Start up, shut down - Screening of pressure sensitive columns with the 8 port 2-position valve

Significance of the topic

The use of multiport valves in high-performance liquid chromatography is critical for efficient sample injection, column switching and fraction collection. Pressure-sensitive polymer columns, such as KNAUER Eurokat, require gentle equilibration and steady flow to prevent damage. Traditional column screening workflows demand manual exchange and gradual ramping, which is time-consuming and prone to pressure spikes. Implementing an 8-port 2-position valve streamlines parallel screening by maintaining continuous flow through two columns.

Study objectives and overview

This work aims to demonstrate how a KNAUER 8-port 2-position valve can be applied to accelerate the screening of pressure-sensitive Eurokat cation-exchange columns. A mixed carbohydrate standard was analyzed sequentially on sodium (Na) and calcium (Ca) forms of Eurokat columns without interrupting flow, thereby comparing resolution and elution behavior under identical conditions.

Methodology and instrumentation

The screening procedure employed two 300 × 8 mm Eurokat columns (Na and Ca) held at 75 °C, with an isocratic water mobile phase at 0.5 mL/min. Samples (20 μL) were injected via an AZURA AS 6.1L autosampler. Detection was performed using an AZURA RID 2.1L refractive index detector at 20 Hz data rate and 0.05 s time constant. Flow distribution between columns was managed by the AZURA VU 4.1 valve drive controlling a high-pressure injection valve (8 port, 2 position). Chromatograms were acquired and processed with ClarityChrom 8.1 software.

Instrumentation

• Pump: AZURA P6.1L HPG (APH35EA)
• Autosampler: AZURA AS 6.1L (AAA00AA)
• Detector: AZURA RID 2.1L (ADC01)
• Thermostat: AZURA CT 2.1 (A05852)
• Valve drive: AZURA VU 4.1 (AWA01)
• Valve: High-pressure injection valve, 8 port, 2 position (AVC38AC)
• Columns: Eurokat Na (30GX210EKN) and Eurokat Ca (30GX360EKN), 300 × 8 mm ID
• Software: ClarityChrom 8.1 (A1670)

Main results and discussion

On the Na-form column, coelution of mannitol/glucose and glycerine/arabinose was observed, limiting resolution. Switching to the Ca-form improved baseline separation for most analytes; however, glucose and xylose remained partially overlapped. The valve enabled direct sample injection onto the second column without manual column exchange or re-equilibration, demonstrating consistent flow maintenance and rapid method comparison.

Benefits and practical applications of the method

• Eliminates downtime associated with column changeover and temperature ramping.
• Maintains steady pressure and flow, protecting pressure-sensitive packings.
• Allows direct comparison of different stationary phases under identical conditions.
• Can be extended to automated 2D-LC workflows such as heart-cutting or multi-dimensional separations.

Future trends and potential applications

Advances may include integration of multiport valves in fully automated screening platforms, coupling with mass spectrometry for orthogonal detection, and miniaturization for high-throughput analyses. The approach could be adapted to other pressure-sensitive phases and expanded to comprehensive 2D-LC method development in pharmaceutical, food and environmental laboratories.

Conclusion

The KNAUER 8-port 2-position valve offers a robust solution for screening pressure-sensitive Eurokat columns, significantly reducing equilibration time and improving workflow efficiency. By enabling parallel flow paths, it facilitates rapid method evaluation and enhances reproducibility in carbohydrate analysis.

References

• Böttcher J., Myrach T., Margraf M., Monks K. Screening of pressure-sensitive columns with the 8-port 2-position valve. KNAUER Application Note VTN0008.