Isotope edited internal standard method for quantitative surface-enhanced Raman spectroscopy

A new isotope edited internal standard (IEIS) method for quantitative surface-enhanced Raman spectroscopy (SERS) is demonstrated using rhodamine 6G (R6G-d(0)) and rhodamine 6G (R6G-d(4)) edited with deuterium. The reproducibility and accuracy of the IEIS method is investigated both under optical resonance (SERRS) and non-resonance (SERS) conditions. A batch-to-batch concentration measurement reproducibility of better than 3% is demonstrated over a concentration range of 200 pM-2 μ M with up to a factor of 3 difference between the concentration of the analyte and its IEIS. The superior performance of the IEIS method is further illustrated by comparing results obtained using absolute SERS/SERRS intensity calibration (with no internal standard) or using adenine (rather than R6G-d4) as an internal standard for R6G concentration quantization. Potential biomedical gene expression and comparative proteomic applications of the IEIS method are discussed.