The ability of surface-enhanced Raman spectroscopy (SERS) to measure the chemotherapy drug 5-fluorouracil in saliva is presented. A silver-doped sol-gel provided SERS and also some chemical selectivity. 5-Fluorouracil and physiological thiocyanate produced SERS, whereas large biochemicals, such as enzymes and proteins, did not, supporting the expectation that the larger molecules do not diffuse through the sol-gel to any appreciable extent. In addition, 5-fluorouracil samples of 2 µg ml −1 were easily measured, and an estimated limit of detection of 150 ng ml −1 in 5 min should provide sufficient sensitivity to perform pharmacokinetic studies and to monitor and regulate patient dosage. This would fill a critical need for this highly used drug, since genetic-based variations in its metabolism can range by as much as five-fold from one patient to another.
Approximately one-third of all drugs can form hydrates, and therefore an in-depth understanding of the factors affecting anhydrate-to-hydrate transformation kinetics in a variety of environments is of interest. In this work, real-time analytical methods, in the form of Raman spectroscopy and optical microscopy, were used to establish representative transformation profiles and growth kinetics for hydrate formation of several drug substances. By comparing and contrasting the behavior of these different hydrates in terms of their specific properties such as solubility, dissolution rate, and growth rate of hydrate phase, and the influence of external factors such as seeding and agitation conditions, an increased understanding of hydrate formation has been achieved. The overall transformation rate from anhydrous to hydrate form was found to be not only a function of compound-specific properties, but was also strongly affected by surface properties and external factors such as the presence of seeds and the degree of shear forces.
This laboratory experiment, using proton NMR spectroscopy to determine the dissociation constant for heterocyclic bases, has been modified from a previously described experiment. A solution of a substituted pyridine is prepared using deuterium oxide (D 2 O) as the solvent. The pH of the solution is adjusted and proton NMR spectra are collected for a variety of pH values. The chemical shifts of the peaks in the NMR spectrum change depending on the degree of protonation of the pyridine ring. Analysis of the spectral data is used to calculate the dissociation constant of the substituted pyridine. This experiment is suitable for a variety of advanced chemistry laboratories including analytical chemistry and instrumental analysis.
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