Volume 78, Issue 3

The progress of computational chemistry in the treatment of liquid systems is outlined, and the combination of the statistical methods (Monte Carlo, MC, and molecular dynamics, MD) with quantum mechanics as the main foundation of this progress is emphasized. The difficulties of experimental studies of liquid systems without having obtained sophisticated theoretical models describing the structural entities and the dynamical behavior of these liquids demonstrate that chemistry research is in a transition phase, where theory and high-performance computing have not only become a valuable supplement, but an essential and almost indispensable component to secure a correct interpretation of measured data.

ThermoML is an Extensible Markup Language (XML)-based new IUPAC standard for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. The basic principles, scope, and description of all structural elements of ThermoML are discussed. ThermoML covers essentially all thermodynamic and transport property data (more than 120 properties) for pure compounds, multicomponent mixtures, and chemical reactions (including change-of-state and equilibrium reactions). Representations of all quantities related to the expression of uncertainty in ThermoML conform to the Guide to the Expression of Uncertainty in Measurement (GUM). The ThermoMLEquation schema for representation of fitted equations with ThermoML is also described and provided as supporting information together with specific formulations for several equations commonly used in the representation of thermodynamic and thermophysical properties. The role of ThermoML in global data communication processes is discussed. The text of a variety of data files (use cases) illustrating the ThermoML format for pure compounds, mixtures, and chemical reactions, as well as the complete ThermoML schema text, are provided as supporting information.

In this document, we define a data exchange format initially formulated from discussions of an International Union of Pure and Applied Chemistry (IUPAC) limited-term task group at the 35th Royal Society of Chemistry-ESR conference in Aberdeen 2002. The definition of this format is based on the IUPAC J oint C ommittee on A tomic and M olecular P hysical D ata E x change (JCAMPDX) protocols, which were developed for the exchange of infrared spectra and extended to chemical structures, nuclear magnetic resonance data, mass spectra, and ion mobility spectra. This standard of the JCAMP-DX was further extended to cover year 2000 compatible date strings and good laboratory practice, and the next release will cover the information needed for storing n-dimensional data sets. The aim of this paper is to adapt JCAMP-DX to the special requirements for electron magnetic resonance (EMR).

This paper gives an introduction to multivariate calibration from a chemometrics perspective and reviews the various proposals to generalize the well-established univariate methodology to the multivariate domain. Univariate calibration leads to relatively simple models with a sound statistical underpinning. The associated uncertainty estimation and figures of merit are thoroughly covered in several official documents. However, univariate model predictions for unknown samples are only reliable if the signal is sufficiently selective for the analyte of interest. By contrast, multivariate calibration methods may produce valid predictions also from highly unselective data. A case in point is quantification from near-infrared (NIR) spectra. With the ever-increasing sophistication of analytical instruments inevitably comes a suite of multivariate calibration methods, each with its own underlying assumptions and statistical properties. As a result, uncertainty estimation and figures of merit for multivariate calibration methods has become a subject of active research, especially in the field of chemometrics.

Factors affecting the NMR titration procedures for the determination of p K a values in strongly basic and strongly acidic aqueous solutions (2 > pH > 0 and 14 > pH > 12) are analyzed. Guidelines for experimental procedure and publication protocols are formulated. These include: calculation of the equilibrium H + concentration in a sample; avoidance of measurement with glass electrode in highly acidic (basic) solutions; exclusion of D 2 O as a solvent; use of an individual sample isolated from air for each pH value; use of external reference and lock compounds; use of a medium of constant ionic strength with clear indication of the supporting electrolyte and of the way the contribution of any ligand to the ionic strength of the medium is accounted for; use of the NMR technique in a way that eliminates sample heating to facilitate better sample temperature control (e.g., 1 H-coupled NMR for nuclei other than protons, GD-mode, CPD-mode, etc.); use of Me 4 NCl/Me 4 NOH or KCl/KOH as a supporting electrolyte in basic solution rather than sodium salts in order to eliminate errors arising from NaOH association; verification of the independence of the NMR chemical shift from background electrolyte composition and concentration; use of extrapolation procedures.

There is no formal terminology used to describe the scope and use of microtechnology in the clinical laboratory. For many laboratory scientists, the word "microchip" is synonymous with high-density microarrays used primarily for investigating gene expression. The document proposes a system of "categories" and "descriptors" that facilitates the classification of a device in a way that communicates details of its function and analytical role, and describes the analytical principle involved and the methods and materials used for its manufacture. Adoption of this system would enable scientists to employ four descriptors that clearly delineate the function, analytical role, and chemical or physical principle involved in the device. Examples of existing commercial devices are given to illustrate the utility of the system.