Mamoru Taki

Analysis of plasma catecholamines by high-performance liquid chromatography with fluorescence detection: simple sample preparation for pre-column fluorescence derivatization.

Analysis of plasma catecholamines (norepinephrine, epinephrine and dopamine) by high-performance liquid chromatography using 1,2-diphenylethylenediamine as a fluorescent reagent is described. We have developed an automatic catecholamine analyser, based on pre-column fluorescence derivatization and column switching. The analysis time for one assay was 15 min. The correlation coefficients of the linear regression equations were greater than 0.9996 in the range 10-10,000 pg/ml. The detection limit, at a signal-to-noise ratio of 3, was 2 pg/ml for dopamine. A new method of sample preparation for the pre-column fluorescence derivatization of plasma catecholamines was used. In order to protect the catecholamines from decomposition, an ion-pair complex between boric acid and the diol group in the catecholamine was formed at a weakly alkaline pH. The stabilities of plasma catecholamines were evaluated at several temperatures. After complex formation, the catecholamines were very stable at 17 degrees C for 8 h, and the coefficients of variation for norepinephrine, epinephrine and dopamine were 1.2, 4.2 and 9.3%, respectively.

High-sensitivity micro ultraviolet absorption detector for high-performance liquid chromatography

Abstract A UV absorption detector with a 0.6-μl flow cell for high-performance liquid chromatography (HPLC) was developed. In order to improve the signal-to-n

Low dead volume coulometric detector for liquid chromatography

Abstract A low dead volume coulometric detector flow cell for liquid chromatography was designed. Its cylindrical flow cell structure is simple and the cell volume is extremely small. The working and counter electrodes are made of bundled carbon fibres, and the working and counter electrode compartments are separated by a cation-exchange tube. The detector is applicable to many types of compounds. The detection limit for catecholamines is 0.05 pmol.