Screening of citalopram, fluoxetine and their metabolites in human urine samples by gas chromatography-mass spectrometry. A global robustness/ruggedness study.

Capillary gas chromatography with mass spectrometry detection in SIM mode (GC-MS-SIM) has been used for the analysis of citalopram (CIT), fluoxetine (FLX), and all of their metabolites in urine samples. The instrumental parameters affecting GC separation and MS-SIM detection were investigated. A validation procedure was performed on urine matrix and a simultaneous robustness/ruggedness evaluation is also presented in this paper. An optimized solid-phase extraction (SPE) has been applied, reaching in this way to limits of detection (LODs) between 0.7 ng L(-1) (CIT) and 33.6 microg L(-1) (CIT-PA). A pharmacokinetic screening in clinical urine samples has been also carried out.

Resolution of ternary mixtures of Tartrazine, Sunset yellow and Ponceau 4R by derivative spectrophotometric ratio spectrum-zero crossing method in commercial foods.

A very simple spectrophotometric method is described for resolving ternary mixtures of the food colorants Tartrazine, Sunset Yellow and Ponceau 4R by using the first derivative of the ratio spectra with measurements at zero-crossing wavelengths. Calibration graphs are linear up to 20 mg l(-1) of Tartrazine (E-102), 40 mg l(-1) of Sunset Yellow (E-110) and 32 mg l(-1) of Ponceau 4R (E-124). Standard deviations of 0.9, 0.8 and 2.4% were obtained for nine standards of 8 mg l(-1) of Tartrazine, 8 mg l(-1) of Sunset Yellow and 8 mg l(-1) of Ponceau 4R, respectively. This method was satisfactorily used for determining synthetic mixtures of these colorants in different ratios (from 1:1:1 to 1:5:5 or even higher) with recoveries in 94-105% range and it was successfully applied over three commercial products containing the three dyes and it did not require any separation step. The results were compared with those obtained by HPLC and very similar values were found by both methods.

Spectrophotometric resolution of ternary mixtures of salicylaldehyde, 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde by the derivative ratio spectrum-zero crossing method.

A new spectrophotometric method for resolving ternary mixtures is proposed. The method is based on the simultaneous use of the first derivative of ratio spectra and measurements of zero-crossing wavelengths. The ratio spectrum is obtained by dividing the amplitudes of the absorption spectrum of the mixture by a standard spectrum of one of the components giving the first derivative of the ratio spectrum. The concentrations of the other components is then determined from their respective calibration graphs established by measuring the ratio derivative analytical signal at the selected zero-crossing points. The method has been applied to resolving ternary mixtures of the isomers salicylaldehyde, 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde. Previously, we also resolved the binary mixture of salicylaldehyde and 3-hydroxybenzaldehyde. The method compares favourably with other spectrophotometric methods.