History of Cobaltabis(dicarbollide) in Potentiometry, No Need for Ionophores to Get an Excellent Selectivity.

This work is a mini-review highlighting the relevance of the θ metallabis(dicarbollide) [3,3'-Co(1,2-C2B9H11)2]- with its peculiar and differentiating characteristics, among them the capacity to generate hydrogen and dihydrogen bonds, to generate micelles and vesicles, to be able to be dissolved in water or benzene, to have a wide range of redox reversible couples and many more, and to use these properties, in this case, for producing potentiometric membrane sensors to monitor amine-containing drugs or other nitrogen-containing molecules. Sensors have been produced with this monoanionic cluster [3,3'-Co(1,2-C2B9H11)2]-. Other monoanionic boron clusters are also discussed, but they are much fewer. It is noteworthy that most of the electrochemical sensor species incorporate an ammonium cation and that this cation is the species to be detected. Alternatively, the detection of the borate anion itself has also been studied, but with significantly fewer examples. The functions of the borate anion in the membrane are different, even as a doping agent for polypyrrole which was the conductive ground on which the PVC membrane was deposited. Apart from these cases related to closo borates, the bulk of the work has been devoted to sensors in which the θ metallabis (dicarbollide) [3,3'-Co(1,2-C2B9H11)2]- is the key element. The metallabis (dicarbollide) anion, [3,3'-Co(1,2-C2B9H11)2]-, has many applications; one of these is as new material used to prepare an ion-pair complex with bioactive protonable nitrogen containing compounds, [YH]x[3,3'-Co(1,2-C2B9H11)2]y as an active part of PVC membrane potentiometric sensors. The developed electrodes have Nernstian responses for target analytes, i.e., antibiotics, amino acids, neurotransmitters, analgesics, for some decades of concentrations, with a short response time, around 5 s, a good stability of membrane over 45 days, and an optimal selectivity, even for optical isomers, to be used also for real sample analysis and environmental, clinical, pharmaceutical and food analysis.

Voltammetric and amperometric determination of 2,4-dinitrophenol metabolites.

Methods for determination of 2-amino-4-nitrophenol and 4-amino-2-nitrophenol, metabolites of 2,4-dinitrophenol, were developed using differential pulse (DP) voltammetry and HPLC with amperometric and spectrophotometric detection. The applicability of these methods was tested by the determination of the analytes in model samples of urine after preliminary separation by solid-phase extraction. Voltammetry enabled parallel determination of both analytes, but its application in real matrix was severely limited due to the interference of other compounds present in urine. HPLC allowed the determination in real urine matrix down to micromolar concentrations; amperometric detection proved to be more sensitive and selective than the spectrophotometric one.

Additive tuning of redox potential in metallacarboranes by sequential halogen substitution.

The first artificially made set of electron acceptors is presented that are derived from a unique platform Cs[3,3'-Co(C(2)B(9)H(11))(2)], for which the redox potential of each differs from its predecessor by a fixed amount. The sequence of electron acceptors is made by substituting one, two, or more hydrogen atoms by chlorine atoms, yielding Cs[3,3'-Co(C(2)B(9)H(11-y)Cl(y))(C(2)B(9)H(11-z)Cl(z))]. The higher the number of chlorine substituents, the more prone the platform is to be reduced. The effect is completely additive, so if a single substitution implies a reduction of 0.1 V of the redox potential of the parent complex, then ten substitutions imply a reduction of 1 V.

Cobaltabisdicarbollide anion receptor for enantiomer-selective membrane electrodes.

A potentiometric sensor for enantiomers has been prepared with no chiral additives, only cobaltabisdicarbollide and the protonated enantiomer.

Application of the cobaltabisdicarbollide anion to the development of ion selective PVC membrane electrodes for tuberculosis drug analysis.

The cobaltabisdicarbollide anion is used as a new material able to generate an ion-pair complex used for PVC membrane ion selective electrodes.

Determination of cobalt in pharmaceutical products.

The aim of this paper is to determine the content of cobalt in pharmaceutical products (B(12) vitamin powder, B(12) ampoules, Centrum, Spectrum ABC and Optima Forte) by spectrometric (FAAS, GFAAS and ICP-AES) and electrometric (AdSV) analytical techniques. The samples (approximately 0.5g) were treated with a mixture of 6mL HNO(3) and 1mL H(2)O(2) in the microwave oven. Due to the matrix effects the method of standard addition is preferred. The validity of the methods was tested by recovery studies of standard addition and results were found to be satisfactory.

Analytical contributions to the evaluation of painting authenticity from Princely church of Curtea de Arges.

The present study contains the analyses performed for pigment samples taken from the Princely church of Curtea de Arges, one of the oldest churches in Romania. The results of our investigations have shown the source of these samples, thus being identified the pigments: natural ultramarine, cinnabar, red earth, and calcium carbonate in the painting from the 14th century, the pigments: lead white, zinc white, and Prussian blue in the repainting from the 19th century and the pigments zinc white, titanium dioxide white, bone white, yellow ochre, red ochre, green earth, artificial ultramarine, and mars red in the interventions carried out in the 20th century. The analyses consisted of light microscopy (LM) and microchemical tests, as well as energy dispersive X-ray (EDX) analysis. This system of analyses allows one to precisely determine the authenticity of certain pigments, thus avoiding the dating errors for different interventions carried out on the original mural painting from the Saint Nicholas Princely church of Curtea de Arges.

Differential pulse cathodic stripping voltammetric determination of selenium in pharmaceutical products.

The aim of this paper is to determine selenium from pharmaceutical products by differential pulse cathodic stripping voltammetry. Firstly, were established the optimum parameters for voltammetric determination of selenium (electrolyte, deposition time, pulse duration, pulse amplitude, etc.) and secondly, the content of selenium was determined in five pharmaceutical products. The drug samples were treated with a mixture of 6 ml HNO(3) and 1 ml H(2)O(2) in the microwave oven. Due to the matrix effects the method of addition is preferred. The peak potential is -0.545 V vs. Ag/AgCl, and the calibration curve is linear up to 0.125 ng/ml, but selenium was determined from pharmaceutical products used the calibration curve in the range 8-64 ng/ml, due to the concentration of selenium in these tablets.