The aim of this paper was to assess the total antioxidant capacity of some commercial fruit juices (namely citrus), spectrophotometrically and by the biamperometric method, using the redox couple DPPH· (2,2-diphenyl-1-picrylhydrazyl)/DPPH (2,2-diphenyl-1-picrylhydrazine). Trolox® was chosen as a standard antioxidant. In the case of the spectrophometric method, the absorbance decrease of the DPPH· solution was followed. For the biamperometric method, the influence of some parameters like the potential diference, ΔE, DPPH· concentration, and Trolox® concentration was investigated. The calibration graph obtained for Trolox® presents linearity between 5 and 30 µM, (y = 0.059 x + 0.0564, where y represents the value of current intensity, expressed as μA and x the value of Trolox® concentration, expressed as μM; r2 = 0.9944). The R.S.D. value for the biamperometric method was 1.29% (n = 10, c = 15 μM Trolox®). In the case of the spectrophotometric method, the calibration graph obtained for Trolox® presents linearity between 0.01 and 0.125 mM (y = -9.5789 x+1.4533, where y represents the value of absorbance and x, the value of Trolox® concentration, expressed as mM; r2 = 0.9963). The R.S.D. value for the spectrophotometric method was 2.05%. Both methods were applied to total antioxidant activity determination in real samples (natural juices and soft drinks) and the results were in good agreement.

The even growing production of both well-known and new derivatives with pharmaceutical action involves the need for developing facile and reliable methods for the analysis of these compounds. Among the widely used instrumental techniques, the electrochemical ones are probably the simplest and the most rapid, also having good performance characteristics. However, the key tool in electroanalysis is the working electrode. Due to the inherent electrochemical and economic advantages of the pencil graphite electrode (PGE), the interest in its applicability in the analysis of different analytes has continuously increased in recent years. Thus, this paper aims to review the scientific reports published in the last 10 years on the use of the disposable eco- and user-friendly PGEs in the electroanalysis of compounds of pharmaceutical importance in different matrices. The PGE characteristics and designs (bare or modified with various types of materials), along with their applications and performance parameters (e.g., linear range, limit of detection, and reproducibility), will be discussed, and their advantages and limitations will be critically emphasized.

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A comprehensive, critical, and an updated review of the applications of flow-injection analysis (FIA) techniques for the analysis of inorganic cations and anions in several types of water samples except marine waters is presented. The preconcentration of metals in water samples and automaton of FIA systems for monitoring water quality are also discussed. The review is documented with 280 references.Key Words: flow-injection analysis, water analysis, analysis of inorganic cations and anions, preconcentration of metals.

Rosmarinic acid (RA) is an important bioactive phenolic acid with significant biochemical activities, including the antioxidant one. It is widely found in plants of the families Lamiaceae and Boraginaceae and has many uses in the food, pharmaceutical and cosmetics industries. RA is an electroactive species owing to the presence of the two catechol groups in its structure. Due to their inherent characteristics, such as sensitivity, selectivity, ease of operation and not too high costs, electrochemical methods of analysis are interesting tools for the assessment of redox-active compounds. Moreover, there is a good correlation between the redox potential of the analyte and its capability to donate electrons and, consequently, its antioxidant activity. Therefore, this paper presents a detailed overview of the electrochemical (bio)sensors and methods, in both stationary and dynamic systems, applied for RA investigation under different aspects. These comprise its antioxidant activity, its interaction with biological important molecules and the quantification of RA or total polyphenolic content in different samples.