Determination of methylisoborneol in channel catfish pond water by solid phase extraction followed by gas chromatography-mass spectrometry

Several compounds exist which are responsible for unwanted taste and odor characteristics that have been found in the edible tissue of the channel catfish (Ictalurus punctatus). Methylisoborneol (MIB), one compound responsible for these off-flavors, is produced through the metabolism of cyanobacteria in aqueous systems such as reservoirs and ponds. The channel catfish accumulates MIB in its tissues from the intake of its culture-pond water. Current methods of analysis for MIB, such as closed- and open-loop stripping, and liquid-liquid extraction, are time-consuming and labor-intensive. A method for the analysis of MIB in catfish culture-pond water is described which, unlike other methods, is rapid, inexpensive, and does not require specialized sample preparation equipment. This method utilizes C18 solid-phase extraction followed by capillary gas chromatography with detection by mass spectrometry. Standard MIB and the internal standard, butylisoborneol (BIB), were prepared from the reaction of -camphor with methylmagnesium chloride and n-butyllithium, respectively. Extraction efficiencies for MIB in channel catfish pond water averaged 89% at 101 parts per trillion (ppt) and 84% at 202 parts per billion (ppb). The detection limit of the method was calculated to be 11.5 ppt.