| On-site analysis is an important task in analytical chemistry. Electrochemical sensors provide unique advantages for on-site analysis because of their remarkable sensitivity, low power consumption, and portable instrumentation. This dissertation focuses on the development of electrochemical sensors and miniaturized instrumentation suitable for the detection of clinically important compounds at the point-of-care, and for the in-situ monitoring of environmental contaminants.; A hand-held potentiometric stripping analyzer was developed for detection of trace metals at the point-of-care, while a pocket-sized square-wave voltammetric stripping analyzer was designed for integration into a remote probe suitable for in-situ monitoring of important environmental contaminants. The compact hardware designs for both the miniaturized analyzers were aimed at addressing the challenges of low power consumption, small size, easy operation, and reliability without compromising analytical performance. The excellent analytical performance was validated with bench-top instruments.; Based on screen-printing technology, a prototype of a reagent-integrated disposable sensor was developed for testing lead levels in children's blood. The composition of the decomplexation reagent. that releases lead(II) from blood cells was carefully optimized. The ‘one-sensor-one-testing’ protocol simplified the sample pretreatment so that the testing can be operated by non-analytically-skilled users with minimum training. Only 20 μL of finger-stick blood sample is needed for one testing. The analytical performance was validated by different methods. A screen-printed electrode strip was used as amperometric detector in a microfabricated capillary-electrophoresis system. The separation channel was micromachined on a glass chip. Such a combination of a microseparation system with a disposable sensor strip obviates the need for permanent attachment of the detector, and allows the easy and fast replacement of the working electrode. The versatility, simplicity, low cost, and applicability were demonstrated by separation and detection of mixtures of nitroaromatic explosives or catecholamines.; A remote reagent-renewable flow sensor was developed for in-situ monitoring of environmental contaminants in waters. The in-situ sampling was achieved by a strand of dialysis hollow fibers integrated in the flow probe. This probe integrated in-situ sampling, on-line reaction and detection in one unit. Different reaction and detection protocols were achieved by manipulating the on-line reagent delivery. |
