Development of electrochemical and colorimetric methods using inorganic nanomaterials for detection of biological and environmental compounds

Abstract

This research comprised of 2 parts including (1) lab-on-paper coupled with electrochemical method for C-reactive protein and colorimetric detection for phosphate ions and (2) the development of chromatographic techniques and its applications. In each part, it can be classified in 2 works. The first work of lab-on-paper is the electrochemical sensor that was fabricated from phosphorylcholine assembled electrodeposited gold nanoparticles onto screen-printed carbon electrode for C-reactive protein detection. Current of ferrocyanide decrease linearly when increase C-reactive protein concentration from 5.0 – 5000 µg L⁻¹. The calculated detection limit equals 1.60 µg L⁻¹. The final part of lab-on-paper is the colorimetry on paper for phosphate ions using 2-mercaptoethanesulfonate modified silver nanoplates. The color changes rely on anti-aggregation mechanism of modified silver nanoplates and europium ions. The paper-based analytical device can use the naked-eye for detection from purple color changing to pink when increase phosphate concentration. The linearity and detection limit are in the range of 1.0 – 30 mg L⁻¹ and 1.0 mg L⁻¹, respectively. For the development of chromatographic techniques and its applications, the first part is the separation of 4 important insecticides; dinotefuran, thiamethoxam, clothianidin, and imidacloprid using ultra-high-performance liquid chromatography coupled with amperometry detection. The complete separation was finished within 8 minutes using reverse-phase chromatography. The analytical signals increase when employing electrodeposited copper-gold nanoparticles. The detection limit and linear range of 4 significant insecticides were in the range of 0.19 – 0.62 mg L⁻¹ and 1.0 – 250 mg L⁻¹, respectively. The second work is the separation of amino acids using open tubular liquid chromatography. The current signals were measured on copper electrode. The separation of amino acids depends on the ion exchange affinity between quaternary amine on the resin and amino acids. The electrochemical detection arises from the oxidation of copper to form complexes between copper and amino acid. The developed method has detection limit of 0.42 mg L⁻¹. Moreover, all presented methods are simple, fast, and inexpensive. The methods are applied in real samples covering food, environmental compounds, and biomarkers.