A Versatile Electrochemical Immunoassay for the Simultaneous Detection of Multiple Analytes

1 page(s

Zeptomole-detecting biosensor for alkaline phosphatase in an electrochemical immunoassay for 2,4-dichlorophenoxyacetic acid

A bienzyme substrate-recycling biosensor in a flow injection analysis system is described for the sensitive measurement of alkaline phosphatase (ALP) and applied to the fast readout of a competitive immunoassay for the widely used pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). The phenol-indicating biosensor consists of a Clark-type electrode covered by a membrane with coentrapped tyrosinase and quinoprotein glucose dehydrogenase. ALP dephosphorylates phenyl phosphate to phenol (K(m) = 36 microM) outside the flow system. Phenol is oxidized in the sensor membrane by the oxygen-consuming tyrosinase via catechol to o-quinone. The quinone is reconverted to catechol by glucose dehydrogenase. This substrate cycling results in a 350-fold amplified sensor response to phenol. The oxygen consumption of the enzyme couple in the presence of phenol is monitored as a decrease in current. A total of 3.2 fM ALP (320 zmol/ 100 microL) has been detected after a 57.5 min incubation with phenyl phosphate. All involved reagents are stable over the time of measurement. The sensor does not produce any measurable blank signals. The immunoassay detects 0.1 microgram/L 2,4-D, the maximum concentration for pesticides allowed in drinking water by European Community regulations. The applicability of this biosensor for fast immunoassay readout is demonstrated by a 2 min incubation. By comparison, a standard photometric method (p-nitrophenyl phosphate) requires overnight incubation

Determination of Manganese in Whole Blood by Cathodic Stripping Voltammetry with Indium Tin Oxide

Manganese (Mn) is a required trace metal in the body. In recent years however, it has garnered significant attention as a developmental neurotoxin in children with chronic exposure. It has been linked to complications such as memory loss with negatively associated IQ scores, attention deficit hyperactivity disorder (ADHD), and in extreme cases, the development of a Parkinson's disease analogue-manganism. Cathodic stripping voltammetry (CSV) has proven to be a suitable method for electroanalytical determination of Mn. We have established Mn CSV using indium tin oxide (ITO) as the working electrode for the determination of Mn in bovine whole blood after an acid digestion. Reliable, accurate, and precise results were obtained, as only 9% variation in the digested blood was observed. The CSV results were compared with graphite-furnace atomic absorption spectroscopy (GF-AAS) and inductively coupled plasmamass spectrometry (ICP-MS) and favorable agreement across the methods was observed. Due to ITO's excellent positive potential window and stability under harsh environments, this method could be applied to other oxide-forming transition metals detectable by CSV

ARGONNE HIGH-FLUX RESEARCH REACTOR-AHFR CONCEPTUAL DESIGN STUDY

This report presents a reactor design to meet the needs of the basic research program at Argonne National Laboratory. The program requires some irradiations in thermal neutron flux approaching 5 x 10/sup 15/n/ (cm/sup 2/ )(sec) and some beam experiments having over 10/sup 15/ n/(cm/sup 2/) available. Parametric studies indicate that the highest peak thermal flux per unit of reactor power can be obtained in an internal H/sub 2/ reflector having a radius of about 6 cm. Since the design effonts recognized total reactor cost as a mator parameter, an all H/sub 2/O-cooled system was adopted as most expedient. Further, the design and calculations effont was directed toward operating conditions which require little or no research effort. This latter point is a recognition both of the over-all cost plus a desire to meet the needs of research in the shortest possible time. (auth