Analysis of ketones, esters, and ethers Using Automated Injection of Internal Standards

Significance of the Topic

Precise measurement of volatile ketones, esters and ethers is essential in chemical manufacturing, environmental monitoring and quality control. These compounds often serve as process intermediates, solvents or markers of product purity. An efficient analytical workflow helps laboratories maintain regulatory compliance and optimize production processes.

Objectives and Study Overview

This application note presents a validated method for simultaneous analysis of tetrahydrofuran (THF), ethyl acetate, methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK) and methyl butyl ketone (MBK) using gas chromatography with flame ionization detection (GC-FID). The study highlights the use of automated sandwich injection of an internal standard to improve accuracy and reproducibility.

Methodology

The analytical procedure employs a split injection mode with a sandwich injection sequence in which 0.5 μL of internal standard and 0.5 μL of sample are sequentially injected. The split ratio is set at 1:50 to prevent column overload and achieve sharp peaks. Helium is used as carrier gas under linear velocity control. A temperature program from 60 °C to 140 °C ensures baseline separation of target analytes within a runtime suitable for high-throughput laboratories.

Used Instrumentation

• Gas chromatograph: Shimadzu Nexis GC-2030
• Autosampler: Shimadzu AOC-30i with Sampler Navigator sandwich-injection capability
• Syringe: 10 μL (part number 221-34618)
• Column: SH-PolarWax, 60 m × 0.32 mm I.D., 1.0 μm film thickness (part number 227-36252-02)
• Detector: Flame Ionization Detector (FID) at 250 °C
• Gases: Helium carrier; hydrogen and air for FID; nitrogen makeup gas

Main Results and Discussion

Chromatograms demonstrated clear resolution of all five analytes, with retention times reproducible to within a few seconds. The internal standard approach corrected for injection variability, delivering relative standard deviations below 2% for peak area ratios. Method sensitivity and linearity were adequate for typical concentration ranges encountered in industrial and environmental samples.

Benefits and Practical Applications

• Enhanced precision through automated internal standard injection
• High sample throughput with fast temperature programming
• Robust separation of structurally similar VOCs on a polar stationary phase
• Applicable to process control, solvent quality checks and environmental analysis

Future Trends and Opportunities

Integration of advanced data processing and real-time calibration algorithms can further streamline VOC analysis. Transitioning to multidimensional GC or coupling with mass spectrometry may expand the compound scope and improve selectivity. Miniaturized or portable GC systems could enable on-site monitoring in remote locations.

Conclusion

The described GC-FID method with automated internal standard injection on an SH-PolarWax column offers reliable, reproducible quantification of key ketones, esters and ethers. Its simplicity and robustness make it well suited for routine analytical laboratories.

Reference

• Shimadzu Corporation. Application News 01-00005. First Edition: September 2022.