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In this master s thesis, electrochemical determination of homovanillic acid (HVA) andˈ vanillylmandelic acid (VMA) was performed on carbon paste electrode. The purpose of this thesis was finding out optimal conditions for determination of these analytes by ndifferential pulse voltammetry (DPV) and high pressure liquid chromatography with a carbon paste electrode as an electrochemical detector (HPLC-ED). The electrochemical behavior of the compounds depends mainly on pH of the solution; the best results are obtained in acidic medium. The limits of detection for DPV method were for HVA 0,38 μmol·dm-3 and for VMA 0,25 μmol·dm-3 . The limits of detection for HPLC-ED were for HVA 0,7 μmol·dm-3 and for VMA 0,2 μmol·dm-3 . Developed method was successfully used for the determination of homovanillic and vanillylmandelic acid in urine samples. With HPLC - ED the limits of detection 0,8 μmol·dm-3 (HVA) and 0,5 μmol·dm-3 (VMA) were achieved. Key words: Homovanillic acid, vanillylmandelic acid, carbon paste electrode, DPV, HPLC

Metabolites of neurotransmitters of dopamine, homomovanillic acid (HVA), and of serotonin, 5-hydroxyindole acetic acid (5-HIAA), were assessed in cerebrospinal fluid by the method of high pressure liquid chromatography with electrochemical detection. The HVA concentration in cerebrospinal fluid rose markedly in a two-month-old infant with intracranial hypertension caused by a communicating hyporesorptive hydrocephalus following administration of tyrosine, the precursor of dopamine. The 5-HIAA concentration in cerebrospinal fluid rose significantly in a 20-month-old boy with epilepsy and arrested psychomotor development after administration of 5-hydroxytryptophan, the precursor of dopamine. Biochemical normalization of concentrations of neurotransmiteed metabolites did not lead to changes in the clinical condition of the children.

Metabolites of neurotransmitters, homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA) were assessed in the cerebrospinal fluid of 149 children of different age from neonatal age to 13 years by the method of high pressure liquid chromatography with electrochemical detection. The mean concentration of the two metabolites in cerebrospinal fluid correlated indirectly with the childrens age--the highest mean concentrations of HVA and 5-HIAA were found in the group of neonates, lower values in infants and the lowest ones in the group of toddlers and older children. In the group of toddlers and older children with severe mental disorders and repeated tonic-clonic or myoclonic seizures a lower mean 5-HIAA was found in the cerebrospinal fluid than in children of equal age, similarly mentally affected but without seizures in the case-history.