Simple, optimized liquid-chromatographic method for measuring total hydroxyproline in urine evaluated

Area of Science:

• Analytical Chemistry
• Biochemistry

Background:

• Hydroxyproline (HYP) is a key component of collagen, and its urinary levels reflect collagen metabolism.
• Accurate measurement of urinary HYP is crucial for diagnosing and monitoring conditions related to collagen turnover.
• Existing colorimetric methods for HYP quantification are often time-consuming and lack specificity.

Purpose of the Study:

• To develop and validate an optimized high-performance liquid chromatography (HPLC) method for the accurate and efficient measurement of total hydroxyproline (HYP) in urine.
• To compare the performance of the new HPLC method with a conventional colorimetric assay.

Main Methods:

• Urine samples underwent solid-phase hydrolysis using Dowex 50W x 8 ion-exchange resin to release HYP from peptides.
• The released HYP was derivatized using 4-chlor-7-nitrobenzo-2-oxa-1,3-diazole.
• Separation and quantification were performed using reversed-phase HPLC with S-carboxymethylcysteine as an internal standard.

Main Results:

• The optimized HPLC method achieved a total assay time of 14 minutes.
• The method demonstrated excellent linearity (3.6 µmol/L to 10 mmol/L), precision (between-batch CV < 5.1%), and recovery (95% ± 1.4%).
• HPLC results correlated well with a colorimetric method but were approximately 15% higher, suggesting more complete hydrolysis.

Conclusions:

• The developed HPLC method offers significant improvements in assay time, specificity, sensitivity, and precision compared to colorimetric methods.
• This optimized HPLC assay provides a more accurate and efficient tool for assessing urinary hydroxyproline levels.
• The method is suitable for routine clinical and research applications involving collagen metabolism studies.