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G Theodoridis

Publications and source records attributed to G Theodoridis.

8 recordsLinked to original sources
PubMed2006

Solid phase microextraction applied to the analysis of organophosphorus insecticides in fruits.

Trace amounts of organophosphorus pesticides (OPs) were determined in various fruits by headspace solid phase microextraction (HS-SPME) and gas chromatography-nitrogen phosphorous detection (GC-NPD). Sampling from the headspace enhanced method selectivity, whereas at the same time improved fiber life time and method sensitivity. Diazinon, parathion, methyl parathion, malathion and fenithrothion were determined in various fruits: more than 150 samples of 21 types of fruits were studied. SPME-GC-NPD provided a useful and very efficient analytical tool: method linearity ranged from 1.2 to 700 ng/ml. Limits of detection (LODs) and quantitation (LOQs) ranged from 0.03 to 3 ng/ml and 0.12 to 10 ng/ml respectively, values well below the residue limits set by the EU. Less than 2% of the samples were found positive containing amounts higher than the EU limits. The effect of fruit peeling and washing was also investigated.

Fruit↗
PubMed2004

Headspace solid phase microextraction for the gas chromatographic analysis of methyl-parathion in post-mortem human samples. Application in a suicide case by intravenous injection.

A simple and rapid procedure for the determination of methyl-parathion (m-p) in post-mortem biological samples was developed using headspace solid phase microextraction (SPME) and gas chromatography (GC) with nitrogen-phosphorous detection (NPD). Methyl-parathion was extracted on 85 microm polyacrylate SPME fiber. Salt addition, extraction temperature, and extraction time were optimized to enhance the sensitivity of the method. The linearity (y = 0.0473x - 0.0113, R2 = 0.9992) and the dynamic range (0.1-40 microg/ml) were found very satisfactory. The recoveries of methyl-parathion were found to be 46% in spiked human whole blood, 53% in spiked homogenized liver tissue, and 54% in spiked homogenized kidney tissue compared with samples prepared in water. The coefficients of variations for 2, 4, and 20 microg/ml of methyl-parathion in blood ranged from 0.9 to 5.1%, whereas the detection limit of the method was satisfactory (1 ng/ml in aqueous samples, 50 ng/ml in whole blood). The developed procedure was applied to post-mortem biological samples from a 21-year-old woman fatally poisoned (suicide) by intravenous injection of methyl-parathion. The intact insecticide was found in the post-mortem blood at a concentration of 24 microg/ml. No methyl-parathion was detected in the liver, kidneys, and gastric contents.

Adult↗
PubMed2002

Immunoaffinity chromatography for the sample pretreatment of Taxus plant and cell extracts prior to analysis of taxanes by high-performance liquid chromatography.

The application of immunoaffinity chromatography for the purification of Taxus plant and cell extracts prior to the HPLC analysis is described. Polyclonal antibodies raised against 10-deacetylbaccatin III (10-DAB III), paclitaxel's main precursor in plant, were characterised by enzymed-linked immunosorbent assay. Immunoglobulins from selected antisera were immobilised on CNBr-activated Sepharose 4B. The immunoaffinity column was used for the purification of plant and plant cell culture extracts prior to their analysis by HPLC. Immunoaffinity chromatography enabled the selective concentration of taxoids and enhanced sample clean-up.

Antibodies↗
PubMed2002

Selective solid-phase extraction sorbent for caffeine made by molecular imprinting.

A molecularly imprinted polymer (MIP) was prepared with caffeine as the template molecule. Thermal polymerisation (60 degrees C) was optimised, varying ratios of monomer, cross linker and template. The polymer was used as a solid-phase extraction (SPE) sorbent, for selective trapping and pre-concentration of caffeine. Caffeine was loaded on the MIP-SPE cartridge using different loading conditions (solvents, pH value). Washing and elution of the caffeine bound to the MIP was studied utilising different protocols. The extraction protocol was successfully applied to the direct extraction of caffeine from beverages and spiked human plasma.

Beverages↗
PubMed2000

Solid-phase microextraction for the analysis of biological samples.

Solid-phase microextraction (SPME) has been introduced for the extraction of organic compounds from environmental samples. This relatively new extraction technique has now also gained a lot of interest in a broad field of analysis including food, biological and pharmaceutical samples. SPME has a number of advantages such as simplicity, low cost, compatibility with analytical systems, automation and the solvent-free extraction. The last few years, SPME has been combined with liquid chromatography and capillary electrophoresis, besides the generally used coupling to gas chromatography, and has been applied to various biological samples such as, e.g., urine, plasma and hair. The objective of the present paper is a survey of the application of SPME for the analysis of biological samples. Papers about the analysis of biologically active compounds are categorised and reviewed. The impact of SPME on various analytical fields (toxicological, forensic, clinical, biochemical, pharmaceutical, and natural products) is illustrated. The main features of SPME and its modes are briefly described and important aspects about its application for the determination of pharmaceuticals, drugs of abuse and compounds of clinical and toxicological interest are discussed. SPME is compared with other sample pretreatment techniques. The potential of SPME and its main advantages are demonstrated. Special attention is paid to new trends in applications of SPME in bioanalysis.

Chromatography, Liquid↗
PubMed1995

Reversed-phase high-performance liquid chromatography--photodiode-array analysis of alkaloid drugs of forensic interest.

A reversed-phase high-performance liquid chromatography-photodiode-array method for the analysis of 23 drugs of forensic interest is presented. The separation method development was based on mobile-phase optimisation, temperature control and use of three ODS stationary phases. Multiwavelength detection and quantitation was performed at 225, 232, 239, 254, 275 and 289 nm. Absorbance rationing proved to be very helpful for the identification of these drugs. Recognition of the analysed compounds was achieved by means of correlation of retention time and absorbance ratios. The method was directly applied to the analysis of illicit heroin and cocaine samples and to the analysis of pharmaceutical preparations containing codeine.

Alkaloids↗
PubMed1989

Microbial transformation of the tetrazolinone herbicide f5231.

Microbial transformation of the tetrazolinone herbicide F5231 was accomplished with the filamentous fungus Absidia pseudocylindrospora Hesseltine et Ellis (ATCC 24169). The fungus converted the herbicide to six metabolites which were identified spectrally by mass, infrared, and nuclear magnetic resonance spectroscopy.

Journal Article↗