Sampling frequency, response times and embedded signal filtration in fast, high efficiency liquid chromatography: A...

Area of Science:

• Analytical Chemistry
• Chromatography
• Spectroscopy

Background:

• Modern high-performance liquid chromatography (HPLC) columns produce increasingly narrow peaks.
• Accurate detection of these narrow peaks requires careful selection of detector response time and data acquisition rate (sampling frequency).
• Existing sampling theory suggests low theoretical minimum sampling frequencies, which may not account for real-world noise and instrument-specific filtering.

Purpose of the Study:

• To evaluate the impact of detector sampling frequency and response time on peak shape in HPLC.
• To assess the adequacy of common sampling guidelines (e.g., 20 points per peak) for high-efficiency separations.
• To investigate the influence of instrument-specific digital filters on chromatographic data.

Main Methods:

• Utilized fast chromatography with a state-of-the-art, high-efficiency column (38,000 plates).
• Evaluated responses from various modern HPLC instruments with different digital filtering characteristics.
• Employed a square-wave driven light-emitting diode source to probe embedded filter behavior.

Main Results:

• The common practice of sampling 20 points per peak is insufficient for high-efficiency HPLC columns.
• Both sampling frequency and response time significantly affect observed peak shape, width, and retention time.
• Instrumental digital filters, often opaque to users, complexly influence signal characteristics like noise amplitude and peak shape.

Conclusions:

• Optimal detector sampling frequency and response time are critical for accurate characterization of narrow peaks in HPLC.
• Users need to be aware of how instrument-specific digital filtering and sampling rates impact chromatographic data.
• Recommendations are provided for optimizing data acquisition to achieve the best results from HPLC systems.