Analysis of Parabens in Soy Sauce and Vinegar by HPLC Using Agilent Chem Elut S Supported Liquid Extraction (SLE) Cartridges

Importance of the topic

Parabens are commonly used preservatives in food products such as sauces, juices and condiments. Their routine monitoring is essential to ensure consumer safety, comply with regulations and prevent overexposure. Accurate and efficient extraction and quantification methods are critical for food quality control, laboratory throughput and environmental sustainability.

Objectives and overview of the study

This work compared traditional liquid–liquid extraction (LLE) with supported liquid extraction (SLE) using Agilent Chem Elut S cartridges and four competing SLE products. The goal was to evaluate recoveries, reproducibility, workflow efficiency and cleanliness for the analysis of seven parabens in soy sauce and vinegar by HPLC-DAD.

Methodology and instrumentation

• Sample preparation: 1 g of soy sauce or vinegar was spiked at 20 ng/g with a mixed paraben standard, salted with 1% NaCl, vortexed and subjected to SLE (3 mL sample loading) or LLE (10 mL ethyl acetate) in six replicates. Extracts were dried under nitrogen, reconstituted in 1 mL methanol and injected.
• HPLC conditions: Agilent 1290 Infinity II LC with diode array detection at 260 nm, Poroshell 120 PFP column (3.0×100 mm, 2.7 µm), gradient from 30% to 95% methanol over 6 minutes, flow 0.5 mL/min, injection volume 2 µL, column at 35 °C.
• Cleanliness assessment: Agilent Intuvo 9000 GC with 7000 triple quadrupole MS full-scan and UV detection at 260 nm were used to detect cartridge-derived interferences.

Used instrumentation

• Agilent 1290 Infinity II LC system with high-speed pump, multisampler, multicolumn thermostat and diode array detector
• Agilent Intuvo 9000 GC and 7000 triple quadrupole MS
• Agilent Chem Elut S 12 cc cartridges and four competitor SLE cartridges
• SPEX GenoGrinder for sample mixing
• Agilent Vac Elut manifold, centrifuge, pipettes and nitrogen evaporator

Main results and discussion

• SLE with Chem Elut S required 50 minutes for six replicates versus 80 minutes for LLE, eliminating emulsion issues and manual phase separation.
• Recoveries for all seven parabens ranged from 88% to 110% with RSDs below 10% for both matrices and both techniques.
• Chem Elut S outperformed or matched LLE and other SLE products, especially for hydrophobic heptylparaben (HP), using a larger sample loading volume (3 mL) to boost sensitivity.
• Cleanliness tests showed minimal extractables from Chem Elut S, while some competitor cartridges exhibited UV and GC/MS interferences.

Benefits and practical applications of the method

• Streamlined workflow suitable for high-throughput or automated laboratories
• Shorter extraction time and reduced solvent consumption
• High sensitivity and reproducibility for regulatory compliance testing
• Minimal matrix interferences and cartridge-derived contamination

Future trends and applications

Advances may include integration of online SLE with LC systems, development of next-generation sorbents with tailored selectivity, expansion to other food matrices and trace contaminants, and automation to further increase sample throughput and reduce operator variability.

Conclusion

Supported liquid extraction using Agilent Chem Elut S cartridges provides a robust, efficient and clean alternative to traditional LLE for paraben analysis in complex food matrices. The method delivers high recoveries, low variability, faster processing and increased sensitivity, making it well suited for routine quality control and regulatory laboratories.

References

1. Chinese National Food Safety Standard – Determination of p-Hydroxybenzoic Acid Esters in Foodstuffs: GB5009.31-2016.
2. Zimmerman D. C. et al., Determination of Parabens in Body Wash using Solid-Supported Liquid-Liquid Extraction, Agilent Technologies Application Note 5991-2735EN, 2013.