An ion-pair extraction detector for the sensitive and selective fluorescence detection of some basic drugs, pesticides, and their metabolites is described. The addition of the ion-pairing reagent dimethoxyanthracene sulfonate (DAS) prior to the column permits a drastic simplification of the detector design. The influence of the DAS concentration, pH, buffer concentration, and organic polarity modifier (methanol) on the separation of the above compounds carried out in the reversedphase mode on various chemically bonded materials has been
We review ion-selective solvent polymeric membrane electrodes for clinical use. The particular requirements that the clinical application set on the membrane are discussed in terms of selectivity, stability, lifetime, and response time. The performance of currently available electrodes is reviewed, with consideration of actual problems that arise in clinical practice.
The authors thank Joel Harris for his helpful comments regarding the treatment of the data. This paper is dedicated to Cheves Walling on the occasion of his 70th birthday.
Requirements for the applicability of anion-selective electrodes in clinical analysis are discussed in terms of selectivity, response time, lifetime and stability. Basically, classical anion-exchangers, electrically charged carriers and electrically neutral carriers may be used as anion-selective components in solvent polymeric membranes. While classical ion-exchanger-based membrane electrodes are only of limited practical relevance, sensors containing ion carriers seem to bear a broad potential with regard to the feasibility of realizing the required properties. The control of the selectivity determining properties of electrically neutral tin organic anion carriers probably allows the development of sufficiently selective membranes for the assay of clinically relevant anions. Furthermore, the incorporation of membrane technology into the design of such carrier membranes may lead to fully optimized sensors.
A series of new neutral hydrogen ion carriers suitable for application in H+-selective microelectrodes is presented. One carrier (ETH 1907) proves to be superior to tridodecylamine currently very much in use. Microelectrodes based on ETH 1907 in an optimized membrane composition exhibit a linear dynamic response function from pH 2 to 9 extended into the acidic range, a response time less than or equal to 5 s, and a resistance of about 35 G omega for a tip diameter of about 1 micron. This makes the electrode suitable for measurements at normal physiological intracellular pH as well as in acid physiological media. Measurements using this microelectrode in proximal tubule cells of isolated perfused frog kidney are presented.
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