Apinya Obma^1,2, Pattamaporn Hemwech^1,2, Sittisak Phoolpho^1,2, Rawiwan Bumrungpuech^1,2, Supa Wirasate^1,3, Sulawan Kaowphong⁴, Prapin Wilairat⁵ & Rattikan Chantiwas^1,2*

¹Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.

²Center of Excellence for Innovation in Chemistry and Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.

³Center for Surface Science and Engineering and Rubber Technology Research Center, Faculty of Science, Mahidol University, Salaya, Nakhon Pathom 73170, Thailand.

⁴Department of Chemistry and Environmental Science Research Center (ESRC), Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand. 5Analytical Sciences and National Doping Test Institute, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.

*email: rattikan.cha@mahidol.ac.th

Abstract:

A hydrothermal sol–gel method for reproducible formation of silica nanolayer on the wall of silica capillaries was developed for electrochromatography. The formulation was optimized by observation of uniform gel formation on an optical microscope. The variables of the formulation include types of solvent, water-TEOS ratio, CTAB and urea contents, and mixing method. The procedure produced a coating of silica ca. 100 nm thick layer on the wall of the capillary. Surface morphology of the coating was characterized by SEM, contact angle and chemical composition by FT-IR spectroscopy and X-ray powder diffraction. The coating reduced the electroosmotic mobility producing enhanced separation performance. Eight standard amines (including tyramine and benzhydrylamine, as an internal standard) were separated with peak resolution R_s ≥ 2 for all adjacent peaks and plate number N ≥ 3.0 × 104 m^-1. Calibration was linear from 5 to 200 µg L-1, with r² > 0.9985 and instrumental LOD of 4.9 μg L^-1. Five samples of food products were diluted and analyzed for the amines using the coated capillary and only tyramine was detected. Intra-day and inter-day precisions were less than 1.2%RSD. Percent recoveries of spiked tyramine in samples were 95 ± 3 to 106 ± 7% (n = 3).

Reference:

A. Obma, P. Hemwech, S. Phoolpho, R. Bumrungpuech, S. Wirasate, S. Kaowphong, P. Wilairat, R. Chantiwas, Silica nanolayer coated capillary by hydrothermal sol–gel process for amines separation and detection of tyramine in food products, Scientific Reports 12(1) (2022) 7460. 10.1038/s41598-022-11078-y. doi: 10.1038/s41598-022-11078-y