Carbohydrate Determination by HPAE-PAD with Disposable Au on PTFE Working Electrodes

Importance of the Topic

High-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAE-PAD) is widely used for direct carbohydrate analysis in diverse matrices such as foods, biological samples, biofuel feedstocks and fermentation broths. Carbohydrates lack strong chromophores, making conventional UV or refractive index detection insufficiently sensitive and prone to interferences. Electrochemical detection at high pH provides selective oxidation‐based measurement without the need for derivatization, but requires stable, easy-to-maintain electrodes to ensure reproducible results in high-throughput laboratories.

Objectives and Study Overview

This work evaluates disposable gold on polytetrafluoroethylene (Au on PTFE) working electrodes for HPAE-PAD carbohydrate determinations. Key goals include assessing electrode lifetime, background and noise stability, and reproducibility across multiple application conditions. A range of analytes—from monosaccharides and oligosaccharides to aminoglycoside antibiotics and sialic acids—were tested under typical hydroxide and hydroxide-acetate eluents to demonstrate broad applicability.

Methodology and Instrumentation

Carbohydrates were separated on Dionex CarboPac columns using both reagent-free and manually prepared hydroxide eluents, with optional post-column addition of concentrated NaOH for enhanced sensitivity. A four-potential pulsed waveform cleaned and prepared the electrode surface during each cycle to minimize fouling. Performance metrics such as peak area response, background current and noise were monitored over weeks of continuous operation.

Instrumental Setup

• Thermo Scientific Dionex ICS-3000 or ICS-5000 RFIC system with EG Eluent Generator and vacuum degas conversion kit
• Electrochemical Detector (ED) with disposable Au on PTFE working electrodes and Ag/AgCl reference electrode
• Dionex CarboPac columns (PA1, PA200, PA20, SA10) and respective guard columns
• Dionex Chromeleon 7 chromatography workstation
• Standard reagents: 50% NaOH, sodium acetate, high-purity water

Main Results and Discussion

Disposable Au on PTFE electrodes provided consistent response for over four weeks with less than 15% signal loss in galactose assays, compared to two-week lifetimes for previous polyester-based electrodes. Electrode-to-electrode precision remained within 8% RSD, and background currents increased by only 10–20 nC over the electrode lifetime. Noise levels ranged from 20–70 pC without post-column reagents and 90–110 pC with post-column NaOH. Linearity was excellent (r2 > 0.99) across broad analyte concentration ranges. Sialic acid analysis exhibited stable response after a 6–12 hour equilibration, followed by a 5.8% decrease over two weeks, demonstrating suitability for glycoprotein hydrolysate monitoring.

Benefits and Practical Applications

• No electrode polishing or re-equilibration is required—simply replace the disposable electrode when performance declines
• Extended lifetime and higher base stability (>100 mM NaOH) simplify carbohydrate and related analyte workflows
• Low background and stable noise support trace-level quantification in complex matrices
• Broad compatibility with automated RFIC systems and manual eluent preparation

Future Trends and Applications

Advances in electrode materials may further extend lifetimes and enable even higher sensitivity for labile or low-abundance carbohydrates. Integration with mass spectrometry or compact, field-portable HPAE-PAD platforms could expand on-site food authenticity, biofuel quality control, and clinical glycomics. Ongoing development of waveform optimization and novel disposable sensor formats will continue to improve throughput and robustness.

Conclusion

The Au on PTFE disposable working electrodes deliver reliable, high-throughput carbohydrate and related analyte determinations by HPAE-PAD. Their ease of use, extended lifetime, and broad applicability make them a practical choice for routine QA/QC, research, and industrial analytics workflows.

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