Fluorescence is a much more intense phenomenon than Raman scattering by several orders of magnitude - if the exciting laser for Raman also excites fluorescence then that can swamp the Raman signal. The way to overcome this is to use a different Raman laser frequency which does not excite fluorescence. The picture below show a sample of motor oil - on the left is the spectrum obtained with a 785nm laser handheld device. On the right is the same sample run using a handheld spectrometer with a 1064nm laser. Moving the excitation to longer wavelengths avoids exciting fluorescence and in this case the Raman spectrum is virtually fluorescence free and readily identified by the handheld's search algorithm.
RESULT: Succsessful implementation of handheld Raman for RMID