CHROMATOGRAPHIC-PHOTODENSITOMETRIC QUANTITATION OF THE SOLANACEOUS ALKALOIDS
Notice bibliographique
Résumé
The thesis work has involved an attempt to improve the accuracy and precision of direct photodensitometric quantitation of thin-media chromatograms. Direct photodensitometric evaluation of paper and thin-layer chromatograms has been used increasingly in the past decade and is now accepted as a standard method of estimation. The bulk of the methods published have been highly empirical in nature. Recently, there has been considerable disenchantment with all types of in situ analysis and there is now considerable interest in developing a theoretical basis for optical assays performed in situ. Little attention has been paid to the fact that the absorbance varies considerably throughout a spot and that the geometry of "'inhume spots may vary considerably from that of standard spots be- cause of the greater complexity of unknown samples. It was felt that the only way to reduce errors of non-linearity due to non-uniform distribution of substance over the illuminating slit and compensate for distortions in spot geometry would be to replace fixed-slit scanning by two-dimensional scanning of spots with a small point of illumination. Because a two-dimensional or "flying-spot" scanner was not available, two-dimensional scanning was simulated by manual collection of density data using a 1 x 1 mm. optical slit over the entire area of the spot, integration being accomplished by summing all data points. Experimental work was done on the Solanaceous alkaloids which were separated electrophoretically on cellulose thin-layers and stained with Dragendorff's reagent. The chromatograms were made translucent with mineral oil before scanning in order to reduce the high light-scattering properties of the support media. In order to expedite analysis and make the scanning process more continuous, an analog computer was later built to convert the output potential of the existing photometer (output varying with transmittance) to absorbance (negative log of the transmittance). Two-dimensional scanning was semi-automatic in nature--scanning across the spot was motorized but the chromatogram had to be advanced manually and the scanning stage had to be returned manually for the next pass over the chromatogram. Output of the density signals Was on a strip-chart recorder with continuous, automatic, digital integration of density peaks. Calibration curves (integrated absorbance vs. concentration) produced were quite linear and assay results on "simulated" unknowns and comparative assays on natural products containing the alkaloids under study were encouraging. Further work in this area necessitates better stabilized equipment as well as rapid flying-spot scanning with continuous electronic integration. This would allow improvements in accuracy, not only by allowing more precision in scanning; but would allow the collection and averaging of more data. Well stabilized equipment is necessary for meaningful study of the proportionality of radiative transfer to concentration.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,005 | 0,004 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».