A dipyridamole (DIP) based surface molecularly imprinted polymer (MIP) was synthesized and applied as a sensing agent in a sensing layer of a new modified potentiometric carbon paste electrode (CPE). The potentiometric modified CPEs (GO@SiO2-NH2-MIP/MWCNTs/CPE, where GO is graphene oxide and MWCNTs is multi-walled carbon nanotubes) showed an improved performance in term of Nernstian slope, selectivity and response time compared to the unmodified CPE. The response time of the sensor in the range of 2.5 × 10-8-1.1 × 10-2 M DIP was 20 s. The obtained DIP sensor showed low limit of detection (1 × 10-8 M), and satisfactory long-term stability (higher than 4 months). The practical application of the sensor was demonstrated by the determination of DIP concentration in urine samples and pharmaceutical preparations, with good precision and acceptable recoveries (96.0-103.0%). The prepared sensor showed high selectivity for DIP over a number of common species (aspirin, caffeine, ascorbic acid, glucose, urea, bipyridine, Na+, Fe3+, Mg2+, Ca2+ and K+).

In this work, for the first time, a highly sensitive method based on dispersive liquid-liquid microextraction coupled with positive corona discharge ion mobility spectrometry as a fast and inexpensive technique has been evaluated for the direct determination of melamine. The effective parameters influencing the microextraction efficiency, such as pH, the properties of extraction and dispersion solvent were investigated. Under the optimum conditions, analytical parameters such as linearity, precision and limit of detection were evaluated. The calibration graph of melamine determination using the proposed method has two regions of linearity from 0.5 to 70 ng mL-1 and 70 to 1500 ng mL-1, the limit of detection and limit of quantification are 0.25 and 0.5 ng mL-1, respectively, and the relative standard deviation was less than 3% for all experiments. The proposed method was successfully applied for the determination of melamine in the milk, dairy products and egg yolk.

A simultaneous solid phase extraction procedure for enrichment of Cu(II), Cd(II) and Mn(II) has been developed. The method is based on adsorption of Cu(II), Cd(II) and Mn(II) ions on polyethylene glycol-silica gel pre-conditioned with acetate buffer (pH 5.5). The adsorbed metal ions are eluted with nitric acid (1 mol L -1) and determined by flame atomic absorption spectrometry. The calibration graph was linear in the range of 2-140 ng mL-1 for Cu(II), 1-40 ng mL-1 for Cd(II) and 4-100 ng mL-1 for Mn(II). The limits of detection were 0.66, 0.33 and 1.20 ng mL-1 for Cu(II), Cd(II) and Mn(II), respectively.