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Biomedical subjects

R A Wallingford

Publications and source records attributed to R A Wallingford.

8 recordsLinked to original sources
PubMed1990

Estimation of free dopamine in the cytoplasm of the giant dopamine cell of Planorbis corneus by voltammetry and capillary electrophoresis.

Voltammetric electrodes having a tip diameter of 2-12 microns and microscale capillary zone electrophoresis have been used for dynamic and static monitoring of dopamine in the somal cytoplasm of the giant dopamine neuron of Planorbis corneus. Intracellular dopamine levels can be altered by extracellular application of dopamine or ethanol. The latter experiment provides a means to estimate total stores of endogenous dopamine, and the evidence presented suggests that at least 98% of these stores are bound and not directly accessible to the cytoplasm.

Animals↗
PubMed1989

Separation of serotonin from catechols by capillary zone electrophoresis with electrochemical detection.

Capillary zone electrophoresis with electrochemical detection is demonstrated with columns having only 9-microns inner diameter. Amperometric detection limits of 0.7 amol are reported for serotonin. The difficult problem of resolving serotonin and dopamine--two neurotransmitters of interest having similar electrophoretic mobilities--is addressed by chemical means to improve selectivity. These include buffer modification with 2-propanol and a system employing borate complexation of the catechol in combination with sodium dodecyl sulfate micelles.

Catecholamines↗
PubMed1989

Capillary electrophoresis.

The combined techniques that comprise capillary electrophoresis are under rapid development for a wide range of molecules and sample types. The capillary format provides fast, highly efficient separations and makes automation possible. At present, systematic approaches to separation methodology are still in the development stages and better detection schemes need to be developed. There is no doubt that electrophoresis in a capillary tube will take its place as a substitute for HPLC in specific applications. This is especially apparent when analysis time, efficiency, or simplicity is of greatest concern. Capillary electrophoresis will prove extremely useful for separations of nucleotides and proteins for analytical purposes in biotechnology. Finally, the ability to use ultrasmall-volume samples makes capillary electrophoresis ideal for the development of separations-based sensors for the analysis of microenvironments.

Electrophoresis↗
PubMed1988

Retention of ionic and non-ionic catechols in capillary zone electrophoresis with micellar solutions.

The use of micellar solutions in capillary zone electrophoresis has been primarily relegated to separations of non-ionic solutes, while its applicability to cationic species has been unexplored. We have found that the use of sodium dodecyl sulfate micelles in phosphate buffer allows for tremendous gains in selectivity for several cationic and non-ionic catechols over what can be obtained with normal capillary zone electrophoresis. Complexation of catechols with boric acid alters the net charge on the solutes and changes the partitioning behavior to produce adequate selectivity with improved analysis times. Although the mechanisms of solute interaction with the micellar phase for the cationic species are not decisively known, evidence is presented supporting the existence of ion-pairing equilibria simultaneously accompanied by micellar solubilization.

Borates↗