Problem solving by expert systems in analytical chemistry

Summary It is expected that artificial intelligence and more particularly, expert systems, will have a profound effect upon analytical chemistry. This paper provides an overview of this rapidly evolving field. General aspects of expert systems are dealt with first, such as knowledge representation, knowledge manipulation, dealing with uncertainty, and the application of software tools to facilitate the construction of expert systems. The accomplishments with respect to the application of expert systems to chemistry — particularly analytical chemistry — are discussed. Future directions of the research and applications are forecasted.

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Expert Systems zur Problemlösung in der analytischen Chemie

Zusammenfassung Es ist zu erwarten, daß künstliche Intelligenz und besonders expert systems einen großen Einfluß auf die analytische Chemie ausüben werden. In dieser Arbeit wird ein Überblick über dieses in schneller Entwicklung befindliche Gebiet gegeben. Zunächst werden die expert systems im allgemeinen behandelt (Darstellung und Handhabung von Wissen, Behandlung von Unsicherheiten, Anwendung von Software zur Konstruktion der expert systems). Anschließend werden Anwendungen in der Chemie — speziell der analytischen Chemie — diskutiert und zukünftige Entwicklungen aufgezeigt.

     

A model to set measurement quality objectives and to establish measurement uncertainty expectations in analytical chemistry laboratories using ASTM proficiency test data

A model is presented that correlates historical proficiency test data as the log of interlaboratory standard deviations versus the log of analyte concentrations, independent of analyte (measurand) or matrix. Analytical chemistry laboratories can use this model to set their internal measurement quality objectives and to apply the uncertainty budget process to assign the maximum allowable variation in each major step in their bias-free measurement systems. Laboratories that are compliant with this model are able to pass future proficiency tests and demonstrate competence to laboratory clients and ISO 17025 accreditation bodies. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/ 10.1007/s007690100398-y. Received: 31 March 2001 Accepted: 11 September 2001     

Monitoring analytical measurements in presence of two component measurement error

Control charts are increasingly adopted by laboratories for effective monitoring of analytical processes. Analytical methods are mostly subject to two types of measurement errors, i—additive and ii—multiplicative, or proportional, error. These errors have been combined in a single model, namely the two component error model (TCME) proposed by [1]. In this study we present a comparison among the performance of three widely used location control charts, i.e. Shewhart, CUSUM and EWMA charts in presence of TCME model. This study will help quality practitioners to choose an efficient chart for the monitoring of analytical measurements.     

A simplified approach to the estimation of analytical measurement uncertainty

The present study summarizes the measurement uncertainty estimations carried out in Nestlé Research Center since 2002. These estimations cover a wide range of analyses of commercial and regulatory interests. In a first part, this study shows that method validation data (repeatability, trueness and intermediate reproducibility) can be used to provide a good estimation of measurement uncertainty.In a second part, measurement uncertainty is compared to collaborative trials data. These data can be used for measurement uncertainty estimation as far as the in-house validation performances are comparable to the method validation performances obtained in the collaborative trial.Based on these two main observations, the aim of this study is to easily estimate the measurement uncertainty using validation data.     

A decision theory approach to fitness for purpose in analytical measurement

The choice of an analytical procedure and the determination of an appropriate sampling strategy are here treated as a decision theory problem in which sampling and analytical costs are balanced against possible end-user losses due to measurement error. Measurement error is taken here to include both sampling and analytical variances, but systematic errors are not considered. The theory is developed in detail for the case exemplified by a simple accept or reject decision following an analytical measurement on a batch of material, and useful approximate formulae are given for this case. Two worked examples are given, one involving a batch production process and the other a land reclamation site.     

Causes of error in analytical chemistry: results of a web-based survey of proficiency testing participants

Results of a voluntary-response survey of respondent-identified causes of unacceptable results in nine proficiency testing schemes are reported. The PT schemes were predominantly environment and food analysis schemes.?111 respondents reported 230 identified causes of error. Sample preparation (16?% of causes reported), Equipment failures (13?%), ??Human error?? (13?%) and Calibration (10?%) were the top four general causes of poor analytical results. Among sample preparation errors, sample extraction or recovery problems were the most important causes reported. Most calibration errors were related to errors in calculation and dilution and not in availability or quality of calibration materials. No failures were attributed to failures in commercial software; software-related problems were largely associated with user input errors. Corrective actions were generally specific to the particular problem identified. Review of all reported causes indicated that about 44?% could be attributed to simple operator errors.     

A scalable approach to diaminopyrazoles using flow chemistry

This Letter reports on how the combination of microwave and continuous flow chemistry facilitated the convenient preparation of aminopyrazoles from commercial aryl halides. The method was applied to a variety of substrates with good to excellent yields and further extended toward the complete flow synthesis of 5,7-dimethyl-3-phenylpyrazolo[1,5-a]pyrimidin-2-amine.     

New approach in teaching analytical chemistry at the Technical Universities of Czechoslovakia

Summary The 5 year study programme of the Technical Universities in Czechoslovakia comprises two courses in Analytical Chemistry. In the second year of study there are 3 h lectures of AC and 9 h of laboratory work per week. In the third year instrumental analysis is taught — 3 h lectures and 7 h practical work per week. For the last two years a subject rearrangement has been going on for the purpose of intensifying the studies.Presented at Euroanalysis III conference, Dublin, August 20–25, 1978     

An approach to detection capabilities estimation of analytical procedures based on measurement uncertainty

Detection capabilities are important performance characteristics of analytical procedures. There are several conceptual approaches on the subject, but in most of them a level of ambiguity is presented. It is not clear which conditions of measurements should be used, and there is a relative lack of definition concerning blanks. Moreover, there are no systematic experimental studies concerning the influence of uncertainty associated with bias evaluation. A new approach based on measurement uncertainty is presented for estimating quantities that characterize capabilities of detection. It can be applied to different conditions of measurement and it is not necessary to perform an additional experiment with blanks. Starting from a modelling process of the combined uncertainty of concentration, it is possible to include in the estimated quantities the effects due to random errors and the uncertainty associated to evaluation of bias. The detection capabilities are then compared with the results obtained using some other relevant approaches. Slightly higher values were obtained with the measurement uncertainty approach due to inclusion of uncertainty associated with bias.     

Selectivity and specificity in analytical chemistry. General considerations and attempt of a definition and quantification

Selectivity and specificity are performance characteristics of analytical methods which are frequently used in analytical literature. In general, the terms are applied verbally and a quantification of selectivity and specificity is given rarely. Excepted are methods like chromatography and ISE sensoring which use individual quantities such as selectivity coefficients, indices and other parameters to characterize analytical procedures and systems. Here a proposal is given to characterize selectivity and specificity quantitatively by relative values in a range of 0 to 1 expressing so a certain degree of selectivity and specificity. By examples it will be shown that the derived quantities characterize analytical methods and problems in a plausible way.     

Trends in using resilient polyurethane foams as sorbents in analytical chemistry

Summary Considerable progress has been made in recent years in the application of polyurethane foams to separation and preconcentration problems in analytical chemistry. The results published in the years 1979 to 1982 have been collected and are presented in tabulated form.

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Trends in der Anwendung von elastischem Polyurethanschaum als Sorbens in der analytischen Chemie

Zusammenfassung In den letzten Jahren haben die Anwendungsmöglichkeiten von Polyurethanschaum zur Trennung und Anreicherung in der analytischen Chemie stark zugenommen. Eine tabellarische Übersicht über die in den Jahren 1979 bis 1982 veröffentlichten Untersuchungsergebnisse wird gegeben.

     

Selectivity and specificity in analytical chemistry. General considerations and attempt of a definition and quantification

Selectivity and specificity are performance characteristics of analytical methods which are frequently used in analytical literature. In general, the terms are applied verbally and a quantification of selectivity and specificity is given rarely. Excepted are methods like chromatography and ISE sensoring which use individual quantities such as selectivity coefficients, indices and other parameters to characterize analytical procedures and systems. Here a proposal is given to characterize selectivity and specificity quantitatively by relative values in a range of 0 to 1 expressing so a certain degree of selectivity and specificity. By examples it will be shown that the derived quantities characterize analytical methods and problems in a plausible way.     

Uncertainty due to the quantification step in analytical methods

The quantification step is an important source of uncertainty in analytical methods, but it is frequently misunderstood and disregarded. In this paper, it is shown how this uncertainty is closely related to the linear response range of a method, and to the Pearson correlation coefficient of the calibration line. So, if there is a need for a pre-fixed quantification uncertainty, the linear response range will be affected. Some practical cases are given showing the quantification uncertainty significance. The theoretical equation giving the value of the quantification uncertainty is deduced from which new conclusions can be taken out. Because of that, the quantification uncertainty can easily be calculated and the parameters that really affect its value are shown along the paper. Some final considerations about detection limits and two-point calibration lines are also given. The paper can also be considered a reflection on uncertainty owed to calibration and on their consequences on the analytical methodology.     

Yury A. Zolotov: Russian contributions to analytical chemistry

Analytical and Bioanalytical Chemistry -     

Spectre: an approach to an expert system in chemometrics

A versatile, dialogue-oriented program package for chemometric data analysis is described. In addition to the data processing modules proper, the system includes modules for selecting appropriate methods for data analysis and for the design of experiments.