Determination of Orotic acid in milk

Significance of the Topic

Orotic acid is a key intermediate in the synthesis of pyrimidine nucleotides and is often known as vitamin B13. Its concentration in milk provides insight into product quality, nutritional value, and potential metabolic markers. Reliable detection of orotic acid supports quality assurance, regulatory compliance, and research into dairy's role in health.

Objectives and Overview

The primary objective of this method is to establish a high-performance liquid chromatography procedure capable of sensitive and selective quantification of orotic acid in milk. The protocol also addresses the separation of related acids to prevent analytical interference and ensure accurate readings.

Methodology and Instrumentation

• Chromatographic system: HPLC with UV detection at 210 nm
• Stationary phase: Eurokat H, 10 µm particle size, 300 x 8 mm column
• Mobile phase: 0.01 N sulfuric acid, isocratic elution
• Flow rate: 0.6 ml/min
• Column temperature: 60 °C
• Injection volume: 5 µl for samples, 20 µl for standards

Sample preparation included dilution of five grams of milk to 25 ml with 4 mM H2SO4, centrifugation at 2000 rpm for 10 minutes, filtration through a 0.45 µm membrane, and subsequent 1:10 dilution prior to injection.

Main Results and Discussion

The developed method achieved clear resolution between orotic acid, lactic acid, acetic acid, and minor impurities. Representative chromatograms showed distinct peaks at designated retention times. Quantitative analysis yielded 2.2 µg/ml orotic acid in the milk sample, while standard solutions at 15.6 µg/ml demonstrated linear response and reproducibility. The use of an acidic mobile phase enhanced peak shape and stability.

Benefits and Practical Applications

This HPLC protocol offers:

• High specificity for orotic acid against common dairy acids
• Rapid analysis with simple isocratic elution
• Applicability to routine quality control in dairy production
• Utility in nutritional labeling and dietary supplement verification

Future Trends and Potential Applications

• Integration with mass spectrometry for enhanced sensitivity and structural confirmation
• Automation of sample preparation to increase throughput
• Miniaturized systems for point-of-care or in-line monitoring
• Extension of the method to other food matrices and biological fluids

Conclusion

The described HPLC method provides a reliable, straightforward approach for orotic acid determination in milk. Its selectivity, reproducibility, and ease of implementation support diverse applications in dairy quality control and nutritional studies.