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H T Tang

Publications and source records attributed to H T Tang.

5 recordsLinked to original sources
PubMed1991

Flow-injection analysis with electrochemical detection of reduced nicotinamide adenine dinucleotide using 2,6-dichloroindophenol as a redox coupling agent.

The determination of reduced nicotinamide adenine dinucleotide (NADH) by electrochemical oxidation requires a more positive potential than is predicted by the formal reduction potential for the NAD+/NADH couple. This problem is alleviated by use of 2,6-dichloroindophenol (DCIP) as a redox coupling agent for NADH. The electrochemical characteristics of DCIP at the glassy carbon electrode are examined by cyclic voltammetry and hydrodynamic voltammetry. NADH is determined by reaction with DCIP to form NAD+ and DCIPH2. DCIPH2 is then quantitated by flow-injection analysis with electrochemical detection by oxidation at a detector potential of +0.25 V at pH 7. NADH is determined over a linear range of 0.5 to 200 microM and with a detection limit of 0.38 microM. The lower detection potential for DCIPH2 compared to NADH helps to minimize interference from oxidizable components in serum samples.

2,6-Dichloroindophenol↗
PubMed1991

Electrochemical enzyme immunoassay for phenytoin by flow-injection analysis incorporating a redox coupling agent.

Using phenytoin as a model analyte, we demonstrate an electrochemical enzyme immunoassay based on flow-injection analysis and incorporating 2,6-dichloroindophenol (DCIP) as a redox coupling agent. DCIP reacts with NADH to form NAD+ and DCIPH2, the reduced form of the coupling agent. The production of DCIPH2 is monitored at +250 mV vs Ag/AgCl. This low applied potential improves selectivity in the biological matrix, differentiating against components that are oxidizable at the more-positive potentials required for direct electrochemical detection of NADH. The kinetics-based assay also eliminates other common interferences, mainly from ascorbic acid and glutathione. This system does not require precolumns or analytical columns for isolation of the NADH response. Good agreement with a routine clinical laboratory procedure for phenytoin is obtained for clinical samples (r = 0.95), illustrating the feasibility of such an approach.

2,6-Dichloroindophenol↗
PubMed1990

Competitive heterogeneous enzyme immunoassay for theophylline by flow-injection analysis with electrochemical detection of p-aminophenol.

A competitive enzyme-linked immunoabsorbent assay based on the flow-injection amperometric detection of p-aminophenol has been investigated with use of the materials and general procedure of a commercial kit for the determination of theophylline in human serum. The antibody is immobilized on glass beads, and the enzyme label is alkaline phosphatase (EC 3.1.3.1). The high currents generated during the electrochemical detection allowed a rapid (35 min) and simple determination of theophylline throughout its therapeutic range (10-20 mg/L) and also in the subtherapeutic range (detection limit of about 80 micrograms/L).

Aminophenols↗