High-Speed Analysis of Total Petroleum Hydrocarbons (TPH)

Significance of Topic

Total petroleum hydrocarbons (TPH) encompass a broad range of hydrocarbon compounds whose uncontrolled release into soil and water poses significant environmental and health risks. Rapid and reliable quantification of TPH is essential for environmental monitoring, regulatory compliance, and contamination remediation.

Objectives and Study Overview

This study presents a high‐speed gas chromatographic method for TPH analysis using the Shimadzu Nexis GC‐2030 configured with an oven insert and hydrogen carrier gas. Key aims include validation of system performance against ISO 9377‐2:2000 standards, development of a mineral oil calibration curve, and evaluation of throughput improvements with dual injectors.

Methodology

Sample preparation followed solvent extraction into heptane and included:

• Background correction sample: heptane blank
• System performance test: 50 μg/mL n‐alkane mixture (C10–C40)
• Calibration curve: mineral oil diluted to 50–1000 μg/mL

Chromatographic separation employed a thick‐film capillary column under a temperature program from 100 °C to 340 °C at high ramp rates. Hydrogen served as carrier gas to enable elevated column flow and faster run times.

Used Instrumentation

• Nexis GC‐2030 gas chromatograph (230 V) with rapid‐heating oven insert
• Dual AOC‐30i autosamplers for overlapping injection and cleaning cycles
• Rxi‐1ms capillary column, 12 m x 0.2 mm I.D. x 0.33 μm film
• Hydrogen flame ionization detector (FID)

Main Results and Discussion

System performance testing yielded C40/C20 area ratios of 0.94–0.96 with repeatability below 1% RSD, exceeding the ISO requirement of ≥0.8. The mineral oil calibration curve demonstrated excellent linearity (R2 > 0.9996) across the concentration range. The total GC run time was 4.3 minutes, with a complete cycle of 7.3 minutes including cooling and equilibration. Dual‐line operation enabled analysis of over 380 samples per day. Comparative tests showed that the 230 V instrument plus oven insert reduced run time by about 5 minutes versus a 100 V model; operating outside the specified oven ramp increased speed by an additional ~1 minute.

Benefits and Practical Applications

By combining hydrogen carrier gas, rapid‐heating inserts, and dual injectors, this approach drastically shortens analysis time while maintaining compliance with ISO standards. High throughput and reliable quantitation make it suitable for environmental laboratories tasked with routine water and soil TPH monitoring.

Future Trends and Applications

Further improvements may come from integration with mass spectrometric detectors for compound‐specific profiling, automated sample preparation workflows, and advanced oven designs accommodating even faster temperature programming. Such developments will broaden applications in regulatory testing, site remediation assessment, and industrial quality assurance.

Conclusion

The high‐speed TPH analysis method using Nexis GC‐2030 with oven insert and hydrogen demonstrates superior performance in terms of speed, precision, and throughput. It meets international standards and offers a practical solution for high‐volume environmental monitoring.

References

• ISO 9377‐2:2000 Determination of hydrocarbon oil index for water quality