High performance liquid chromatography with fluorescence and ultraviolet detection of polynuclear aromatic hydrocarbons in barley malt.

A simple, rapid method has been developed for the separation and determination of polynuclear aromatic hydrocarbons (PAHs) in barley malt. An ultrasonic-cyclohexane extraction method was used to separate the PAHs from ground barley malt. The cyclohexane extracts were purified by chromatography through a water-deactivated silica gel-alumina column. The eluate from the column was concentrated and purified further by partitioning between dimethyl sulfoxide (DMSO) and cyclohexane. The DMSO extract was diluted with water and the PAHs were extracted back into cyclohexane. The cyclohexane extract was washed with water, dried through sodium sulfate, and evaporated, and the resulting residue was dissolved in 80% aqueous acetonitrile-methanol (1 + 1) and subjected to reverse phase high performance liquid chromatography. Thirty barley malt samples were analyzed using this procedure. Peaks having the same retention time as the carcinogen benzo(a)pyrene were isolated from 18 of the samples, and were equivalent to trace levels ranging from less than 0.1 to 0.2 ppb. Average recoveries of 11 PAHs, including benzo(a)pyrene, benzo(b)fluoranthene, indeno(1,2,3-cd)pyrene, and benz(a)anthracene, added to 25 g samples at 2.5 and 5 ppb, ranged from 78 to 97%, with a mean relative standard deviation of 6.6%.