NBS standards

Fig. 19. Plot of viscosity vs temperature for NBS standard glass No. 710. To convert Pa s to P, multiply by 10.

ISCC-NBS Centroid Color Charts, NBS Standard Reference Material No. 2106, National Institute of Standards and Technology, Washiagton, D.C.,... 

PhCH(OCH2CH2CH=CH2)2, CSA, NBS. Standard methods failed because of cleavage of the dispiroketal (dispoke) protective group. 

Sample cells were fabricated from tungsten. Additional crucibles composed of a Pt-40 w/o Rh-8 w/o W alloy were also used in experiments on the PuPt phase. Each tungsten cell was vacuum outgassed at 1800 for 1 h before an experiment. The cell temperature was determined during the measurements by sighting with a pyrometer (Pyrometer Instrument Co.) onto a blackbody hole in each cell base. The pyrometer and sight glasses were calibrated with an NBS standard lamp. 

Only one isotope, Pu-244, is presently available as a NBS Standard Reference Material and can be obtained from the DOE New Brunswick Laboratory. A second NBS/SRM as a 1 1 mixture of... 

Procedures for determining the spectral responslvlty or correction factors In equation 2 are based on radiance or Irradlance standards, calibrated source-monochromator combinations, and an accepted standard. The easiest measurement procedure for determining corrected emission spectra Is to use a well-characterized standard and obtain an Instrumental response function, as described by equation 3 (17). In this case, quinine sulfate dlhydrate has been extensively studied and Issued as a National Bureau of Standards (NBS) Standard Reference Material (SRM). 

The mean radon concentrations determined by the passive detectors are based on calibrations using NBS standard radium-226 solutions and also from participation in the OECD (Nuclear Energy Agency)/CEC radon dosimeter intercomparisons (Commission of the European Communities, 1986) held at the U.K. National Radiological Protection Board (NRPB). Recent calibrations of the new LR-115 based detectors, in terms of response to radon concentrations and F factors have been carried out at the NRPB, which assistance is greatly appreciated. For the etching and track counting procedures used the inner LR-115 piece in the detectors has a mean sensitivity of approximately 1.6 tracks cm 2 kBq l m hr l. 

Based upon studies with the NBS standard reference materials, the linear calibration method appears to give equivalent accuracy compared to a peak position method irrespective of sample disperslty provided that the sample elute over the elution volume range covered by the polydlsperse standard and low dispersion SEC column are utilized. 

NBS standard polyethylenes where the Mjj is known. Commercial polyethylenes may also be useful because the Mj is frequently in the 10 to 15 thousand range which corresponds to the sensitivity available with most C-13 NMR spectrometers. 

ES—samples compared with NBS standards and SQ powder visually, semiquantitative... 

MS—solid bronze electrodes made from drillings. Tin content from slurry technique (above) used for internal standard. Rel. sensitivity factors obtained from NBS standards C1115, C1116, C1117, 124, and CA4. 

NBS Standards and Analysis Methods for Trace Elements in Coal. 

As a measure of accuracy, we checked our method against NBS standards and mixtures of elements of known concentration and also participated in a round-robin analysis with NBS and EPA. We analyzed four NBS standards containing 60 elements in glass. Comparisons of results are given in Table VIII. With the exception of the cobalt result in the NBS 610 Standard, agreement is generally within 25% of the NBS value. 

Although the NBS standards were collected from several sources, some tentative conclusions can be reached concerning the combustion process. Using selected elements for comparison which are of a refractory nature and would be expected to be conserved in the ash following the combustion process, it becomes apparent that other elements such as selenium and antimony are not being conserved, but rather are lost from the ash. Refractory elements selected for illustration are Eu, Hf, Sc, Ta, Tb, and La, although most other elements display the same conservative behavior. Table VI shows the concentrations of these elements in both... 

Precision and Accuracy. Table I shows the results of tests on the linear polyethylene NBS Standard Reference Material No. 1475. This reference material has a pellet-to-pellet coefficient of variation of 3% in the limiting viscosity number according to the NBS Certificate. At least 50 pellets are recommended for a representative sample on which limiting viscosity number is obtained. Nine analyses were performed over a period of about one month on the pellets, using approximately three pellets per determination. The analysis of these data is shown in Table I along with a comparison with the NBS data and their estimate of precision. 

This procedure has been tested by applying it to known distribution chromatograms formed by blending of fractions and to NBS Standards 705 and 706 for which experimentally measured values of Mw, Mn> and [rj] are available. 

NBS Standards. Obtaining Mn, Mw, [77], and MWD. Chromatograms of two NBS standard polystyrenes, NBS 706 (broad distribution) and NBS 705 (narrow distribution), have been analyzed. Calculated results have been obtained using the two previously mentioned fitting procedures (1) 0.4-count separations between basis chromatograms and digitized data points and (2) 0.2-count separations. 

Table IV. Calculated Values of Average Molecular Weights and Viscosities for NBS Standards...

Fig. 18. Mossbauer spectra of Cr-Fc304 catalyst after room temperature exposure to air and COz/CO treatment at 703 K. (a) Spectrum in air at 296 K after sample has been stored in air. (b) Sample from (a) reduced in a C02/CO = 4 mixture at 703 K for 10 hr. Spectrum obtained in reaction mixture at 703 K. (c) After cooling (b) to 483 K. (d) After cooling (c) to 296 K. (e) Spectrum of a 0.001-in. Fe NBS standard foil at 296 K. Zero velocity is with respect to a 7Co in copper source. Reproduced from Tops0e and Boudart (96) with permission.

SRM (NBS) Standard reference material (National Bureau of Standards) a Direct oxidation method, n = 3 b HN03-H202,m = 5... 

Some results obtained on NBS standard reference plant materials are listed in Table 7.5. 

Table 7.5. Acid-soluble lead and cadmium levels (jxg/g) in NBS standard reference materials (from [96])...

Schramel [103] discusses the conditions for multi-element analysis of over 50 trace elements, giving detection limits. Wolnik [104] described a sample introduction system that extends the analytical capability of the inductively coupled argon plasma/polychromator to include the simultaneous determination of six elemental hydrides along with a variety of other elements in plant materials. Detection limits for arsenic, bismuth, selenium and tellurium range from 0.5 to 3 ng/ml and are better by at least an order of magnitude than those obtained with conventional pneumatic nebulisers, whereas detection limits for the other elements investigated remain the same. Results from the analysis of freeze-dried crop samples and NBS standard reference materials demonstrated the applicability of the technique. Results obtained by the analysis of a variety of plant materials are presented in Table 7.10. 

Detection limits range from 0.02ng/ml for arsenic to 0.80ng/ml for selenium, and precision values at lOng/ml are less than 6% relative standard deviation. Results of analyses of NBS standard reference materials (wheat flour, rice flour, spinach and orchard leaves) demonstrate the application of the method to the matrices. The layout of the apparatus is illustrated in Fig. 7.6. 

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