Standards, NIST

In the analysis of solid samples (e.g., LA-ICP-MS, SEM), synthetic standards cannot easily be prepared to the required concentrations, and accurate calibration of such techniques is often challenging. In some cases (e.g., SEM) pure element or single mineral standards are used, ideally with an appropriate standard for each element to be quantified. (It is possible in SEM, within limits, to use fewer standards than the number of elements to be determined, with the calibration for other elements being predicted from the response of the nearest element.) More often, however, multielement primary standards are used as the means of calibrating the instrument, e.g., for LA-ICP-MS of glasses, volcanics, and ceramics, two glass standards, NIST 610 and 612 (Pearce et al. 1996), are often used. It is always advisable to use more than one multielement standard in order to cover as wide a range of concentrations as possible, and to use at least one additional independent reference material as an unknown, for quality assurance purposes (see below). 

Am, 90Sr, 239Pu, 240Pu, 137Cs, 129I, or 14C, which also lack solution standards. NIST has an active program to address the development of all of these radionuclide standards except 14C. 

Schoenberg et al. (2008) presented the first set of Cr isotope data for rocks and Cr(ll) rich ores. Mantle derived rocks and chromite ores from layered intrusions have a uniform Cr/ Cr isotope ratio very close to the certified Cr standard NIST SRM 979. The Cr isotope composition of hydrothermal lead chromates is substantially heavier (S Cr from 0.6 to 1.0%o) than the rocks from which the chromium was leached. 

FIGURE 8.11 The Direct-EI mass spectrum of lindane is shown in the upper trace, and it is compared with the standard NIST El library spectrum shown in the lower trace. 

In Figure 8.14, the Cold El mass spectrum of corticosterone in methanol solution is shown in the upper trace, and is compared with the standard NIST 98 El library mass spectrum shown in the lower trace. Note the similarity of the library mass spectrum to that obtained with the SMB apparatus. All the major high mass ions of m/z 227, 251, 269, and 315 are with practically identical relative intensity and thus good library search results are enabled with the NIST library-matching factor of 829, and the reversed matching factor of 854% and 86.5% confidence level (probability) in corticosterone identification. In addition, the molecular ion at m/z 346 is now clearly observed while it is practically missing in the library (very small in the shown mass spectrum and absent in the other three replicate mass spectra). 

Figure 6.13 LA-ICP-MS results for trace elements on basalt glass (KL2-G from the Kilauea Volcano on Hawaii) using different glass standards (NIST SRM 612 and BCR-2G) compared to recommended value.

One problem is the availability of reliable reference materials for isotope ratio measurements. Certified isotope standard reference materials are available from NIST (National Institute of Standard Reference Materials, http //www.nist.gov/srd/, formerly NBS - National Bureau of Standards) and IRMM (Institute for Reference Materials and Measurements, http //www.irmm.jrc.de). There are isotope standard reference materials for light elements (H, Li, , C, N, O), Mg (magnesium metal isotopic standard NIST SRM 980), and for moderately heavy elements such as (potassium chloride isotopic standard NIST SRM 985), Cr (chromium metal isotopic standard NIST... 

SRM 979), Ni (nickel metal isotopic standard NIST SRM 986), Rb (rubidium chloride isotopic standard NIST SRM 984) and Sr (strontium carbonate isotopic standard NIST SRM 987). In addition, isotope reference materials are available for heavy elements such as T1 (thallium metal isotopic standard NIST SRM 997), Pb (NIST lead standard reference materials SRM 981-983) or U (uranium oxide NIST isotope standard U 005, U020, U350, U500 or U930) and others. The most important isotope standard reference materials applied in inorganic mass spectrometry are summarized in the table in Appendix V.17... 

The isotope variation of boron isotopic composition in aqueous fluids in environments on the Earth s surface has been reviewed by You.185 The boron isotope composition (8nB) is expressed as a per mil (%o) deviation from the boron isotope standard NIST SRM 951 ... 

MWCO molecular weight cutoff m/z mass-to-charge ratio NBS National Bureau of Standards NIST National Institute of Standards and Technology... 

National Institute of Standards (NIST) Special Publication 330,2001 Edition, Engl, version of The International System of Units (SI), 7th ed. Bureau International des Poids et Mesures Sevres, France, 1998. http //physics.nist.gov/Pubs/SP330/sp330.pdf. Quantities and Units International Organization for Standardization Geneva, Switzerland, 1993. http //www.iso.org/iso/en/prods-service/ISOstore/store.html. 

Standard NIST oyster tissue Total N and P as nitrate and phosphate... 

Babrauskas. V., NBSIR 82-2611, U.S. Bureau of Standards, NIST Wa.shington, 1982. 

In 1995, the first caesium fountain atomic clock was constructed at the Paris Observatory in France. A fountain clock, NIST-Fl, was introduced in 1999 in the US to function as the country s primary time and frequency standard NIST-Fl is accurate to within one second in 20 x 10 years. While earlier caesium clocks observed Cs atoms at ambient temperatures, caesium fountain clocks use lasers to slow down and cool the atoms to temperatures approaching 0 K. For an on-line demonstration of how NIST-Fl works, go to the website http //tf.nist.gov/cesium/fountain.htm. Current atomic clock research is focusing on instruments based on optical transitions of neutral atoms or of a single ion (e.g. Sr ). Progress in this area became viable after 1999 when optical counters based on femtosecond lasers (see Box 26.2) became available. 

Data compiled from the National Institute of Standards (NIST) Standard Reference Database Number 69, July 2001 Release, Accessed via NIST Chemistry WebBook (http //webbook.nist.gOv/chemistrv/i Copyright 2000. Data from CRC Handbook of Chemistry and Physics, Updated 3rd Electronic Edition Lide, David R., ed. DH values were obtained directly or calculated from heat of formation (Hf) data using the equation DH° [A-B]= Hf [A.] + Hf [B.] - Hf [A-B]. 

One of the main drawbaeks in the generation of thermal eonduetivity data on plasties remains the paucity of reference materials. Reference materials are important because they provide an important baseline for the calibration of instruments. Most thermal conductivity instruments require calibration to materials of known thermal conductivity. The National Institute of Standards (NIST) and other standards-setting institutions have characterized a number of metals, ceramics, glasses, and even insulation. These are not suitable as reference materials because they tend to possess a thermal conductivity that is higher or lower than those of plastics. For example, the NIST reference glass materials Pyrex 7740 and Pyroceram 9606 possess a thermal conductivity of 1 W/m-K which is five times greater than that of most plastics. The other reference materials are still more inapplicable. Many fluids, on the other hand, possess thermal conductivities similar to plastics. The transient line-source technique, however, is the only technique that can use such reference materials. 

A declaration that the source is traceable to a national standard - NIST, NPL, or whatever. 

Accuracy is defined as how close the measured value is to the actual value, if one exists [8]. Often an actual value is one accqjted as a standard NIST provide isothermal and isobaric density data electronically [3] with an uncertainty of 0.02 %. We refer to all calculations associated with data thus obtained as NIST-derived. Comparison of the specific surface excess amount via the P-R EoS analysis with that fixim NIST-derived density toa is shown in Fig. 2. The P-R EoS delivers values of the surface excess amount within 6.4 % of the NIST-derived over the range 0.25 < P < 17 MPa. To demonstrate which of the parameters listed in Table 1 has the greatest impact on the surface excess amount and its RCSU, we calculate the RCSU by vfflying individually each of the SU in Table 1 over the range - 100 % < SU < + 1000 %, to give the u. ( ). For the P-R EoS-derived data, (7 a ,6) greatest impact... 

CODATA = committee on data for science and technology DIPPR = design institute for physical property data lUPAC = international union of pure and applied chemistry NBS = national bureau of standards NIST = national institute of standards and technology. 

Quality Control Standard—NIST SRM 1838" can be used to check the accuracy of the calibration. 

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