Systematic errors in analytical measurement results

Definitions of the concepts of bias and recovery are discussed and approaches to dealing with them described. The Guide To Uncertainty in Measurement (GUM) recommends correction for all significant systematic effects, but it is also possible to expand measurement uncertainty to take account of uncorrected bias. Run, laboratory and method bias can be defined as components of the bias of a particular measurement result, and can be useful as concepts used in method validation. Estimation of run bias allows a simplification of the estimation of measurement uncertainty. Multivariate calibration brings its own biases that must be quantified and minimised.     

Criterion for quantifying the reliability of analytical results in method development and evaluation

An important characteristic in judging analytical results for their suitability for a particular use is the reliability of the results. A procedure is developed for quantifying the reliability in a single measure, the maximum total error. This measure comprises both the bias and the precision of the results, and takes account of the statistical uncertainty of these estimates. The applicability of the procedure in method development and method evaluation is illustrated by means of a practical example, the flow-injection determination of orthophosphate.     

Sensors in analytical chemistry

Chemical sensorics is an independent domain of modern analytical chemistry. In Germany and Japan, multivolume encyclopedias dedicated to sensors were published. The publication of the nine-volume encyclopedia [1] in Germany was immediately followed by the appearance of the annual publication [2] incorporating additional data available from US. The preparations to publication of the next encyclopedia of sensors are under way now. It san be said with a good reason that chemical sensorics is a well-established sphere which is still under active development. This is specifically a testing ground for novel ideas and novel materials. This issue of Rossiiskii Khimicheskii Zhurnal (Zhurnal Rossiiskogo Khimicheskogo O-va im. D. I. Mendeleeva) is dedicated to chemical and biochemical sensors. It makes readers acquainted with the current state of the art in this sphere and covers various types of sensors. Here, we attempt to outline the general situation in this domain of analytical chemistry.     

Nucleation in analytical chemistry

Precipitation involves two processes, nucleation and subsequent crystal growth. The nucleation process is of extreme importance in determining the number and size of the final crystalline particles. The significance of experimental studies of nucleation is discussed and the need for further research indicated.     

Chemiluminescence in analytical chemistry

Analytical applications based on chemiluminescence are reviewed. Analyses in the gas phase for atmospheric pollutants such as sulphur compounds, ozone and oxides of nitrogen are described. The commonest chemiluminescent systems used in the liquid phase are then discussed. Their applications as indicators in different types of titration are outlined. Determinations of organic and inorganic substances are classified according to their action as oxidant, catalyst or inhibitor. Special applications are described in fields such as forensic science, microbiology, polymer technology, radiation chemistry and flow mechanics.     

Quality in analytical chemistry

Summary In order to enhance the quality of analyticochemical statements it is common practice, to optimize the analytical method. But furthermore it is also necessary to fit the design of the study including sampling procedures and calibrations to the aims of the investigation and its consequences as close as possible. The presentation of results should mention all premises which were not empirically tested. To prevent misinterpretation of the results, their respective field of application should be specified. As regards the characterization of methods, it must be explained whether it is to be valid for a specific analysis series, for a measuring system or for the method as such. Thus, the quality in analytical chemistry is measurable in terms of the scientific nature of the statements; that is in terms of their degree of objective verifiability and in terms of their deduction by recognized methods of all disciplines involved, including statistics.     

Markers in analytical chemistry

The growing use of markers in analytical literature in the 10 years, 1991-2000, is presented and discussed because of their relevance in modern analytical chemistry. The complementary and contradictory aspects of markers and others related words, such as tracer, indicator, index, labelling compound, etc., are clarified. To offer a general overview, several classifications of markers are outlined. The main distinction between markers is their internal or external fitness for purpose. Selected examples are assessed on this basis.     

Ultrasound in analytical chemistry

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection. A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the main area of application. In sample preparation ultrasound is used to assist solid-sample treatment (e.g. digestion, leaching, slurry formation) and liquid-sample preparation (e.g. liquid–liquid extraction, emulsification, homogenization) or to promote heterogeneous sample treatment (e.g. filtration, aggregation, dissolution of solids, crystallization, precipitation, defoaming, degassing). Detection techniques based on use of ultrasonic radiation, the principles on which they are based, responses, and the quantities measured are also discussed.     

Traceability and analytical chemistry

 The basic concepts of traceability as they are defined by the Comité Consultatif pour la Cluantité de Matière are contrasted with the practical exploitation in chemical analysis. The applicability of traceability concepts are tested for their practical applicability on four different analytical methodologies, neutron activation analysis, plasma mass spectrometry, beam microscopical analysis and speciation analysis of organometallic compounds. Received: 31 March 1998 · Accepted: 6 June 1998     

Kurnakov and analytical chemistry

The paper appreciates the role of Academician N.S. Kurnakov in holding the All-Union Conference on Analytical Chemistry (1939) and creating the Commission on Analytical Chemistry at the Academy of Sciences of the USSR. The scientific works of Kurnakov relating to chemical analysis are indicated; brief review is given to studies on analytical chemistry that were carried out in the collectives headed by Kurnakov are.