All-in-one square capillary platform for nanoliter sampling and sample-efficient micro-scale optical measurements

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Microfluidics

Background:

• Traditional analytical techniques often require large sample volumes (milliliters) despite small optical probe volumes (pico- to femtoliters).
• This high sample consumption is due to microchannel filling, sample preparation challenges, and transfer losses.
• This inefficiency is particularly problematic for analyzing extremely rare or hazardous samples.

Purpose of the Study:

• To introduce a square capillary as an integrated sampling and measurement platform.
• To demonstrate sample-efficient optical detection for scarce and hazardous materials.
• To overcome the discrepancy between probe volume and actual sample consumption in analytical measurements.

Main Methods:

• Utilizing a square capillary as an all-in-one analytical platform.
• Confining sample volume to the nanoliter scale within the capillary.
• Combining capillary sampling with photothermal detection for optical absorption measurements.

Main Results:

• Achieved optical absorption-based detection of uranyl ions in aqueous solution.
• Demonstrated a limit of detection of 0.2 mM.
• Required only 50 nL of sample per measurement, showcasing high sample efficiency.

Conclusions:

• The square capillary serves as an effective platform for handling minute sample volumes.
• This approach significantly enhances measurement efficiency for rare and hazardous samples.
• Capillary sampling combined with photothermal detection enables highly sample-efficient optical measurements.