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.

     

Environmental biotechnology: a tandem of biocatalytic and engineering approaches

The review gives examples of integrated approaches based on a tandem of biocatalytic and engineering methods to problems in the biotechnological protection of three basic constituents of the environment, namely, soil, water, and atmosphere, from dangerous pollution. The current situation associated with oil pollution of soils and water surfaces in Russia is analyzed. The results of the field tests of the biopreparation Roder recently developed for bioremediation of these surfaces are presented. New solutions aiming at extending the area of application of high-rate anaerobic wastewater treatment at low temperatures (4—10 °C) are discussed. The efficiency of a novel anaerobic-aerobic hybrid reactor for mineralization of recalcitrant wastewater containing azo dyes was estimated. The last two lines relate to a traditional function of the environmental biotechnology (so-called end of pipe treatment). A biocatalytic technology for the removal of hydrogen sulfide and the recovery of elementary sulfur from contaminated gases was proposed. This highlights a new phase in the development of environmental biotechnology allowing waste recycling.     

Some features of electrochemically initiated copolymerization of acrylic acid and acrylamide

Some features of the electrocopolymerization of acrylic acid and acrylamide in aqueous ammonium persulfate have been studied. UV spectroscopic and polarographic data attest to the intermolecular interaction of acrylic acid with acrylamide with the formation of 31, 32, and 11 complexes; the former complex is the strongest. Electrochemical initiation of polymerization of monomers whose _1/2 differ by 0.3 V can result in a copoiymer. The composition of the cathode polymeric coating has been determined by IR-spectroscopy and elemental analysis data. The molar ratios of acrylic acid to acrylamide in this coating and in the complex of the monomers are identical. The role of these complexes as elementary units in copolymerization is noted.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 250–254, February, 1994.     

Complex formation between polyethylene oxide-containing nonionic surfactants and α- and β-cyclodextrins

The inclusion complexes based on polyethylene oxide (PEO)-containing nonionic surfactants and ()-cyclodextrins (CD) were synthesized. Their composition and crystal structure were studied. The inclusion complexes of the surfactants with -CD form a crystal structure similar to that of the -CD—PEO complex. The inclusion complexes of the nonionic surfactants with -CD form a structure similar to that of the -CD—PEO complex. The structural models of the crystalline complexes were proposed. The micelle-forming abilities of the surfactants in dilute solutions in the presence of CD were studied. The CD binding to a surfactant molecule in aqueous solutions begins from the PEO fragment. Possible reasons for the formation of inclusion complexes between noncomplementary surfactant and -CD molecules were discussed. The thermal stability was studied, and the possibility of thermal dissociation of the pseudo-complementary -CD—surfactant complexes was shown.     

A kinetic study of trace element leachability from abandoned-mine-polluted soil treated with SS-MSW compost and red mud. Comparison with results from sequential extraction

The effect of adding treated red mud, a by-product of alumina production, to soil polluted by an abandoned mine and characterised by high concentrations of heavy metals, relatively low reaction grade, and low organic carbon content, was investigated. Also studied was addition of both red mud and compost (produced from source-separated municipal solid waste)—the synergistic action of red mud and compost could be exploited to achieve both metal trapping and an increase in organic carbon content. Leaching batch tests were performed on four different systems: soil, soil and treated red mud, soil and compost, soil and compost plus treated red mud. Dilute sulfuric acid and EDTA solution (liquid/solid ratio 10:1) were used in the tests—sulfuric acid to mimic acid rain and EDTA in accordance with general methods for estimating plant-available metals. Sequential extraction was also applied to the same samples. The use of relatively non-specific extractant reagents in the leaching tests led to a kinetic approach (already proposed in literature), because measurements of trace elements extracted at equilibrium cannot be related to their speciation. Comparison of information obtainable by the kinetic approach to evaluation of data from leaching tests with results from sequential extraction enabled evaluation whether the kinetic fractionation method, a relatively rapid and simple procedure, furnishes adequate information about the mobility and bioavailability of trace elements. Especially interesting results were obtained for Mn, Zn, and Ni, present in large amounts in the soil studied—their leachability was significantly reduced by addition of red mud and compost, suggesting interesting perspectives in soil-remediation activity.     

TG and EGA investigations of the decomposition of magnesium ammonium phosphate hexahydrate by means of the Derivatograph under conventional and quasiisothermal — Quasi-isobaric conditions

An investigation was made of the thermal decomposition of MgNH₄PO₄ · 6H₂O under conventional and under quasi-isothermal—quasi-isobaric conditions. The experiments were carried out with a Derivatograph-suitable for simultaneous TG and EGA examinations. It was found that the thermal decomposition of MgNH₄PO₄·6H₂O consists of three, more or less overlapping partial processes. First 5 moles, then 1 mole of water of crystallization depart, and finally, strictly simultaneously and in an inseparable way, the departure of the ammonia and water of constitution takes place. The three processes can be separated best under quasi-isothermal and quasi-isobaric conditions.

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Zusammenfassung Die Autoren untersuchten die thermische Zersetzung von MgNH₄PO₄·6H₂O unter konventionellen und quasi isothermischen — quasi isobaren Bedingungen. Die Versuche wurden mit einem zur TG- und EGA-Analyse geeigneten Derivatograph-Typ durchgeführt. Die Autoren fanden, daß die thermische Zersetzung von MgNH₄PO₄·6H₂O aus drei mehr oder weniger überlappenden Teilvorgängen besteht. Zuerst werden 5, dann 1 Mol Kristallwasser entfernt, das Konstitutionswasser und Ammoniak werden streng simultan und von einander untrennbar entfernt. Die drei Vorgänge können am besten unter quasi isothermischen und quasi isobaren Bedingungen von einander getrennt werden.

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Résumé Les auteurs ont étudié la décomposition thermique de MgNH₄PO₄·6H₂O dans les conditions conventionelles ainsi que dans des conditions presque isothermes et presque isobares. On a effectué les expériences à l'aide d'un Derivatograph qui se prête aux études simultanées par TG et AGE. Dans les conditions conventionnelles, la décomposition thermique de MgNH₄PO₄·6H₂O s'effectue en trois processus élémentaires qui se recouvrent plus ou moins. Le départ de 5 puis d'une molécule d'eau de cristallisation est suivi de celui d'ammoniac et d'eau de constitution, celui-ci étant strictement simultané et indissociable. Ces trois processus peuvent être mieux séparés si l'on opère dans des conditions voisines du régime isotherme et isobare.

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MgNH₄PO₄·6₂ - - . , TG GA . , MgNH₄PO₄·6₂ . , , . - - .

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The authors wish to thank Prof. E. Pungor for valuable discussions and Mr. M. Arnold for his assistance in performing the experiments.     

Influence of nucleation mechanisms on the multiplicity of steady states in isothermal CMSMPR crystallizers

The influence of primary and secondary nucleation on steady-state behavior of CMSMPR crystallizers is analyzed. Secondary nucleation may lead to one, two, or three steady states over some region of parameters, while the appearance of primary nucleation tends to eliminate the steady-state multiplicity. In case of dominance of primary nucleation, the crystallizer always exhibits a unique steady state.

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CMSMPR. , , , . .

     

Analysis of the heat capacities of group IV chalcogenides using debye temperatures

The low temperature heat capacities of 13 group IV chalcogenides are examined. The heat capacity of crystals with largely isotropic structure (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) can be represented within ±3% by a three-dimensional Debye function ( ₃=205, 230, 175, 225, 150 and 130, respectively). The heat capacity of crystals with anisotropic structures (GeS, GeSe, SnS, GeS₂ and SnS₂) could only be represented by pairs of two-dimensional Debye functions for the longitudinal and transverse lattice vibrations (error ±0.5 to 3%; ₂ (l)=505, 345, 400, 705, 480 and 570, respectively, and ₂ (t)=200, 185, 160, 175, 100 and 265, respectively).Since the two-dimensional Debye function has not been tabulated in detail, we offer in the appendix a five place table of it. Raman and infrared data support this analysis.

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Zusammenfassung Die Wärmekapazität bei niedrigen Temperaturen wurde für 13 Chalcogenide der Gruppe IV untersucht. Die Wärmekapazität der Kristalle von hauptsächlich istotroper Struktur (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) kann innerhalb von ±3% durch eine. dreidimensionale Debye-Funktion dargestellt werden ( ₃=205, 230, 175, 225, 150 bzw. 130). Die Wärmekapazität von Kristallen anisotroper Struktur (GeS, GeSe, SnS, GeS₂, GeSe₂ und SnS₂) konnte für longitudinale und transversale Gittervibrationen nur durch Paare zweidimensionaler Debye-Funktionen dargestellt werden (Fehler: ±0,5 bis 3%; ₂ (l)=505, 345 400, 705, 480 bzw. 570 und ₂(t)=200, 185, 160, 175, 100 bzw. 265).Da die zweidimensionale Debye-Funktion nicht in allen Einzelheiten tabellarisiert worden ist, wird im Anhang eine fünfstellige Tafel dafür gegeben. Raman- und Infrarot-Angaben bestätigen diese Analyse.

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Résumé On a examiné les capacités calorifiques à basses températures de 13 chalcogénure du groupe IV. Les capacités calorifiques des cristaux de structures principalement isotrope (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) peuvent être représentées à ±3%, par une fonction Debye à trois dimensions ( ₃=205, 230, 175, 225, 150 et 130 respectivement). Les capacités calorifiques des cristaux à structures anisotropes (GeS, GeSe, SnS, GeS₂, GeSe₂ et SnS₂) ne peuvent être représentées que par des paires de fonctions Debye à deux dimensions, pour les vibrations du réseau longitudinales et transversales (erreur de ±0,5 à 3%; ₂(l)=505, 345, 400, 705, 480 et 570, et ₂,(t)=200,185, 160, 175, 100 et 265).Comme il n'existe pas de tableaux détaillés pour la fonction Debye à deux dimensions les auteurs donnent en appendice un tableau à cinq positions. Des données Raman et infrarouges sont fournies à l'appui de cette analyse.

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13 IV. (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) ±3% ( ₃=205, 230, 175, 225, 150 130, ). (GeS, GeSe, SnS, GeS₂, GeSe₂, SnS₂) ( ±0.5 3%; ₂ (.)=505, 345, 400, 705, 480 570 , ₂ (.)=200, 185, 160, 175, 100 265). , . .

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The authors would like to acknowledge the help of Professor H. H. Hollinger and Professor M. S. Krishnamoorty with the solution of the two-dimensional Debye function. The authors would also like to acknowledge the support of this work in part by the National Aeronautics and Space Administration and by the National Science Foundation, Polymer Programs, Contract No. DMR 78-15279.     

Cheometrics in the daily laboratory practice

Summary Developments in computing technology have drastically changed the way analyses are performed in the analytical research and routine laboratory. More complex calculations are possible on data measured by microcomputer controlled instruments. Moreover affordable hardware and software became available for the development and implementation of knowledge based systems, which are an important tool to tackle problems which can not be solved in an algorithmic way. As the extraction of relevant analytical information from large and complex data structures became more accessible, instrument development was further pushed in the direction of higher complexity of operation and data.Chemometrics and, recently, knowledge engineering, have produced tools to support the analyst at various stages during the analysis; method development, calibration, optimisation, signal processing and method validation.Apparently these tools are becoming the building blocks of intelligent analytical workstations arranged in the socalled intelligent laboratory.By a system analysis of the activities in an analytical laboratory, the functionalities of the intelligent laboratory are discussed. Furthermore, the current status of the intelligent laboratory is evaluated in terms of available systems, systems expected to become available in the near future and black spots are identified for which no tools are yet available, requiring more chemometrics input.This overview comprises aspects of method development, the validation of analytical results and the processing of these results into information. Examples are chosen from the intelligent chromatography and intelligent spectroscopy laboratory.     

A new differential thermal analysis method

A new differential thermal analysis method has been developed which allows fast and accurate determinations of phase equilibria in condensed systems between 400 and 1100°. In this method the temperature is increased stepwise, heat effects being determined by analysis of the transient thermoelectric effects after each step. Between steps the temperature is kept constant until equilibrium is attained. The method has been tested in measurements of displacive solid-state transformations and melting points.

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Zusammenfassung Eine neue Methode der Differentialthermoanalyse wurde entwickelt, welche rasche und genaue Bestimmungen von Phasengleichgewichten in kondensierten Systemen zwischen 400° und 1100° ermöglicht. Bei dieser Methode wird die Temperatur stufenweise erhöht und die Wärmeeffekte durch Analyse der thermoelektischen Übergangseffekte nach jeder Stufe bestimmt. Zwischen den Stufen wird die Temperatur bis zum Erreichen des Gleichgewichts konstant gehalten. Die Methode wurde bei Messungen von Verschiebungsumsetzungen in festem Zustand und von Schmelzpunkten erprobt.

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Résumé Une nouvelle méthode d'analyse thermique différentielle a été mise au point. Elle permet de déterminer de façon rapide et exacte les équilibres de phases dans des systèmes condensés, entre 400 et 1100°. Selon cette méthode, on augmente graduellement la température en déterminant les effets thermiques par analyse des effets thermoélectriques intermédiaires après chaque palier. A chaque palier, on maintient la température constante jusqu'à ce que l'équilibre soit atteint. On a contrôlé la méthode par l'étude de changements de phases displacifs dans l'état solide et par mesure de points de fusion.

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, 400° 1100°. , . . .

     

Influence of carbon dioxide on the position of oxygen adsorption equilibrium on silver

Due to interaction with carbon dioxide, when some adsorbed oxygen atoms on silver surfaces are converted into carbonate groups, the binding energy diminishes and the volatility of adsorbed oxygen rises.

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, , .

     

Hydrogenolysis of n-butane on Ni-Pd/SiO2 catalysts

Supported Ni-Pd/SiO₂ catalysts of different Ni and Pd composition were studied in n-butane hydrogenolysis. The reaction rate, selectivity towards methane, ethane and propane were determined. On the basis of these data the relationship between the size and composition of the active center and the possibility of surface segregation of one of the components is discussed.

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Ni-Pd/SiO₂ Ni Pd -. , . .

     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.

     

Marked differences between acetonitrile/water and methanol/water mobile phase systems on the thermodynamic behavior of benzodiazepines in reversed phase liquid chromatography

Summary Two different methods were used to determine the separation factor at different temperatures and the Gibbs-Helmholtz parameters ((H), (S)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of ln versus 1/T. We first studied each factor (fraction of water in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes in (H) and (S) in relation to a volume fraction of water in an ACN/water mixture were examined. In the ACN/water system, (H) was fairly constant in the acetonitrile region of 0.52 and appears to be a roughly linear function of for 0.52. In this system (S) is approximately a parabolic function of with an optimum at 0.52. The retention mechanism of ten benzodiazepines was found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44°C gave the most efficient separation conditions in the ACN/water mixture.     

Simplest model of self-oscillations in association reactions

The simplest scheme of association reactions is suggested, whose mathematical model permits the existence of self-oscillations.

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, .

     

A new approach to the adsorption kinetics of gas mixtures on heterogeneous surfaces

An attempt is made to develop a general theory for describing the adsorption kinetics of gaseous mixtures on heterogeneous surfaces. This can be made by generalization of the equations obtained for equilibrium adsorption of gas mixtures.

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. .

     

Characterization of citrus and kiwi flavors and their degradation processes by combination of GC/FTIR and GC/MS

Flavor samples are complex mixtures with components of sometimes very similar chemical behavior (e.g. isomeres). As an approach towards their characterization an integrated analytical method on the basis of capillary gas-chromatography (HRGC) was applied consisting of two molecular specific techniques for component-identification in unknown samples: GC-FTIRS (GC-Fourier transform infrared spectrometry) and GC-MS (GC-mass spectrometry).In addition GC-retention indices-from simultaneous GC on two columns (nonpolar/polar) —were stored in a database for routine retrieval and quantitative monitoring. To correlate this information with sensory perception sniffing chromatograms were generated with the human nose as a high performance detector.Because of the high information contents of GC-FTIR spectra in this field a small but specific vapor-phase-FTIR flavor library was accumulated, which dramatically improved the fast identification power of GC-FTIRS alone.     

Epoxidation of cyclohexene with tert-butyl hydroperoxide catalyzed by polymer anchored molybdenum complexes

Catalytic activity of molybdenum hexacarbonyl anchored on various polymers was investigated for the epoxidation of cyclohexene with tert-butyl hydroperoxide. The activity was increased by anchoring on the polymer. The catalyst on polystyrene showed much higher activity than Mo(CO)₆ used under homogeneous conditions.

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, , .— . . ]qt, Mo(CO)₆, .

     

Obtimization of separation conditions in reversed phase liquid chromatography using complex solvent mixtures

Summary Four different methods of calculation of retention in ternary mobile phases were compared and it was found that the simple calculation based only on two values of the capacity factors (one for each binary system that composes the ternary mobile phase) provides the accuracy of prediction that is, at least, comparable to the other methods of calculation that require a large number of preliminary experiments. The deviations from ideal behaviour in ternary solvent mixtures are discussed; some sources of errors can be avoided, at least partially, using binary systems of adequate compositions for preparation of ternary mobile phases. Several examples show the comparison of calculated and experimental selectivities in ternary solvent systems. A simple calculation can be used for rapid selection of an adequate ternary (or more complex) mobile phase, if it is necessary to achieve the separation of a given sample mixture.Presented at the 14th International Symposium on Chromatography London, September, 1982     

DFT study of the mechanism of alkane hydrogenolysis by transition metal hydrides. 1. Interaction of silica-supported zirconium hydrides with methane

Model reactions of silica-supported zirconium hydrides (Si—O—)₃ZrH and (Si—O—)₂ZrH₂ with methane, resulting in cleavage of a C—H bond in the methane molecule and the formation of (Si—O—)₃ZrCH₃ and (Si—O—)₂Zr(H)CH₃ as products were studied using the DFT approach with the PBE density functional. The processes proceed as bimolecular reactions without preliminary formation of agostic complexes. According to calculations, zirconium dihydrides (Si—O—)₂ZrH₂ are more reactive toward the methane C—H bonds than zirconium monohydrides (Si—O—)₃ZrH. The calculated activation energies of the reactions with participation of zirconium dihydrides (Si—O—)₂ZrH₂ are in better agreement with the known experimental data for the Yermakov—Basset catalytic system.