UBC Theses and Dissertations
Molecularly imprinted polymers-based colorimetric-SERS dual biosensor for the detection of atrazine in apple juice Zhao, Bowen
Atrazine is a harmful herbicide that can disrupt the hormonal system in humans and animals. Contamination of atrazine in various agri-food products occurs due to illegal uses. Detection of atrazine in foods is time consuming and expensive when the official methods such as gas chromatography-mass spectrometry are applied. In this thesis project, we developed a dual biosensor integrating molecularly imprinted polymers (MIPs) with gold nanoparticles (AuNPs)-based colorimetric assay and surface enhanced Raman spectroscopy (SERS), which can be applied for rapid, high-throughput and sensitive determination of trace levels of atrazine in agri-food products (e.g., apple juice). This biosensor includes three functions: separation, screening, and quantification. For separation, MIPs were synthesized using molecular imprinting technology by employing atrazine as the template molecule. MIPs-based solid phase extraction (MIPs-SPE) could selectively separate atrazine from apple juice with high recoveries (~93%). AuNPs-based colorimetric assays were able to rapidly detect atrazine due to ligands between atrazine molecules and the surface of AuNPs. High-throughput screening of a large number of samples could be achieved with simple color variation with the limit of detection (LOD) as low as 0.01 mg L-¹. For quantification, SERS tests were conducted using AuNPs for Raman spectral collection. Raman spectra of apple juice samples with different concentrations of atrazine were rapidly collected and analyzed by chemometrics. The calculated LOD equals to 0.0012 mg L-¹ and limit of quantification (LOQ) was 0.0040 mg L-¹, both of which meet the guidelines set up by Health Canada (i.e., 0.005 mg L-¹). Three types of AuNPs with different diameters (i.e., 43 nm, 27 nm, 11 nm) were synthesized and compared for the use of this biosensor. The largest AuNPs worked best for colorimetric assays while the medium-size AuNPs were the most suitable candidate for SERS tests. The extremely low LOD and LOQ strongly validate the potential application of this innovative dual biosensor for accurate and high-throughput determination of atrazine in foods.
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