-ray diffraction measurements.
Received : 27 November 1995/Revised: 5 February 1996/Accepted: 10 February 1996 相似文献
11.
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
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.
N. Cardellicchio S. Cavalli V. Piangerelli S. Giandomenico P. Ragone 《Fresenius' Journal of Analytical Chemistry》1997,358(6):749-754
A reverse-phase high-performance liquid chromatography procedure with gradient elution and electrochemical detection is described
for the determination of phenolic compounds, including several priority pollutant chlorophenols, in sea-water and sediments.
In addition, a method for concentrating phenols from sea-water was examined. A solid-phase extraction using a derivatized
poly(styrene-divinylbenzene) copolymer is discussed. The recovery, repeatability and detection limits are shown. Electrochemical
detection provided selectivity as well as sensitivity. Phenols at the ng/l level were detected. The method was applied to
the analysis of the most important phenolic compounds in sea-water and marine sediments.
Received: 12 April 1996 / Revised: 30 October 1996 / Accepted: 28 November 1996 相似文献
14.
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
15.
An analytical method is described to determine simultaneously cis/trans N-n-alkyl-dimethylmorpholines and their metabolites,
the 4-(ω-carboxy-n-alkyl) cis/trans-2,6-dimethylmorpholines by pyrolytic alkylation and high resolution GC/MS in aqueous systems
and sediments. The substances in the sediment phase were analyzed by GC/MS after extraction with methanol and water, substances
in the water phase could be directly determined by GC/MS. The analytical procedure also allows the determination of further
carboxylic acids in complex aqueous systems.
Received: 9 April 1996 / Revised: 10 June 1996 / Accepted: 14 June 1996 相似文献
16.
The large-volume sampling of aqueous samples in a programmed temperature vaporizer (PTV) injector was used successfully for
the target and non-target analysis of real samples. In this still rarely applied method, e.g., 1 mL of the water sample to
be analyzed is slowly injected direct into the PTV. The vaporized water is eliminated through the split vent. The analytes
are concentrated onto an adsorbent inside the insert and subsequently thermally desorbed. The capability of the method is
demonstrated using a sample from the river Elbe. By means of coupling this method with a mass selective detector in SIM mode
(target analysis) the method allows the determination of pollutants in the concentration range up to 0.01 μg/L. Furthermore,
PTV enrichment is an effective and time-saving method for non-target analysis in SCAN mode. In a sample from the river Elbe
over 20 compounds were identified.
Received: 17 June 1996 / Revised: 22 November 1996 / Accepted: 25 November 1996 相似文献
17.
The large-volume sampling of aqueous samples in a programmed temperature vaporizer (PTV) injector was used successfully for
the target and non-target analysis of real samples. In this still rarely applied method, e.g., 1 mL of the water sample to
be analyzed is slowly injected direct into the PTV. The vaporized water is eliminated through the split vent. The analytes
are concentrated onto an adsorbent inside the insert and subsequently thermally desorbed. The capability of the method is
demonstrated using a sample from the river Elbe. By means of coupling this method with a mass selective detector in SIM mode
(target analysis) the method allows the determination of pollutants in the concentration range up to 0.01 μg/L. Furthermore,
PTV enrichment is an effective and time-saving method for non-target analysis in SCAN mode. In a sample from the river Elbe
over 20 compounds were identified.
Received: 17 June 1996 / Revised: 22 November 1996 / Accepted: 25 November 1996 相似文献
18.
Z. Mo J. Luo Xiaohui Long Ziling Xia 《Fresenius' Journal of Analytical Chemistry》1997,358(4):556-558
A fast and simple method for the determination of procaine hydrochloride by ion-pairing flow injection analysis has been
developed. It is based on the formation of an ion-pair with sodium dodecyl phenylsulphonate and piezoelectric detection. The
calibration curve was linear between 0.02 and 2.00 mg/mL, with a detection limit of 0.01 mg/mL, a relative standard deviation
of 0.3% (10 replicates) and a sampling frequency of 120/h. The proposed method has been satisfactorily applied to the determination
of procaine hydrochloride in pharmaceutical preparations.
Received: 19 August 1996 / Revised: 6 November 1996 / Accepted: 12 December 1996 相似文献
19.
Some parameters affecting the accuracy of various approaches to methylmercury (MeHg) determination in biological and environmental samples were studied. Different isolation techniques (ion-exchange, extraction, volatilization, distillation) and final measurement via cold vapour atomic absorption spectroscopy (CV AA) or gas chromatography (GC) were compared. Results obtained by the various isolation techniques are comparable for almost all biological and environmental samples, except for soils and some sediments, where disagreement between the results obtained by GC and CV AA was found. In order to resolve these problems, a new separation technique based on distillation of MeHg from the sample followed either by CV AA or GC was developed. The new method results in very good recovery and reproducibility (95 ± 2%) for all samples examined (fish, mussel, shrimp, blood, hair, algae, sediment, etc.), is specific for MeHg and provides for its differentiation from other species by an indirect CV AA determination. Gas-chromatographic measurement of the isolated MeHg using different packings and conditioning of the columns is also discussed. The distillation method with GC detection is advantageous in producing cleaner chromatograms and in prolonging the life-time of the packing and the intervals between reconditioning. 相似文献
20.
Mark S. Lowenthal James Yen David M. Bunk Karen W. Phinney 《Analytical and bioanalytical chemistry》2010,397(2):511-519
An isotope-dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) measurement procedure was developed to accurately
quantify amino acid concentrations in National Institute of Standards and Technology (NIST) Standard Reference Material (SRM)
2389a—amino acids in 0.1 mol/L hydrochloric acid. Seventeen amino acids were quantified using selected reaction monitoring
on a triple quadrupole mass spectrometer. LC-MS/MS results were compared to gravimetric measurements from the preparation
of SRM 2389a—a reference material developed at NIST and intended for use in intra-laboratory calibrations and quality control.
Quantitative mass spectrometry results and gravimetric values were statistically combined into NIST-certified mass fraction
values with associated uncertainty estimates. Coefficients of variation (CV) for the repeatability of the LC-MS/MS measurements
among amino acids ranged from 0.33% to 2.7% with an average CV of 1.2%. Average relative expanded uncertainty of the certified
values including Types A and B uncertainties was 3.5%. Mean accuracy of the LC-MS/MS measurements with gravimetric preparation
values agreed to within |1.1|% for all amino acids. NIST SRM 2389a will be available for characterization of routine methods
for amino acid analysis and serves as a standard for higher-order measurement traceability. This is the first time an ID LC-MS/MS
methodology has been applied for quantifying amino acids in a NIST SRM material. 相似文献