AutoDilution using Chromeleon 7 CDS software and two injection loops

Significance of the topic

In environmental and industrial analysis, samples such as wastewater frequently exhibit analyte concentrations above calibration limits. Manual dilution and reanalysis of these outliers are time-consuming and prone to error. AutoDilution within Chromeleon 7 CDS automates this process, enhancing laboratory efficiency and data quality.

Study objectives and overview

This technical note aims to illustrate how to configure Thermo Scientific Chromeleon 7 CDS with Intelligent Run Control (IRC) to perform automated dilution of over-range samples using two injection loops. The goal is to detect threshold exceedances and rerun samples with a smaller injection volume without operator intervention.

Methodology

The AutoDilution workflow employs:

• A large sample loop (e.g., 100 µL) for initial injection
• A small sample loop (e.g., 10 µL) for conditional reinjection
• An optional 10-port high-pressure valve to switch between loops
• IRC test cases in Chromeleon to define pass/fail criteria and actions

The software monitors calibration responses and, upon detecting a concentration above the maximum standard, automatically schedules a reinjection using the small loop and an alternate instrument method.

Instrumentation used

• Chromeleon 7 CDS software with Intelligent Run Control
• Dionex Integrion HPIC or ICS-5000+ DC with Automation Manager
• Dionex AS-DV or AS-AP autosampler equipped with a 10-port valve
• Two concentric sample loops (100 µL and 10 µL) and PEEK tubing for plumbing

Main results and discussion

By implementing AutoDilution, the system automatically:

• Identifies out-of-range injections based on calibration curve limits
• Switches valve positions to load and inject from the appropriate loop
• Applies a dilution factor derived from calibrated loop volume ratios
• Maintains sequence continuity without manual method switching

Loop volumes are verified by measuring RSD (<5 %) and calculating relative loop areas to ensure accurate dilution factors.

Advantages and practical applications

AutoDilution with Chromeleon 7 CDS offers:

• Elimination of manual dilution steps and reruns
• Reduced operator workload and faster turnaround
• Consistent data quality through automated threshold checks
• Enhanced throughput in QA/QC and environmental testing labs

Future trends and potential applications

Emerging developments may include:

• Expanded use of machine learning for dynamic threshold setting
• Integration with cloud-based data management and remote monitoring
• Application to additional chromatography and detection platforms
• Further automation of sample preparation and inline dilution

Conclusion

Chromeleon 7 CDS AutoDilution using dual injection loops streamlines the analysis of over-range samples by automating dilution and reinjection steps. This approach improves laboratory efficiency, reduces errors, and ensures reliable quantitative results without additional manual handling.