K. Torkos

Determination of phenols and chlorophenols as trimethylsilyl derivatives using gas chromatography-mass spectrometry

A rapid and simple method is described for the simultaneous determination of 6 phenols (phenol, o-, m-, p-cresol, catechol and resorcinol) and 19 chlorophenols (all mono-, di-, tri-, and tetrachlorophenol isomers and pentachlorophenol) present in aqueous samples. The method is based on derivatization with trimethylsilyl-N,N-dimethylcarbamate (TMSDMC). In contrast to other derivatization agents, TMSDMC instantaneously reacts with the phenolic compounds at room temperature and no further sample processing is necessary prior to instrumental analysis. The determination of the derivatives was performed by capillary gas chromatography-mass spectrometry (GC-MS). The stability of the most instable trimethylsilyl derivative (pentachlorophenol) was studied using different excess levels of the derivatization reagent. The derivatization method was tested on spiked water samples preconcentrated by solid phase extraction on Isolute ENV+ cartridge. The overall method gave detection limits of 0.01-0.25 microg/L for all compounds and < 0.05 microg/L for 17 of them.

Study of water clusters in insulating oils by Fourier transform infrared spectroscopy

The electrical parameters of insulating oils applied in HV transformers strongly depend on the moisture content. The water/oil system was studied in the practical important concentration range of 0 to 130 /spl mu/g/g to explain the unusual decrease of the breakdown strength. The relationship between water concentration and oil breakdown strength was determined in the range 0 to 50 /spl mu/g/g, using almost 100 oil samples taken from functioning transformers from each part of Hungary. The plotted data can be approached by two straight lines having very different slope, from which we conclude that the water/oil system has two different structures in this concentration range. The water in oil structure was examined by both theoretical and experimental methods. By a Hartree-Fock calculation the distance between water and hydrocarbon molecules was estimated. The water molecules arrangement and distance were calculated by a geometrical model. Fourier transform infrared spectroscopy was applied for experimental structure determination. Three oil samples were selected in the range 0 to 50 /spl mu/g/g. Assigning the OH vibration bands revealed that water is present in low concentration as monomer and at higher concentration in cluster forms (dimers, tetramers etc.). Similar graphs were found of the total dipole moment of water clusters vs. The resistance of insulating oil and the water concentration vs. the breakdown strength. The latter curve can be explained with the different state of water in oil. Water is present in molecular disperse state at /spl gsim/10 /spl mu/g/g. Above this value water clusters appear. Due to the similar total dipole moments of different water clusters there is practically no change of the breakdown strength in the range 10 to 50 /spl mu/g/g.

Determination of antihypertensive and anti-ulcer agents from surface water with solid-phase extraction-liquid chromatography-electrospray ionization tandem mass spectrometry.

Pharmaceuticals are emerging contaminants in surface water and they must be measured to follow their effects on the aquatic environment. We developed a solid-phase extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (SPE-LC-ESI-MS/MS) method for the determination of twenty-six pharmaceutical compounds - which belong to antihypertensive and anti-ulcer agents - from surface water samples. The selection of pharmaceuticals was based on usage frequency in Hungary. During method development Oasis HLB, SampliQ Polymer SCX and Si-SCX SPE cartridges were tested. As LC eluent ammonium formate, ammonium acetate buffers at pH 3 and 5 were investigated and for quantitation both matrix-matched and internal standard calibration was used. For matrix effect assessment post-extraction spike method was applied which can separate the extraction efficiency from ion suppression for better determination of recovery. Method detection limits (MDLs) varied between 0.2 and 10 ng/L. Precision of the method, calculated as relative standard deviation (RSD), ranged from 0.2 to 14.6% and from 1.2 to 22.4% for intra- and inter-day analysis, respectively. The method was applied to analyze Danube water samples. Measured average concentrations varied between 2 and 39 ng/L for eleven compounds and another one could be detected under LOQ.

Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors

SummaryA complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes.

Analysis of hydrocarbon contamination with membrane-assisted solvent extraction: comparison of agitation and sonication methods.

Membrane-assisted solvent extraction (MASE) coupled to large volume injection was applied to the determination of (gasoline-type) hydrocarbon contamination in water samples. Hexane was used as acceptor phase. 50 microL extract was injected in the programmed temperature vaporizer injector using combined split-splitless evaporation. The extraction conditions were optimized both for MASE with agitation and for MASE with sonication. In the course of optimization the effect of extraction time, extraction temperature, agitation speed, solvent volume, pH, ionic strength and the addition of methanol were tested. Over 75% recovery was accomplished in the range of diesel oil hydrocarbons (n-C(9)-n-C(24)). The developed method was validated. Linearity, accuracy and precision were tested. The method showed excellent linearity between 1 and 1000 microgL(-1) for n-alkanes and between 0.05 and 50 mgL(-1) for gasoline. The method was tested with comprehensive GCxGC as well and found to be non-discriminative to all major compounds of diesel oil.

Study of decomposition of sulphur hexafluoride by gas chromatography/mass spectrometry

When electrical discharges occur in sulphur hexafluoride gas (SF6) lower fluorides are produced within the discharge, and they in turn react readily with impurities, insulators and the electrodes. The final stable compounds formed include sulphur oxyfluorides and sulphur oxides. The aim of the present work was to optimize an analytical method for determining the decomposition products, and finding the dependence of the reaction route followed on the reaction conditions (input energy, contaminants present in the system). By performing model experiments and using various GC/MS techniques, several decomposition products were identified and correlations found between the abundances of the individual components and the decomposition conditions

Determination of furanic compounds in insulating oil by high performance liquid chromatography/mass spectrometry using atmospheric pressure chemical ionization

A method has been developed to determine furanic compounds in insulating oil matrix using liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. The examined samples were provided from model experiments and also from several high voltage functioning transformers. To increase sensitivity of the method six furanic compounds (determined by model experiments) were quantified by selected ion monitoring, and quantitation was based on the marker peaks. Oil samples were prepared using solid phase extraction. The results are suitable for evaluation of model experiments and also to solve problems of calibration. From extracts of oil samples taken from functioning transformers cellulose depolymerization products have been identified, and their amounts were found to be valuable in assessing the condition of the transformer (fault diagnosis).

Identification of phase I metabolites of cardiovascular and anti-ulcer drugs in surface water samples with liquid-chromatography-mass spectrometry methods.

In our study we have identified phase I metabolites of cardiovascular and anti-ulcer agents with the application of predictive multiple reaction monitoring (pMRM) methods with liquid-chromatography-triple-quadrupole mass spectrometry (LC-QQQ-MS) in surface water samples. Targeted accurate mass spectrometry measurements were also carried out for confirmation with liquid-chromatography-time-of-flight mass spectrometry (LC-TOF-MS). pMRM followed by a targeted accurate mass spectrometry measurement can provide a sound basis for the selection of metabolites to be included in analytical methods for the investigation of environmental load of pharmaceuticals. Using LC-QQQ-MS twenty-one metabolites could be identified with two independent transitions at the same retention time and six of them could also be confirmed with LC-TOF-MS.

Seasonal Monitoring of Cardiovascular and Antiulcer Agents’ Concentrations in Stream Waters Encompassing a Capital City

Nowadays monitoring pharmaceutical residues from surface waters is a widespread analytical task. Most of the studies are conducted from river waters or sewage treatment plants and mainly in Western Europe or North America. Such studies are seldom published from Eastern Europe, especially from stream waters, even though the prescription and consumption patterns of drugs as well as wastewater treatment procedures are very dissimilar. In Hungary the active substance of the most often prescribed drugs are cardiovascular and antiulcer agents. Hence in our study compounds belonging to these two groups were seasonally monitored in two main streams encompassing the Buda side of the Hungarian capital city and flowing into the Danube. To obtain data on the occurrence, fate, and seasonal variation of the compounds, samples were taken from altogether eleven points located near wastewater treatment plants and confluences. The results gave no identifiable pattern in the seasonal variation of concentrations but the contribution of the tributaries and wastewater treatment plants could be followed as expected. From the runoff corrected estuary concentrations the annual contribution of these streams to pharmaceutical pollution of the Danube could be estimated to be in excess of 1 kilogram for atenolol, famotidine, metoprolol, ranitidine, and sotalol.

Matrix effect for several derivatives of benzene in water by solid phase microextraction (SPME)

SummaryLevels of several derivatives of benzene were examined in natural surface water (river Zala, West-Hungary) by solid phase micro extraction. Results from the river water samples were compared to the results from spiked double distilled water. The difference in extraction efficiency is termed a “matrix effect”. Large matrix effect causing the change of extraction efficiency experienced in this study. Relationship was found between the matrix effect and TOC, TIC, suspended and the dissolved matter content.