Fast Readout of Split-Ring Resonators Made Simple and Low-Cost for Application in HPLC

Abstract

Split-ring resonators (SRR) are simple electrical circuits that show a significant shift in resonance frequency even with the smallest changes in split capacitance, and thus in permittivity, electric conductivity, and dielectric losses of the split capacitor’s dielectric. Usually, the resonance frequency is derived from the frequency response, but recording the frequency spectrum takes a certain amount of time. Here, we present a new capillary split-ring resonator CaSRR with fast readout for liquid chromatography (LC), which is capable of accurately detecting very fast changes in split capacity. The proposed method is based on the detection of the transmitted signal at a single frequency that is analyzed by demodulation. The demodulated signal changes its amplitude depending on the shift of the resonance frequency. Our simple low-cost electronics enables an average sampling rate of 42 Hz with 128 averages of the demodulated signal and has a frequency stability of 840 mHz. Thus, a minimum change in permittivity of Δεr,min = 11.26 × 10−3 can be detected. Finally, a chromatogram of one sugar (glucose) and one sugar alcohol (xylitol) is recorded using the SRR and is compared to a standard refractive index detector.

P31 - Electronics for Continuously Measuring the Resonance Frequency and Attenuation of a Split-Ring Resonator

“…6. In all measurements, the electronics was tested in combination with an SRR consisting of a transmission line on PCB (FR4) and a stainless-steel capillary splitring structure forming the split-ring resonator (CaSRR) as used in Hitzemann et al [6]. This CaSRR is specifically developed for liquid analysis in LC applications.…”

“…Dielectric losses and conductivity can be also seen in the quality factor. Usually, the resonance frequency of SRRs used in sensor applications are in the triple-digit MHz range, however, the electronics must be able to accurately detect changes in the frequency in the lower Hz range [6].…”

Split-Ring Resonator Based Sensor for the Detection of Amino Acids in Liquids

“…They are needed for the growth and maintenance of cells, part of the cytoskeleton, protein components of enzymes, signaling molecules, and receptors [19] (pp. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. However, essential amino acids cannot be produced by the organism and thus must be supplied through the nutrition [20].…”

“…However, the most common use for split-ring resonator-based sensors are biosensors for measuring liquid samples including detecting biological substances such as C-reactive protein (CRP) [ 4 ], DNA-hybridization [ 5 ], prostate-specific antigen (PSA) [ 6 ] and Heparin [ 7 ]. An additional application for SRRs is determining the dielectric properties of liquids [ 8 , 9 , 10 , 11 ]. Detecting changes in the dielectric properties has specific relevance for chromatographic applications in the liquid phase including high performance liquid chromatography (HLPC), ultra-high pressure liquid chromatography (UHPLC) or ion chromatography (IC) [ 10 , 11 ].…”

P20 - Split-Ring Resonator for measuring low amounts of glutamic acid in pure water

“…Therefore, SRRs are very sensitive to changes in the dielectric properties of a sample at the split capacitor that sets the resonant circuit and can be used as sensitive detectors to measure the properties of liquids [4]. For highest sensitivity, the split capacitor needs to be as large as possible in relation to the parasitic capacitances [3].…”