Quantitative analysis via Surface Enhanced Raman Scattering from Ag nano-colloids utilizing an oscillating cell and right-angle collection geometry

We examine the application of an oscillating cell in combination with right-angle Raman scattered light collection geometry for quantitative Surface Enhanced (Resonance) Raman Scattering (SER(R) S) measurements from nano-colloidal noble metal solutions. This excitation/collection Raman configuration allows specific SERS and SERRS signatures of aqueous solutions of mitoxantrone, an antitumor drug, to be easily resolved at (sub)-ng/mL and (sub)-pg/mL concentration levels. A partial least-squares (PLS) chemometric algorithm was applied to predict the concentration of 25 mL of aqueous solutions of mitoxantrone added in 0.5 mL of a silver colloidal solution in a test tube attached to the oscillating cell. For SERS (514.5 nm) measurements, this was performed over the range from 0 to 13 ng/mL with a correlation coefficient R-2 of 98.5% and RMS error of prediction equal to 0.5 ng/mL. SERRS (632.8 nm) measurements performed over a range of 0 to 7 pg/mL gave R-2 = 98.92% and RMSE = 0.2 pg/mL.