An advanced optic-fiber differential sensing system enhanced by molecularly imprinted polymer for specific sodium benzoate detection

A molecularly imprinted polymer (MIP) based microfiber differential demodulation sensing system for sodium benzoate (SB) concentration detection is proposed. The specific binding of MIP on the surface of microfibers with SB can lead to changes in local refractive index (RI). RI change induces a drift in the interference wavelength, which can be monitored by the power difference between two fiber Bragg gratings (FBGs). The sensing system can detect SB in the concentration range of 0.1–50 μg/ml, and interference wavelength and FBG power difference sensitivities are 0.55 nm/(μg/ml) and 2.64 dB/(μg/ml) in the low concentration range of 0.1–1 μg/ml, respectively, with a limit of detection (LOD) of 0.1 μg/ml. This microfiber differential demodulation sensing system is not only simple to fabricate, but also simplifies the demodulation equipment to reduce the cost, which providing a simple, reliable and low-cost technique for the quantitative detection of SB concentration in beverages and flavoured foods.