Full length articleA label-free detector for liquid chromatography systems using mm-wave technology: First proof of concept

- A millimeter-wave detector is made for liquid chromatography for the first time.
- The mechanism relies on dielectric permittivity change of liquids.
- Detections with and without stationary phase are demonstrated.
- UV-absorbing and non-UV absorbing compounds can be detected without labeling.
- The signal-concentration relations are monotonic and fitted with quadratic models.

The development of millimeter-wave (mm-wave) technology has enabled the study of bio-molecular interactions by means of electromagnetic waves with frequencies between 30 and 300 GHz. In this study, an attempt has been made to exploit the possibility of mm-wave technology as alternative detection technique for liquid chromatographic (LC) systems. The goal is to design and fabricate a label-free mm-wave detector that is compatible with LC systems. As proof-of-concept experiments, the UV absorbing compounds praziquantel and trans-stilbene-oxide as well as a non-UV absorbing compound sorbitol are injected in an open capillary as well as a capillary with stationary phase and measured by both mm-wave and UV detectors. The in-house developed mm-wave detector is capable of detecting all compounds without the need for labelling. Although the detection limit of such detector still needs to be verified and occasionally improved in the future, it already shows great potential as an additional detection technique for LC systems.