Analysis of aromatics Using Automated Injection of Internal Standards

Importance of the Topic

Understanding and accurate quantification of aromatic compounds such as benzene, toluene, xylene is crucial due to their prevalence in environmental monitoring, petrochemical analysis, and quality control processes. Automated injection methods enhance throughput and precision in routine laboratory settings, reducing manual errors and improving reproducibility.

Objectives and Study Overview

This study presents an automated method for analyzing six aromatic compounds using internal standard calibration and the Shimadzu Nexis GC-2030 coupled with an AOC-30i autosampler. The goal is to demonstrate robust quantification and efficient sample handling for routine analysis.

Methodology and Instrumentation

• Instrumentation
• Gas chromatograph: Shimadzu Nexis GC-2030
• Autosampler: AOC-30i with sandwich injection mode
• Column: SH-PolarWax, 60 m × 0.32 mm, 1.0 µm film thickness
• Detector: Flame Ionization Detector (FID)
• Sample Preparation and Injection
• Internal standard injection: 5 % of syringe volume (0.5 µL)
• Analyte injection: 0.5 µL mixture
• Injection temperature: 200 °C; split mode at 1:30
• Chromatographic Conditions
• Carrier gas: Helium at linear velocity 35 cm/s
• Temperature program: 90 °C initial, ramp 20 °C/min to 200 °C, hold 5 min
• FID settings: 250 °C, H₂ at 32 mL/min, air at 200 mL/min, makeup N₂ at 24 mL/min

Key Results and Discussion

The method achieved baseline separation of six target aromatics—benzene, toluene, o-xylene, ethylbenzene, p-BFB, and tetralin—within a 10-minute run. Calibration curves exhibited linearity with R² > 0.999. Repeatability tests showed relative standard deviations below 2 %. Internal standard normalization corrected injection variability, demonstrating high precision.

Benefits and Practical Applications

• High throughput: automated sampling reduces analysis time and manual intervention
• Enhanced reproducibility: internal standard method corrects injection fluctuations
• Minimal sample volume: requires only 0.5 µL per injection, conserving reagents
• Versatile application: suitable for environmental, petrochemical, and quality control laboratories

Future Trends and Opportunities

• Integration with mass spectrometry for improved selectivity and lower detection limits
• Development of smaller, portable GC units for on-site analysis
• Advanced software for real-time data processing and remote monitoring
• Expansion to broader compound classes using tailored stationary phases

Conclusion

The automated GC-FID method using an internal standard and Shimadzu instrumentation provides reliable, high-throughput analysis of aromatic compounds. Its precision and minimal sample consumption make it ideal for routine laboratory operations.

References

1. Application News 01-00005 (JP, ENG), Shimadzu Corporation, First Edition Sep. 2022