Standard reference collections

Standard reference collections. The Law Enforcement Standards Laboratory of NBS has been investigating the needs and uses of standard reference files or collections of select groups of forensic materials. 

Two standard reference collections have been constructed and are in the process of being distributed to crime laboratories in the United States. The first is a set of auto paint color chips for 197 domestic vehicles. Each set contains samples of approximately lltO colors plus information concerning the makes and models of automobiles on which each color was used. 

Because of the risk of lead poisoning, the exposure of children to lead-based paint is a significant public health concern. The first step in the quantitative analysis of lead in dried paint chips is to dissolve the sample. Corl evaluated several dissolution techniques. " In this study, samples of paint were collected and pulverized with a Pyrex mortar and pestle. Replicate portions of the powdered paint were then taken for analysis. Results for an unknown paint sample and for a standard reference material, in which dissolution was accomplished by a 4-6-h digestion with HNO3 on a hot plate, are shown in the following table. 

Physical or artifactual standards are used for comparison, caUbration, etc, eg, the national standards of mass, length, and time maintained by the National Institute of Standards and Technology (NIST) or the standard reference materials (SRMs) collected and distributed by NIST. Choice of the standard is determined by the property it is supposed to define, its ease of measurement, its stabiUty with time, and other factors (see Fine chemicals). 

The present volume presents the results of an attempt to collect all relevant data as complete as possible. In a few cases original sources were not accessible despite considerable efforts. To provide a critical review and a complete reevaluation of the reported data is not the purpose of this collection. Consequently all data are reported, only conversion into standard units and with respect to standard references were made when necessary and reasonable, obvious printing errors were corrected. 

For standard or proprietary polymer additive blends there is the need for analytical certification of the components. Blend technology has been developed for two- to six-component polymer additive blend systems, with certified analytical results [81]. Finally, there exist physical collections of reference additive samples, both public [82] and proprietary. The Dutch Food Inspection Service reference collection comprises 100 of the most important additives used in food contact plastics [83-85]. Reference compounds of a broad range of additives used in commercial plastics and rubber formulations are generally also available from the major additive manufacturers. These additive samples can be used as reference or calibration standards for chromatographic or spectroscopic analysis. DSM Plastics Reference Collection of Additives comprises over 1400 samples. 

The HS samples used in this work were obtained from the Standard and Reference Collection of HAs and FAs of the International Humic Substances Society (IHSS), with the exception of the HA from an alluvial soil. The origin and nature of HS, with the corresponding codes, abbreviations and concentrations used, are shown in Table 1. 

While the broad mission of the National Bureau of Standards was concerned with standard reference materials, Dr. Isbell centered the work of his laboratory on his long interest in the carbohydrates and on the use of physical methods in their characterization. Infrared spectroscopy had shown promise in providing structural and conformational information on carbohydrates and their derivatives, and Isbell invited Tipson to conduct detailed infrared studies on the extensive collection of carbohydrate samples maintained by Isbell. The series of publications that rapidly resulted furnished a basis for assigning conformations to pyranoid sugars and their derivatives. Although this work was later to be overshadowed by application of the much more powerful technique of nuclear magnetic resonance spectroscopy, the Isbell— Tipson work helped to define the molecular shapes involved and the terminology required for their description. 

A QC assessment was done for all samples. De-ionized water field blanks were collected on seven different days to evaluate process contamination. Site duplicates were taken at eight sites to evaluate repeatability and site variation. Instrumental precision was constrained by analysis of laboratory duplicate solutions, and is typically less than 5%. Finally, standard reference material (SRM) water standards were analyzed with sample batches, to assess instrumental accuracy. 

Then, to tidy up a bit and make absolutely sure of the relative retention times, I decided to run standards from my reference collection. Reference harmine gave the second peak with identical retention time and MS spectrum. It was when I injected a sample of my reference harmaline that I got my surprise. Here, a sample of E. Merck AG, Darmstadt yellow crystalline material labeled Harmalinhydrochlorid, was very much looking as if it was a mixture of about two parts harmaline and one part harmine. Only 70% pure Wow. 

Two publications by Burklin (References, Section 1.1, Part B) are devoted to standards of importance to the chemical industry. Listed are about 50 organizations and 60 topics with which they are concerned. National Bureau of Standards Publication 329 contains about 25,000 titles of U.S. standards. The NBS-SIS service maintains a reference collection of 200,000 items accessible by letter or phone. Information about foreign standards is obtainable through the American National Standards Institute (ANSI). 

Samples of sand spiked with 36 nitroaromatic compounds, 19 haloethers, and 42 organochlorine pesticides, and a standard reference soil (certified for 13 polynuclear aromatic hydrocarbons, dibenzofuran, and pentachlorophenol) were extracted with supercritical carbon dioxide in a two- or four-vessel supercritical fluid extractor to establish the efficiency of the extraction and the degree of agreement of the parallel extraction recoveries. Furthermore, the many variables that influence the extraction process (e.g., flowrate, pressure, temperature, moisture content, cell volume, sample size, extraction time, modifier type, modifier volume, static versus dynamic extraction, volume of solvent in the collection vessel, and the use of glass beads to fill the void volume) were investigated. 

In a typical experiment, noninvasive spectra are collected continuously as the in vivo glucose concentration is controlled by intravenous infusion of fluids.50 Glucose concentrations are held low and constant for the first 3 h. Then, glucose concentrations are increased to more than 30 mM. Glucose is maintained at this level for approximately 1 h, after which the glucose concentration is allowed to decay naturally to basal levels over the next hour. During the course of the experiment, arterial blood samples are collected periodically for analysis by a standard reference method. 

Inductively Coupled Plasma. Analyses by ICP were performed on the same dissolutions used for the AA analyses for Cd and Pb. The solutions were diluted as necessary and were then nebulized and introduced into the plasma. Line spectra were collected with a multichannel analyzer and corrections were made for reagent blanks and background shifts. For all analyses, NBS Standard Reference Material 1632 was used for instrument calibration. 

In 2005, De Laeter discussed the role of isotope reference materials for the analysis of non-traditionaT stable isotopes. At present, no isotopically certified reference materials exist for a large number of elements, including Cu, Zn, Mo and Cd, and it is important that this situation be rectified as soon as practicable. Before the isotopically certified reference materials become available for selected elements, suitable reference materials can be created as a standard if sufficient and reliable isotope data have been obtained by interlaboratory comparisons. For example, the Hf/ Hf isotope ratio was measured using hafnium oxide from Johnson Matthey Chemicals, JMC-475, for hafnium isotope ratio measurements with different multi-collector mass spectrometers (ICP-MS and TIMS) as summarized in Table 8.1. However, no isotope SRM is certified for the element Mo either. Mo isotope analysis is relevant, for example, for studying the isotope fractionation of molybdenum during chemical processes or the isotope variation of molybdenum in nature as the result of the predicted double (3 decay of Zr or 18.26-28 spectroscopically pure sample from Johnson Mattey Specpure is proposed as a laboratory standard reference material if sufficient and reliable isotope data are collected via an interlaboratory comparison. 

The dipole moments were collected from a variety of standard reference sources such as 1206a and 2160. The values of A/fare from Appendix B,... 

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