AutoDilution using Chromeleon 7 CDS software and two injection loops

Importance of the Topic

Challenging samples with analyte concentrations beyond calibration limits can compromise data integrity and lead to labor-intensive manual re-analysis. Implementing an automated dilution workflow streamlines the analytical process, reduces errors, and enhances throughput in routine and high-throughput laboratories.

Objectives and Study Overview

This technical note describes the integration of AutoDilution within Chromeleon 7 Chromatography Data System (CDS) using Intelligent Run Control to automatically detect over-range samples, switch injection loops, and reinject diluted aliquots. The aim is to illustrate a robust method for secondary loop injection via a 10-port valve in Thermo Scientific Dionex autosamplers or HPIC systems.

Methodology and Instrumentation

• Injection loops: large (100 µL) and small (10 µL) loops configured on a 10-port high-pressure valve.
• Hardware platforms: Dionex AS-DV or AS-AP autosamplers with optional valve, Integrion HPIC system, or ICS-5000+ with Automation Manager.
• Valve plumbing: pump to port 1, small loop ports 4/8, large loop ports 6/10, sample line port 5, column port 7, waste port 9, with specific PEEK tubing dimensions for microbore (0.125 mm i.d.) or standard bore (0.25 mm i.d.).
• Chromeleon 7 CDS instrument methods: two files named Large Loop and Small Loop, each including valve actuation commands for load and inject states.
• Intelligent Run Control setup: create a System Suitability Test (SS AutoDilution template), define evaluation criteria for sample concentrations exceeding calibration range, and configure fail actions to switch to Small Loop method with adjusted injection volume ratio.
• Loop calibration: determine actual loop volumes by injecting a standard solution, calculate the loop ratio from average peak areas, and apply the dilution factor in sample properties.

Key Results and Discussion

Automated loop switching returned reproducible precision with relative standard deviations below 5% for both loop sizes at 1 mg/L standard. The calculated loop ratio enabled accurate dilution to bring over-range samples within calibration limits. Integration of AutoDilution in CDS eliminated manual sample re-prep and saved operator time.

Benefits and Practical Applications

• Eliminates manual identification and dilution of out-of-range samples.
• Improves laboratory productivity and reduces operational costs.
• Enhances data integrity by standardizing reinjection protocols.
• Flexible configuration across different Dionex instrumentation platforms.

Future Trends and Opportunities

Anticipated developments include tighter integration of automated sample preparation modules, expanded use of microfluidic flow paths for ultra-low volume injections, and incorporation of machine learning algorithms to dynamically adjust dilution strategies based on historical data trends.

Conclusion

The AutoDilution feature in Chromeleon 7 CDS, leveraging Intelligent Run Control and dual-loop injection hardware, offers a reliable and efficient solution for processing samples with analyte concentrations exceeding calibration ranges. This workflow enhances throughput, ensures accuracy, and can be adapted to various chromatography systems.

References

• Khor D, Lorch J, Rohrer J. Technical Note TN17247-EN: AutoDilution using Chromeleon 7. Thermo Fisher Scientific; 2016.