Quantification of dopamine in biological samples by surface-enhanced Raman spectroscopy: Comparison of different calibration models

- An attempt was made to quantify dopamine in plasma and urine using SERS technique.
- The performance of different models for determining dopamine was compared.
- Only MEMSERS achieved quite accurate and precise concentration predictions for DA.
- This work has further proved the ability of MEMSERS in quantitative SERS assays.

In this contribution, an attempt was made to quantify dopamine (DA) in complex biological samples (i.e., plasma and urine) using surface-enhanced Raman spectroscopy. Silver nanoparticles modified with iron-nitrilotriacetic acid (DA-selective probe) and 4-mercaptobenzoic acid (internal standard) were used as enhancing substrate. The performance of different calibration models for the quantification of DA in plasma and urine samples spiked with DA was evaluated and compared. The calibration models investigated were univariate ratiometric model based on the intensity ratio between the characteristic SERS peaks of DA and 4-mercaptobenzoic acid, PLS models built on the raw, standardized or pre-processed SERS measurements, and multiplicative effects model for surface-enhanced Raman spectroscopy (MEMSERS). Experimental results showed that among the models considered in this contribution, only MEMSERS achieved quite accurate and precise concentration predictions for DA in the spiked plasma and urine samples with recovery rates varying within the range of 91.9-112%, surprisingly better than the corresponding values of the quantitative results obtained by LC-MS/MS. This work provided further evidence of the effectiveness of MEMSERS in solving the problem of poor accuracy of quantitative SERS assays.