A colorimetric and fluorometric microplate assay for the detection of microcystin-LR in drinking water without preconcentration.
Protein phosphatase inhibition assays currently used for the detection of cyanobacterial peptide hepatotoxins in drinking water require an enrichment step using C18 cartridges to achieve lower the detection limit. This paper describes a colorimetric and fluorometric protein phosphatase inhibition method for the direct detection of microcystin-LR (MCYST-LR) in drinking water without complex clean-up steps and preconcentration procedures. In this assay three different substrates, p-nitrophenyl phosphate (p-NPP) and two fluorogenic compounds, 4-methylumbelliferyl phosphate (MUP) and 6,8-difluoro-4-methylumbelliferyl phosphate DiFMUP), were tested. The detection limits of the assay are 0.25 and 0.1 microg/l using colorimetric and fluorometric methods, respectively. These levels are well below the provisional guideline value for MCYST-LR of 1 microg/l of drinking water. The detection limit of the fluorometric method is comparable to that of the classical ELISA test. Although both the latter tests allow the detection of MCYST-LR in drinking water directly without pretreatment, the protein phosphatase inhibition assay remain less expensive and therefore more attractive for use in the routine assessment of drinking water contamination by microcystins.
Bouaícha
N
N
Laboratory of Public Health-Environment, University of Paris XI, Faculty of Pharmacy, 5, Rue J.B. Clément, 92296 Châtenay-Malabry, France. noureddine.bouaicha@cep.u-psud.fr
Maatouk
I
I
Vincent
G
G
Levi
Y
Y
D001427:Bacterial Toxins / Q000032:analysis; D003124:Colorimetry / Q000379:methods*; D000458:Cyanobacteria; D004791:Enzyme Inhibitors / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay; D005470:Fluorometry / Q000379:methods*; D006923:Hymecromone / Q000031:analogs & derivatives* / Q000378:metabolism; D008387:Marine Toxins; D052998:Microcystins; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010456:Peptides, Cyclic / Q000032:analysis*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water / Q000032:analysis*
C119285:6,8-difluoro-4-methylumbelliferyl phosphate; D001427:Bacterial Toxins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010456:Peptides, Cyclic; D014867:Water; C008644:nitrophenylphosphate; C005359:4-methylumbelliferyl phosphate; D006923:Hymecromone; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR