The voltammetric behavior of selected nitrophenols (2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol) was investigated by differential pulse voltammetry (DPV) and by adsorptive stripping voltammetry (AdSV) at an unmodified electrode (CPE) and a clay-modified carbon paste electrodes modified by montmorillonite (MMT-CPE) and sepiolite (SEP-CPE) using electrochemical reduction and oxidation in Britton-Robinson buffer. For reduction, optimum conditions have been found at pH 2 for 2-NP and 4-NP, at pH 3 for 2,4-DNP and at pH 4 for 2,4,6-TNP. For oxidation, optimum conditions have been found at pH 2 for 2-NP and 4-NP and at pH 5 for 2,4-DNP. Voltammetric determination using electrochemical oxidation is not a suitable method for 2,4,6-TNP. The lowest detection limits were obtained for 2-NP using cathodic AdSV on SEP-CPE with 2,9·10-7 mol.dm-3 , for 4-NP using cathodic DPV on MMT-CPE with 2·10-6 mol.dm-3 , for 2,4-DNP using cathodic AdSV on SEP-CPE with 2,7·10-7 mol.dm-3 and for 2,4,6-TNP using cathodic DPV on unmodified electrode with 4,8·10-7 mol.dm-3 . Determination of mixture 2-NP and 4-NP and the possibility of the selective determination using open circuit sorption with DPV detection was further studied.

Amino derivatives of polycyclic aromatic hydrocarbons are well-known chemical carcinogens which should be carefully monitored in our environment. They are amenable to anodic oxida- tion on suitable solid or paste electrodes. This fact was exploited for voltammetric determina- tion of 4-aminobiphenyl on unmodified carbon paste electrode and carbon paste electrodes modified by montmorillonite and sepiolite. The optimum pH of BR buffer for measurement on unmodified carbon paste electrode is pH 2, pH 10 for CPE-SEP and pH 11 for CPE-MMT. It was possible to increase sensitivity of the determination using adsorptive stripping voltam- metry on modified electrodes. The optimum time for accumulation of 4-aminobiphenyl is 5 minutes. The limits of quantification of the order of 10−6 mol dm−3 were obtained for each electrode. After accumulation, the limits of quantification decreased to the 10−7 mol dm−3 . The newly developed method was tested for the determination of 4-aminobiphenyl in model sam- ples of drinking and river water, reaching limits of quantification of the order of 10−7 mol dm−3 .

This study employed spectral analyses for acoustic measures of sustained vowel productions from a group of 20 adolescents and young adults with Friedreich's Ataxia (FA) and compared findings with a group of 20 age-equivalent and gender-matched normal control participants. State-of-the art spectral analyses from the Analysis of Dysphonia in Speech and Voice (ADSV) program, developed for various voice disorders from Kay Elemetrics, were applied to initial 2 second sustained vowel segments of the vowels /a/, /i/, and /o/. Spectral analyses included averages and standard deviations of Cepstral Peak Prominence (CPP), Cepstral Peak Prominence Standard Deviation (CPP SD), Low/High Spectral Ratio (L/H Ratio), Low/High Spectral Ratio Standard Deviation (L/H Ratio SD), Cepstral/Spectral Index of Dysphonia (CSID), and Mean Cepstral Peak Prominence Fundamental Frequency (Mean CPP F0). Statistical analyses revealed significant differences between the spectral analyses of voice characteristics of individuals with FA and those of normal controls for all measures except for CPP SD. The aim of these analyses was to determine spectral differences evident in vowel productions of individuals with FA using new cepstral-derived measures that characterize the phonatory instability and dis-coordination present in this disorder. Such research may not only help develop early non-invasive indicators of ataxia and track disease progression, but also serve to stimulate research into alleviating the symptoms of this devastating disease.