Biomedical subjects

M C Hennion

Publications and source records attributed to M C Hennion.

22 records · Page 2Linked to original sources

PubMed1997

[Determination of phycotoxins in aquatic medium by capillary electrophoresis].

Marine phycotoxins present a major public health problem due to their ability to contaminate seafoods. Toxic phytoplankton is not limited, however, to the coastal areas in Europe. There are more and more problems in freshwater reservoirs, in lakes, and in ponds from which grazing animals get their water. Okadaic acid (OA), a polyether toxin from the marine dinoflagellate, Prorocentrum lima, and microcystins (MCYSTs), a potent hepatotoxic cyclic heptapeptides produced by many strains of cyanobacteria have been shown to be a powerful tumor promotor. Thus, considerable effort has been undertaken to find sensitive and easy detection techniques for the determination of phycotoxins from various matrices (microalgae, freshwater, mussels, fish, ...). Different biological and chemical methods have been developed to identify these toxins in shellfish and fish. The mouse bioassay method has been widely used for the detection of toxins such as maitotoxin and ciguatoxin, which are not easily identified by chemical procedures. In this report we describe a capillary electrophoretic method that enables us to detect okadaic acid, microcystins (MCYST-YR, MCYST-LR, MCYST-RR) and maitotoxin in picogram range.

Animals↗

PubMed1996

Detection of cyanobacterial toxins (microcystins) in cell extracts by micellar electrokinetic chromatography.

A micellar electrokinetic chromatography (MEKC) method with UV detection is described for the rapid and efficient separation of three microcystins: microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR) and microcystin-RR (MCYST-RR). A detection limit of 7.5 pg for each toxin was achieved. The UV intensities of these toxins measured at 200 nm showed good linearity in the range 7.5-150 pg. The production of MCYST-LR in three cultured strains of cyanobacteria, namely Microcystis aeruginosa strain IP7806, Microcystis aeruginosa strain IP7813 and Oscillatoria agardhii strain IP7805, was evaluated.

Bacterial Toxins↗

PubMed1993

Determination of carbaryl and some organophosphorus pesticides in drinking water using on-line liquid chromatographic preconcentration techniques.

Reversed-phase high-performance liquid chromatography (HPLC) was adapted for the determination of trace concentrations of carbaryl and seven organophosphorus pesticides in drinking water. Between 100 and 300 ml of water sample is passed through a 1.5-cm precolumn, packed with C18-bonded silica or styrene-divinylbenzene copolymer (PRP-1) sorbent at a flow-rate of 3 ml/min. The HPLC system is then switched to an acetonitrile-water gradient elution programme. The analytes that have been concentrated on the precolumn are eluted and separated on a 15-cm C18 analytical column and are determined by measuring their UV absorption at 254 nm. This wavelength was selected as the optimum for the simultaneous determination of these pesticides. The preconcentration yields of the examined solutes obtained with the two types of precolumn are almost identical. Band broadening is avoided by a suitable choice of the C18 precolumn and the analytical column. With 200 ml of tap water, the recoveries for most of the examined pesticides were ca. 90%, except for carbaryl (54%). The detection limits are in the range 0.03-0.2 micrograms/l.

Carbaryl↗

PubMed1993

Determination of phenoxyacid herbicides in drinking water at the ppt-level by liquid chromatography and on-line selective preconcentration.

On-line precolumn sample handling using an anion-exchanger is applied to preconcentrate phenoxyacid herbicides in aqueous samples prior to their LC separation. Since direct percolation of large sample volumes through the ion-exchanger has to be avoided owing to the high content of inorganic anions in natural waters, a two-step preconcentration is carried out: phenoxyacids are concentrated in their neutral (acidic) form by percolation of natural samples at pH 1 first through a precolumn packed with the copolymer-based PRP-1 sorbent. Then, the PRP-1 precolumn is coupled on-line with a second one packed with the anion-exchanger and 3 ml of deionised water with 35% of acetonitrile allows the phenoxyacids to be desorbed from the PRP-1 sorbent and reconcentrated on the anion-exchanger in their ionic form. The content of the anion-exchanger is analysed on-line by coupling with a C18 analytical column and elution is made with a water-acetonitrile gradient. Detection limits in drinking water from a 500-ml sample are between 15 and 35 ng/l (ppt) and identity of phenoxyacids is reinforced by the fact that analytes are preconcentrated by the anion-exchanger. This methodology can be fully automated.

2,4-Dichlorophenoxyacetic Acid↗