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Metrological traceability for organic chemical measurements is a documented unbroken chain of calibrations with stated uncertainties that ideally link the measurement result for a sample to a primary calibrator in appropriate SI units (e.g., mass fraction). A comprehensive chemical purity determination of the organic calibrator is required to ensure a true assessment of this result. We explore the evolution of chemical purity capabilities across metrology institute members of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology’s Organic Analysis Working Group (OAWG). The OAWG work program has promoted the development of robust measurement capabilities, using indirect “mass balance” determinations via rigorous assessment of impurities and direct determination using quantitative nuclear magnetic resonance spectroscopy methods. A combination of mass balance and qNMR has been shown to provide a best practice approach. Awareness of the importance of the traceability of organic calibrators continues to grow across stakeholder groups, particularly in key areas such as clinical chemistry where activities related to the Joint Committee for Traceability in Laboratory Medicine have raised the profile of traceable calibrators.

Gravimetric preparation method is one of the most precise and accurate methods for preparing primary standard gas mixtures (PSMs). Although the principle and execution of the gravimetric method are not complicated, the uncertainty of the gravimetric method is so small that a seemingly minor error can result in an incorrect amount fraction of the PSM. Therefore, verifying the amount fraction of the PSMs is a necessary step. We perform a high-precision comparison between the PSMs of oxygen in nitrogen (∼100 µmol per mol) using a well-stabilized gas chromatograph with a thermal conductivity detector (GC-TCD) system in conjunction with high-precision pressure monitoring for sample amount correction and a quality-control cylinder technique in which the PSMs were analyzed against a reference cylinder, which leads to the cancellation of the drift in the sensitivity of the GC-TCD. After optimization of the measurement conditions, the relative expanded uncertainty reaches 0.022% (coverage factor k = 2), which is equivalent to the uncertainty of the PSMs. The Consultative Committee for Amount of Substance of the Comite International des Poids et Mesures performed a key comparison CCQM-K53, in which one of the PSMs used in this work was compared and agreed well with PSMs prepared by other National Metrology Institutes. These results show that the GC-TCD system developed in this work is sufficiently reliable, precise and accurate to verify PSMs.

Fractal is a set owning an infinitely fine structure in a self-similar or self-affine way covering all scales, and is widely used to model the structure of porous media. Hydrate-bearing sediments belong to porous media, so this paper attempts to construct a structure model of hydrate-bearing sediments with the three-component fractal extended from the two-component fractal. The three-component fractal is capable to display structural details at arbitrarily small scale. Additionally, in the three-component fractal, any parameter defined as the ratio (such as porosity and hydrate saturation) of two different volumes approaches a determined value when considering the infinitesimal scale. The interface between hydrate elements and pore elements is suggested to be a potential way to classify the hydrate-bearing sediments. Using the proposed three-component fractal model to calculate the interface between one arbitrary hydrate particle and surrounding pores, we obtain the theoretical solutions of the amount of substance, the dissociation rate and maximal dissociation time of one arbitrary hydrate element in sediments. It is found that the effective reacting surface of one hydrate element in sediments could be equal to even greater than that of the pure hydrate element in the late period of hydrate dissociation, during which the amount of substance of one hydrate element in sediments is still greater though. Finally, we further extend the three-component fractal to any-component fractal, and show how to model more complex porous media by using a suitable generator.

Оригинал опубликован в журнале Metrologia (2013. V. 50. № 5. P. 158-163) под названием "The mole, amount of substance and primary methods". Материал получен 25 февраля 2013 г., в окончательной форме - 8 марта 2013 г., опубликован 2 апреля 2013 г. Оригинальный текст доступен на сайте IOP Science. URL:stacks.Iop.org/Met/50/158. В данном докладе представлены принципы, разработанные для применения метрологии в сфере химии и, в частности, аналитической химии. Доклад начинается с обсуждения моля, основной единицы Международной системы единиц (СИ), которая более всего относится к аналитической химии. Моль стал предметом отдельной дискуссии совсем недавно, с момента публикации предложений дать ему новое определение вместе с тремя другими основными единицами СИ. Эта дискуссия также породила интерес к происхождению термина «количество вещества», которое используется как количество, а моль - как единица. В данном докладе рассматривается происхождение термина и объясняется, почему недостаточно было бы заменить его альтернативными вариантами, такими как «число единиц». В заключение идет дискуссия о том, как используется моль в первичных методах измерений.

Within the Working Group on Inorganic Analysis (IAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) international key comparisons and pilot studies related to inorganic analysis are carried to ensure consistency in this field at the highest level. Some of these comparisons deal directly with the preparation and characterization of monoelemental solutions or with topics, closely related. The importance of monoelemental solutions lies in the fact that almost every measurement in inorganic analysis relies on the comparison with either a reference material, or references in form of solutions, usually (mono)elemental solutions. All quantitative measurement approaches, e.g. isotope dilution or standard addition, need an accurate reference solution made from a well characterized reference material, prepared under full gravimetric control. These primary (monoelemental) solutions do not only serve as arbitrary references/calibration solutions, but they also link up measurement results to the International System of units (SI), this way establishing the so-called metrological traceability to a measurement unit of the SI. Without such solutions on the highest possible level of accuracy and with the smallest possible associated uncertainties (for e.g. element content and/or impurities), an analysis itself can never be as good as it could be with appropriate reference solutions. This article highlights select key comparisons and pilot studies dealing with monoelemental solution-related topics within the IAWG from the foundation of CCQM—25 years ago—up to latest achievements in the field of inorganic analysis.

This discussion puts a case of advocatus diaboli: that the Treaty of the Metre, its associated administrative apparatus and the International System of measurement units (SI) has basically failed for chemical measurement and is largely irrelevant to modern analysis, much of practical measurement in modern economies and much of recent technology. The practical use of the chemical unit termed the mole, the introduction to the SI units of the thermodynamic mole and the invention of a new physical quantity called “amount of substance” are each reviewed with the conclusion that the current means of expressing the results of chemical measurements are unsatisfactory in both practice and theory and are imposing large and readily avoidable costs on all advanced economies.

Stripping voltammetry analysis using a hemispheroidal mercury microelectrode is assessed as a possible candidate "primary method" for amount of substance measurement. It has been shown that this measurement methodology can be described completely by a set of measurement equations. Novel proposals are made to improve the accuracy and traceability of the quantification process by measuring the limiting deposition current over an optimum time instead of employing an analyte stripping step. The range of application and the limitations of the technique are discussed, and the requirement for underpinning traceability from electrical standards is shown. It is concluded that the lack of amount-independent diffusion coefficient data limits the status of the technique to a high-accuracy "definitive method" at present

Traditional XPS imaging produces a map of the XPS peak intensity. It is well known that the peak intensity carries limited information on the total amount of material as well as on the depth distribution of atoms. Such images can therefore be strongly misleading. Elaborate methods for improved quantification by analysis of the peak shape were developed by Tougaard et al. in the past but they require operator interaction and are therefore not suitable for imaging where thousands of spectra must be analyzed. Recently, Tougaard proposed a new algorithm [S. Tougaard, J. Vac. Sci. Technol. A 21 (2003) 1081] which is less accurate but sufficiently robust to allow for automatic data processing. In the present paper, we have successfully demonstrated the ability of the algorithm to produce detailed images of a plasma patterned polymer on Teflon. In general, four images are produced which show the distribution of pixels where F atoms are at the surface, in the bulk, or homogeneous in depth as well as an image of the amount of F atoms within the outermost three inelastic electron mean free paths.

Gas analysis has become an important task in various fields of science and industry, especially through techniques based on laser spectroscopy. Common applications are, for example, the monitoring of the atmosphere to assess human impact on ecosystems and the climate, the monitoring of airborne molecular contamination to supervise sensitive high-tech processes like semiconductor manufacturing, or the analysis of combustion processes. High resolution laser spectroscopy lends itself particularly well for gas analysis, as it is fast, selective, and the results can be made traceable to the SI units. Traceability is of particular importance to maximize the reliability of measurement results, especially if such measurements are the input for complicated models like those used in climate research or if impacting political decisions. In this contribution we give an overview on our approach to achieve traceability of results from spectroscopic amount fraction measurements of H2 O, CO2 , and NH3 including the TILSAM method (traceable infrared laser-spectrometric amount fraction measurement). We discuss how this method applies to tunable diode-laser absorption spectroscopy (TDLAS), cavity ring-down spectroscopy (CRDS), and photoacoustic spectroscopy (PAS). This research is partly embedded in projects within the European Metrology Research Programme (EMRP).

After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.

The unwieldy term 'amount of substance' for the base quantity n has led to conflicting authoritative choices for abbreviations, especially when forming terms for derived quantities. A proposed substitute, the neologism 'chemon', is a derivative from the Greek χηµα (chemistry). A systematic terminology is achieved by forming derivatives and complex terms in the usual way, e.g. 'chemonity' (nB/msolvent), 'chemon concentration' (nB/Vsystem), 'chemonic volume' (V/nB). The harmonization of terms in thirteen European languages is accomplished according to the respective linguistic rules.

As a consequence of the globalisation of trade and industry and other human activities, reliability of and confidence in measurement results is increasingly required, also in the field of chemical analysis, so that measurements made in one country will be accepted in other countries without the necessity to repeat them. The prerequisite for confidence is comparability on the basis of known uncertainties which in turn are based on traceability to recognised references. Traceability structures for chemical measurements are required which, by providing calibration means traceable to national standards, allow uncertainty statements to be made at field level, thus establishing comparability. Such traceability structures are now being developed in all industrialised countries. To ensure international comparability, mutual recognition of the national activities in metrology in chemistry is required in addition. The Mutual Recognition Agreement (MRA) for national measurement standards and calibration certificates issued by national metrology institutes, which is currently under way within the framework of the Metre Convention, aimes at providing the necessary international confidence for all kinds of measurements. The field of chemical analysis is included in the international metrological infrastructure through the new Consultative Committee for Amount of Substance (CCQM). Carefully selected key comparison measurements, which cover the most important areas where traceability is required, and which are carried out by national metrology institutes in cooperation with other national institutes entrusted with the provision of part of the national references for chemical measurements, form the basis for declarations of equivalence under the MRA. The results of the first key comparisons and studies carried out so far clearly show that the group of laboratories involved in the key comparisons is capable of establishing the international references (key comparison reference values) for chemical measurements with sufficient accuracy, also in complicated matrices.

The aim of the International Measurement Evaluation Programme (IMEP) is to give an objective picture of state-of-the-practice analytical measurements by comparing them to a reference value obtained by a primary method of measurement. The referencevalue is therefore as traceable to the SI system of measurements as can presently be achieved and is independent of human or political decisions. Thus a large scale field test is made to achieve (international) comparability of measurements by comparing them with an independent metrologically established value. In the fourth measurement round, IMEP-4, three trace elements, Li, Cu and Zn, at three different levels in (bovine) serum were measured by about 12 participating laboratories using their routine methods. The (coded) results are graphically reported and compared to certified reference values established by an isotope-specific method, isotope dilution mass spectrometry, defined as a primary method of measurement by the Consultative Committee on Amount of Substance. Results indicate a spread of more than ±50%, asymmetrically distributed around the reference value with its own uncertainty range, although the self-declared accuracy of the laboratories was 5–10%. Self-assessment by participants of their analytical capabilities does not show a high correlation between self-rating ("more experienced" or "less experienced") and actual performance. In the way they have been applied, all methods seem to produce results of approximately the same quality.

Metrology is the science of measurement and its application. Whenever one performs a measurement one compares the measurand to an appropriate unit. The number of these units has changed since the metre convention in 1875 to 1960 when the 11th CGPM (Conference Generale des Poids et Mesures) decided the actual SI (Systeme International d’Unites). Currently the SI is based on seven units – kilogram for mass, second for time, metre for length, ampere for electric current, Kelvin for thermodynamic temperature, candela for luminous intensity and – since 1971 – mol for amount of substance. Their definition also sometimes changes, due to demands on the unit or the advent of new methods for a possible better realisation. The metre, for instance, was incipiently defined as a part of a meridian of the earth. This definition was impractical to realise, so for the realisation the length between the ends of a platinum bar was used. To overcome the difficulties of the handling and measurement of this length standard, the definition was again revised to the distance between two marks on a new, x-shaped Pt-Ir rod. Although the measurement capabilities grew and even though interferometry was discovered early, the next redefinition took two ages. Eventually, in 1960 the metre was defined by a multiple of the wavelength of the radiation of 86krypton. And since 1983, for the present finally, the metre is defined by a time-of-flight definition: one metre is the distance which light travels in 1/299792458 seconds where this special number is given by the fixed value of the speed of light.

The potential role of isotope dilution (ID) in the future organization of traceability and therefore comparability of chemical measurements (amount measurements in SI terms) is described. Essential is that ID (e.g. in isotope dilution mass spectrometry IDMS), directly measuring in our SI unit for amount of substance (the mole), gives matrix-independent results and reduces a complicated chemical measurement to a simple physical measurement. It is possible to borrow from the ultra-high accuracy isotopic measurement techniques needed in the continuous improvement of the Avogadro constant in order to make high accuracy measurements of the amount of substance: both fields have in common the determination of isotope abundance ratios with small but well known total uncertainties (conditions for so-called “absolute” measurements). In addition, the use of such ratio measurements in an isotope dilution procedure for amount measurements seems to constitute a form of direct traceability of amount measurements to the “Avogadro measurement procedure” and therefore to the closest realisation of the mole so far. All of this will have far-reaching consequences: Will enriched isotopes be available in a systematic, continuous, affordable supply to ensure the possibility of isotope dilution in the future? Will simpler and, above all, cheaper isotope mass spectrometers be available for the key laboratories of future measurement networks needed in the organization of the traceability of chemical measurements? Will the difference between “chemical” and “physical” measurements not gradually fade away in the organization of traceability of amount measurements? Is further development and application of IDMS — but also of ID using other isotope-specific measurement techniques — not needed for all elements?

The symbolic time course equations corresponding to a general model of a linear compartmental system, closed or open, with or without traps and with zero input are presented in this chapter. From here, the steady state equations are obtained easily from the transient phase equations by setting the time towards infinite. Special attention is given to the open systems, for which an exhaustive kinetic analysis has been developed to obtain important properties. Besides, the results are particularized to open systems without traps. The software COEFICOM, easy to use and with a user-friendly format of the input of data and the output of results, allows the user to obtain the symbolic expressions of the coefficients involved in the general symbolic equation and all the information necessary to derive the symbolic time course equations for closed or open systems as well as for the derivation of the mean residence times.

Numerical cognition is essential to many aspects of life and arithmetic abilities predict academic achievements better than reading (Estrada et al., 2004). Accordingly, it is important to understand the building blocks of numerical cognition, the neural tissue involved, and the developmental trajectories. In the last two decades research has made impressive strides forward in studying numerical cognition and brain mechanisms involved in arithmetic. This advance was marked by suggestions of a numerical core system that can be characterized as a set of intuitions for quantities innately available to humans (Brannon et al., 2006) and animals (Cantlon and Brannon, 2007). We suggest that another system, evolved to perceive and evaluate non-countable dimensions like size or amount of substance may be important for the evolution of the numerical system and numerical abilities. The current opinion article examines this idea and the possible interplay between, on the one hand perception and evaluation of continuous dimensions and, on the other, the numerical system.

Chemical measurements play a rapidly increasing role in modern society and more and more form the basis of important decisions and regulations (legal, medical, environmental, etc.). Therefore, their reliability is of the utmost importance. Environmental measurements are becoming a particular case in point with the public's and governments' growing awareness about the environment. These measurements will also have to be comparable across borders. Chemists must worry more about this reliability in order not to lose credibility and not to generate a loss of faith in chemistry. In order to achieve both credibility and comparability, the fulfilment of the following requirements seems to be needed: express all results of (environmental) measurements in the SI unit for amount of substance, the mole; ensure their traceability to the mole, our SI unit for amount of substance; assess their real performance through regular participation in external (border-crossing) quality assessment programmes using undis...

The Consultative Committee for Amount of Substance (CCQM) has the task of organizing a comprehensive set of international comparisons to establish the technical basis for the mutual recognition of measurement capabilities among the national measurement institutes (NMIs) in the field of chemical measurement. The challenge that the CCQM faces is to identify, design, and conduct a limited number of key comparisons to enable the assessment of measurement comparability among NMIs across the entirety of ’chemical measurement space’. This is no easy task because the field of chemical metrology is extremely diverse and multidimensional, owing to the number of measurand types, concentrations, and matrix types of importance. The ”CCQM primary methods symposium: how far does the light shine?” was organized to provide information and initiate discussions to assist in this challenge, and clarify how the concept of a primary method of measurement could be instrumental in achieving this goal.

In Germany a system of primary amount of substance standards for elemental analysis is being developed, which forms the material's basis for the National Standards for element determination. The metrological concept and technical approach is briefly described. The objective of traceability in chemistry, in this case for elemental determination, is illustrated on the example of copper.

Summary Biologists in the aquatic sciences are often guilty of numerous errors in the presentation of their chemical data. This paper reviews the use of units in the representation of the inorganic constituents of aquatic solutions for their benefit. It explains the relationship between salinity, total dissolved solids and conductivity, and between the amount of substance and concentration, and specifies conditions in which each can be used. Methods for the mathematical verification of analytical results are briefly discussed. Tables of recommended units, conversion factors and molar conductivities are provided. It is concluded that chemical data can easily be reported correctly and that both authors and referees have a duty to ensure that this is done.

We investigated whether people can use haptic liquid-specific information made available by shaking the vessel containing the liquid. In experiment 1 we studied to what extent people can discriminate between liquid and solid substances and determine the amount of substance in the shaken vessel, as well as the effects of exploratory procedures on these abilities. Exploratory procedures including horizontal shaking of the vessel produced accurate identification of the content and more precise judgments for a liquid than for a solid, but vertical lifting produced an overestimation of the amount of liquid. In experiment 2 we demonstrated that people can discriminate between the amount of liquid and the amount of solid in the same vessel. Three theories of what liquid-specific stimulus properties are picked up by shaking the vessel are preliminarily examined.

Publisher Summary This chapter provides an introduction to the technique called isotope dilution mass spectrometry (IDMS) which is recognized as a primary method of measurement by the Comite Consultatif pour la Quantite de Matiere (CCQM) or as it is named in English, the consultative committee for amount of substance. The basic principles, derived IDMS equations, and the main benefits of IDMS as well as some pitfalls are outlined and explained. The isotope dilution technique is used in many fields of analytical science, from biochemistry to geology. . A primary method of measurement is a method having the highest metrological qualities, whose operation can be completely described and understood, for which a complete uncertainty statement can be written down in terms of SI units. IDMS is the most important technique for accurate measurements of amount content and at the highest metrological level, which the key comparisons represent. IDMS is transparent and can be very precise. It is a solid technique because it works even if there are non-quantitative recoveries from digestion or separation steps.. It is also independent of instrument sensitivity.

Publisher Summary The concept of traceability is a basis of scientific work. It is well established and has a long tradition in physical measurements. This chapter explains the concept of traceability and its implications for isotopic measurements in a consistent way. Exemplified are the cases of amount of substance measurements by isotope dilution mass spectrometry (IDMS), isotope amount ratio measurements and differential measurements of so called 6- values. Traceability is a property of values of a standard or of values resulting from a measurement. It can and must be applied to isotopic measurements. It is a powerful tool to establish comparability of measurement results in time and space. In isotopic measurement lack of traceability is observed caused by lack of a correct comparison and less frequently by problems related to stated or varying references, wrong or missing uncertainty statements or broken chains. It is very desirable as it avoids dispute and confusion, thus enhances development and saves resources.

The International System of Units—commonly abbreviated as SI from the French term Systeme International d’Unites—has served the scientific community well. It allows for standardization and uniformity of measurements across the world, and beyond. From the system’s earliest conception, standards for length, time, mass, and the other base units were sought, with the intention that such standards would be unchangeable and permanent. Over the past 100-plus years, however, scientific and technological advances have led to an evolution of standards, away from those originally envisioned by the authors of the system. In fact, the International Committee for Weights & Measures is proposing a fairly dramatic revision of the entire SI system at this time. To see how these changes will affect how we use and teach the SI system, consider this short quiz: 1. The current definition of the mole is a. The amount of substance containing as many entities (atoms or ...

In this article the role of reference materials is confined to chemical measurements only. Recognized reference materials are one of the tools to obtain comparability of analytical results. Recognition demands confidence in the reference materials and in the reference material producers. A reference material producer is a technical competent body that is fully responsible for the certified or other property values of the reference material. The "analyte" has to be specified in relation to the selectivity of analytical procedure. The full range of reference materials can be presented as a three-dimensional space of the coordinates: analyte, matrix and application. If reference materials are used for calibration or correction of calibrations they establish the traceability of results of chemical measurements. The traceability is only valid within a stated range of uncertainty. Pure substances can represent the unit of amount of substance. A precondition is the microscale specification of the analyte and the accurate determination of the main component and/or the impurities.

It is the central aim of the current activities of metrology in chemistry to build confidence in the reliability of chemical measurement results so that they are accepted without costly duplication being necessary. An important prerequisite for such confidence is comparability based on traceability to recognised common references, ideally the SI units. Since metrology is organised within a national framework according to the national laws and regulations, a two-step procedure is to be followed to achieve international comparability for chemical measurements which is increasingly required as a result of the globalization of trade and economy: (1) establishment of national traceability structures for chemical measurements and (2) mutual recognition of the national traceability structures on the basis of equivalence criteria. The first step is at present being taken in many countries. Examples are presented for Germany. The second step has been initiated by the Mutual Recognition Arrangement (MRA) of the Meter Convention for national measurement standards and measurements and calibrations provided by national metrology institutes, which is based on international comparison measurements (key comparisons) carried out on the national standards level. Chemical analysis is included in this process through the Consultative Committee for Amount of Substance (CCQM).

The chapter focuses on the international system of units. The international system of units or the SI units are evolved from the mass-length-time-temperature system. It derived from the seven base units of length, mass, time, temperature, amount of substance, electric current, and luminous intensity. SI provides prefixes for decimal multiples and submultiples of the base supplementary and approved derived units. The SI is established as an evolving system, thus prefixes and units are created and unit definitions are modified through international agreement as the technology of measurement progresses. SI is one of the widely used systems of measurement, which is used in both everyday commerce and science. The system is globally accepted with the United States being the only industrialized nation that does not mainly use the metric system in its commercial and standards activities. In addition to learning the new units and symbols, conversion is required when numerical values are reported in imperial or the c.g.s units. The conversion of units is mainly handled through the use of conversion tables.

Awide variety of competing factors (ie, turnaround time, cost, and ease of use) affect the use and value of a clinical laboratory test; however, a primary determinant in proper test selection is expected test performance. The key elements of interest in defining performance vary, depending on the nature and type of the test (quantitative, qualitative, or semiquantitative testing). Virtually all diagnostic tests have common features of interest. Performance has traditionally been grounded in studies to establish the accuracy, trueness, or bias of the test; the precision, repeatability, or reproducibility of the test; and the test’s analytic and diagnostic sensitivity and specificity. Given the laboratory testing scientific community’s heterogeneous nature, inconsistencies have developed in the basic definition of terms for test performance. These differences have become increasingly obvious and problematic over the past few years. With heightened concerns over the quality and cost of health care and with the need to minimize health care errors, the value of simplified and standardized approaches for defining and communicating test performance has never been more self-evident. At least 3 publications in the US medical literature in the past 5 years have specifically addressed selected problems in the area of nomenclature. Saah and Hoover 1 in the ‘‘Lingua Medica’’ section of the Annals of Internal Medicine highlight the tension between the terms ‘‘analytical’’ and ‘‘diagnostic sensitivity’’ and ‘‘specificity.’’ They point out that analytic sensitivity represents the smallest amount of substance that can be measured in a sample. They note that this parameter does not always correlate in a direct manner with diagnostic sensitivity, the percentage of persons with a given disorder who test positive with a given test. Conversely, they show that analytic specificity refers to the ability of an assay to measure a particular substance rather than similar but different substances. This parameter can profoundly affect diagnostic sensitivity but is again quite different from diagnostic specificity, the ability of an assay to detect true negative results. Ekins and Edwards 2 and Pardue 3 in a special ‘‘Point/ Counterpoint’’ publication in Clinical Chemistry indicate that analytic sensitivity itself is a term with variable and

Substance use factors were examined and cross-validated in a cluster analytic approach in two independent samples of college students: N = 291 and N = 602. Reported frequency, intensity, and amount of substance use were examined for beer, hard liquor, marijuana, amphetamines, barbiturates, psychedelics, cocaine, and heroin. Variables were reduced using Principal Components Analysis (PCA) to form four substance use composites. Composite scores were entered into two different methods of cluster analysis that each identified four distinct clusters of substance use groups. External validity was obtained by showing that these four groups differed on a set of relevant variables. The four groups served as levels of the independent variable, substance use type, in four MANOVAs examining group differences on peer and family influence, psychosocial functioning, habit acquisition, and self-efficacy. Findings indicate that as frequency and intensity of substance use increased, individuals reported more problems in living, although a causal direction cannot be established. The findings are of potential value in early identification, prevention, and education regarding substance use among college populations.

To determine whether a faculty development program was effective in increasing clinical skills and the amount of substance abuse teaching of individual general medical faculty.Program participants were evaluated with a structured assessment before and several months after participating in a faculty development program in substance abuse education.Eighty percent were general internal medicine faculty, who on average devoted 25% of their time to teaching. The remainder of the participants were family medicine, psychiatry, or other internal medicine faculty and nonphysician teachers.The participants attended a learner-centered, largely experiential faculty development program in substance abuse education to improve their clinical and teaching skills relevant to substance abuse among patients in the general medical setting.Eighty-six percent of the participants completed the evaluation. The participants reported increased confidence in their clinical skills in recognizing substance abuse, presenting the problem to the patient, and referring the patient for treatment. The participants also reported improved attitudes toward patients and increased teaching about the management of the primary problem of substance abuse, but not at the expense of teaching about medical complications.Clinically oriented, interactive faculty development courses in substance abuse education can contribute to increased confidence in clinical skills in substance abuse as well as teaching about substance abuse.

In clinical chemistry and medical diagnostics, the reliability of the results obtained by numerous testing protocols has a major impact on the critical decision-making processes. Considerable efforts are made by international institutes to promote and give guidance on measurement comparisons and metrological traceability using appropriate certified reference materials. The concentration values or amount of substance contents are usually assigned to chemical analytical results. In contrast, the most relevant quantity is the activity of ions in clinical chemistry. Activity corresponds to the available biologically active part of these components in a mixture. Many measurement methods and instruments currently in use do not differentiate between the total substance concentration and its biologically active component. In physiological solutions, such as blood plasma, the chemical activity makes a clear difference between ion or substrate concentration. Ion selective electrodes (ISE) are widely used to directly measure the activity of ions. Measurement by means of ion-selective electrodes is a standard method in point of care testing units (POCT) for continuous monitoring for e.g. haemodialysis, cardiac surgery and in intensive care units. A metrological approach to ISE potentiometric measurements is proposed, to determine the activity with their uncertainty. A prerequisite is to develop an activity calibration scale for complex electrolyte solutions with known and traceable ion activities.

SCIENTISTS HAVE SPENT the better part of the past four centuries, since the early days of the Enlightenment, discovering the truth about how the natural world works. A critical part of this endeavor is determining the physical constants of the universe and establishing standards for measuring them. Exactly how this process shakes out is fascinating to observe, even if the details are sometimes painful to endure. Take the kilogram, for example. The kilogram (mass) is one of the seven base units of the International System of Units (SI). The others are the meter (length), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (light intensity). The kilogram is the last of the SI base units that is still defined by a physical artifact rather than by an unvarying physical property of nature. It’s currently equal to the mass of a golf-ball-sized cylinder of platinum-iridium alloy. This surprisingly small lump of metal, ...

Following-up the key comparison CCQM-K1c, EUROMET organized a regional key comparison involving ten laboratories. The objectives of this EUROMET key comparison were essentially the same as for the CCQM-K1c comparison: to compare the measurement capabilities of national metrological institutes (NMIs) in measuring amount of substance fractions of nitrogen monoxide in nitrogen. The nominal amount of substance fraction of the standards used for the comparison was 100 µmol/mol. The pilot laboratory in this key comparison also piloted the CCQM key comparison and has long-term experience in the behaviour of these mixtures and the technical challenges in preparing batches of very similar mixtures. Most participants used chemiluminescence as the measurement method; two participants used UV techniques and one ND-IR. The degrees of equivalence between this comparison and CCQM-K1c were calculated; four laboratories participated in both key comparisons, thus providing sufficient data for demonstrating the comparability. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the Mutual Recognition Arrangement (MRA).

It is shown from the analysis of metrological validation of all physical quantities measured in chemistry that only for ‘concentration’ and ‘amount of substance’ is there no admitted measurement compatibility system like that for other physical quantities. Based on the fundamental notions of metrology, an attempt is made to derive a general concept of traceability and reliability of the measurement of concentration. Special attention is paid to metrological uses of standard samples and reference materials. Specific features of the quantity ‘amount of substance’ and its unit, the mole, are discussed in terms of metrology.

Because of high labour costs, a prerequisite for economic running of an organic elemental analysis laboratory was the development of rapid methods for the most frequently determined elements, which in our case are N, C, H, O, halogens and S. The methods must be capable of automation to the fullest extent, and the analytical results available in the shortest possible time. The data must therefore be presented in digital form for processing by computer, which can (in a fully automated version) print out a complete analytical record. To avoid dependence on physical calibrations, the end-determination methods should yield physical values strictly proportional to the amount of substance. Titration or gas volume measurement seems to fulfil this condition most closely. The methods developed and used at BASF has been reported, along with some new techniques and modifications to apparatus. A crucial point is the possibility of automating the different methods of analysis, and the economics of different degrees of automation have been discussed.

This chapter presents some basic definitions of science, matter, and chemistry. It explains the subdivisions of chemistry. The SI system defines a single base unit to measure each of seven quantities such as length, mass, time, electric current, temperature, amount of substance, and luminous intensity. Other necessary units, such as that for volume, are derived from the base units. The chapter reviews the modern units of measurement and a problem-solving method, the factor-dimensional method. With the factor-dimensional method, a unit-conversion calculation, and the calculation needed to solve a problem, can be set up in a single expression. The chapter describes the role of chemistry in coping with the major problems facing mankind.

Notwithstanding the fact that much of modern physiology has concerned itself with the maintenance of constancy of the milieu interieur, a definite lag persisted in the study and understanding of those factors regulating the normal volume and distribution of body fluids. Starling, with his rare insight, had early called attention to the fact that such control must exist, 200 and experiments supporting this idea were subsequently reported, 1,8 but the implications of the results—far ahead of the conceptual thinking of the time—fell upon soil unprepared for germination. Historically, several factors contributed to the delayed growth of knowledge of fluid volume regulation. Measurements of body fluid constituents by the standard chemical methods are reported, in the language of chemists, as concentrations, and so accustomed have we become to this method of expression that students frequently find it difficult to associate a normal concentration with a highly abnormal amount of substance in