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Biomedical subjects

M Jekel

Publications and source records attributed to M Jekel.

28 records · Page 2Linked to original sources
PubMed2000

Analysis of sulfonated naphthalene-formaldehyde condensates by ion-pair chromatography and their quantitative determination from aqueous environmental samples.

An ion-pair solid-phase extraction (IPE), ion-pair chromatography (IPC) procedure with fluorescence detection for the quantitative analysis of sulfonated naphthalene-formaldehyde condensates (SNFC) was developed, which provides full resolution of SNFC up to a degree of condensation n = 5 and partial resolution up to n = 15. Liquid chromatography-electrospray ionization-mass spectrometry confirmed that SNFC elute in the order of condensation. Response factors in fluorescence detection proved to be mass-constant, thereby allowing us to determine total SNFC amounts. With this IPC method, the weight- and the number-average molecular weights of these high-volume production chemicals (kiloton per annum), used as synthetic tanning agents, concrete plasticizers, and dispersants, can be determined. Recoveries in IPE range from 73 to 85% in river Rhine water and from 79 to 93% in tap water for n = 2 to n = 7 with limits of detection of 3-8 ng/L for individual homologues from 500 mL of water. The IPE-IPC procedure was applied to samples of secondary industrial effluents, river Rhine water, a river bank filtrate, and a groundwater sample. SNFC up to n = 6 were detected in the treated effluents. Total concentrations ranged from 208 micrograms/L in a secondary treated SNFC production effluent to < 1.4 micrograms/L in groundwater. These first analyses suggest a widespread occurrence of the lower oligomers of SNFC in the aquatic environment.

Chromatography, Liquid↗
PubMed2000

Occurrence of triiodinated X-ray contrast agents in the aquatic environment.

High concentrations of adsorbable organic iodine (AOI) are found in municipal treatment plant effluents and surface waters by specific organic halogen determination. The high AOI is caused by widely used triiodinated X-ray contrast agents, which are very stable and hydrophilic. We have analysed specifically surface water influenced by a municipal treatment plant effluent, the surface water after bank filtration and raw drinking water. The X-ray contrast agents were determined by liquid chromatography-mass spectrometry with positive electrospray ionization after enrichment by solid phase extraction. Diatrizoate and iopromide, two triiodinated contrast agents are detectable in all samples, whereby the less polar component iopromide seems to be reduced during bank filtration. Just a trace of iopromide is identified in surface water after bank filtration and in the raw drinking water. Approximately 60% of the initial AOI is extractable and approximately 25% of the extractable AOI can be identified as specific triiodinated contrast agents.

Chromatography, High Pressure Liquid↗
PubMed2000

Application of ion-chromatography for the determination of the organic-group parameters AOCl, AOBr and AOI in water.

A method of differential AOX-analysis, i.e. the simultaneous determination of AOCl, AOBr and AOI is described. Individual steps of the method including enrichment at activated carbon, combustion in an oxygen stream and ion-chromatographic detection were optimized. In most cases quantitative recoveries of various organic Cl, Br and I containing substances of different polarity and structure were obtained. The method was applied to the determination of AOX-fractions in municipal and hospital wastewater. A good agreement between conventional coulometric and the described ion-chromatographic determination was found. High concentrations up to 130 microg/L I of organic iodine compounds were measured in the influent and effluent of a municipal treatment plant in Berlin and up to 10 mg/L I in a hospital waste-water.

Chromatography, Ion Exchange↗
PubMed2000

Ultrasound conditioning of suspensions--studies of streaming influence on particle aggregation on a lab- and pilot-plant scale

Suspension conditioning by ultrasound induced particle aggregation in a 3.3 MHz standing wave field was investigated in lab- and pilot scale sedimentation reactors (sonicated volume approx. 375 ml and 10 l). These were equipped with a variable number of acoustically transparent film (ATF) elements, inserted perpendicular to the sound propagation direction. ATFs control the development of undesired large-range Eckart-type acoustic streaming and thermal convection. ATF insertion led to increased separation efficiency especially for particles smaller than 10 microns. Results with a varied geometric set-up indicate the existence of an optimum for the number of ATFs inserted. Optical investigation of particle behaviour in different pilot plant configurations showed reduced streaming within the divided 24 mm pathlength sonic chamber, whereas at 100 mm pathlength, turbulent streaming dominated.

Journal Article↗
PubMed2000

Observation of yeast cell movement and aggregation in a small-scale MHz-ultrasonic standing wave field.

Aggregation of suspended yeast cells in a small-scale ultrasonic standing wave field has been monitored and quantified. The aggregation effect is based on the acoustic radiation force, which concentrates the cells in clumps. The ultrasonic chamber employed (1.9 MHz, one wavelength pathlength) had a sonication volume of 60 microl. The aggregation process was observed from above the transducer through a transparent glass reflector. A distinct, reproducible, pattern of clumps formed rapidly in the sound field. The sound pressure was estimated experimentally to be of the order of 1 MPa. Microscopic observations of the formation of a single clump were recorded onto a PC. The time dependent movement patterns and travelling velocities of the cells during the aggregation process were extracted by particle image velocimetry analysis. A time dependent change was seen in the particle motion pattern during approach to its completion of clump formation after 45 s. Streaming eddies were set-up during the first couple of seconds. The scale of the eddies was consistent with Rayleigh micro-streaming theory. An increase in the travelling velocity of the cells was observed after 30 s from initially about 400 microm s(-1) to about 1 mm s(-1). The influence of a number of mechanisms on particle behaviour (e.g. micro-streaming, particle interactions and convective flow) is considered. The experimental set-up introduced here is a powerful tool for aggregation studies in ultrasonic standing waves and lays the foundation for future quantitative experiments on the individual contributions of the different mechanisms.

Acoustics↗
PubMed1999

Detection and identification of sulphonamide drugs in municipal waste water by liquid chromatography coupled with electrospray ionisation tandem mass spectrometry.

High-performance liquid chromatography coupled with positive-ion electrospray ionisation tandem mass spectrometry was used for the determination and confirmation of 13 sulphonamide drugs in environmental water samples in the low ng/L-range. Enrichment with concentration factors of 130-670 was performed by solid phase extraction, achieving recoveries of 50 to 90%. After gradient elution HPLC, detection and quantification was performed using selected reaction monitoring (SRM) with limits of detection between 0.2 and 3.7 microg/L. Confirmation was obtained by either SRM transitions of collision induced dissociation reactions or daughter ion mass spectra. Primary and secondary effluents of municipal waste water treatment plants and different surface waters were examined. The compounds sulphamethoxazole and sulphadiazine were detected and confirmed with concentrations ranging between 30-2000 ng/L and 10-100 ng/L, respectively. The compound sulphamethizole was detected in low amounts but could not be positively confirmed.

Chromatography, High Pressure Liquid↗
PubMed1999

Use of volatile amines as ion-pairing agents for the high-performance liquid chromatographic-tandem mass spectrometric determination of aromatic sulfonates in industrial wastewater.

The use of trialkylamines (triethylamine, N,N-dimethyl-n-butylamine, and tri-n-butylamine) as volatile ion-pairing agents for the high-performance liquid chromatographic separation of aromatic sulfonates was investigated. Negative ion electrospray tandem mass spectrometry was used to detect both singly and multiply charged analyte ions. Sensitivity of detection was strongly reduced by amine concentrations above 2.5 mmol l(-1) in the eluent. With tributylamine as ion-pairing agent 19 aromatic sulfonic acids could be determined using time-scheduled selected reaction monitoring. Lowest orders of detection range from 3 to 74 microgl(-1). Several naphthalenesulfonic acids were determined in dyeing baths and textile wastewater in concentrations ranging from 0.1 mgl(-1) to 2.1 mgl(-1). A degradation product of sulfonated azodyes was identified in the effluent of a laboratory treatment plant.

Amines↗
PubMed1995

The periplasmic endonuclease I of Escherichia coli has amino-acid sequence homology to the extracellular DNases of Vibrio cholerae and Aeromonas hydrophila.

The gene endA, encoding the periplasmic endonuclease I (EndoI) of Escherichia coli, was identified on a cloned chromosomal 1.5-kb HindIII fragment. The nucleotide sequence of the fragment revealed an open reading frame (ORF) coding for a polypeptide of 235 amino acids (aa). The ORF preceeded by a region with two possible promoter sites displays promoter activity when cloned into an expression vector. On the C-terminal side, two sequences with putative transcription termination function are present. The predicted aa sequence suggests the presence of a signal peptide of 22 aa and a signal peptide cleavage site. A cold-shock supernatant from cells harbouring a multicopy endA+ plasmid contained an approx. tenfold higher amount than wild-type cells of the DNA double-strand- and single-strand-cleavage activities characteristic of EndoI. The growth rate and viability of the cells was not affected. The predicted aa sequence of the ORF is 60 and 54% identical to the sequence of extracellular DNases from Vibrio cholerae and Aeromonas hydrophila, respectively.

Aeromonas hydrophila↗
PubMed1977

Studies on the effect of parenteral iron, Ferastral, an iron-poly(sorbitol-gluconic acid) complex, on blood coagulation in man.

The possible influence of Ferastral, an iron-poly(sorbitol-gluconic acid) complex, on blood coagulation in man was investigated. Ferastral added to plasma produced no changes in blood coagulation until a final concentration of 2 000 microgram/ml (35.8 mmol/1) was used, when minimal changes in blood coagulation factors were observed. Five patients were given an intramuscular injection of 250 mg Ferastral. No changes in blood coagulation and thrombocyte function were observed up to 5 hours after the initial iron injection.

Adult↗