Increased Throughput with Nexera™ GPC system: Overlapped Injection and Simultaneous Determination of Polymer Additives

Importance of the Topic

Gel permeation chromatography (GPC) is a fundamental technique in polymer analysis for determining molecular weight distribution and additive content. With rising demands for rapid sample throughput in research, quality control, and industrial settings, optimizing GPC workflows is crucial for efficient material characterization.

Objectives and Study Overview

This work introduces a novel GPC approach that combines overlapped injection with spectral peak deconvolution to achieve simultaneous determination of polymer additives and molecular weight distribution in a single high-throughput run. The study evaluates the performance on polystyrene containing three common antioxidants.

Methodology and Instrumentation

A dual-detector configuration was employed, comprising a refractive index detector (RID) for polymer molecular weight analysis and a photodiode array detector (PDA) for additive quantitation. Overlapped injection exploits the void interval of size-exclusion columns to start a new injection before complete elution of the previous sample, halving the cycle time. Analytical conditions included:

• Columns: Shim-pack GPC 805 + GPC 801 (300 mm × 8 mm I.D. each)
• Mobile phase: tetrahydrofuran (THF) at 0.8 mL/min
• Column temperature: 40 °C
• Injection volume: 10 µL, sample concentration: 0.5 % polystyrene with three antioxidants
• Detectors: RID for molecular weight; PDA (220–400 nm) for additives
• Cycle time: 31 min; overlapped interval: 15.5 min

Peak deconvolution was performed using LabSolutions i-PDeA II software to resolve three incompletely separated antioxidant peaks (Irganox 1010, Tinuvin 144, Tinuvin 120) based on three-dimensional PDA data.

Key Results and Discussion

Overlapped injection reduced analysis time by approximately 50 % compared to conventional sequential runs. The RID trace provided reliable molecular weight averages (Mn = 2.63×10^4, Mw = 4.89×10^4, PDI = 1.86; RSD ≤ 1.5 %). PDA chromatograms showed two peaks before deconvolution; application of i-PDeA II revealed three distinct antioxidant signals. Calibration curves were linear (r² = 0.995–0.999) over 0.01–0.10 % (w/v). Determined additive contents were 49.2 mg/g (Irganox 1010), 23.1 mg/g (Tinuvin 144), and 27.4 mg/g (Tinuvin 120) with RSDs below 2 %.

Benefits and Practical Applications

• Substantially increased sample throughput via overlapped injection.
• Simultaneous molecular weight profiling and additive quantitation reduces solvent and instrument usage.
• Peak deconvolution enhances resolution of compounds with similar molecular sizes.
• Applicable to routine polymer QA/QC, materials research, and formulation development.

Future Trends and Opportunities

Further integration of multi-detector systems and advanced chemometric algorithms could extend this approach to more complex polymer blends and trace additive analysis. Automation of injection scheduling and AI-driven peak processing may drive even higher throughput and robustness in polymer characterization workflows.

Conclusion

The combination of overlapped injection and spectral peak deconvolution in GPC enables rapid, accurate determination of polymer molecular weight distribution and additive content. This methodology demonstrates significant time savings and improved analytical performance, making it well-suited for high-volume polymer analysis.

Reference

• Shimadzu Technical Report C191-E042
• Shimadzu Application Note No. L537