Detecting the Cylindrospermopsin using HPLC-PDA and NMR Assignment

Detecting the Cylindrospermopsin using HPLC-PDA and NMR - Assignment ExampleNuclear magnetic resonance (NMR) on the other hand is an analytical technique that uses magnetic nuclei which absorb and re-emit electromagnetic radiations at a specific resonance frequency. This frequency is however dependent on the strength of the magnetic field. The resonance obtained in a magnetic field for any particular compound analyzed is always directly proportional to the strength of the magnetic field. Detection and analysis of cylindrospermopsin using HPLCCylindrospermopsins extradite few methods of detection compared to the well-known microcystins and saxitoxins. High-performance liquid chromatography-photodiode array (HPLC-PDA) has been shown to be a good method for the detection of cylindrospermopsins and its analogs because of their characteristic UV spectra (max at 262 nm). The only limitation of this method is that sample purification is necessary because it is normally co-eluted with othe r contaminants (Welker et al. 2002). Purification of cylindrospermopsin is normally performed using HP-20 resin, which removes most of the ionic components from the fraction.Before the detection of cylindrospermopsins by HPLC, they have to be extracted. Water samples containing the cyanobacterial cells are filtered by glass fiber filters.Extraction procedure The air- dried-out frozen filter samples should be placed on the borosilicate glass tubes and freeze-thawed twice to obtain maximum recover after which 1.2ml of methanol is added and mixed in the bath ultrasonicator for 15 minutes. The samples should further be ultrasonicated individually for 1 minute and the aliquots of the extracts centrifuged at 10,000 ? g for 10 min after which 500 l of the supernatants are transferred to borosilicate vials and evaporated to dryness at 40C under argon. The dried extracts can then be reconstituted in 100 l of 75% methanol and centrifuged in vials at 10,000 ? g for 10 min or filtered by means of the HPLC grade filter. Before running the HPLC, the HPLC system should be set up as described in the manufacturers instructions including degassing, priming and ever-changing columns. The column oven should be set at 40?C and the HPLC changed gradually to starting conditions. The chromatogram samples and standards should be set as per the recommended HPLC gradients using 10