Stanley D. Rasberry

Laser probe excitation in spectrochemical analysis.I: characteristics of the source.

A modified laser probe for spectrochemical analysis is described. A high energy laser beam is focused onto a specimen to vaporize a sample from a small area, and the vapor thus formed is further excited by a spark discharge. The characteristics of emission spectra with and without auxiliary spark excitation are compared. Spectrograph illuminating systems for qualitative and quantitative analysis were investigated. Some difficulties were encountered with the laser probe, and modifications were made to the instrument to alleviate some of these problems. Some typical analytical applications are discussed.

Trust and traceability in electronic commerce

Ⅵ Electronic commerce (EC) will modify some of the traditional models for the conduct of business. However, it is important that many of the long-standing elements of commerce be replicated in the electronic world. Commerce, electronic or otherwise, requires several elements: trading partners, goods and services, units of exchange (money), transaction infrastructures, and delivery and distribution mechanisms. These elements have been developed over centuries of legal, governmental, technological, and commercial practices and have resulted in a business infrastructure that people understand and trust. We explore two important elements of that infrastructure, trust and traceability, in the context of the evolving EC infrastructure. We look at a number of trust enhancers, i.e., technology or other processes that can help increase the level of confidence that people have in electronic commerce. We also examine the concept of traceability, an important trust enhancer, in detail. Finally, we discuss some specific technologies that can increase the overall level of trust in electronic commerce. ommercial practice and common law, developed over several thousand years, provide the context into which electronic commerce must fit, if it is to succeed. Early commerce, one step above the simplest trading of two articles between two people, was conducted face-to-face, possibly in front of a witness for the more complex transactions. The advent of reliable mail service in the eighteenth century, the telegraph in the nineteenth century, and the spread of telephones in the twentieth allowed commerce to be conducted on a remote basis. Computer-based commerce via networks such as the Internet is simply one more step in that evolution. Prior to the era of remote transactions, money was basically precious metal. The Pound Sterling was exactly that. Because transporting large amounts of precious metal in the service of remote trading was both labor intensive and hazardous, improvements to the banking system were needed to permit keeping of accounts and issuing letters of credit, drafts, checks, and vouchers of various kinds. Money, over the last century, has become disconnected from any underlying metal, and is essentially based on trust in the stability of the issuing country. In recent times financial accounts have been kept almost exclusively on computer based systems. Despite pressures for rapid development of electronic methods of conducting traditional business activities , the underlying structures, relationships, conventions , and methods of traditional methods will remain the dominant way of doing business. Electronic methods must be developed to coexist …

Laser Probe Excitation in Spectrochemical Analysis. II: Investigation of Quantitative Aspects

A study has been made of quantitative analysis by a laser probe with spark excitation of the sample vapor. Random errors come largely from variations in laser energy and from photometric errors. The parameters of the spark circuit affect the line intensities; however, these factors are well controlled. Correlations have been established between the energy of the laser beam, the size of the pit formed, and spectral intensities. For most purposes, single-spike laser operation has been found to be preferable to multiple-spike operation. At present, the coefficients of variation for analysis are 15% to 40%.

Application of digital computers in spectrochemical analysis—computational methods in photographic microphotometry

Abstract A new method of computation is described for calibration of photographic emulsions and conversion of microphotometer readings to relative intensities on a digital computer with special application to spectrochemical analysis. The method for emulsion calibration replaces graphical procedures by a numerical method which is well suited for digital computations. The method of computation and its underlying assumptions are described, and results are given of tests of the procedure. It is recognized that the entire experimental arrangement is being calibrated, not merely the photographic emulsion, and it is shown how malfunctions of the microphotometer which affect the calibration can be recognized from the output of the computer. The program for conversion of microphotometer readings to relative intensities provides for several alternate calculations, including selection of the proper calibration parameters according to the wavelength of the line when these data are supplied for more than one wavelength region, as well as correction for step and background where required. The program is written to provide for automatic selection of the required alternative calculation, based on a preliminary analysis of the input data.

The certification, development and use of standard reference materials

Abstract Analytical measurements are increasingly important to industrial quality assurance (QA) and to critical decision making in such fields as clinical, nutritional and environmental chemistry. Several factors are important to attaining analyses that are reliably accurate. Some of these include well-designed methods, trained staff, adequate instrumentation, reliable reference materials, laboratory QA procedures, and periodic proficiency testing. This paper will focus on the role of reference materials in accurate chemical analysis. Fundamental attributes of reference materials will be discussed together with details on how limits of uncertainty are established for certified values. Examples will be drawn from the results of one of the NISTs oldest biological Standard Reference Materials and two of its most recently certified SRMs. Matrices for these types of materials are very wide-ranging, including orchard leaves, river sediment and human serum.

NBS activities in biological reference materials

SummaryNBS activities in biological reference materials during 1986–1988 are described with a preview of plans for future certifications of reference materials. During the period, work has been completed or partially completed on about 40 reference materials of importance to health, nutrition, and environmental quality. Some of the reference materials that have been completed during the period and are described include: creatinine (SRM 914a), bovine serum albumin (SRM 927a), cholesterol in human serum (SRMs 1951–1952), aspartate aminotransferase (RM 8430), cholesterol and fat-soluble vitamins in coconut oil (SRM 1563), wheat flour (SRM 1567a), rice flour (SRM 1568a), mixed diet (RM 8431a), dinitropyrene isomers and 1-nitropyrene (SRM 1596), and complex PAHs from coal tar (SRM 1597). Oyster tissue (SRM 1566a) is being analyzed and should be available in 1988.

Biological reference materials from the US National Bureau of Standards - An update

SummaryThis paper provides an update covering the change in availability of NBS Biological Reference Materials between the First and the Second Symposium on Biological Reference Materials. In the intervening 30-month period, 15 new reference materials of biological interest have been issued by NBS and 8 more are being prepared. Newly issued reference materials that are described include: corn kernel, corn stalk, lead in blood, trace elements in human serum, inorganic constituents in bovine serum, PCBs in human serum, blood gases, toxic elements in urine, dioxin in isooctane, ethanolwater solutions, chlorinated pesticides and chlorinated biphenyls in isooctane.Several new Standard Reference Materials have been introduced to aid analysts in testing instrument performance. These are intended to provide a baseline of instrument performance, independent of the matrix analyzed. Described are 36 solution standards for spectrometric methods, a wavelength standard for spectrophotometers, a temperature standard, and one for evaluating GC/MS system performance.

Protocols for traceability in chemical analysis

The authors propose definitions and terminology for protocols on traceability links, generally to the international system of units, for specific chemical-analytical measurements in accordance with recognized principles of science. These definitions and terms could be useful in science, technology, commerce or law. A chain of such links leads from a measurand in a sample up to a unit in the International System of Units or, if unavailable, to a value on an internationally recognized measurement scale. The quality of such a chain is quantified by combining all recognized uncertainties estimated for all its links. These uncertainties of the measured values arise from many potential error sources. The protocols should give details of specific uses of reference materials, measuring instruments and standard measurement methods.

REMCO, the ISO Council Committee on Reference Materials – its first 25 years

Abstract The 25th Anniversary of the first meeting of REMCO presents an occasion to summarize the events preceding and leading up to the establishment of this Committee, the ever growing use of reference materials, the ISO Guides REMCO has prepared, the help for Technical Committees to achieve valid measurements, the help for Developing Countries in upgrading their laboratories, its structure and contact points.

REMCO — The ISO council committee on reference materials

SummaryThe purpose of this paper is to provide readers with an insight into the work of REMCO, the worlds main body for considering matters related to the production and use of reference materials. The terms of reference for REMCO and its three task groups are given. Contents of the four ISO Guides issued by REMCO illustrate the range of topics covered in the work of the committee.