Solid-phase analytical derivatization: enhancement of sensitivity and selectivity of analysis.

Analytical derivatizations enhance the sensitivity and selectivity of determinations for organic compounds. Classical techniques are often based on solution chemistry. Most modern sample preparation techniques, however, are based on solid-phase extractions. Solid-phase analytical derivatization bridges this gap and facilitates sample preparation by combining the isolation step with the derivatization. The solid-phase retains both reagents and derivatized analytes and often permits facile separation of excess reagent or selective elution of the desired products. The most recent solid-phase extraction techniques have been used in conjunction with analytical derivatization to automate the analysis. In this review, analytical derivatizations are presented as functional group analysis.     

A new and consistent parameter for measuring the quality of multivariate analytical methods: Generalized analytical sensitivity

Generalized analytical sensitivity (γ) is proposed as a new figure of merit, which can be estimated from a multivariate calibration data set. It can be confidently applied to compare different calibration methodologies, and helps to solve literature inconsistencies on the relationship between classical sensitivity and prediction error. In contrast to the classical plain sensitivity, γ incorporates the noise properties in its definition, and its inverse is well correlated with root mean square errors of prediction in the presence of general noise structures. The proposal is supported by studying simulated and experimental first-order multivariate calibration systems with various models, namely multiple linear regression, principal component regression (PCR) and maximum likelihood PCR (MLPCR). The simulations included instrumental noise of different types: independently and identically distributed (iid), correlated (pink) and proportional noise, while the experimental data carried noise which is clearly non-iid.     

Alternative methods providing enhanced sensitivity and selectivity in capillary electroseparation experiments

The study of alternative and novel techniques for altering selectivity and enhancing sensitivity as well as injection and detection protocols are important in the ongoing development of capillary electroseparation protocols. Some recent research from our laboratory in these fields is presented and discussed in this review. To improve sensitivity an off-line sample enrichment technique utilising solvent evaporation in a levitated drop or an on-line solid-phase extraction protocol was used. The selectivity was tuned by the use of protein gels or molecularly imprinted polymer mediated capillary electrochromatography. Furthermore, a picolitre droplet injection method is described as well as a detection protocol based on laser-induced fluorescence imaging.     

On the use of non-hierarchical classification methods in analytical chemistry

Summary Microprocessor-controlled analytical methods produce large amounts of data in a short time. This wealth of information is difficult to handle with conventional methods. Numerical classification is a valuable tool for reducing large arrays of data and revealing structure therein. Non-hierarchical methods have been used with good results for the classification of spectral analytical data of ancient glass samples. With the newly developed program APART, a classification was obtained according to technological aspects of glass production. The narrow clusters found were caused by local traditions and the use of similar raw materials. The colouring materials and decolourants contribute most to the trace element content, and are therefore dominant in the classification.

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Nicht-hierarchische Klassifikation in der analytischen Chemie

Zusammenfassung Mit neuen mikroprocessor-gesteuerten analytischen Methoden erhält man eine Fülle von Daten in kurzer Zeit. Solche Datenmengen erweisen sich mit herkömmlichen Methoden als nur schwer überschaubar. Mit der Methode der numerischen Klassifikation ist es möglich geworden, auch große Datenmengen zu verarbeiten und zu interpretieren. Für die Klassifikation der meisten analytischen Daten empfiehlt sich die Verwendung nichthierarchischer Algorithmen. Spektralanalytische Daten von antiken Glasfunden wurden für eine Klassifikationsanalyse herangezogen. Dazu wurde ein neu entwickeltes Programm namens APART verwendet, das eine Klassifikation nach produktionstechnischen Gesichtspunkten ermöglichte. Lokale Tradition in der Herstellung und die Verwendung ähnlicher Rohstoffe ergaben eine Struktur gut definierter enger Cluster im vorhandenen Probenmaterial. Färbe- und Entfärbemittel der Glasherstellung bewirken besonders hohe Spurenelementgehalte und bestimmen daher weitgehend die Klassifikation.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Energy dissipation and selectivity in the catalytic oxidation of ammonia

A qualitative interpretation of selectivity changes in ammonia oxidation, based on considerations of energy dissipation processes is presented.

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Some remarks on the information power and selectivity of analytical processes

The consistency of the equation given by Shannon for the transfer of maximum amount of information in one channel, and the equation deduced by Kaiser for the expression of the information power of analytical methods is shown. The fundamental difference between the maximum amount of information obtainable by an instrument and that by an analytical procedure is reported. In the second case the selectivity of the analytical procedure also has to be taken into consideration.     

Effect of gamma-irradiation on the catalytic activity and selectivity of gamma-alumina

Methanol conversion reaction was carried out in contact with a poorly crystalline -alumina pre-irradiated with different doses of -rays. The reaction was conducted at 140–440°C using a flow technique under atmospheric pressure. The results obtained revealed that -irradiation of Al₂O₃ resulted in drastic modifications of its activity and selectivity in methanol conversion reaction. The dose of 15 Mrad was sufficient to suppress completely the formation of dimethyl ether (DME) and stimulated the formation of methane, which started at 200°C instead of 300°C in the case of the unirradiated alumina specimen. However, the rate of CH₄ formation was found to decrease as a function of the dose employed. When the dose reached 140 Mrad, DME was reproduced with a rate comparable to that measured for the unirradiated catalyst sample. These results permitted us to conclude that DME is produced on the weak acidic sites (Brönsted acidity of Al₂O₃) and is not necessarily an intermediate compound for methane formation that takes place directly from methanol on strong acidic sites (Lewis acidity). The doses of 15–75 Mrad expelled completely the Brönsted acidic sites from Al₂O₃ surface, and the doses above this limit brought about a transformation of Lewis acidic sites into Brönsted acidity that is responsible for dimethyl ether formation. This transformation occurs by the action of liberated water from the dehydration of methyl alcohol.     

脂质组学及其分析方法

脂质组学的研究属于生命科学的范畴,与人类的健康密切相关。目前,脂质组学已成为代谢组学最重要的分支之一,且是一个非常活跃的研究领域,尤其在研究疾病方面的重要性已经引起了科学界的广泛关注。该文简要介绍了脂质组学的研究内容,重点评述了脂质组学分析方法,包括样品处理、轮廓分析、目标分析、成像分析以及数据处理。最后提出了脂质组学分析技术和方法的展望。     

Standardisation and codification of analytical methods

1. The necessity of standardising an analytical method nationally or internationally depends on the nature of the method. Research methods will hardly be suitable for standardisation, but routine methods especially those of an empirical nature (not general chemical and physical methods) demand international agreement. 2. If analytical methods are published they should be printed in a standard format to facilitate comparison and standardisation and as a safeguard against the lack of details important to the execution of the method.     

Complex activators in analytical catalytic reactions

Summary The influence of pairs of carboxylic acids on the oxidation ofp-phenetidine hydrochloride by chlorate and traces of vanadium(V) as catalyst is studied. The activator systems used are sulphosalicylic acid + tartaric acid, sulphosalicylic acid + citric acid, tartaric acid + citric acid. It is shown that in some cases the joint activating effect is much higher than that of either activator alone. The kinetic data obtained with complex activator systems confirm the concept of different types of activating action in the two stages of the catalytic reaction. Some combinations of activators could be used in catalytic analysis.

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Zusammenfassung Der Einfluß von Carbonsäurepaaren auf die Oxydation von p-Phenetidin-hydrochlorid durch Chlorat und Spuren von Vanadin(V) als Katalysator wurde untersucht. Als Aktivierungssysteme wurden Sulfosalicylsäure und Weinsäure, Sulfosalicylsäure und Zitronensäure, Weinsäure und Zitronensäure verwendet. In manchen Fällen ist der gemeinsame Aktivierungseffekt größer als der eines der jeweiligen Aktivatoren allein. Die kinetischen Daten der komplexen Systeme bestätigen die Annahme einer verschiedenartigen Aktivierung der zwei Stufen der katalytischen Reaktion. Manche Aktivatorkombinationen könnten für die katalytische Analyse von Wert sein.

     

Investigations on the selectivity of catalytic no reduction by ammonia

The activity and selectivity of V₂O₅/γ-Al₂O₃ catalyst were studied in the catalytic reduction of nitrogen oxide by ammonia. The activity of the catalyst monotonically increases as a function of temperature, however, its selectivity decreases. The DeNOx reaction of nitrogen oxides with ammonia can be described well by a mathematical model, which considers selectivity-decreasing side reactions as well in a wide temperature range (220–420°C).     

Investigations on the mechanism of some analytical catalytic reactions

Summary One of the catalytic oxidation reactions of arylamines in the presence of phenols (which are used for the detection and determination of micro-amounts of metalic ions) has been studied in detail. The results obtained by infrared spectrophotometry show that the coloured substances formed in reactions of this type are quinoneimines and arylidoquinones. Depending on the conditions and particularly on the kind of phenols used as activators, the reactions may produce compounds of one or other type. If the more rapid process is the oxidation of the activator to quinone, the latter will react with the available arylamine, and arylidoquinone will be mainly obtained. Sometimes, however, in such cases, quinoneimine-products may be formed instead. It is shown that on the basis of these conclusions other reactions hitherto unused for this purpose can be proposed.

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Zusammenfassung Eine der katalytischen Oxydationsreaktionen von Arylaminen in Gegenwart von Phenolen, die zum Nachweis und zur Bestimmung von Metallmikromengen Anwendung finden, wurde eingehend untersucht. Die Ergebnisse IR-spektrophotometrischer Untersuchungen zeigen, daß die bei solchen Reaktionen entstehenden gefärbten Substanzen Chinonimine und Arylidochinone sind. Je nach den Versuchsbedingungen und besonders je nach der Art des zur Aktivierung verwendeten Phenols entstehen Verbindungen dieser oder jener Art. Ist die Oxydation des Aktivators zum Chinon der rascher verlaufende Prozeß, so reagiert dieses mit dem verfügbaren Arylamin und man erhält hauptsächlich Arylidochinon. Mitunter entstehen in solchen Fällen aber doch Chinonimine. Auf der Grundlage dieser Erkenntnisse können bisher nicht verwendete Reaktionen für solche Zwecke vorgeschlagen werden.

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Résumé On a étudié en détail l'une des réactions d'oxydation catalytique des arylamines en présence de phénols (utilisées pour la recherche et le dosage de microquantités d'ions métalliques). Les résultats obtenus par spectrophotométrie infrarouge montrent que les substances colorées formées dans des réactions de ce type sont des imines-quinoniques et des arylidoquinones. Suivant les conditions et, en particulier, suivant la nature des phénols utilisés comme activateurs, les réactions peuvent conduire à des composés de l'un ou l'autre type. Si le processus le plus rapide est l'oxydation de l'activateur en quinone, ce dernier réagira avec l'arylamine disponible et l'on obtiendra principalement l'arylidoquinone. Quelquefois, cependant, dans de tels cas, des imines quinoniques peuvent prendre naissance à sa place. D'après ces conclusions, on montre que d'autres réactions inutilisées jusqu'ici peuvent être proposées pour cela.

     

Effect of explosion on the catalytic activity and selectivity of natural fluorite

The effect of various types of shock waves on the catalytic activity of natural fluorite in isopropanol dehydrogenation and dehydration reactions has been studied. Shock treatment is shown to decrease the catalytic reaction temperature and to increase the selective

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