Ultrafast Analysis of Food Preservatives Using Automated Column Regeneration and Dual-Needle Injection

Importance of the Topic

Rapid, reliable detection of food preservatives supports quality control and consumer safety. Traditional HPLC methods, while robust, can be time-consuming. Ultra high-performance liquid chromatography with sub-2 μm particle columns combined with dual-needle injection and automated column regeneration addresses the growing need for high-throughput analysis in food testing, enabling faster turnaround without sacrificing accuracy.

Objectives and Study Overview

This study evaluates an ultrafast workflow for analyzing common food preservatives using an Agilent 1290 Infinity II system equipped with dual-needle injection and automated alternating column regeneration (ACR). The main goals were to:

• Reduce analysis cycle time by over 60% for a seven-compound preservative mix
• Assess injection volume linearity and carryover with caffeine and chlorhexidine
• Investigate retention time and peak area precision across inter- and intraneedle, and inter- and intracolumn setups

Methodology and Instrumentation

• Instrumentation:
  • Agilent 1290 Infinity II LC with dual G7120A high-speed pumps
  • Multicolumn thermostat, 2-position/10-port switching valve, and Agilent OpenLAB CDS ChemStation
  • Diode array detector and 1290 Infinty II multisampler with dual-needle option
• Columns:
  • ZORBAX SB C18, 4.6 × 150 mm, 5 μm
  • ZORBAX RRHD Eclipse Plus C18, 2.1 × 50 mm, 1.8 μm
• Samples and standards:
  • Preservative mix: benzoic acid, sorbic acid, methyl-, ethyl-, propyl-, butyl-4-hydroxybenzoates, butylated hydroxyanisole
  • Caffeine dilutions (0.5–16 μL injections) for volume linearity
  • Caffeine and chlorhexidine injections at 1,000 ng for carryover assessment
• Chromatographic conditions:
  • Mobile phase: water + 0.1% TFA / acetonitrile + 0.1% TFA or ammonium formate buffer with acetonitrile
  • Flow rates: 0.5–1.5 mL/min; column temperatures 40–50 °C
  • Ultra-fast gradient cycles of 0.7–1.1 minutes with smart overlap enabled

Key Results and Discussion

• Injection volume linearity exhibited excellent correlation (R2 > 0.9999) and area precision below 1.2% (0.7% for 1–16 μL)
• No detectable carryover for caffeine or chlorhexidine analyses with both needles
• Retention time precision was outstanding, with RSDs under 0.01% for most compounds
• Area precision across the full dual-needle ACR setup remained below 0.82% RSD
• Limits of detection fell into the low-picogram range; LOQs were below 1 ng for most analytes
• For 100 runs, total analysis time decreased from approximately 260 minutes (sequential) to 110 minutes using parallel injection and ACR, achieving over 60% time savings

Benefits and Practical Applications

• Substantially higher sample throughput supports routine QC laboratories in food and beverage industries
• Maintains high chromatographic precision and sensitivity despite ultra-short gradients
• Automated ACR and dual-needle sampling reduce idle time between injections
• Minimal carryover ensures data integrity and lowers the need for extensive wash cycles

Future Trends and Opportunities

• Integration with automated sample preparation systems to further increase efficiency
• Application of dual-path UHPLC workflows to other trace-level analytes in complex matrices
• Coupling high-throughput UHPLC with high-resolution mass spectrometry for enhanced compound identification
• Development of greener solvent systems and microflow techniques to reduce reagent consumption
• Advanced data analytics and machine learning for real-time quality control monitoring

Conclusion

Combining dual-needle injection with automated alternating column regeneration on a UHPLC platform enables ultrafast and reliable analysis of food preservatives. This approach delivers significant time savings, excellent precision, and low detection limits, making it a valuable solution for high-throughput food safety testing.

Reference

Huesgen AG, Naegele E. Automated alternating column regeneration on the Agilent 1290 Infinity LC. Agilent Technologies Application Note 5990-5069EN (2009).