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Two thin layer chromatographic (TLC) procedures were evaluated for the capacity screening of cyanobacterial peptide hepatotoxins and anatoxin-a in laboratory-cultured strain samples and in natural bloom samples. Seventy-five samples previously investigated with the reference methods, the chief of which was mouse bioassay, were analyzed blindly by TLC. Forty-three of the samples were hepatotoxic according to the reference methods, and 39 of them were found to contain peptide hepatotoxins by TLC coupled to u.v.-densitometry. Seven samples contained anatoxin-a according to the reference methods, and five of these were found to contain anatoxin-a by TLC, using derivatization with Fast Black K salt. Four of the samples which were neurotoxic by mouse bioassay also contained hepatotoxins by TLC. Twenty-four samples were nontoxic according to the reference methods, and in 23 of these no toxins were found by TLC either.

Reverse osmosis and vacuum distillation are commonly used for desalination when purifying drinking water from sea or brackish water. The ability of these methods to remove nodularin, a hepatotoxin produced by the cyanobacteria Nodularia spumigena , was investigated. For this purpose, natural brackish water was contaminated with toxic algal material. Nodularin concentrations of raw and purified water were determined after a solid-phase extraction procedure employing high-performance liquid chromatography. In the case of reverse osmosis (Freshwater R MT 5000B) the initial nodularin concentration was 10.0 μg/litre, but, after a concentration programme which included recycling the wastewater and discharging the purified water, the final nodularin concentration after 19.5 h was 32.3 μg/litre. The nodularin concentration of the purified water always remained below the limit of quantitation, which was 0.5 μg/litre, but, by the end of the experiment, when both the nodularin and salt concentrations had increased threefold, traces of nodularin were detected. The specific conductivity of the purified water increased simultaneously. In the case of vacuum distillation, the nodularin concentration of brackish raw water was 70 μg/litre and the test was performed using a Rotavapor R-114 instrument at 60°C to simulate an existing purification method. No nodularin was detected in the distillate. Both reverse osmosis and vacuum distillation removed nodularin effectively. When brackish water is to be purified by reverse osmosis, conductivity measurement can be used to monitor the effectiveness of the purification result.

A method for facile high-capacity screening of algal samples for anatoxin-a (ANTX-a), a potent neurotoxin of Anabaena flos-aquae, is presented. The method is based on in situ colour reaction of algal extracts containing ANTX-a on a thin-layer chromatographic plate with the diazonium reagent Fast Black K salt, and subsequent separation of the orange-red product. The product, shown to be a stable 3,3-dialkyltriazene, is derived from a reaction involving the aliphatic secondary amino group of ANTX-a. The detection limit for ANTX-a is 10 micrograms g-1 of lyophilized algal material, which is comparable to earlier methods using more complex instrumentation.

The selenium content of Finnish bedrock is low, and the availability of selenium to plants is poor for climatological and geochemical reasons. Therefore all multinutrient fertilizers sold in Finland have been enriched with selenium (selenate) since 1984. Selenate is known to be soluble for at least 3 months after this addition. Soluble selenium can leach into surface and ground waters. The sorption of added selenate in 18 different types of cultivated Finnish soils was studied. In a 7-day incubation trial the sorbed fraction varied from 3.6 to 24.6% from the added amount of 5000 μg Se kg −1 soil. Sorption correlated positively with the clay content, iron content and surface area of the soils and negatively with sulphuric acid-extractable phosphorus. By stepwise multiple linear correlation analysis a model revealed that sulphuric acid-extractable phosphorus explained 63.7% of the variation in sorption, iron content increased the explanation rate to 74.7% and the clay content to 81.5%. The results suggest that in Finnish soils the sorption tendency is higher in fine textured soils and increases with weathering.

Visualization reactions for the thin-layer chromatographic (TLC) analysis of cyanobacterial hepatotoxins microcystins and nodularin were studied. Of the 17 potential reactions tested, nine yielded either coloured, fluorescent, or both products with the purified toxins. The detection limit of pure microcystin-LR in these reactions ranged from 10 to 250 ng. Feasibility of the reactions for water analysis was studied in fortified 50–500 ml water samples. The best result was obtained with N,N-dimethyl-1,4-phenylendiammonium dichloride (N,N-DPDD). A water analysis method meeting the WHO drinking water guideline concentration value, 1 μg/l of microcystin-LR, was developed employing N,N-DPDD. The method was tested by analyzing blind 38 authentic natural water samples, studied earlier by the enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PP). In 31 samples the results of all three methods were consistent. Two apparently false positive results were obtained by TLC, and in two samples results were positive by ELISA and TLC but not PP. In one sample the result was positive by PP but not ELISA or TLC. Two samples were positive by ELISA and PP and not TLC, but a full 50 ml sample for TLC was not available in these cases, thus making the detection limit higher. Results suggest that the present TLC method is comparable with the ELISA and PP assays, and TLC can be used for cost-effective monitoring of water samples according to the WHO guidelines.