On-column cryofocusing and analyte enrichment device for gas chromatography systems

The objective of this work was to design, construct and test the sample focusing and concentration enrichment device for gas chromatography. The device was based on four metal rings, between which a capillary column and two wire heaters were placed. The metal rings were connected to each other and cooled down using liquid nitrogen. The column was connected to the gas chromatography system using a heated transfer line. The research was conducted on how the length of the cooled column influences focusing and enrichment capabilities of the system. It was found that the analytes were focused better by using a longer cooled part of the column. The longer cooled column was also able to retain a greater volume of the analytes, injected consecutively. By using the 95 cm cooled column length, it was possible to retain 20 injections and detect a 20 times bigger peak area. By changing the temperature of the cooling zone, it was also observed that peak symmetry is heavily dependent on it. Lower cooled zone temperatures produced narrower and more symmetrical peaks.

Ultrasensitive SERS-Based Plasmonic Sensor with Analyte Enrichment System Produced by Direct Laser Writing

We report an easy-to-implement device for surface-enhanced Raman scattering (SERS)-based detection of various analytes dissolved in water droplets at trace concentrations. The device combines an analyte-enrichment system and SERS-active sensor site, both produced via inexpensive and high-performance direct femtosecond (fs)-laser printing. Fabricated on a surface of water-repellent polytetrafluoroethylene substrate as an arrangement of micropillars, the analyte-enrichment system supports evaporating water droplet in the Cassie–Baxter superhydrophobic state, thus ensuring delivery of the dissolved analyte molecules towards the hydrophilic SERS-active site. The efficient pre-concentration of the analyte onto the sensor site based on densely arranged spiky plasmonic nanotextures results in its subsequent label-free identification by means of SERS spectroscopy. Using the proposed device, we demonstrate reliable SERS-based fingerprinting of various analytes, including common organic dyes and medical drugs at ppb concentrations. The proposed device is believed to find applications in various areas, including label-free environmental monitoring, medical diagnostics, and forensics.