Urinary free methyldopa determined by reversed-phase high-performance liquid chromatography

Area of Science:

• Analytical Chemistry
• Pharmacology

Background:

• Accurate quantification of free methyldopa is crucial for pharmacokinetic studies and clinical monitoring.
• Existing methods may lack the sensitivity or specificity required for reliable analysis in complex biological matrices like urine.

Purpose of the Study:

• To develop and validate a sensitive and specific chromatographic method for determining free methyldopa in human urine.
• To establish a reliable analytical procedure adaptable for both research and routine clinical laboratory applications.

Main Methods:

• A reversed-phase high-performance liquid chromatography (HPLC) method was developed using octadecyl-bonded silica.
• 3,4-dihydroxybenzylamine served as the internal standard for quantification.
• Urine samples were processed via alumina adsorption and elution prior to direct injection.
• Detection was performed using ultraviolet (UV) at 280 nm with an acetate buffer mobile phase (pH 2.7).

Main Results:

• The method demonstrated excellent separation of methyldopa from other urinary biogenic amines and common antihypertensives/diuretics.
• Sensitivity was adequate for quantifying 8.0 mg/L in 30 mL samples, with a lower limit of detection of 25 ng.
• High analytical recovery (95-102%) and low coefficients of variation (2.7% within-run, 3.8% day-to-day) were achieved.

Conclusions:

• The described chromatographic method provides a sensitive, specific, and reliable means for quantifying free methyldopa in human urine.
• This validated procedure is well-suited for pharmacokinetic investigations and routine clinical laboratory analysis.