Direct and replacement ion chromatography with potentiometric detection using a silver/silver bromide electrode

The use of Ag/AgX electrodes as potentiometric detectors in modern ion chromatography methods is re-examined. Contrary to previous reports, in both flow-injection and chromatographic experiments the Ag/AgBr electrode is shown to exhibit the greatest sensitivity to the widest range of anions tested. For direct detection in non-suppressed ion chromatography systems, use of the Ag/AgBr electrode permits the measurement of separated anions at levels lower than those obtainable by the conventional conductivity method. The Ag/AgBr electrode is further shown to be useful as a sensitive detector in replacement ion chromatography. In this case, all anions separated in a suppressed system are quantitatively replaced by bromide before the effluent passes through the electrochemical detector. Cation measurements can also be made by monitoring the exchange of bromide for co-eluting counter hydroxide ions following the replacement stage of the system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28132/1/0000583.pd

Measurement of melatonin in body fluids: Standards, protocols and procedures

Abstract: The circadian rhythm of melatonin in saliva or plasma, or of the melatonin metabolite 6‐ sulphatoxymelatonin in urine, is a defining feature of suprachiasmatic nucleus function, the endogenous oscillatory pacemaker. These measurements are useful to evaluate problems related to the onset or offset of sleep and for assessing phase delays or advances of rhythms in entrained individuals. Additionally, they have become an important tool for psychiatric diagnosis, its use being recommended for phase typing in patients suffering from sleep and mood disorders. Thus, the development of sensitive and selective methods for the precise detection of melatonin in tissues and fluids of animals emerges as necessary. Due to its low concentration and the co‐existence of many other endogenous compounds in blood, the determination of melatonin has been an analytical challenge. This review discusses current methodologies employed for detection and quantification of melatonin in biological fluids and tissues

Ion-chromatographic monitoring of main components of rain water in industrial and rural sites in Germany

The paper discusses long-term changes in concentrations of major inorganic ions in rain water collected in urban and rural areas in Germany. Ion chromatography with conductivity detection is applied for the chemical analysis of precipitation samples. A comparison of concentrations measured at two stations is presented. In addition, those results are correlated with other parameters of rain water such as conductivity and pH