Preparation of sensors for the amaranth detection in beverages

Within the scope of the study, an Amaranth imprinted surface plasmon resonance (SPR) sensor was prepared for the determination of Amaranth, an azo group food dye used in beverages and various food products and reported to be harmful to health, using molecular imprinting technique. First of all, Amaranth imprinted nanoparticles (MIP) were prepared by polymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxy ethyl methacrylate (HEMA) using methacrylic acid (MAA) and acrylamide (AM) as functional monomers. For the control group experiments, Amaranth non-imprinted nanoparticle (NIP) synthesis was made with the same chemicals without using Amaranth. The prepared nanoparticles were characterized by Zeta-size analysis, FTIR-ATR spectroscopy and scanning electron microscopy (SEM). SPR gold chip surface was modified with allyl mercaptan to bind nanoparticles and Amaranth imprinted nanoparticles were immobilized on SPR chip surface. The sensor chip surface was characterized by ellipsometry, contact angle and atomic force microscopy (AFM). After the characterization processes, Amaranth solutions with different concentrations (0.1-150 mg/mL) were prepared with pH 7.4 phosphate buffer with the Amaranth imprinted sensor were analyzed and the measurement sensitivity of the sensor was investigated. As a result of the calculations were made with the obtained sensorgrams, it was found that the prepared sensor measured with 99% accuracy, the calculated limit of detection (LOD) was 0.0180 mg/mL, and the limit of quantification (LOQ) was 0.06 mg/mL. Measurements and evaluations were made with Amaranth solutions at different concentrations were used to determine the adsorption kinetics and it was determined that the most suitable adsorption model Langmuir model for the prepared sensor. For the selectivity studies of the sensor, Tartrazine and Allura Red solutions, which are the same azo group at food dyes which were used. Real sample analysis of the sensor prepared for the determination of Amaranth from beverages, Amaranth was determined from fruit juice samples which were sold in the market, and the amount of Amaranth in fruit juices was determined with the sensorgrams obtained. Liquid chromatography-mass spectrometry (LC-MS) technique was used for validation studies. After all the analyzes, the reusability and stability of the sensor were investigated with kinetic analyzes performed on the same day consecutively and at 1, 2, 4, and 6 months as the last operation. As a result of the studies have shown that the prepared Amaranth-imprinted SPR sensor is a sensitive, fast, simultaneous and reusable, cost-effective technique for the determination of Amaranth from beverages.