HPLC Analysis of Soft Drinks Using Alliance™ iS HPLC System

Importance of the Topic

Ensuring accurate quantification of common soft drink additives such as caffeine, benzoate, sorbate, acesulfame K, saccharin and aspartame is critical for product consistency, safety and regulatory compliance. Aspartame, in particular, degrades in solution to diketopiperazine and related species, which can interfere with additive measurements. A robust analytical method is therefore essential in beverage quality control and research settings.

Objectives and Overview of the Study

This study evaluates a 17-minute isocratic HPLC method implemented on the Waters Alliance iS HPLC System to simultaneously separate and quantify six soft drink additives and aspartame degradation products. Key aims were:

• Assess injection precision and linearity over a wide volume range (0.2–20 µL).
• Confirm resolution of aspartame degradants from target analytes.
• Demonstrate method performance in real commercial beverage samples.

Methodology and Instrumentation Used

Standards and mobile phases were obtained from the Waters Beverage Analysis Kit. The final standard contained 150 mg/L acesulfame K, 100 mg/L saccharin, 200 mg/L benzoate, 100 mg/L sorbate, 100 mg/L caffeine and 50 mg aspartame. Carbonated soft drinks were sonicated, filtered (0.2 µm PVDF) and directly injected.

Chromatographic conditions:

• Column: XBridge BEH Phenyl XP 4.6×150 mm, 2.5 µm, 130 Å, 35 °C.
• Mobile phase: Waters preformulated beverage buffer, isocratic.
• Flow rate: 1.6 mL/min, run time: 17 min.
• Detection: Tunable UV at 214 nm, 10 Hz data rate.
• Sample manager washes: preformulated wash solvents.
• Data system: Empower 3.6.

Main Results and Discussion

Injection precision was excellent: six replicates at each volume yielded R2>0.9999 over 0.2–20 µL, with residual errors within ISO limits for pipettes. Aspartame degradation was induced by aging standards for two weeks; two degradant peaks (2.1 min and 4.34 min) were fully resolved from all additives with a critical resolution of 2.3. Method migration from an Arc HPLC system required no major adjustments, demonstrating robustness.

Analysis of five commercial beverages showed caffeine levels from 96 to 300 mg/mL. The high injection precision allowed injection volume adjustment in lieu of manual dilution to align sample peaks with calibration curves. Aspartame exhibited higher RSD over two days due to instability, whereas other analytes remained stable.

Benefits and Practical Applications of the Method

• Fast 17-minute isocratic run for six additives and degradants.
• High injection accuracy enabling direct analysis of high-content samples.
• Complete separation of aspartame degradants from analytes.
• Reduction of manual sample dilution steps.
• Use of preformulated reagents simplifies preparation and lowers disposal costs.

Future Trends and Opportunities

Advances in column technology and high-pressure capabilities will further shorten analysis times and enhance resolution. Integration with online sample preparation and mass detection could extend applicability to trace-level contaminants. Data-driven quality control and automated method transfers between platforms will streamline beverage analytics in regulated environments.

Conclusion

The Alliance iS HPLC System provides a fast, precise and robust solution for simultaneous separation and quantification of key soft drink additives and aspartame degradation products. Its injection accuracy and high-pressure capability enable direct analysis of diverse beverage matrices with minimal sample preparation.

Reference

1. Li R, et al. Simultaneous Determination of Synthetic Edible Pigments in Beverages by Titania-Based RP-HPLC. Arabian J Chemistry. 2020;13(2):3875–3881.
2. Lino CM, Peña A. Occurrence of Caffeine, Saccharin, Benzoic Acid and Sorbic Acid in Soft Drinks and Nectars in Portugal. Food Chemistry. 2010;121(2):503–508.
3. Yang J, Rainville PD. Analysis of Soft Drink Additives with No Interference from Aspartame Degradants Using Arc HPLC System with PDA Detection. Waters Corp. 2021;720007219.
4. Pipette Standards Handbook. Troemner. Available from manufacturer documentation.
5. Van Vliet K, et al. Aspartame and Phe-Containing Degradation Products in Soft Drinks Across Europe. Nutrients. 2020;12(6).
6. Perzborn M, Syldatk C, Rudat J. Enzymatic and Microbial Degradation of Cyclic Diketopiperazines. AMB Express. 2013;3(1):51.