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1.
Application of ring study: water toxicity determinations by bioluminescence assay with Vibrio fischeri 总被引:1,自引:0,他引:1
Acceptance of toxicity bioassays as effective analytical tools in environmental areas needs guarantees of standardization but also validation. Ten European laboratories took part in an inter-laboratory study using different commercial devices based on bioluminescence inhibition of bacteria Vibrio fischeri. Reproducibility and stability by short toxicity endpoints, effective concentration that gives 10%, 50% and 80% of inhibition (EC10, EC50 and EC80) is evaluated. Parametric and non-parametric statistic is applied and performance of participant laboratories is addressed by z-scores calculated by non-parametric statistic. z-Score classification was based on harmonised protocol for proficiency testing of analytical laboratories (satisfactory |z| ≤ 2; questionable 2 < |z| ≤ 3; unsatisfactory |z| > 3). Tested samples were phenol, 3,5-dichlorophenol and influent wastewater. Based on z-score classification, more than 70% of the laboratories showed a satisfactory performance for phenol, 3,5-dichlorophenol and influent wastewater (86%, 90% and 70%, respectively). Reproducibility and stability was observed in toxicant references and in wastewater samples. EC80 determination appears to be more robust that EC10 and EC50. EC determinations can be considered favorable at 5 and 15 min of exposition, in particular for EC80. The use of different commercial devices can not be considered an additional source of variation. 相似文献
2.
Luigi Falciola Patrizia R. Mussini Torquato Mussini 《Journal of solution chemistry》2000,29(12):1199-1210
Determination of primary standards for pH measurements in glycerol + water solventmixtures has been carried out based on reversible emf measurements of the cellPt|H2|KHPh (m
PS) + KCl (m
Cl)|AgCl|Ag|Ptwhere KHPh denotes the potassium hydrogen phthalate buffer solution of molalitym
PS = 0.05 mol-kg–1, at glycerol mass fractions w
G = 0.2 and 0.4, within thetemperature range –10 to 40°C. A multilinear regression procedure as a functionof electrolyte molality, glycerol mass fraction w
G, and temperature T has beenapplied for the data processing leading to the values of primary standards pHPS.These can be represented by the following regression equationpHPS = (4.007037±0.001113) + (3.55844±0.01776)x
G+(0.39622±0.01410)z + (4.3084±0.3377)z
2– (50.66±10.53)x
G
z
2 + (457.10±78.48)x
G
2
z
2where z = (T – 298.15)/298.15. Parallel values of the first ionization constantof o-phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid, the parent acid of KHPh),which are essential for the above calculations, have been determined fromreversible emf measurements of the cellPt|H2|H2Ph (m
1) + KHPh (m
2) + KCl (m
3)|AgCl|Ag|Ptover the range of solvent composition and temperatures mentioned above. 相似文献
3.
Kenji Ishikawa Kenji Metoki Hiroshi Miyamoto 《Journal of solid state chemistry》2009,182(8):2096-2103
Variation of the phases of Nd2NiO4+δ with the excess oxygen concentration δ has been examined at room temperature in the range 0.067≤δ≤0.224 using the X-ray powder diffraction technique. The phases observed at room temperature are orthorhombic-I (0.21<δ≤0.224), orthorhombic-IV (0.175<δ≤0.21), orthorhombic-II (0.15<δ≤0.175), orthorhombic-II+quasi-tetragonal-I (0.10<δ≤0.15), and quasi-tetragonal-I (0.067<δ≤0.10). 相似文献
4.
Chouhaid Nasr Prashant V. Kamat Surat Hotchandani 《Journal of Electroanalytical Chemistry》1997,420(1-2)
A photoelectrochemical cell with a coupled SnO2|CdSe nanocrystalline semiconductor electrode has been prepared by sequential deposition of SnO2 and CdSe films onto an optically transparent electrode (OTE), and its photoelectrochemical behavior has been studied. The results show that the coupling of CdSe with SnO2 leads to an improvement in the performance of OTE|SnO2|CdSe over OTE|CdSe cells in terms of increased incident photon-to-current conversion efficiency, increased stability and smaller reversal of current. The favorable positioning of the energy bands of SnO2 and CdSe is responsible for the above observations. Various photoelectrochemical parameters of the OTE|SnO2|CdSe cell obtained for an incident light power of 0.31 mW cm−2 at 470nm, are as follows: Isc ≈ 25–30 μA cm−2, Voc ≈ 0.5–0.6 V, ƒƒ = 0.47 and a power conversion efficiency of about 2.25%. 相似文献
5.
Phillips KM Wolf WR Patterson KY Sharpless KE Holden JM 《Analytical and bioanalytical chemistry》2007,389(1):219-229
Over a 6.5-year period a total of 2554 values were reported by nine laboratories for 259 certified or reference nutrient concentrations
in 26 certified reference materials (CRM) submitted to contract laboratories, blinded, as part of the qualifying process for
analytical contracts and in the routine sample stream as part of the National Food and Nutrient Analysis Program. Each value
was converted to a Z′-score, reflecting the difference from the assigned value related to the combined expected analytical uncertainty plus the
uncertainty in the CRM value. Z′-scores >|3.0| were considered unacceptable. For some nutrients (Na, folate, dietary fiber, pantothenic acid, thiamin, tocopherols,
carotenoids, monounsaturated, and polyunsaturated fatty acids), >20% of Z′-scores were >|3.0|. For total fat, vitamin C, and niacin >25% of Z′-scores were >|2.0|. Components for which CRM data were
best (more than 90% of Z′-scores <|2.0|) were Mg, P, Mn, Se, and vitamin B12. In some cases deviations from assigned values were not uniform across
laboratories and materials. For Na almost all high Z′-scores were for low-Na matrices, suggesting analytical problems related to concentration.
Figure Z′-scores for vitamins in certified reference materials
Disclaimer: Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental
procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute
of Standards and Technology, or the United States Department of Agriculture, nor is it intended to imply that the materials
or equipment identified are necessarily the best available for the purpose. 相似文献
6.
For La1−xThxNbO4+x/2, three phases with broad homogeneity regions occur, for 0.075 ≤ x ≤ 0.37, 0.41 < x < 0.61, and 0.65 ≤ x ≤ 0.74. All are related to the scheelite structure type, with at least the first exhibiting an incommensurate structural modulation. An analogous structurally modulated phase was found for LaNb1−xWxO4+x/2 for 0.11 ≤ x ≤ 0.22. Additional phases occur at La0.2Th0.8NbO4.4 and LaNb0.4W0.6O4.3. The electrical conductivity and the direction and wavelength of the structural modulation have been characterized for the La1−xThxNbO4+x/2 phase with 0.075 ≤ x ≤ 0.37. 相似文献
7.
A soil proficiency test (PT) was administered to 50 participant laboratories in which two sets of samples, consisting of 20 yearly
PT samples and 5 ‘blind’ samples in clients’ names were analyzed for pH, organic matter, total acidity, extractable calcium,
magnesium, potassium and phosphorus by the laboratories. Our objective was to determine whether laboratories take extra care
to analyze clients’ samples as they do with regular PT samples. The analytical data were evaluated essentially by the procedure
described in the international harmonized protocol for proficiency testing of analytical chemistry laboratories. Performance
of participant laboratories was assessed by z-scores and summary z-scores statistics involving sum of squared z-scores interpreted as chi-square ( cn2 ) \left( {\chi_{n}^{2} } \right) distribution for zero-centered z-scores with unit variance. From 8 750 determinations, outliers and stragglers accounted for less than 2% of the entire data.
Over 93% of the data were satisfactory, whereas between 2 and 4% were either unsatisfactory or questionable in both the PT
and ‘blind’ tests. On the basis of sum of squared z-scores interpreted from cn2 \chi_{n}^{2} distribution table, between 30 and 40% of the laboratories had more than 90% probability of having their measurement data
within the robust mean and standard deviation for each soil parameter, while another 30–42% of the laboratories had less than
50% probability of having measurement data within the robust mean and standard deviation. Overall, 21 laboratories (42%) were
ranked in Class A either in the PT or ‘blind’ tests out of which 12 of them (57%) retained this ranking in both tests. Fourteen
laboratories (28%) were ranked in Class C in either the PT or ‘blind’ tests with only 5 of them (36%) consistently ranking
in this class in both tests. 相似文献
8.
Turetta C Cozzi G Barbante C Capodaglio G Cescon P 《Analytical and bioanalytical chemistry》2004,380(2):258-268
Direct and simultaneous determination of Al, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Sb, U, V and Zn in diluted (1:10 v:v) seawater from the Antarctic Ocean and the Venice Lagoon at the ng mL–1 and pg mL–1 level has been performed by using an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Samples were analysed by using a PFA microflow nebulizer coupled with a desolvation system or a PFA microflow nebulizer coupled with a Teflon spray chamber, respectively. Measurements were carried out at low (LR, m/m=300), medium (MR, m/m=3,000) and high (HR, m/m=7,500) resolutions depending on the studied isotope. To avoid contamination, sample pre-treatment was carried out in a clean laboratory equipped with a Class 100 vertical laminar flow hood. Concentration ranges (minimum–maximum in ng mL–1) found in the Antarctic seawater samples (in depth profiles) were: Ag 0.0004–0.0018, As 0.69–1.32, Cd 0.031–0.096, Co 0.018–0.065, Cr 0.18–0.46, Cu 0.04–1.58, Fe 0.13–1.63, Mn 0.02–0.12, Mo 5.97–12.46, Pb 0.007–0.074, Sb 0.033–0.088, U 0.5–1.9, V 0.6–2.5 and Zn 0.16–0.80. Concentration ranges (min–max in ng mL–1) found in the Venice Lagoon water samples (temporal profile from a benthic chamber experiment) were: Al 0.24–0.61, Ag 0.007–0.031, As 1.42–2.27, Cd 0.050–0.182, Co 0.440–1.461, Cr 0.15–0.34, Cu 0.81–2.46, Fe 0.25–1.66, Mn 11.6–31.7, Mo 6.50–10.6, Pb 0.047–0.225, Sb 0.240–0.492, U 1.7–3.3, V 1.3–2.8 and Zn 5.20–21.5. The detection limits range between 0.06 pg mL–1 for Ag and U to 15 pg mL–1 for Fe. In order to check the accuracy of the analytical procedure, measurements of the trace elements in a certified reference material (coastal Atlantic seawater, CASS-4-NRCC) were compared with the certified values. In addition, the results from the Antarctic and Venice Lagoon samples were compared with those obtained by using different analytical techniques. 相似文献
9.
The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals were calculated by using the INDO method and the molecular geometry adjusting method. Our previous calculations of o-benzosemiquinone anion radical in the lithium ion solution showed that the total energy of the minimal energy conformation in the case of the assignment |A3| > |A4| were lower by approximately 320 kcal/mol than that in the case of the assignment |A3| > |A4|. Therefore, the calculations of the minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions were carried out in the cases of the assignment |A3| > |A4|. The conformations in both assignments A3 < A4 < 0 and (A3 < 0 < A4 and |A3| > |A4|) were calculated. Although the metal ions were not explicitly contained in the molecular geometries, the minimal energy conformations are considered to be close to the real minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions. The C? O bond lengths has a good positive rank correlation with the stabilities of o-benzosemiquinone radicals in the divalent metal ion solutions and the bond angles ∠C3C4H4 had a good negative rank correlation with those stabilities. 相似文献
10.
P. Medina-Pastor M. Mezcua C. Rodríguez-Torreblanca A. R. Fernández-Alba 《Analytical and bioanalytical chemistry》2010,397(7):3061-3070
The obligation for accredited laboratories to participate in proficiency tests under ISO 17025, performing multiresidue methods
(MRMs) for pesticide residues, involves the reporting of a large number of individual z scores making the evaluation of the overall performance of the laboratories difficult. It entails, time and again, the need
for ways to summarise the laboratory’s overall assessment into a unique combined index. In addition, the need for ways to
continually evaluate the performance of the laboratory over the years is equally acknowledged. For these reasons, following
14 years of the European Union Reference Laboratory for Pesticide Residues in Fruits and Vegetables (EUPT-FV), useful formulas
have been designed to globally evaluate the assessment of the participating laboratories. The aim is to achieve a formula
which is easy to understand, which can be applied and which fits the purposes of long-term evaluation detecting positive and
negative trends. Moreover, consideration is needed for a fair compensation of bad results in MRM, taking into account the
large number of compounds that are covered. It is therefore important to be aware of the difficulties in getting satisfactory
values from a wide range of compounds. This work presents an evaluation of the main well-established combined z score formulas together with those new ones developed here which have been applied to the European proficiency test results
(EUPTs) over the years. Previous formulas such as the rescaled sum of z score (RSZ), the sum squared of z score (SSZ) and the relative laboratory performance (RLP) are compared with the newer ones: the sum of weighted z scores (SWZ) and the sum of squared z scores (SZ2). By means of formula comparisons, conclusions on the advantages, drawbacks and the most fit-for-purpose approach
are achieved. 相似文献
11.
Ram Kripal Pragya Singh Har Govind 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):357-362
EPR studies are carried out on Cr3+ ions doped in d-gluconic acid monohydrate (C6H12O7·H2O) single crystals at 77 K. From the observed EPR spectra, the spin Hamiltonian parameters g, |D| and |E| are measured to be 1.9919, 349 (×10−4) cm−1 and 113 (×10−4) cm−1, respectively. The optical absorption of the crystal is also studied at room temperature. From the observed band positions, the cubic crystal field splitting parameter Dq (2052 cm−1) and the Racah interelectronic repulsion parameter B (653 cm−1) are evaluated. From the correlation of EPR and optical data the nature of bonding of Cr3+ ion with its ligands is discussed. 相似文献
12.
The minimal energy conformations of o-benzosemiquinone anion radical were calculated for several cases of assignments by using the INDO method and the molecular geometry adjusting method. In order to know the effect of lithium ion in the solvent, the minimal energy conformations of the system of Li? O? H and o-benzosemiquinone anion radical were calculated. The calculations of the minimal energy conformations of this radical in t-butyl alcohol, alkaline aqueous ethanol, alkaline water, neutral methanol, and acetonitrile were carried out. The total energies of the minimal energy conformations in the assignment |A3| > |A4| were lower than those in the assignment |A3| < |A4|. 相似文献
13.
Stephen W. C. Chung Jeff C. H. Tran W. W. Wong 《Accreditation and quality assurance》2012,17(1):35-44
A proficiency test (PT) to assess the capabilities of laboratories to determine nutrients in a biscuit sample was carried
out in September 2009. The need for such interlaboratory comparison arose from an increasing nutrition labeling requirements
of different countries around the world. Forty-eight laboratories worldwide participated in this PT program for the determination
of total lipids, saturated fat, trans-fat, protein, sugars, total dietary fiber (TDF), ash and sodium in food. This program
was organized under the auspices of the Asia-Pacific Laboratory Accreditation Cooperation (APLAC). APLAC considers PT programs
as one of the objective means of assessing the performance of the accredited laboratories. The program is one of the APLAC
PT series whose primary purposes are to establish mutual agreement on the equivalence of the operation of APLAC member laboratories
and to provide an opportunity to identify testing deficiency so that corrective actions can be taken, if necessary. The results
of this program indicated that the consensus mean values estimated by robust statistics were in good agreement with the corresponding
values obtained in the homogeneity tests except for trans-fat and TDF. The relative standard deviations of participant results
for trans-fat and TDF were also found to be higher (19 and 24%, respectively) than the other test parameters. The relative
standard deviations for other test parameters were less than 10%. One-half of the laboratories obtained satisfactory z-scores
(| z | < 3) (\left| z \right| < 3) for all their reported results. Although participants were instructed to provide the measurement uncertainties of their reported
results, only 27.5% of them had done so. Albeit many of the measurement uncertainties appear to be reasonable, some of them
were found to vary widely, indicating that some laboratories still have difficulties in estimating measurement uncertainties.
Although the overall measurement capability can be considered to be satisfactory, there is still room for improvement of analytical
procedures. 相似文献
14.
The Li+ and Na+ binding of substituted cyclopentadienyl (Cp) anions were investigated using computational techniques. The ring centroid-metal distances and the binding energies of the Cp-metal complexes correlate very well with the ∑σm of the substituted Cp ring. These properties also correlate well with the Cp Θzz values. The trend in the correlations is the more electron-rich the Cp (negative ∑σm and Θzz values values), the shorter the Cp-metal bond and the stronger the binding energy. The NBO metal charges correlate, though not very well in either case, with the Cp Θzz and ∑σm values. However, there is a substantial increase in correlation when the sum of the absolute value of the Hammett σm (∑|σm|) is employed. The significantly improved correlation when the ∑|σm| values are employed leads us to propose a model for substituted Cp charge transfer upon Li+ or Na+ complexation, and it also informs us that the Hammett substituent constant σm contains information about substituent polarizabilities, at least in the case of Li+- and Na+-substituted Cp anions. 相似文献
15.
Andreas Breidbach Katrien Bouten Katy Kröger Franz Ulberth 《Analytical and bioanalytical chemistry》2010,396(1):503-510
A proficiency test to assess the capabilities of laboratories to determine melamine in a milk powder and a baking mix, representing
starch-containing foods like bread and biscuits, was carried out in January 2009. The need for such an interlaboratory comparison
arose from a health scare in China about melamine-tainted powdered milk in the second half of 2008. Laboratories in 31 countries,
including Australia, China, India, Japan, New Zealand and the USA, and 21 of the 27 Member States of the European Union participated
and reported back 114 results for the milk powder and 112 for the baking mix test materials. The reported results were compared
to reference values determined by exact-matching double isotope dilution mass spectrometry. The so-determined assigned values
were 10.0 ± 0.6 mg/kg melamine in the milk powder and 3.18 ± 0.17 mg/kg melamine in the baking mix. A coverage factor k of 2 was applied to calculate the expanded uncertainties. Three quarters of all reported results for both materials had associated
z scores which were satisfactory (z ≤ |2|). Of the reported results, 90% was accompanied by a measurement uncertainty statement, and the majority of the measurement
uncertainty ranges were reasonable. A number of laboratories were found to underestimate their measurement uncertainties.
Methods that involved the use of stable-isotope-labelled melamine were shown to be clearly advantageous with regard to the
accuracy of the results. However, no significant influence by other method parameters could be identified. 相似文献
16.
J. Grannec A. Yacoubi L. Fournes A Tressaud P. Hagenmuller 《Journal of solid state chemistry》1987,70(2)
The FeF3---ZrF4 system has been investigated using X-ray diffraction, micro-DTA, magnetic measurements, and Mössbauer spectroscopy. At 850°C two solid solutions with formulas Fe1−xZrxF3+x have been obtained, which are based on the VF3 type for 0 ≤ x < 0.10 and on the ReO3 type for 0.10 ≤ x ≤ 0.23, respectively. A phase transition occurs in the VF3-type domain: the transition temperature decreases with increasing x. All phases exhibit an antiferromagnetic behavior. The thermal variation of Mössbauer parameters has been studied for x = 0.05 and x = 0.23 as well as their variation vs composition at 300 K. The magnetic behavior is discussed on the basis of the structural data presently available. 相似文献
17.
Stanislas Pechev Thierry Roisnel Bernard Chevalier Bernard Darriet Jean Etourneau 《Solid State Sciences》2000,2(8):2447
Neutron powder diffraction experiments were performed on selected compositions of the UCuxSi2−x system exhibiting an interesting magnetic phase diagram towards the composition: spin fluctuation behaviour for x<0.49, ferromagnetism for 0.49≤x<0.80, spin glass state for 0.80<x<0.92 and finally antiferromagnetism for 0.92<x≤0.96. At 1.5 K, the compounds UCu0.49Si1.51 (hexagonal AlB2 modification) and UCu0.65Si1.35 show a collinear ferromagnetic structure where the uranium magnetic moments equal to 1.1(1) and 2.5(1)μB, respectively, are aligned in the basal plane of the [U6] trigonal prisms. On the contrary, UCu0.96Si1.04 adopts a non-collinear antiferromagnetic structure similar to that observed for UCuSn. Moreover, the study confirms the absence of long range magnetic order for UCu0.90Si1.10. 相似文献
18.
Electrical resistivity (ρ) and thermoelectric power (α) measurements were carried out in air on CuCr2-xAlxO4(0.06 ≤ x ≤ 0.10) spinel oxides in the temperature range 300-675 K. Carrier concentration (n), optical phonon frequency (γo), and mobility (μ) values have been calculated from resistivity and thermoelectric power data. The results show that CuCr2-xAlxO4 spinel oxides are compensated semiconductors and the total compensation of the hole carriers by electrons occur when 0.09 chromium ions are replaced by aluminium ions. 相似文献
19.
Yasuko Shinagawa Seiji Koyama Yoshiya Shinagawa 《International journal of quantum chemistry》1983,23(2):477-481
The observed proton hyperfine coupling constants of radicals from resorcinol and 2-carboxylic, 5-carboxylic, and 5-methyl resorcinols in acidic and alkaline solution were reproduced by means of the INDO (intermediate neglect of differential overlap) with molecular geometry adjusting method. The bond lengths of C? O were longer in acidic solution than in alkaline solution and the total energies were lower in acidic solution than in alkaline solution. The assignments of the coupling constants of the radicals from resorcinols were |A2| > |A5| in alkaline oxidation and |A2| < |A5| in acidic oxidation. 相似文献
20.
Cemalettin Baltacı Huri İlyasoğlu Sevim Beyza Öztürk Sarıkaya Sevda Cavrar Nurettin Yaylı 《Accreditation and quality assurance》2011,16(10):507-513
A proficiency test (PT) was organized for quality control analysis of black tea. Test materials for the analyses of total
content of powder tea, moisture, total ash, acid-insoluble ash, water-soluble ash, alkalinity of water-soluble ash, water
extract, crude fiber and caffeine were sent to the participant laboratories (n:43) in 2009. The assigned value, standard deviation of the parameters and z-scores of the participant laboratories were calculated using the data reported by the participants. The percentage of the
reported results for analytes was found to be ranged from 67.5 to 100%. Acceptable z-scores were achieved by 80.5–97.5% of the participant laboratories. More than 15% of unacceptable results were obtained for
acid-insoluble ash and caffeine analyses. The quality control material for quality control analysis of black tea was developed
from the remaining material. 相似文献