ISSN:0886-9383    

DOI:10.1002/cem.1180030502

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe calibration curve is based on a deterministic relationship betweenY, the observed response,f, the instrumental function, andx, the concentration of the analyte. When the instrumental function is linear the model is\documentclass{article}\pagestyle{empty}\begin{document}$$ Y = a_0 + a_1 x + \varepsilon $$\end{document}witha0the blank anda1the sensitivity.In fact calibratio is a two‐step procedure consisting of the ‘calibration’, itself (computation of the curve coefficients) and the ‘counter‐calibration’, when the curve is used to predict the concentration of an unknown sample. Least‐squares regression (LSR) can be simply used in order to solve the first step. However, an error may occur when the classical results of LSR are used to compute the detection limit. The detection limit can be defined as the smallest concentration that can be detected with certainty from the blank with a risk of error α and a probability of being right 1 − β. If we define the critical level (CL) as\documentclass{article}\pagestyle{empty}\begin{document}$$ y({\rm CL)} = a_0 + t_{(1 - \alpha)} {\rm}\sqrt {{\rm var(}a_0)} $$\end{document}the detection limit (DL) is then\documentclass{article}\pagestyle{empty}\begin{document}$$ y({\rm DL)} = y({\rm CL}) + t_{(1 - \beta)} {\rm}\sqrt {{\rm var(}a_0)} $$\end{document}Since the units used to expressy(DL) are the same as the units ofy, it must be divided bya1in order to be expressed as a concentration. This creates a contradiction however, becausea1is a random variable. Therefore the detection limit cannot be computed according to its previous definition.If we use tolerance interval theory, it is possible to define a new criterion called the minimum allowable concentration which does not have such a drawback. This new concept is based on an improved approach to co

ISSN:0886-9383    

DOI:10.1002/cem.1180030503

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractOrthogonal rotations, e.g. the varimax rotation, are common practice in factor anlaysis. However, the term varimax rotation does not refer to a unique procedure, since several different types of rotation are possible. In this paper six different types of rotation are examined (raw varimax of loadings, normal varimax of loadings, raw and normal varimax of scores, eigenvalue‐weighted varimax of loadings and Arthur varimax) from both a theoretical and practical point of view. It can be concluded that an adequate application of these methods can often simplify the interpretation of the calculated factor

ISSN:0886-9383    

DOI:10.1002/cem.1180030504

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe automatic procedures for optimizing the composition of a binary mobile phase in reversed phase liquid chromatography have been intensively studied for the past ten years. The performance of these procedures, based on either the black box approach or on other methods such as the experimental design, are very often limited by the large number of time‐consuming experimental runs that are necessary for the determination of the analysis conditions to be optimized.The proposed method reduces this number of experiments: two experiments, run under linear variation of the composition of the binary mobile phase (the linear gradient elution mode), make it possible to determine the mobile phase composition corresponding to the maximum resolution between peaks, the final analysis being assumed to be carried out under isocratic conditions.The method requires two steps: the determination of the retention characteristics for each solute, which depend upon the composition of the mobile phase; the selection of the optimum composition of the isocratic mobile phase, by using a criterion such as the maximum resolution normalized by the square root of the plate number, for the least separated pair of adjacent peaks.The interest, performance and limits of use of such an optimization procedure are discussed by means of the chromatographic analysis of different complex mixture

ISSN:0886-9383    

DOI:10.1002/cem.1180030505

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractIn order to get a better knowledge of the air pollution levels of the urban air of Barcelona, twelve samples from three stations of the air‐monitoring control network were analysed. Each control station is representative of a different environmental situation. Thus the station at Plaça Molina responds to a simple domestic and urban traffic situation; the station at Poble Nou to the influence of medium and small industries, mainly metallurgical; and the station at Montcada to a zone in which there exist important industries, a cement factory, two highways and railroads.The total content of unsedimentable particles, three inorganic anions (chlorides, sulphates and nitrates) and six heavy metals (Fe, Pb, Cu, Mn, Cr and Cd) were determined on all the samples obtained during the same period of time. The use of an analytical scheme of sequential extraction has also permitted the subdivision of the total content of each metal into the following four fractions: (1) soluble or exchangeable; (2) associated with carbonates and/or with iron and manganese oxides; (3) bound to organic matter; and (4) residual.The use of principal component analysis applied to the data as a whole showed the associations and correlations between the various parameters as well as between the different above mentioned fractions. The predominant presence of Cd in the ‘soluble or exchangeable’ fraction is confirmed, while the other metals are mainly associated with the ‘carbonates and/or Fe and Mn oxides’ and ‘bound to organic matter’ fractions.Hierarchical cluster analysis applied to the twelve samples showed clearly the presence of three different classes closely related to the origin (station) of the samples. Thus it becomes feasible to propose for each station a possible profile of the content in terms of the different paramet

ISSN:0886-9383    

DOI:10.1002/cem.1180030506

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractApplication of principal component analysis to Cu(II)–ethanolamine complex formation data is shown. Determination of the number of complex species is obtained from the rank of the matrix of spectral data using either Gauss elimination or factorial analysis. Relevant information concerning species distribution versus pH is obtained from the plot of the signficant factors upsurging from the evolution of spectral titration dat

ISSN:0886-9383    

DOI:10.1002/cem.1180030507

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThirteen different components of six samples belonging to staind medieval glass windows and twelve similar samples found in the archives of Girona Cathedral (Catalonia, Spain) during restoration work were determined by x‐ray fluorescence analysis. The use of display and cluster analysis methods, principal components analysis, non‐linear mapping, minimal spanning tree and agglomerative hierarchical clustering applied to these results, together with those of nine samples from the same cathedral previously studied, showed the presence of a quite compact cluster formed by the soda‐type samples, indicating a probably similar origin and confirming the peculiarities of this Mediterranean area. The potash‐type glasses were highly scattered with little similarity among them, suggesting a likely different source of these samples. The twelve glasses of strictly unknown origin were found to have a high degree of resemblance to the samples of known context, thus excluding the possibility of them being samples made in a very different age or site. Three of them were classified into the same group as the well‐defined soda‐type glasses by the pattern recognition m

ISSN:0886-9383    

DOI:10.1002/cem.1180030508

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSEXIA is an expert system that uses a new methodological approach to identify foods, particularly olive oils according to varieties, olive zones and denominations of origin. The methodological approach provides identification tools, associating a confidence degree or a belief interval to the final hypotheses. The certainty factor and the Dempster–Shaffer theory, with some modifications, have been implemented in SEXIA. The computer can work with 50 chemical parameters whose data have previously been acquired by the food analyst via a dialogue in the Spanish language. The system has been verified with 144 olive oil samples. In this paper some results obtained for distinguishing the Arbequina variety from other varieties using SEXIA and the BMDP stepwise discriminant analysis program are presented. Finally, promising directions for future research are suggeste

ISSN:0886-9383    

DOI:10.1002/cem.1180030509

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractIn the present paper, the possible analytical applications of two toplogical models, the DARC model and the group contribution model, are discussed. Both models are applied to obtain calibration laws, which relate UV and IR characteristics with the chemical structure of ethylene oxide condensates.The group contribution model is also applied to determine the contribution of each part of the different compounds involved in a chemical interaction process, having established the sensitization parameters of benzodiazepines and anionic surfactants from the micellar enhancement fluorescence.

ISSN:0886-9383    

DOI:10.1002/cem.1180030510

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe program SOL1, written in Turbo‐PASCAL for use on a personal computers (IBM‐PC or compatible), has been developed for calculating the equilibrium concentrations of the species in the multicomponent ligand–metal mixtures of up to 21 components and 150 species. The main features are the easy data input system, the possibility of three different tasks (calculating the composition of a single solution, simulating titration curves and calculating the species distribution as a function of pH) and procedures for drawing the calculated curves on Roland DXY plotters. The program has been tested by a study of six different complex sy

ISSN:0886-9383    

DOI:10.1002/cem.1180030511

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY