Method development for determination of ß-agonists using colorimetric and electrochemical sensors

Abstract

This dissertation focused on the development of analytical sensors for quantitative analysis of various electroactive compounds such as β-agonists and neurotransmitters, which could be considered as important indicators for food-safety monitoring, drug doping control in sports, clinical testing, and health care inspection. Up to date, colorimetry and electrochemistry are the two attractive approaches that have extensively been employed as analytical sensing tools, due to their simple operation and interpretation, fast analysis time, good ability of coupling with other techniques, and high capability of miniaturization. With these two detection platforms, this dissertation would then be divided into two main parts: (1) The development of integrated platforms for the colorimetric sensor and its application; and (2) The development of integrated platforms for the electrochemical sensor and its application. In the first section, the transparency-based colorimetric sensor for salbutamol determination relying on the redox reaction was developed. Digital camera was used as the optical readout, and the noticeable color change, induced through the oxidation of salbutamol by strongly oxidizing permanganate (KMnO4), could then be monitored. In the second part, the selective electrochemical sensors were developed and classified into three sub-sections. For the first sub-section, the anti-fouling PdNPs-modified BDD electrode was combined with UHPLC separation system for the simultaneous determination of four β-agonists. The remarkable improvement in analytical efficiency regarding fast analysis and fouling resistance capability was attained. In the second sub-section, the molecularly imprinted polymer (MIP) with selective recognition of salbutamol was electrochemically synthesized and immobilized onto the polyaniline (PANI)-modified screen-printed graphene electrode. A great enhancement in selectivity of the proposed sensing system towards the oxidation of the target analyte (Salbutamol ; SAL), could be obtained. Lastly, in the third sub-section, the synergistically electrocatalytic activity and the selectivity improvement of the trimetallic CuNiAu alloy towards the oxidation of monoamine neurotransmitters were first examined. The corresponding trimetallic CuNiAu composite was modified onto the screen-printed graphene electrode, and the developed electrochemical sensor was subsequently used for the simultaneous determination of serotonin (5-HT) and norepinephrine (NE). The enhanced analytical performance regarding the sensitivity and selectivity of this sensor could be achieved. Conclusively, the developed colorimetric and electrochemical sensors thoroughly studied in this dissertation could offer good sensitivity, high selectivity, affordability, simplification, and high-throughput analysis with great potential to be further developed for on-site applications.