Dramatic Improvements in Assay Reproducibility for Water-Soluble Vitamins Using ACQUIT Y UPLC and the Ultra-Sensitive Xevo TQ-S Mass Spectrometer

Significance of the Topic

Fortification of infant formula and adult nutritional products with essential water-soluble vitamins is critical to meet dietary requirements and ensure consumer safety. Accurate quantification of vitamins over the product shelf life is necessary to balance initial overages against degradation. High reproducibility in measurements across different batches and laboratories underpins regulatory compliance and label claim verification.

Objectives and Study Overview

This study aimed to develop and validate a single UPLC-MS/MS method for simultaneous quantification of seven water-soluble vitamins (biotin, folic acid, pantothenic acid, niacin, pyridoxine, riboflavin, and thiamine) in fortified products. The focus was to achieve relative standard deviations below 3% and accuracy within acceptable limits over extended periods to improve assay reproducibility and minimize formulation overages.

Methodology and Instrumentation Used

The analytical workflow combined reversed-phase UPLC separation with tandem mass spectrometry detection in positive electrospray ionization mode. Key parameters included:

• Chromatographic system: ACQUITY UPLC with HSS T3 C18 column (1.0 × 100 mm, 1.8 µm) at 60 °C.
• Mobile phases: 0.05% formic acid and 0.01% heptafluorobutyric acid in water (A) and methanol with 10 mM ammonium hydroxide (B) in a gradient elution at 0.15 mL/min.
• Mass spectrometer: Xevo TQ-S triple-quadrupole with MRM transitions optimized for each vitamin and corresponding isotopically labeled internal standards.

Sample preparation involved mixing powdered or ready-to-feed formulations with 1% ascorbic acid, pH adjustment with ammonium hydroxide, settling, and filtration into autosampler vials. Working standards spanned low nanogram to microgram per milliliter ranges and were stabilized in ascorbic acid solution.

Main Results and Discussion

Calibration curves for all vitamins exhibited linearity with r² ≥ 0.999. Intra-day precision across four days yielded RSD values between 0% and 2.8%. Nineteen independent preparations over eight months produced inter-day RSDs below 2.5% for most analytes, with biotin and riboflavin slightly higher. Accuracy relative to NIST SRM 1849a reference values ranged from 100% to 108%. Comparison with literature methods demonstrated a marked improvement, particularly for vitamins that historically showed RSDs above 5%.

Benefits and Practical Applications of the Method

Implementing this multi-analyte UPLC-MS/MS approach offers:

• Rapid, high-throughput analysis of all seven vitamins in a single injection.
• Enhanced precision and accuracy, supporting stricter quality control and regulatory standards.
• Reduced formulation overages and associated cost savings.
• Improved inter-laboratory reproducibility to resolve label claim disputes.

Future Trends and Potential Applications

Ongoing advancements may include expanding the analyte panel to additional vitamins and metabolites, integrating automated sample preparation, and applying high-resolution MS for improved specificity. Collaborative harmonization of methods across laboratories will further strengthen assay reliability. Real-time process monitoring and miniaturized platforms could extend applications to on-site quality control.

Conclusion

The developed UPLC-MS/MS method utilizing the ACQUITY UPLC system and Xevo TQ-S mass spectrometer achieves exceptional reproducibility and accuracy for water-soluble vitamin analysis in fortified nutritional products. This approach supports regulatory compliance and cost-effective manufacturing by minimizing analytical variability and formulation overages.

References

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