Infrared-based temperature measurements in capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Instrumental Analysis

Background:

• Temperature is a critical parameter in capillary electrophoresis (CE).
• Accurate temperature measurement is necessary for Analytical Instrument Qualification (AIQ) of CE systems.
• Joule heating, generated by electrical power, influences capillary temperature.

Purpose of the Study:

• To present an accurate method for measuring temperature generated by electrical power in CE.
• To evaluate the linearity and precision of infrared (IR) thermometry for capillary temperature measurement.
• To compare IR thermometry with indirect methods for temperature estimation.

Main Methods:

• Utilized an infrared (IR) thermometer to measure temperature on the outside of the capillary.
• Investigated thermometer linearity across varying electrical field strengths, buffer systems, and capillary inner diameters.
• Compared the IR thermometry method with indirect methods calculating temperature from conductance, electroosmotic velocity, or current.

Main Results:

• Demonstrated IR thermometer linearity with a slope of 6.3 °C m/W at an optimal distance of 8 mm.
• Found temperature measurements to be highly precise, primarily dependent on current variability.
• Indirect methods yielded estimated slopes ranging from 7 to 10 °C m/W.
• Estimated maximal suitable electrical power per unit length for CE, noting sensitive analytes can be affected by >1 W/m.

Conclusions:

• Infrared thermometry provides a precise and reliable method for measuring capillary temperature in CE.
• Accurate temperature monitoring is essential for Analytical Instrument Qualification (AIQ), method optimization, and method transfer in CE.
• Understanding Joule heating effects is critical for successful CE method development and application.