Liquid-chromatographic determination of 5-S-L-cysteinyl-L-dopa with electrochemical detection in urine prepurified with a phenylboronate affinity gel.
A phenylboronate affinity gel has been investigated for use in the prepurification of urine before "high-performance" liquid chromatography and electrochemical determination of 5-S-L-cysteinyl-L-dopa. At pH 5.6 this naturally occurring 5-S-cysteinyldopa was adsorbed on a phenylboronate column and was quantitatively eluted with trichloroacetate, pH 3.0. This pretreatment of urine before "high-performance" liquid chromatography produced satisfactory chromatographic separations, and the results were further improved when the purification procedure also included treatment on a cation exchanger. By using 5-S-D-cysteinyl-L-dopa--a diastereomer to 5-S-L-cysteinyl-L-dopa--as an internal standard, we have developed a practical routine method for the quantitative determination of urinary 5-S-L-cysteinyl-L-dopa. The precision (CV = 2.4%) and analytical recovery (96.9%, SD 5.3%) were satisfactory and the results obtained correlated well with a previously described method.
D001897:Boronic Acids; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003548:Cysteinyldopa / Q000302:isolation & purification / Q000652:urine*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives*; D004563:Electrochemistry; D005260:Female; D006801:Humans; D008297:Male; D012015:Reference Standards; D013223:Statistics as Topic; D013237:Stereoisomerism
D001897:Boronic Acids; D003548:Cysteinyldopa; D004295:Dihydroxyphenylalanine; C010686:benzeneboronic acid