Determination of Sweeteners, Preservatives, and Caffeine in Various Food and Consumer Products Using the Agilent 1290 Infinity II LC

Importance of the topic

Precise monitoring of food additives such as artificial sweeteners, preservatives, and caffeine is essential for regulatory compliance, consumer safety, and quality control. These compounds influence product shelf life, taste, and functionality, and their levels are strictly regulated due to potential health impacts.

Objectives and study overview

This study aimed to develop a rapid, sensitive, and robust liquid chromatography method using an Agilent 1290 Infinity II system with a diode array detector (DAD) and evaporative light scattering detector (ELSD) to simultaneously determine nine common additives in various food and consumer product matrices within a 10-minute run time.

Instrumentation used

• Agilent 1290 Infinity II High-Speed Pump (G7120A)
• Agilent 1290 Infinity II Multisampler (G7167B)
• Agilent 1290 Infinity II Multicolumn Thermostat with 2-position/6-port valve (G7116B, G4231B)
• Agilent 1290 Infinity II Diode Array Detector (G7117B)
• Agilent 1290 Infinity II Evaporative Light Scattering Detector (G7102A)

Methodology and sample preparation

Samples (soft drinks, dairy products, marmalade, candy, toothpaste) underwent minimal preparation including degassing, dilution with methanol or water, centrifugation, and filtration. Chromatographic separation used a ZORBAX Eclipse Plus C18 RRHD column (2.1×100 mm, 1.8 µm) with a water/methanol/triethylamine/formic acid and acetonitrile/methanol gradient at 0.6 mL/min. A valve diverted highly polar, nonretained solutes to waste for the first minute to minimize ELSD baseline noise. DAD wavelengths (235 nm for most additives; 285 nm for caffeine) and ELSD settings were optimized for sensitivity.

Main results and discussion

All nine target additives were baseline resolved within 10 minutes. The valve switch significantly improved ELSD baseline stability by excluding early-eluting matrix components. Calibration across 10–600 ppm showed linearity (R²>0.998) and repeatability (RSD<5%). Application to real samples demonstrated accurate quantification of sweeteners, preservatives, and caffeine with recoveries ranging from 74 % to 126.5 % under minimal sample preparation.

Benefits and practical applications

• Rapid analysis with total run time below 10 minutes including re-equilibration.
• Minimal sample preparation streamlines routine QC workflows.
• Simultaneous UV and ELSD detection enables accurate quantification of both UV-active and non-UV analytes.
• Valve switching enhances ELSD performance in complex matrices.

Future trends and potential applications

Integration with mass spectrometry could broaden analyte coverage and improve specificity. Automated online cleanup and high-throughput platforms may further increase sample throughput. Expanding the approach to other food and beverage matrices and adapting the method for regulatory monitoring can support evolving quality and safety requirements.

Conclusion

The described Agilent 1290 Infinity II LC method with DAD-ELSD and valve diversion offers a fast, sensitive, and reliable solution for quantifying sweeteners, preservatives, and caffeine in diverse products. Its robust performance and minimal sample preparation make it well suited for routine food testing and quality control laboratories.