AN ANALYTICAL METHOD FOR ANATOXIN-a, A BLUE GREEN ALGAL
NEUROTOXIN, IN RESERVOIR WATER
Report No FR0363
C P James and H A James
The ability to determine the levels of the blue-green algal neurotoxin, anatoxin-a, in reservoir water will enable monitoring work to be undertaken to determine its environmental levels, its persistence, and its removal during water treatment.
To develop an analytical method for anatoxin-a in reservoir water down to levels of 100 ng l-1.
Anatoxin-a is a blue-green algal neurotoxin which is known to have caused animal deaths following ingestion of toxin-containing blue-green algal cells. As some species of blue-green algae which produce this toxin occur in waters used, after treatment, for public supply there is a need to determine its levels (if any) in such waters.
IV RESUME OF CONTENTS
A method has been developed which allows levels of anatoxin-a in reservoir water to be measured. Several alternative detection techniques have been investigated. The most sensitive, negative ion chemical ionisation mass spectrometry (applied following the formation of the pentafluoropropionyl (PFP) derivative of anatoxin-a) allows levels above 10 ng l-1 to be determined. Gas chromatography with electron capture detection, using the same derivatisation procedure, allows levels down to 150 ng l-1 to be measured. A more rapid analysis, by examination of water extracts using high performance liquid chromatography, allows levels down to 250 ng l-1 to be detected. In all cases, reproducibility and coefficients of variation are acceptable.
Anatoxin-a can be quantified in reservoir waters at levels well below 100 ng l-1 using GCMS analysis with negative chemical ionisation. If many samples require analysis, HPLC analysis provides more rapid results although the limit of detection is higher.
Toxicity data on anatoxin-a are required to establish a level of interest for this toxin in reservoir waters. This will determine which of the alternative detection techniques is most appropriate. Although the reproducibility and coefficients of variation are acceptable, the use of an internal standard would provide improvements in this respect.
The method needs to be applied to reservoir waters when blue-green algae are present, to provide data on levels of anatoxin-a present.
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