Determination of Formic Acid in Acetic Acid for Industrial Use by Agilent 7820A GC

Significance of the Topic

The purity of acetic acid directly affects the quality of downstream products such as polyethylene, cellulose acetate and synthetic fibers. Formic acid is a common impurity in industrial acetic acid, and reliable quantification is essential for quality control in coal‐to‐chemicals processes and routine laboratories.

Objectives and Study Overview

This application brief describes the development of a robust gas chromatographic method using the Agilent 7820A GC with a micro‐thermal conductivity detector (µTCD) to determine formic acid levels in acetic acid. The aim was to improve separation, sensitivity, repeatability and ease of use compared to existing packed‐column approaches.

Methodology and Instrumentation

Analytical Conditions:

• Column: Agilent J&W DB-FFAP capillary column (30 m × 0.32 mm, 0.25 µm)
• Carrier gas: He, constant flow 1.5 mL/min
• Inlet: 150 °C, split 10:1, injection volume 1 µL
• Oven program: 80 °C (3 min) → 8 °C/min → 150 °C (5 min)
• Detector: µTCD at 200 °C (reference 15 mL/min, makeup 6.5 mL/min)
• Autosampler: Agilent 7693A automatic liquid sampler
• Data system: EZChrom Elite Compact software

Internal standard: Ethyl acetate following GB/T 1628.5-2000. Calibration standards ranged from 0.1 to 10 wt% formic acid.

Key Results and Discussion

Chromatographic separation on the FFAP column achieved clear resolution of formic acid eluting after acetic acid, confirmed by both µTCD and FID detectors. The µTCD provided superior baseline stability without a reference column and enhanced sensitivity due to a small‐volume cell design.

• Detection limit: 0.05 wt% (S/N = 6.8)
• Precision: 1.75% RSD at 0.05 wt% (n = 5)
• Linearity: r2 = 0.9917 over 0.1–10 wt%

Electronic pressure control and automated sampling ensured excellent repeatability suitable for routine QA/QC workflows.

Benefits and Practical Applications

This method offers:

• High sensitivity and stable baselines with µTCD;
• Improved separation using a capillary FFAP column;
• Automated sampling and pressure control for reproducible analyses;
• Flexibility to handle high‐ and low‐concentration samples.

It is particularly well suited for feedstock and intermediate quality control in coal chemical plants and industrial laboratories.

Future Trends and Opportunities

Emerging developments may include coupling µTCD with mass spectrometry for enhanced selectivity, further miniaturization of detectors, greener carrier gases, and integration of advanced data analytics for real‐time process monitoring. Expanded automation and high‐throughput configurations will support growing industrial demands.

Conclusion

The Agilent 7820A GC with µTCD and FFAP capillary column provides a simple, sensitive and reproducible method for quantifying formic acid in acetic acid. Its robust performance, ease of operation and compatibility with routine QA/QC make it an attractive choice for industrial and research laboratories.

References

• GB/T 1628.5-2000. Determination of formic acid in acetic acid by gas chromatography.