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Due to their electrochemical and economical characteristics, pencil graphite electrodes (PGEs) gained in recent years a large applicability to the analysis of various types of inorganic and organic compounds from very different matrices. The electrode material of this type of working electrodes is constituted by the well-known and easy commercially available graphite pencil leads. Thus, PGEs are cheap and user-friendly and can be employed as disposable electrodes avoiding the time-consuming step of solid electrodes surface cleaning between measurements. When compared to other working electrodes PGEs present lower background currents, higher sensitivity, good reproducibility, and an adjustable electroactive surface area, permitting the analysis of low concentrations and small sample volumes without any deposition/preconcentration step. Therefore, this paper presents a detailed overview of the PGEs characteristics, designs and applications of bare, and electrochemically pretreated and chemically modified PGEs along with the corresponding performance characteristics like linear range and detection limit. Techniques used for bare or modified PGEs surface characterization are also reviewed.

Extraction of polyphenols from Sea Buckthorn leaves using microwave assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) by Folin-Ciocalteu method or by differential pulse voltammetry (DPV) and the concentration of the main polyphenolic compounds by HPLC. The specific microwave energy was also determined. MAE leads to a shorter extraction time (7.5 min versus 30 min for the conventional method). The best results of MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction.

The present paper describes the voltammetric analysis of dipyridamole (DIP) at a cheap, disposable pencil graphite electrode (PGE). The working conditions were optimized with regard to the electrode material and the supporting electrolyte. Cyclic voltammetric investigations emphasized that DIP is irreversibly oxidized at the PGE. The electrode process is pH-dependent and controlled by both diffusion and adsorption. For DIP quantitative determination a differential pulse voltammetric (DPV) method in phosphate buffer solution pH 7.00 was developed. DIP's oxidation peak current varied linearly with the analyte concentration, presenting two linear ranges, namely 5.00 $\times $ 10$^{-7}$-2.50 $\times $ 10$^{-5}$ M and 2.50 $\times $ 10$^{-5}$-2.50 $\times $ 10$^{-4}$ M, with detection and quantification limits of 1.21 $\times $ 10$^{-7}$ M and 4.03 $\times $ 10$^{-7}$ M DIP, respectively. The newly developed DPV method using the inexpensive, disposable PGE was successfully applied for the simple and rapid determination of DIP from pharmaceutical formulations.