Biomedical subjects

C G Georgakopoulos

Publications and source records attributed to C G Georgakopoulos.

6 recordsLinked to original sources

PubMed2001

Determination of ephedrines in urine by gas chromatography-mass spectrometry.

A selective gas-liquid chromatographic method with mass spectrometry (GC-MS) for the simultaneous confirmation and quantification of ephedrine, pseudo-ephedrine, nor-ephedrine, nor-pseudoephedrine, which are pairs of diastereoisomeric sympathomimetic amines, and methyl-ephedrine was developed for doping control analysis in urine samples. O-Trimethylsilylated and N-mono-trifluoroacetylated derivatives of ephedrines--one derivative was formed for each ephedrine--were prepared and analyzed by GC-MS, after alkaline extraction of urine and evaporation of the organic phase, using d3-ephedrine as internal standard. Calibration curves, with r2>0.98, ranged from 3.0 to 50 microg/ml depending on the analyte. Validation data (specificity, % RSD, accuracy, and recovery) are also presented.

Calibration↗

PubMed2001

Study of excretion of ecdysterone in human urine.

A study of excretion in human urine of ecdysterone, which is the active component of several over-the-counter supplements such as "Ecdysten", reportedly used by athletes, is presented. The study was performed after oral administration of 20 mg of ecdysterone. The collected urine samples were prepared using the standard screening extraction procedure for the free and conjugated fraction of anabolic steroids, and analyzed by gas chromatography (GC) coupled with quadrupole mass spectrometry (MS) and also with high-resolution mass spectrometry (HRMS). Two ecdysterone metabolites were identified and detected along with unchanged ecdysterone. Accurate mass measurements were made for diagnostic ions, including the molecular ion of the main metabolite of ecdysterone, deoxyecdysone, which, to our knowledge, has not previously been reported in the literature. These accurate mass measurements support the proposed fragmentation scheme.

Administration, Oral↗

PubMed1999

Excretion study of the beta2-agonist reproterol in human urine.

An excretion study of the beta2-agonist 7-[3-[(beta-3,5-trihydroxyphenethyl)amino]-propyl]theophylline (reproterol) in human urine, which is reportedly misused by athletes and horses as a doping agent, is presented. The study was performed after an oral administration of 20 mg of reproterol hydrochloride. The collected urine samples were prepared using the standard anabolic steroid extraction procedure and analyzed by gas chromatography coupled with quadrupole mass spectrometry and, also, with high-resolution mass spectrometry (HRMS). The main reproterol metabolite was found, whereas unchanged reproterol was not detected. The structure of the main metabolite was confirmed by an accurate HRMS measurement of diagnostic ions. Finally, an excretion urine profile of the main metabolite is presented. The mass spectrum of another possible unidentified reproterol metabolite is also reported.

Adrenergic beta-2 Receptor Agonists↗

PubMed1996

Quantitative structure-retention relationships in doping control.

Regression equation modelling was used for the correlation of gas chromatographic relative retention times tRR of anabolic steroids, stimulants and narcotics with their molecular characteristics in order to create a model for the prediction of tRR values of unanalyzed molecules. Predicting chromatographic retention parameters is one of the main goals of the quantitative structure-retention relationships (QSRR) methodology. To be performed, QSRR studies require two tools; a methodology for the extraction of the structural characteristics and a statistical program for the correlation of these characteristics with the chromatographic data.

Anabolic Agents↗

PubMed1991

Prediction of gas chromatographic relative retention times of stimulants and narcotics.

The ADAPT software system was used to create models for the prediction of gas chromatographic relative retention times (RRTs) of stimulants and narcotics that are analyzed in doping control of athletes. The two main methods that were followed for building the models were the quantitative structure-retention relationship (QSRR) and multiple linear regression analysis. The main proposed model for the entire data set had a multiple correlation coefficient R = 0.991 and standard error s = 0.046 or approximately 4.5%. Because of the relatively high standard error of the main model, a second model was built on a subset of compounds with R = 0.982 and s = 0.027 or approximately 2.5%.

Central Nervous System Stimulants↗

PubMed1991

Prediction of gas chromatographic relative retention times of anabolic steroids.

The prediction of gas chromatographic relative retention times (RRTs) of anabolic steroids, used in the doping control of athletes, was performed by a quantitative structure-retention relationship (QSRR) and multiple linear regression analysis study. A nine-variable model was generated with a multiple correlation coefficient R = 0.991 and relative standard error of less than 3%. Preliminary results indicated that the application of the model, especially in the prediction of RRTs of metabolites of the anabolic steroids, will be helpful.

Anabolic Agents↗