Pattern recognition techniques screening for drugs of abuse with gas chromatography-Fourier transform infrared spectroscopy

As many drugs of abuse are relatively volatile substances, gas chromatography-mass spectrometry (GC-MS), and more recently gas chromatography-Fourier transform infrared spectroscopy (GC-FTIR) became the most powerful techniques applied for their identification. We are presenting a combination of pattern recognition techniques discriminating illicit amphetamines according to the substitution pattern associated with the psychotropic activity (stimulants and hallucinogens) for which they are abused, and with the corresponding level of health hazard. As we determined, GC-FTIR provides the best selectivity in identifying the structural features associated with the full constellation of pharmacological effects of amphetamines. The toxicological questions to be answered and the spectroscopic features enabling the screening based on soft independent modeling of class analogy (SIMCA) are discussed. The accuracy, sensitivity and selectivity of the system recommend its use for automating the investigations of illicit drugs for epidemiological, clinical, administrative and forensic purposes. As opposed to the traditional tests screening for drugs of abuse, the system may also be applied as a broad-spectrum screening test. The extent to which the output of a query for amphetamines may be used for assessing the class identity of a negative (i.e. other hallucinogens or stimulants, sympathomimetic amines, narcotics and precursors) was determined by a systematic principal component analysis (PCA). The basic information is summarized in tables according to the category or class of compounds found suitable for screening.     

Optimisation of flow schemes for ion-exchange separations by dynamic programming

Summary This article compares two operational research methods for the choice of the optimal flow scheme in separation chemistry. It is concluded that dynamic programming offers more advantages than the application of the theory of graphs.

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Optimierung von Fliediagrammen für Ionenaustauschtrennungen durch dynamische Programmierung

Zusammenfassung 2 Methoden zur Auswahl des optimalen Fließdiagramms für Trennungsverfahren werden verglichen, wobei gezeigt wird, daß die dynamische Programmierung mehr Vorteile bietet als die Anwendung der Graphentheorie.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg.     

Quantitative structure-retention and retention-activity relationships of beta-blocking agents by micellar liquid chromatography

Sixteen beta-blocking agents (acebutolol, alprenolol, atenolol, bisoprolol, carteolol, celiprolol, esmolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol, practolol, propranolol, sotalol and timolol) showing a large range of hydrophobicity (octanol-water partition coefficients, log P between -0.026 and 2.81) were subjected to micellar liquid chromatography with sodium dodecyl sulfate as micelle forming agent, and n-propanol as organic modifier. The correlation between log P and the retention factor extrapolated to a mobile phase free of micelles and organic modifier was investigated. The use of an interpolated retention factor or the retention factor for specific individual experimental mobile phases was however advantageous since the retention factors of all beta-blocking agents were measurable in the selected mobile phases. Good correlations with log P and with in vitro biological parameters (cellular permeability coefficients in Caco-2 monolayers and apparent permeability coefficients in rat intestinal segments) were found.     

Parallel co-ordinate geometry and principal component analysis for the interpretation of large multi-response experimental designs

In the evaluation of large or complex data sets the use of visualization methods can be of great benefit. In this paper, the use of parallel co-ordinate geometry (PCG) plots, principal component analysis (PCA) and N-way PCA as visualization procedures for large multi-response experimental designs was compared with the more traditional approach of calculating factor effects by multiple linear regression. PCG plots are a recent addition to the visualization tools and offer a possibility to visualize multi-dimensional data in two dimensions while no calculations are required. It was found that PCA and PCG each have their own benefits and disadvantages. Both methods can be used to some extent to select optimal conditions. Moreover, it was possible to use the PCA score plot as a Pareto optimality plot that allowed to select the experiments considered to be Pareto optimal. Therefore, the examined visualization methods can be useful and complementary aids in the interpretation of large multi-response experimental design data and they add a multivariate dimension to the more classical univariate analysis of such data.     

Local factor analysis of rank-deficient reaction systems

A variety of biochemical and physical properties of proteins are regulated by calcium ion (Ca²⁺) binding with varying specificity and affinity. Calcium ion binding can adjust the phospholipid-protein interactions through changing the properties of phospholipid membrane. As an attractive detection technique, whole column imaging detection (WCID) coupled to capillary isoelectric focusing (cIEF) displays several advantages in the study of protein-ligand and protein-protein interactions, including fast and high-efficient separation, high resolution, and simple operation. In this study, a cIEF-WCID method was evaluated for studying the effect of Ca²⁺ binding on protein structural changes and phospholipid-protein interactions. Four proteins with different isoelectirc point (pI), trypsin inhibitor (pI = 4.5), β-lactoglobulin B (pI = 5.2), phosphorylase b (pI = 6.3), and trypsinogen (pI = 9.3), were used for this purpose. The targeted proteins exhibited altered cIEF profiles due to protein conformation changes resulting from the Ca²⁺ binding. The study showed that Ca²⁺ can be buried in the phospholipid membrane, modify the membrane property, and change the phospholipid-protein interactions. The utility of the cIEF-WCID technique demonstrates that the calcium binding plays a crucial role in the protein structural changes and the phospholipid-protein interactions, and elucidates the possible mechanisms involved in calcium-protein binding and calcium bound phospholipid-protein interactions.     

Using FTIR spectroscopy to detect sericin on historic silk

Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa...     

Expert systems for chemical analysis (ESPRIT Project 1570)

Summary This paper gives an overview of the structure and processes going on in the project Expert Systems for Chemical Analysis (ESCA), an international project within the ESPRIT research programme of the European Community. The application area, HPLC method development, is explained and broken down into four domains. The methods used for representing knowledge in the project are discussed.     

Distribution coefficients of Rb(+) on zirconium phosphate in mixed aqueous-organic media

The distribution coefficients have been determined for Rb(+) distributed between zirconium phosphate and 0.85M hydrochloric acid in aqueous solutions of methanol, ethanol, n-propanol, isopropyl alcohol, t-butyl alcohol, dimethylsulphoxide, dimethylformamide, tetrahydrofuran, acetone, dioxane, "Methylcellusolve", "Propylcellosolve" acetic acid and sulpholane, in 0-88% concentration.     

Relationship between gas chromatographic behaviour and topological, physicochemical, and quantum chemically calculated charge parameters for neuroleptica

Gas chromatographic retention indices for a number of neuroleptic drugs on an apolar phase, OV-101, and a polar phase, OV-17, are correlated with parameters describing various properties of the separated molecules. The gas chromatographic behaviour is related to the same parameters as those used in quantitative structure activity relationships. The molecular connectivity indices and log k' in a reversed-phase HPLC system were chosen as parameters describing the apolar interactions of the molecules with the stationary phase. As properties involved in more specific interactions, and related to the presence of overall or local polarity, the molecular dipole moment and the charge on the N-atom were selected and quantum chemically calculated. It is found that the retention indices on the apolar phase, OV-101, can be successfully correlated with molecular connectivity indices, which are also used in QSAR studies. The retention indices on OV-17 show a high correlation with the charge on the N-atom. Evidence of the importance of this N-atom in pharmacological activity is known.