Characterization of a micro-helium discharge detector for gas chromatography

• Multiple micro helium discharge ionization detectors (μHDID) were fabricated.
• Designs with bias and collector electrode proximity to the discharge showed highest response.
• Enhancement of response with discharge voltage and bias voltage was observed.
• A mathematical relation between the detector response and the parameters was developed.
• Mechanism of the effect of the bias voltage is proposed.

The characterization of a miniaturized helium discharge ionization detector (μHDID) for micro gas chromatography through a number of parameterized experimental measurements is presented. The response of the detector is directly related to the He discharge voltage, bias electrode-to-discharge distance, and collector-to-bias distance by a simple mathematical expression. The effect of the bias voltage and the bias and collector electrode spacings relative to the He discharge were found to improve the detector response as much as 12-fold depending on the design and various operational parameters. The detection of octane from a headspace injection was performed over 24 h of continuous operation with no noticeable degradation. Finally, a sensitivity test for octane in air was conducted using the design and parameters with the best response to obtain an absolute limit of detection of 60 pg for octane in air at 3.3 mW.