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61.
This paper reports the results of the interlaboratory peer validation study of AOAC Peer-Verified Method (PVM) 1:2,000 for the determination of niacin in infant formula by solid-phase extraction/liquid chromatography. We have used a Data Quality Objectives (DQO) approach to address not only method variability and robustness but also accuracy of data through the use of an appropriate reference material in conjunction with the interlaboratory validation study. Our DQO included the following: (1) statistical agreement of analytical results and quantitative recovery between 2 collaborating laboratories; (2) the repeatability relative standard deviation (RSDr) values and the HORRAT (Horwitz ratio) obtained (1.07), which satisfied the criteria of the Horwitz "limits of acceptability" at the analyte level present; (3) validation of lack of interference; and (4) accuracy agreement within assigned values for a certified reference material. National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula, with a certified value of 63.3 +/- 7.6 microg/g for niacin content, was used as a test material for collaborative study and accuracy assessment. Niacin values obtained by the originating laboratory were 59.7 +/- 4.0 microg/g (95% confidence interval [CI] = 1.4 microg/g with a relative standard deviation [RSD] of 6.7%) and by the peer laboratory were 56.6 +/- 6.6 microg/g (95% CI = 4.1 microg/g, with an RSD of 11.7%). Statistical evaluation using the means equivalence test showed that nicotinic acid values obtained by the peer laboratory were equivalent to those values obtained by the originating laboratory. Linear calibration curves and quantitative recovery were obtained. Integration of the PVM process with a readily available certified reference material gives the user confidence in the accuracy of the data generated by the method through traceability to the reference material used. 相似文献
62.
The Chemical Transport of VO2 with Cl2 and HCl + Cl2 and the Influence of the O2-Coexistence Equilibrium Pressure on the Transport Behaviour The transport behaviour of VO2 with Cl2, HCl, and Cl2 was calculated and compared with the experimental results. VO2 with the upper phase boundary transports with HCl and HCl + Cl2 from the colder to the hotter zone, VO2 of the lower phase boundary does not transport with HCl. The composition of the deposited VO2 is near the upper boundary oxygen richer than in the start space. VO2 does not transport with Cl2. 相似文献
63.
Thermodynamics of the System Si? Cl? H By static and dynamic methods the equilibria 4SiHCl3,g = 3SiHCl4,g + Si,s + 2H2,g (1) between 800 and 1140 K and SiCl4,g + H2,g = SiHCl3,g + HCl,g (2) between 1170 and 1450 K were investigated. The expression for the temperature dependence of the equilibria were found to be lg Kp [Torr] = (5.688–1520/T) ± 0.32 (1) and lg Kp = (1.38/3250/T) ± 0.16 (2). The values measured for reaction pressures and equilibrium constants lead to the conclusion, that the difference of enthalpies of formation of SiCl4 and SiHCl3 found in literature is nessecarily to be corrected by 5–6 kcal/mole. With ΔH(SiCl4,g) = ?157.1 kcal/mole the equilibrium measurements lead to the enthalpy of formation for SiHCl3,g of ΔH(SiHCl3,g) = ?118.2 kcal/mole. 相似文献
64.
Werner H Schwab P Bleuel E Mahr N Windmüller B Wolf J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(24):4461-4470
A series of carbenerhodium(I) complexes of the general composition [(eta5-C5H5)Rh(=CRR')(L)] (2a-2i) with R = R'= aryl and L = SbiPr3 or PR3 has been prepared from the square-planar precursors trans-[RhCl(=CRR')(L)2] and NaC5H5 in excellent yields. Reaction of the triisopropylsibane derivative 2a. which contains a rather labile Rh-Sb bond, with CO, PMe3, and CNR (R = Me, CH2Ph, tBu) leads to the displacement of the SbiPr3 ligand and affords the substitution products [(eta5-C5H5)Rh(=CPh2)(L)] (3-7). In contrast, treatment of the triisopropylphosphane compound 2c with CO and CNtBu leads to the cleavage of the Rh=CPh2 bond and gives besides [(eta5-C5H5)Rh(PiPr3)(L)] (10, 12) by metal-assisted C-C coupling diphenylketene Ph2C=C=O (11) or the corresponding imine Ph2C=C=NtBu (13). While the reaction of 2a, c with C2H4 yields [(eta5-C5H5)Rh(C2H4)(L)] (14, 15) and the trisubstituted olefin Ph2C=CHCH3 (16), treatment of 2a, c with RN3 leads to the cleavage of both the Rh-EiPr3 and Rh=CPh2 bonds and gives the chelate complexes [(eta5-C5H5)Rh(kappa2-RNNNNR)] (19, 20). The substitution products 3 (L=CO) and 4 (L= PMe3) react with an equimolar amount of sulfur or selenium by addition of the chalcogen to the Rh=CPh2 bond to generate the complexes [(eta5-C5H5)Rh(kappa2-ECPh2)(L)] (21-24) with thio- or selenobenzophenone as ligand. Similarly, treatment of 3 with CuCl affords the unusual 1:2 adduct [(eta5-C5H5)(CO)Rh(mu-CPh2)(CuCl)2] (25), which reacts with NaC5H5 to form [(eta5-C5H5)(CO)Rh(muCPh2)Cu(eta5-C5H5)] (26). The molecular structures of 3 and 22 have been determined by X-ray crystallography. 相似文献
65.
A series of Pd complexes of 3'-diphenylphosphino-2,2':5'2' '-terthiophene (1a, dppterth) in which the metal is coordinated in three different modes have been prepared and electropolymerized, resulting in the formation of conductive thin films. In [Pd2(mu-Cl2)(dppterth-P,C3)2] (3a) the metal is P,C-coordinated, in [PdCl2(dppterth-P)2] (4a) the coordination is monodentate via the phosphine, and in [Pd(dppterth-P,C3)(dppterth-P,S1)][PF6] (5a) both P,C- and P,S-coordination modes are found. In 5a, the coordinated thiophene is hemilabile and may be displaced by reaction with more strongly coordinating ligands such as isocyanides. To probe the effect of blocking the alpha-position of the terthienyl moiety with methyl groups, 3'-diphenylphosphino-5-methyl-2,2':5'2' '-terthiophene (1b, Me-dppterth) and 3'-diphenylphosphino-5,5' '-dimethyl-2,2':5'2' '-terthiophene (1c, Me2-dppterth) were prepared, and the corresponding series of Pd complexes was synthesized. One of these complexes, [Pd(Me2-dppterth-P,C3)(Me2-dppterth-P,S1)][PF6] (5c), has been crystallographically characterized. The electropolymerized films prepared from 5a react with isonitriles, and shifts in the absorption spectra of the electropolymerized materials are observed upon reaction. A Pd complex has also been prepared from 5-diphenylphosphino-2,2':5'2' '-terthiophene (2, 5dppterth), and this complex has been electropolymerized. All the electropolymerized thin films have been characterized using EDX analysis, which demonstrates good correspondence with the elemental analysis of the respective monomers, and the maximum conductivities of the films are near 10(-4) S x cm(-1). Comparing the electropolymerization behavior of the complexes, along with their electrochemical and spectroscopic data, allows conclusions to be drawn regarding the involvement of pi-delocalization and the metal group in the conductivity of the materials. 相似文献
66.
Krishnaswamy Vasudevan Sigrid D. Peyerimhoff Robert J. Buenker Wolf E. Kammer Hsiang-lin Hsu 《Chemical physics》1975,7(2):187-209
A series of ab initio calculations is reported for the ground and low-lying valence and Rydberg states of diimide N2H2. Symmetric bending potential curves for both the cis and trans forms of this system have been obtained at the SCF level of treatment. In addition Cl calculations have been carried out for the trans-diimide ground state equilibrium nuclear conformation, using a configuration selection procedure described elsewhere; an associated energy extrapolation scheme is also employed which enables the effective solution of secular equations with orders of up to 40000. The ensuing Cl wavefunctions are interpreted in the discussion and the corresponding calculated energy differences between the various electronic states are compared with experimental transition energy results for both diimide and for related systems such as trans-azomethane. A more detailed analysis of the observed absorption bands in the 1Bg-X1Ag transition in N2H2 is also given, making use of calculated potential curve data as well as the pertinent Cl vertical energy difference. The dipole-forbiddenness of the excitation process is thereupon concluded to result in a distinct non-verticality for this electronic band system, causing its absorption maximum to occur at a position some 0.6 eV to the blue of the so-called vertical transition, i.e., that for which maximum vibrational overlap is obtained. 相似文献
67.
Application of instrumental radioanalytical techniques to nuclear waste testing and characterization
S. F. Wolf 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):207-212
This paper describes the validation of a multi-technique analytical methodology that uses inductively coupled plasma-mass
spectrometry, α-spectrometry, and γ-spectrometry for the routine analysis of samples containing transuranic radionuclides.
This methodology is capable of the determination of concentrations of both238Pu and241Pu in the presence of238U and241Am without the need for chemical separations. The relative merits of these three techniques were evaluated as they are applied
in a nuclear waste material and spent nuclear fuel testing program by analytical (1) standards and (2) solutions prepared
from the dissolution of glasses doped with237Np,239Pu, and241Am. The uncertainty associated with technique was within ±4% for standards and ±10% for doped nuclear waste glasses. The methodology
was then used to analyze three fully radioactive waste glasses. 相似文献
68.
Viktoriya V. Skripacheva Ella Kh. Kazakova Nelly A. Markarova Vladimir E. Kataev Ludmila V. Ermolaeva Wolf D. Habicher 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(1-2):77-81
The binding of different sized and shaped metal complexes [Co(His)2]ClO4(1), [Co(en)2C2O4]Cl (2) and [K18-crown-6]SCN (3)(en-ethylendiamine, His-L-histidynate-anion) with a new tetrasulfonatomethylcalix[4]resorcinarene([H8X]Na4) was investigated in neutral and alkaline aqueous media by NMR and pH-metrictitration methods and compared with those of recently studied NMe4Br (4). The resultsobtained indicate that the outer-sphere coordination of complexes 1–3 by[H8X]4- proceeds via the interaction of hydrophobic fragments of the guestswith both the negatively charged rim and the hydrophobic cavity as a -base. Thenature of binding does not change for cations 1, 2 and 4 on going from[H8X]4- in neutral to [H4X]8- in alkaline media, while the inclusionof 3 decreases on going from [H8X]4- to [H4X]8-. 相似文献
69.
Wolf Dietrich Krautgartner Ljubomir Vitkov Matthias Hannig Klaus Pelz Walter Stoiber 《Microscopy and microanalysis》2005,11(1):2-8
To examine new cytochemical aspects of the bacterial adhesion, a strain 41452/01 of the oral commensal Streptococcus sanguis and a wild strain of Staphylococcus aureus were grown with and without sucrose supplementation for 6 days. Osmiumtetraoxyde (OsO4), uranyl acetate (UA), ruthenium red (RR), cupromeronic blue (CB) staining with critical electrolytic concentrations (CECs), and the tannic acid-metal salt technique (TAMST) were applied for electron microscopy. Cytochemically, only RR-positive fimbriae in S. sanguis were visualized. By contrast, some types of fimbriae staining were observed in S. aureus glycocalyx: RR-positive, OsO4-positive, tannophilic and CB-positive with ceasing point at 0.3 M MgCl2. The CB staining with CEC, used for the first time for visualization of glycoproteins of bacterial glycocalyx, also reveals intacellular CB-positive substances-probably the monomeric molecules, that is, subunits forming the fimbriae via extracellular assembly. Thus, glycosylated components of the biofilm matrix can be reliably related to single cells. The visualization of intracellular components by CB with CEC enables clear distinction between S. aureus and other bacteria, which do not produce CB-positive substances. The small quantities of tannophilic substances found in S. aureus makes the use of TAMST for the same purpose difficult. The present work protocol enables, for the first time, a partial cytochemical differentiation of the bacterial glycocalyx. 相似文献
70.
Photochemistry of ε,ζ-Methano-α,γ-dienones and 7,8-Methano-1,3,5-trienes Irradiation of the δ-cyclopropyl-dienone (E)- 6 (λ ≥ 347 nm) gives (Z)- 6, 10 (1,5-sigmatropic H-shift), (E/Z)- 9 (electrocyclic process involving C(ε), C(ζ)-cleavage) and 11 (ring opening). The corresponding 6-cyclopropyl-triene (E)- 7 gives on singlet excitation (δ > 280 nm) 14 (1,5-sigmatropic H-shift) and, to a smaller extent, the bicyclo [3.2.0] heptenyl-dienes (E/Z)- 13 . However, on triplet excitation (λ ≥ 347 nm, benzophenone) (E)- 7 gives (E/Z)- 13 as the main products. On both 1π,π*- and 3π,π*-excitation, (Z)- 7 and 15 are formed in small amounts. 相似文献