Monolithic stationary phases in analysis of neurotransmitters
Martina Komendová, Jiří Urban
Department of Chemistry, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
Dopamine belongs to a group of compounds known as neurotransmitters. Disorders of
dopamine metabolism are associated with many neurological illnesses, such as schizophrenia,
depression, Parkinson's disease, and tumors. The aim of the presented dissertation thesis is
a development of monolithic stationary phases applicable in chromatographic screening
of diseases related to a dopamine metabolism. The main focus of the thesis is the preparation
and characterization of monolithic capillary columns and especially their surface modification
providing fine control over the separation selectivity and efficiency.
At first, UV-initiated two-step photografting has been utilized to prepare monolithic
capillary columns providing two zwitterion functionalities. Segments of five sulfobetaine
polymer monoliths have been modified by phoshorylcholine and columns with 0, 33, 50, 66,
and 100% of modified length. Effect of the length of the modified segment and mobile phase
composition have been tested to improve selectivity of prepared columns.
Next, we have used grafting technique to hypercrosslink the surface of monolithic
columns with poly(ethylene glycol) dimethacrylate. Length of crosslinking monomer, its
concentration in the modification mixture, and a time of the modification reaction have been
selected to control the extent of hypercrosslinking modification by a design of experiments
protocol. Hypercrosslinked monolithic stationary phases provided lower effect of mass
transfer resistance and allowed isocratic separation of dopamine-related compounds
at higher mobile phase linear velocity.
An important part of the thesis is a development of a miniaturized separation device with
electrochemical detection that might be applicable in integrated and portable analytical
systems. Separation selectivity of monolithic stationary phases was controlled by different
crosslinking monomers. We have developed a four-channel 3D printed separation device with
integrated electrochemical detection allowing parallel analysis of a single sample.