Simultaneous fluorimetric determination of acetylsalicylic acid metabolites in urine by partial least squares multivariate calibration.

A method is described for the simultaneous determination of the main urinary acetylsalicylic acid (aspirin) metabolites, salicyclic, salicyluric and gentisic acids, based on their native fluorescence. The urine was extracted into diethyl ether in acid medium, and back-extracted with glycine/sodium hydroxide buffer solution at pH 9.4. A comparative study of the results found using the excitation, the emission and the combination of the excitation plus the emission spectral data, as analytical signals, was performed. The data set, composed of the excitation plus the emission spectra, was selected as the analytical signal. The optimum wavelengths to record the excitation (lambda(em)=444 nm) and the emission spectra (lambda(ex)=323 nm) were selected to maximize the contribution from gentisic acid, which is the minor urinary metabolite. Partial least squares (PLS-1) multivariate calibration was then applied for the determination. Recovery values from urine samples spiked with salicyclic, salicyluric and gentisic acids varied from 90.1 to 97.6% (mean 93.6%), from 90.0 to 110% (mean 97.9%) and from 89.9 to 104.7% (mean 98.5%), respectively.

Host-guest stabilized room temperature phosphorescence in beta-cyclodextrin/ bromoalcohol solutions from 2-naphthyl-oxy-acetic acid and 1-naphthyl-acetic acid.

Room temperature phosphorescence (RTP) from 2-naphthyl-oxy-acetic acid (NOA) and 1-naphthyl-acetic acid (NAA), with stabilization by use of beta-cyclodextrin (beta-CD) as a host system, has been examined. 2-Bromoethanol and 2,3-dibromopropanol have been evaluated as external heavy atom perturbers to enhance the rate of intersystem crossing and, consequently, populating the triplet state for phosphorescence emission. The deoxygenation of the solutions was achieved chemically by use of sodium sulphite. The spectral characteristics of the phosphorescence emission from these relatively polar compounds and the optimization of the chemical variables involved are reported. The role of the bulkiness of the bromoalcohol employed, in comparison with the unoccupied space of the interior of the cyclodextrin cavity by the guest, is an important factor in the attainment of an effective RTP emission, and should be taken into account in the selection of the appropriate external heavy atom for the observation of RTP from other organic molecules of interest by this approach. 2,3-Dibromopropanol seems a more adequate bromoalcohol than 2-bromoethanol for the observation of RTP emission in the systems investigated.

Psychometric differentiation of psychogenic and organic erectile disorders.

A study was conducted to assess the discriminant validity of patient responses to a questionnaire in distinguishing between organic and psychogenic erectile dysfunction. A total of 56 urologist-referred veterans slept for 3 nights in a sleep laboratory for nocturnal penile tumescence recording. Based on nocturnal penile tumescence results 48 patients were assigned to an organic group and the remaining 8 were assigned to a psychogenic group. A discriminant function analysis of questionnaire responses yielded a highly significant discriminant function [chi-square (19) equals 63.88, p less than 10(-6)], and all 56 patients were classified correctly into the nocturnal penile tumescence-defined organic and psychogenic groups. It was concluded that verbally reported data contain diagnostically meaningful information and that such information can compare favorably with information collected through standard laboratory-based nocturnal penile tumescence techniques.

Phototautomerism in the lowest excited singlet state of 1-hydroxy-2-carboxyanthraquinone.

The dependence of the absorption and fluorescence spectra of 1-hydroxy-2-carboxy-anthraquinone on pH and Hammett acidity have been studied. This compound exhibits phototautomerism in its uncharged and its singly-charged anionic species in aqueous media. Its ground state (pK(a)) and lowest excited singlet-state (pK(a)( *)) dissociation constants have been determined by absorptiometric and fluorimetric titrations and the assignment of the pK(a) and pK( *)(a) values to the equilibria concerned has been carefully considered.