Fluorimetric Method for the Determination of Histidine in Random Human Urine Based on Zone Fluidics

Abstract

In the present study, the determination of histidine (HIS) by an on-line flow method based on the concept of zone fluidics is reported. HIS reacts fast with o-phthalaldehyde at a mildly basic medium (pH 7.5) and in the absence of additional nucleophilic compounds to yield a highly fluorescent derivative (λex/λem = 360/440 nm). The flow procedure was optimized and validated, paying special attention to its selectivity and sensitivity. The LOD was 31 nmol·L−1, while the within-day and day-to-day precisions were better than 1.0% and 5.0%, respectively (n = 6). Random urine samples from adult volunteers (n = 7) were successfully analyzed without matrix effect (−1 with percentage recoveries in the range of 87.6%–95.4%.

Keywords

• histidine
• random human urine
• zone fluidics
• <i>o</i>-phthalaldehyde
• derivatization
• stopped-flow