UV Raman detection of micro-organisms and their toxins in fish tissue

H. Ne1son', Department of Chemistry and J.F. Sperry, Department of MicrobiologyUniversity of Rhode Island, Kingston, RI 02881P.E. Hargraves, Graduate School of Oceanography, Bay CampusUniversity of Rhode Island, Narragansett, RI 02882andE.G. Hanlon, R.R. Dasari and M. FeldHarrison Spectroscopy LaboratoryMassachusetts Institute of Technology77 Massachusetts Avenue, Cambridge MA 02139AbstractIt has been determined that domoic acid(DA) can be quantitated from homogenizedshellfish tissue by means of resonance Raman spectra excited by 25 1 nm light. Detectionlimits have been found to be substantially below the 20 micrograms DA per gram tissuedeemed by regulators to be unfit for human consumption. Clam tissue obtained from asupermarket has been prepared for analysis by direct homogenization for 2 minutes in aWaring blender. The homogenized samples were placed in a flow system and subjectedto a 5- 10 mw 25 1 nm excitation. Back-scattering collected for 20-30 seconds providedsufficient information for analysis. The method is extremely simple to use since the DAproduces a single intense peak at 1652 cm'. Because relatively-weak protein, nucleicacid and lipid spectra are excited from the tissue, background interference is surprisinglylow. Bacteria can be detected using the same approach, but sensitivities are much lowerprimarily due to spectral interference from tissue nucleic acids.a. to whom correspondence should be addressed.