Detection of total protein in milk using phosphomolybdic acid-mediated surface-enhanced Raman spectroscopy

Abstract

Although many surface-enhanced Raman scattering (SERS)-based methods for detecting specific proteins have been studied, simple and direct detection of total protein in liquid using a SERS-based method remains difficult. In this study, a distinguishable effect on the SERS spectra from pre-mixture of phosphomolybdic acid (PMA) with protein was found, indicating that PMA could be used as a SERS reporter for total protein detection in a liquid sample. Further experiments confirmed a good linear relationship between a premixed concentration of protein (casein, whey protein or bovine serum albumin) and the SERS intensity of PMA in our SERS system. Using casein as a reference, a PMA-mediated SERS method was proposed that can quantitatively analyze protein at 2.5–25 µg/ml with a limit of detection of 1.5 µg/ml. Our PMA-mediated SERS method is a simple and rapid method for quantitative analysis of total protein in milk. Copyright © 2015 John Wiley & Sons, Ltd.