CHEMICAL PURITY ANALYSIS

Význam tématu

Monocyclic aromatic hydrocarbons such as benzene, toluene and xylenes serve as fundamental building blocks in polymer and chemical production. Their applications span plastics manufacturing, solvents and specialty chemicals. Ensuring high product purity is critical to meet regulatory specifications (ASTM D16 series) and to guarantee consistent performance in end-use applications.

Cíle a přehled studie / článku

This work illustrates the application of ASTM D7504 for routine chemical purity assessment of monocyclic aromatics using gas chromatography with an effective carbon number (ECN) approach. The study evaluates the Agilent Intuvo 9000 GC with an auto-ranging flame ionization detector (FID) to achieve a wide dynamic range and eliminate extensive sample preparation and calibration.

Použitá metodika

• The D7504 method relies on ECN-based response factors to quantify analytes without external calibration standards.
• No sample derivatization or multi-point calibration is required; the ECN model accounts for detector response differences.
• One single run detects components spanning from 0.0001 wt % up to 99.5 wt % in a single injection.

Použitá instrumentace

• Gas chromatograph: Agilent Intuvo 9000 GC platform with click-and-run column mounting
• Detector: Auto-ranging flame ionization detector (FID) operating at 300 °C
• Column: Agilent Intuvo HP-Innowax, 60 m × 0.32 mm, 0.5 µm film thickness
• Inlet conditions: 100:1 split at 270 °C, injection volume 0.5 µL
• Carrier gas: Helium at constant flow of 2.1 mL/min
• Oven program: 60 °C hold 10 min, ramp 5 °C/min to 150 °C, hold 10 min

Hlavní výsledky a diskuse

• Ten sequential injections of a mixed xylene sample yielded consistent quantitation of four primary C8 isomers and trace impurities, with relative standard deviations below ASTM limits.
• The FID’s auto-ranging capability accurately measured peak currents from 0.16 pA up to 13 500 pA, corresponding to impurity levels around 18 ppm and major components up to 99.97 wt %.
• Precision for all analytes met single-lab reproducibility criteria defined by ASTM D7504.

Přínosy a praktické využití metody

• Simplified workflow allows manufacturing technicians to perform routine purity checks without specialized GC expertise.
• Elimination of calibration curves and sample prep reduces analysis time and resource consumption.
• Compact footprint and intuitive touchscreen interface make the system suitable for production environments and QA/QC labs.

Budoucí trendy a možnosti využití

• Expansion of ECN-based methods to other hydrocarbon classes and multi-component mixtures.
• Integration with laboratory information management systems (LIMS) for automated reporting.
• Development of miniaturized GC-FID platforms for on-line process monitoring.
• Application of machine learning algorithms to enhance peak deconvolution and impurity detection.

Závěr

The combination of the ASTM D7504 ECN approach with the Agilent Intuvo 9000 GC and auto-ranging FID delivers a robust, high-precision method for routine purity analysis of monocyclic aromatics. This streamlined technique meets industry demands for fast, easy-to-use instrumentation without compromising analytical performance.

Reference

1. ASTM D7504-15e1 Standard Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography and Effective Carbon Number, ASTM International, 2015