Shortening of Cycle Time in Organic Acid Analysis by Overlapped Injection

Importance of Topic

Organic acids play key roles in food flavor, preservation and pharmaceutical formulations. Rapid and reliable quantification is essential for quality control in high-throughput environments, where minimizing analysis time without compromising accuracy accelerates decision-making and reduces operational costs.

Objectives and Study Overview

The study demonstrates how overlapped injection of samples into a high-performance liquid chromatography (HPLC) system can shorten overall cycle time for organic acid analysis. By injecting a subsequent sample before the previous run is complete, the approach aims to increase sample throughput while maintaining resolution, sensitivity and repeatability.

Methodology and Instrumentation

Analysis was performed in ion-exclusion mode using two Shim-pack SCR-102H columns connected in series. A post-column pH-buffered conductivity detector provided high selectivity for organic acids. The mobile phase comprised preadjusted solutions of p-toluenesulfonic acid with Bis-Tris and EDTA for stable pH control. Standard solutions of eight organic acids at 2.0 mmol/L each were used to evaluate performance under typical and overlapped injection regimes.

Instrumentation Used

• Shimadzu Nexera ultra high performance liquid chromatograph
• SIL-40C autosampler configured for overlapped injection
• Shim-pack SCR-102H analytical columns (300 mm × 8.0 mm, 7 μm) and guard column
• Conductivity detector with post-column pH buffering (CDD-10AVP)
• Mobile phase reagent set containing p-toluenesulfonic acid, Bis-Tris and EDTA

Main Results and Discussion

Overlapped injection reduced the total analysis time for three consecutive injections from 120 minutes to 100 minutes, saving 20 minutes per batch. Retention times remained unchanged, avoiding the need for software adjustments. Calibration curves for each acid were linear (r2 ≥ 0.999) over 2.0–20.0 mmol/L. Repeatability of peak areas was maintained below 0.5 %RSD under both injection modes, confirming that throughput gains did not compromise precision.

Benefits and Practical Applications

• Significant reduction in total analysis time improves laboratory efficiency and sample throughput.
• Preprepared mobile phase reagents ensure consistent pH control and reduce preparation errors and costs.
• Maintained analytical performance supports use in food, pharmaceutical and industrial quality control.

Future Trends and Opportunities

Continued integration of overlapped injection into fully automated workflows and multi-channel systems could further boost throughput. Advances in column chemistry and detector sensitivity may allow shorter run times without loss of resolution. Coupling with data-driven process control and predictive maintenance will enhance robustness in large-scale quality assurance.

Conclusion

The overlapped injection technique using a SIL-40C autosampler in a Nexera HPLC system achieved a 17 % reduction in analysis time for organic acid quantification while preserving linearity and precision. This approach offers a practical solution for high-volume laboratories seeking to optimize cost and efficiency.