It is very necessary to develop sensitive, selective, and reliable methods for the direct determination of trace catecholamines due to its physiological function and the diagnosis of some diseases in clinical medicine. Generally, the determination of them is carried out by various methods. In order to overcome the large capacitance encountered with these pastes which affects the measured signal, microelectrodes were used to minimize the background current and improve the signal to background respons. In this research application of ionic liquid, 1-butyl-3-methyl imidazolium hexafluoro phosphate and multiwall carbon nanotubes for modification of an electrode surface for the analysis of dopamine and epinephrine has been studied. Ionic liquids (ILs) were utilized in preparing carbon paste electrodes with improved sensitivity, linearity, and stability. Several parameters affect on the fabrication of the sensors such as percentage of ionic liquid and carbon nanotubes were studied. The electrochemical behavior of the compounds at the modified electrode was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV). The electrochemical behavior of dopamine and epinephrine on the MWCNTs/CILE was carefully studied by cyclic voltammetry and the electrochemical parameters such as the charge transfer coefficient (??) and the diffusion coefficient were calculated. Differential pulse voltammetry was used to determine the linear calibration ranges of these compounds. The interferences of foreign substances were investigated. The modified electrodes were successfully applied to the determination of biological compounds in real samples. In the second section an ionic liquid modified carbon nanotubes paste electrode (IL/CNTPE) has been fabricated using hydrophilic ionic liquid (1-hexyl-3-methylimidazolium hexafluoro phosphate) as a binder. Cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy as diagnostic and measurement techniques were used. Diclofenac and morphine are widely used in clinical medicine for the treatment of inflammatory conditions such as rheumatoid arthritis, osteoarthritis and ankylosing spondilytis. The efficacy of diclofenac equals that of many newer and established NSAIDs. Therefore, determination of these compounds are very important. This electrode showed enhanced electrochemical response and strong analytical activity towards the direct electrochemical oxidation of diclofenac (DCF) and morphine. The electron transfer coefficient, ?, and charge transfer resistant (R ct ) of DCF and morphine at the modified electrode were calculated. Under the optimized conditions, the calibration curves were linear in the concentration range of 0.5-300.0 ??M for diclofenac, with a limit of detection 0.2 ??M and 0.6-600.0 ??M for morphine with a limit of detection of 0.17 ??M. The interferences of foreign substances were investigated. The results confirm the high selectivity, good sensitivity, and stability of the modified electrodes. The proposed sensor was successfully used for determination of diclofenac and morphine in real sample such as human urine, tablet and other pharmaceutical product. The reasons for this electrocatalytic behavior were evaluated and it was found that different factors such as increase in the ionic conduction of the binder, decrease in the resistance of the modified electrode, increase in ion exchange properties of the electrode and the inherent catalytic activity of ionic liquids are responsible for the considerable improved electrochemical response obtained in the presence of traces of ionic liquid.