Fig. 1: Variations in piperacillin Raman spectra in human urine due to sample treatment.

Representative vector normalized median Raman spectra of a 1000 µM solution of piperacillin in human urine before (orange) and after treatment (blue) and their difference (black). The effects of freezing (a), filtration (b), centrifugation (c), and a combination of filtration and centrifugation (d) were investigated, showing only small changes in the overall spectra and signal intensities.