ABSTRACT
Effects of adsorption to plastics and solvent conditions in the high performance liquid chromatographic analysis of the cyanobacterial toxin microcystin-LR were investigated. Aqueous microcystin-LR readily adsorbed to the disposable polypropylene pipette tips commonly used in laboratory manipulations. This was not affected by the pH or salinity of the solution. Furthermore, dilutions of microcystin-LR in varying concentrations of methanol and acetonitrile influenced the quantification of the microcystin-LR concentration by high performance liquid chromatography.
Subject(s)
Chromatography, High Pressure Liquid/methods , Peptides, Cyclic/analysis , Plastics/chemistry , Solvents/chemistry , Water/chemistry , Adsorption , Hydrogen-Ion Concentration , Marine Toxins , Microcystins , Peptides, Cyclic/chemistry , Sodium ChlorideABSTRACT
The effect of plastic and methanol on the loss of microcystin-LR from solution was analysed by HPLC with photodiode array detection (HPLC-PDA). With plastic disposable pipette tips, the loss from an aqueous microcystin-LR (MC-LR) solution was 4.2% per tip operation. Using the same pipette tip, four operations were required to completely saturate a single tip with toxin. MC-LR attached to plastic pipette tips could subsequently be eluted by methanol and detected by HPLC-PDA. At methanol concentrations below 25% (v/v), recovered concentrations of MC-LR decreased significantly. Differences in MC-LR concentration were also noted by performing 50% dilution with Milli-Q water or methanol. The results are discussed in relation to the hydrophobicity of MC-LR, analytical procedures and the avoidance of toxin losses from solution during laboratory manipulations.
Subject(s)
Bacterial Toxins/isolation & purification , Peptides, Cyclic/isolation & purification , Adsorption , Chromatography, High Pressure Liquid , Marine Toxins , Microcystins , SolutionsABSTRACT
Two types of commercially available ELISA kits for the immunoassay of cyanobacterial microcystins were evaluated for potential interference effects due to methanol, salinity, pH, plasticware and cyanobacterial extract. Of the treatments examined, methanol had the greatest effect, giving false positive microcystin concentrations with increasing methanol concentrations up to 30% (v/v) compared with the negative calibrators of each kit. False positive microcystin results were also produced with increasing salinity up to full strength seawater. Decreases in microcystin-LR equivalents were observed when assaying purified microcystin-LR at pH values between 6.25 and 10. Aqueous microcystin-LR solutions in plastic microcentrifuge tubes after pipetting with disposable plastic tips had lower toxin concentrations than expected when analysed by ELISA. Indicated microcystin concentrations in cyanobacterial extracts varied between kit types and the choice of blanks used. Although ELISAs can be useful tools for the screening of water and cyanobacterial blooms for microcystins and nodularins, users should be aware that commercial kits can be susceptible to interference by commonly encountered environmental and laboratory conditions and materials.
