Purge & Trap using the 7300 Auto-Sampler

Significance

Trace-level volatile organic compound (VOC) monitoring in aqueous matrices is essential for environmental compliance, drinking water safety and industrial process control. At the same time, detailed polymer characterization using combined chromatographic and spectroscopic techniques yields critical insights for formulators, quality assurance and competitive analysis, particularly in complex systems such as conductive silver ink pastes.

Study Overview

This application note comprises two complementary studies:

• Quantitative analysis of fifteen VOCs in water over the 10–100 ppb range using an automated purge & trap-GC-MS workflow.
• Separation and infrared characterization of a multi-component polymer mixture derived from silver ink paste employing GPC-IR hyphenated technology to identify monomers and latent additives.

Methodology and Instrumentation

• Purge & Trap GC-MS protocol:
  – CDS 7300 autosampler (72-vial capacity, 5 mL transferred per run) coupled to a Model 7000 purge & trap unit.
  – Purge: 11 min at 35 mL/min; trap adsorption on a Vocarb trap; automated rinsing and blank runs.
  – GC: split ratio 20:1, 130 m × 0.25 mm 5% phenylmethylsilicone column; oven program 40 °C (4 min) to 210 °C at 10 °C/min.
  – MS: EI, mass range 35–550, source at 230 °C.
• GPC-IR hyphenated analysis:
  – GPC separation of polymer blend using size-exclusion columns.
  – Inline full-range FTIR detection (full FTIR range) capturing infrared spectra of each eluting fraction.
  – Database matching of characteristic IR bands to assign polymer types and latent additive structures.

Main Results and Discussion

• VOC analysis:
  – Chromatogram at 50 ppb clearly resolved all target compounds.
  – Calibration linearity between 10 and 100 ppb yielded R² values from 0.994 to 0.999, demonstrating excellent quantitative performance.
• Polymer identification via GPC-IR:
  – Polymer A: aliphatic polyester resin (Amoco-type), high molecular weight with broad distribution, flexible and adhesive to polyester/ polyimide films.
  – Polymer B: aliphatic polyurethane (Spensol L-53), medium molecular weight and narrow distribution, elastomeric and cross-linkable with tri-functional isocyanates.
  – Component C: latent cross-linker Desmodur LS-2800 (blocked HDI trimer), stable at room temperature, de-blocks at 150 °C to generate active tri-isocyanate for 3D network formation.
  – Additive C (ketoxime-blocked HDI trimer) confirmed by IR bands and low molar mass about 766 g/mol, consistent with CAS #93919-05-2.

Practical Benefits

• Automated purge & trap reduces manual handling, increases sample throughput, and enhances reproducibility for trace VOC monitoring in environmental and QC laboratories.
• GPC-IR provides orthogonal data: molecular size distribution coupled to IR spectral fingerprints enables unambiguous assignment of polymer components and additives in complex formulations.
• Formulators and QA teams gain actionable insights into intellectual property and competitive profiling through rapid structural analysis.

Future Trends and Applications

• Integration of high-resolution mass spectrometry with automated purge & trap for lower detection limits and improved compound identification.
• Expanded GPC-IR libraries for novel polymer chemistries and advanced additives to support materials innovation and failure analysis.
• Online and at-line process monitoring using hyphenated chromatography-spectroscopy techniques for real-time quality control in coatings, inks and polymer manufacturing.

Conclusion

The combined application of automated purge & trap-GC-MS and GPC-IR hyphenated analysis delivers robust, high-throughput solutions for trace contaminant quantitation in water and detailed polymer formulation characterization. These methods support regulatory compliance, product development and competitive benchmarking by providing reliable, reproducible data and structural insights.

References

• Experimental Conditions for Model 7000 P&T, CDS 7300 Autosampler, Varian GC-MS (350–550 amu).
• Table 1: VOC targets including Bromochloromethane, Chloroform, Benzene, Naphthalene, etc.
• LC-GC article: Polymer Characterization by Combined Chromatography-Infrared Spectroscopy (Spectra Analysis Instruments).