Strategy of education in modern Analytical Chemistry and model curriculum

Summary An analysis of the present situation of Analytical Chemistry is performed, taking into consideration the difference to be observed between the large and further increasing importance of Analytical Chemistry in industrial research, development and quality control and the poor reputation of the subject at many universities. The main reason for the latter can be located in the existence of outdated curricula for Analytical Chemistry. Many chairs or departments of Analytical Chemistry leave the education in modern physical methods for separation and identification as well as Computer Based Analytical Chemistry (COBAC) and its applications to life-, environmental- and material sciences to other departments and restrict themselves to classical subjects. According to a survey of the Working Party on Analytical Chemistry of the Federation of European Chemical Societes (Chairman: Prof. Dr. E. Pungor) this holds true especially for universities without an own chair or department of Analytical Chemistry. Modern Analytical Chemistry, however, is definitively no longer an appendix of any other subject but the interdisciplinary science of the generation of information about the composition and the structure of matter. Furthermore Analytical Chemistry is the key to solve problems related to material systems. It is the — certainly difficult but fascinating — task of the professor of Analytical Chemistry to present together with his team the complex modern curricula (chemical analysis, biochemical analysis, chemometrics, analytical strategies, material analysis, clinical analysis, environmental analysis etc.) according to the principle of the reduction to the scientific basis.Students should be able to read and understand the present literature but must be able to deal with future developments as well. Such a presentation of the basic principles of the methods of Analytical Chemistry is superior to any phenomenological way. The idea of an intellectual School of Analytical Chemistry with a coordinated distribution of duties has turned out to be very successful in the realization of this ambitious teaching concept. Based on these and further thoughts an ideal model curriculum for Analytical Chemistry at Technical Universities is presented and compared with actual situations.

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Strategie der Lehre und Modellehrplan für das Studium der modernen analytischen Chemie

Zusammenfassung Ausgehend vom derzeit immer noch zu beobachtenden Gegensatz zwischen der großen und weiter steigenden Bedeutung der Analytischen Chemie in industrieller Forschung, Entwicklung und Qualitätskontrolle und der geringen Reputation dieses Faches an vielen Universitäten wird eine Analyse der Ursachen dieser Situation und der möglichen Entwicklung vorgenommen. Als Hauptursache wurde gefunden, daß die meisten Universitätslehrpläne für Analytische Chemie veraltet sind. Sie überlassen die Erziehung in den modernen physikalischen Trenn- und Bestimmungsverfahren und der COBAC (Computer Based Analytical Chemistry) sowie deren Anwendung auf Lebensmittel-, Umwelt-, Werkstoffkontrolle usw. anderen Abteilungen und beschränken sich auf die Vermittlung überwiegend klassischer Lehrinhalte. Nach einer 1983 durchgeführten Studie der Working Party on Analytical Chemistry der Federation of European Chemical Societies (Chairman: Prof. Dr. E. Pungor) trifft dies besonders für Universitäten zu, die keinen eigenen Lehrstuhl oder Bereich für Analytische Chemie aufweisen. Moderne Analytische Chemie ist jedoch endgültig kein Anhängsel irgendeines anderen Faches mehr, sondern die fachübergreifende Wissenschaft von der Erzeugung von Information über die Zusammensetzung und Struktur von Materie. Darüber hinaus ist sie der Schlüssel zur Problemlösung in materiellen Systemen. Es ist die — sicher schwierige aber reizvolle — Aufgabe des Professors für Analytische Chemie, gemeinsam mit seinem Team die modernen komplexen Lehrinhalte (Chemische Analyse, Physikalische Analyse, Biochemische Analyse, Chemometrie, Analysenstrategie, Werkstoffanalyse, klinische Analyse, Umweltanalytik usw.) nach dem Prinzip der Reduktion auf ihre wissenschaftlichen Grundlagen zu präsentieren, so daß die Studenten die derzeitige Literatur lesen können, aber auch für zukünftige Entwicklungen offen sind. Eine solche die Zusammenhänge betonende Präsentation der Grundlagen chemischer und physikalischer Methoden der Analytischen Chemie ist einer phänomenologischen Darstellung weit überlegen. Zur Realisierung dieses ehrgeizigen Lehrkonzeptes zur Erziehung eines kritikfähigen Analytischen Chemikers erweist sich die Form der geistigen Schule der Analytischen Chemie mit deren koordinierter Aufgabenteilung als sehr erfolgreich. Auf der Basis dieser und weiterer Überlegungen wird ein idealer Modellehrplan für Analytische Chemie an Technischen Universitäten präsentiert und mit gegenwärtigen Gegebenheiten verglichen.

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Because of the fact that this paper — heavily discussed at the symposium New Trends in Chemistry — The Role of Analytical Chemistry in National Development, Cairo, January 3–7, 1984, has got a tremendous interest we feel it should be presented also to the readers of this journal in order to further stimulate the discussion     

Determination of citric acid by means of competitive complex formation in a flow injection system

A photometric method for the determination of citrate and other organic acids based on their ability to complex Fe³⁺-ions is presented. The red colored complex of [Fe(SCN)₂]⁺, used as reagent, is destroyed upon contact with the sample because the organic acid complexes the Fe³⁺-ion. The decrease in absorption is monitored at 460 nm. The reaction is carried out in a simple flow injection system either in single or preferably double channel configuration.The influence of pH was investigated. Best results were obtained by adjusting the carrier stream to pH 2.0–2.5 with a KCl/HCl-buffer. With an increasing concentration of reagent the linear range is shifted to higher citrate concentrations. The slope of the calibration graph and the linear range are influenced by the sample volume. Other variations of parameters include flow rate, reactor volume and diameter of tubing. Generally speaking, optimum conditions for the flow system are not specified because they vary with the application.The typical conditions for a calibration graph from 1 to 8 mmol/l citrate were a reagent concentration of 2.6 mmol/l [Fe(SCN)₂]⁺, a flow rate of 2.4 ml/ min, a reactor length of 50 cm with tubing of 0.97 mm inner diameter and a sample volume of 100 l. At these system settings the coefficients of variation were 2.5% and 1.6% for eight replicate measurements of samples containing 4 mmol/l and 8 mmol/l citrate, respectively. Up to 180 samples can be analyzed per hour.Naturally the method is disturbed by all other ions that form complexes or precipitates with Fe³⁺-ions. Therefore its application is limited to samples with a known matrix, which was given in the analysis of citrate in lemon flavored soft drinks, where the citric acid usually accounts for 95 to 99% of the total acidity and other interfering ions are absent.     

Determination of α-amylase activity using Fourier transform infrared spectroscopy

A new method for the determination of -amylase activity in aqueous solutions and human serum with FTIR-spectroscopy is proposed. The chemical reaction catalyzed by the enzyme under study can be followed directly when applying FTIR-spectroscopic detection also in the case, where no colored or electrochemical active species are generated or consumed during the course of the reaction of -amylase with simple starch. Therefore the determination of the -amylase activity could successfully be performed by recording two FTIR-spectra, one immediately after mixing the sample and a substrate (starch-) solution and the other after a 20 min reaction time. From these two FTIR-spectra a difference spectrum was calculated hereby eliminating an unspecific absorption of the matrix. The intensities of the resulting difference spectra corresponded to the extent of the reaction which took place during the investigated time interval and hence could be related to the activity of the enzyme in the sample. The developed method is linear from 80 to 1400 U/l (r.s.d.=5% for 700 U/l) in aqueous solutions and was also successfully applied to the determination of -amylase activity in human serum where a linear working range from 100 to 800 U/l (r.s.d.=11% for 150 U/l) was achieved.     

IR-spectroscopic investigations on solute-solvent interactions Part 1: Solvation of triethylphosphine oxide in aprotic and CH-acidic solvents

A systematic study has been carried out on the solvent and concentration dependence of the P=O stretching vibrationv(PO) of the model compoundEt ₃PO in various aprotic and several CH-acidic solvents. Evidence has been found for the existence of dipole-dipole complexes in concentrated solutions ofEt ₃PO in solvents of low acceptor numbers. In dilute solutions, however, the P=O stretching band generally occurs as a single symmetrical peak which shows that only one kind of solvate species is present in solution. In CH-acidic solventsEt ₃PO is present in the form of hydrogen bonded complexes. Informations about the structure of these complexes have been obtained by means of spectrophotometric titrations. It has been shown that the wavenumbersv°(PO) obtained by extrapolation ofv(PO) values to zero concentration are linearly related to the acceptor numbers of the solvents, previously derived from³¹P-chemical shift measurements. The existence of this linear relationships proves that both parameters are linearly related to the strength of the intermolecular interactions and are virtually free from unspecific contributions such as magnetic anisotropy or vibrational coupling effects. The results of the present study show that the P=O stretching vibration ofEt ₃PO represents an ideal probe for the investigation of solvent effects and solvation mechanisms.

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Infrarotspektroskopische Untersuchungen über Substrat-Lösungsmittel-Wechselwirkungen. Teil 1: Solvatation von Triethylphosphinoxid in aprotischen und CH-aciden Lösungsmitteln

Zusammenfassung Es wurde die Konzentrations- und Lösungsmittelabhängigkeit der P=O-Valenzschwingungv(PO) der ModellverbindungEt ₃PO in verschiedenen aprotischen und CH-aciden Lösungsmitteln systematisch untersucht. In hinreichend verdünnten Lösungen tritt die P=O-Valenzschwingung als einzelne symmetrische Bande auf, was beweist, daß nur eine einzige Solvatform vorliegt. In Lösungsmitteln niedriger Akzeptorzahl konnte bei höheren Konzentrationen die Existenz von Dipol-Dipol-Komplexen nachgewiesen werden. In CH-aciden Lösungsmitteln liegtEt ₃PO in Form von Wasserstoffbrückenkomplexen vor. Aussagen über die Struktur dieser Komplexe konnten mit Hilfe spektrophotometrischer Titrationen erhalten werden. Die durch Extrapolation auf Konzentration null erhaltenen Wellenzahlenv° (PO) hängen linear von den aus den³¹P-chemischen Verschiebungen vonEt ₃PO bereits früher bestimmten Akzeptorzahlen der Lösungsmittel ab. Die Existenz dieser linearen Beziehung beweist, daß beide Parameter frei von störenden Einflußfaktoren (magnetische Anisotropie- und Schwingungskopp-lungseffekte) sind und tatsächlich linear mit der Stärke der intermolekularen Wechselwirkung variieren. Die Ergebnisse der vorliegenden Studie zeigen, daß die P=O-Valenzschwingung vonEt ₃PO eine hervorragende Sonde zur Untersuchung von Lösungsmitteleffekten und Solvatationsmechanismen darstellt.

     

Infrarotspektroskopische untersuchungen an metallcupferronaten im bereich 4000-32 cm-1

The preparation and empirical interpretation of the m.i.r. and f.i.r. spectra of the cupferronates of Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Pb²⁺ und Bi³⁺ in the range 4000—32 cm^-1 is described. The bands in the range 1700—500 cm^-1 and the C—H valency vibrations can be assigned to vibrations of the pure ligand; differentiation of individual metal chelates in this range is therefore difficult. In contrast, the far i.r. region (below 500 cm^-1) contains many absorption bands (the metal chelate fingerprint region) which differ in position and intensity. The position of the bands with the highest v—M—O character, which can be recognised on the basis of the large metal-dependent frequency shifts, depends linearly on the second ionization potential of the metal atom, except for the Mn and Sn chelates. The relative absorptions, E_M—O/E, of the far i.r. bands of these cupferronates allow classification of the chelates into groups corresponding to the metal—ligand bonding involved (tetrahedral, octahedral and planar). The characteristic value used for this classification (the quotient of the absorption at the M—0 frequency and the absorbance of the strongest remaining band in the far i.r.) covers the range 0.92–2.17 for tetrahedral chelates, and 5.30–6.20 for planar chelates, with the octahedrally coordinated chelates having intermediate values.     

Beitrag zum problem der bandenverschiebungen in den ir-spektren von dialkyldithiocarbamidaten: Teil V. Pyrroldithiocarboxylate. Der bereich von 500—32 cm-1

The far i-r. spectra of the pyrroledithiocarboxylates of Ni, Cu, Zn, Cd, Hg(II) and Pb are described. Evaluation of the spectra by means of the relative absorptions of the bands below 400 cm^-1 allows these chelates to be classified in terms of the coordination of the central metal atom. The characteristic value used for classification (the quotient of the absorption at the M-S frequency and the absorption at the strongest remaining band in the far i.r.) covers the range 0.6–2.1 for tetrahedrally coordinated chelates, and 8.7–10 for planar chelates. The characteristic values for the pyrroledithiocarboxylates, diethyl-and tetramethylene-dithiocarbamates and cupferronates, are compared.     

A rapid automated method for wine analysis based upon sequential injection (SI)-FTIR spectrometry

A new process control methodology for the simultaneous determination of sugars, alcohols and organic acids in wine based on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to ethanol several lower level wine components (glucose, fructose, glycerol, citric-, tartaric-, malic-, lactic- and acetic acid) were determined. To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel, fully automated sequential injection (SI) system with Fourier transform infrared (FTIR) detection. The resulting spectra were evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the analysis of real wine samples containing 79–91 g L^–1 ethanol, 5.9–8.1 g L^–1 glycerol, 0.4–6.9 g L^–1 glucose, 1.5–7.5 g L^–1 fructose, 0.3–1.6 g L^–1 citric acid, 1.0–1.7 g L^–1 tartaric acid, 0.02–3.2 g L^–1 malic acid, 0.4–2.8 g L^–1 lactic acid and 0.15–0.60 g L^–1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR). The short analysis time (less than 3 min) together with high reproducibility makes the newly developed method applicable to process control and screening purposes (average of the standard deviations calculated from four repetitive measurements of six different real samples: ethanol: 0.55 g L^–1, glycerol: 0.037 g L^–1, glucose: 0.056 g L^–1, fructose: 0.036 g L^–1, citric acid: 0.020 g L^–1, tartaric acid: 0.010 g L^–1, malic acid: 0.052 g L^–1, lactic acid: 0.012 g L^–1 and acetic acid: 0.026 g L^–1). Received: 21 January 1998 / Revised: 5 March 1998 / Accepted: 6 March 1998     

Inclusive production of neutral kaons inK − p interactions at 32 GeV/c

The inclusive production of neutral kaons inK ^? p interactions at 32 GeV/c is studied in final states with one, two and three strange particles (K ⁿ or Λ). Inclusive and topological cross sections are obtained and their energy dependence discussed by comparison with lower energy data. The invariant differential cross sections of neutral kaons are studied as a function of Feynmanx, the c.m. rapidity and the transverse momentum, and a comparison is made with data at 14.3 GeV/c. Invariantx-distributions are obtained separately for “indirect” neutral kaons from \(\bar K*(890)\) decays and for “prompt” kaons. We also discuss the possibility of connecting quark structure functions with hadron fragmentation spectra at this c.m. energy \(\sqrt s \simeq 8 GeV\) .