Urinary free norepinephrine and dopamine determined by reverse-phase high-pressure liquid chromatography

Area of Science:

• Biochemistry
• Analytical Chemistry
• Clinical Chemistry

Background:

• Accurate measurement of catecholamines like norepinephrine and dopamine in urine is crucial for diagnosing various medical conditions.
• Traditional methods for urinary catecholamine analysis can suffer from imprecision and interference.
• A need exists for a more robust and reproducible assay for free norepinephrine and dopamine.

Purpose of the Study:

• To develop and validate a reverse-phase high-pressure liquid chromatography (RP-HPLC) method for the simultaneous quantification of free norepinephrine and dopamine in human urine.
• To assess the precision, sensitivity, and reliability of the developed HPLC assay.
• To compare the performance of the HPLC method against the established trihydroxyindole fluorometric assay.

Main Methods:

• Human urine samples were processed using alumina extraction to isolate catecholamines.
• Extracted catecholamines were analyzed using RP-HPLC with an octadecyl-silica column and acetic acid mobile phase.
• Ultraviolet detection at 280 nm was employed for quantification.
• Assay sensitivity was determined, and intra-assay and inter-assay coefficients of variation were calculated for norepinephrine and dopamine.

Main Results:

• The HPLC method demonstrated high precision, with day-to-day coefficients of variation of 4.7% for norepinephrine and 3.5% for dopamine.
• The assay is sensitive, detecting urinary concentrations as low as 5 µg/liter.
• Comparative studies indicated that the liquid-chromatographic procedure is more precise and less prone to interference than the trihydroxyindole fluorometric method.

Conclusions:

• The developed reverse-phase high-pressure liquid chromatography method provides an efficient, reproducible, and accurate means for simultaneously measuring free norepinephrine and dopamine in human urine.
• This assay is readily adaptable for routine clinical laboratory use, offering advantages over traditional methods.
• The improved precision and reduced interference make this HPLC technique a valuable tool for clinical diagnostics involving catecholamine analysis.