Chronoamperometric determination of lead ions using PEDOT:PSS modified carbon electrodes

A new simple chronoamperometry methodology was developed for the ultrasensitive determination of lead ions using a PEDOT:PSS coated graphite carbon electrode. The polymer was directly coated on a graphite carbon electrode and characterized using simple cycle voltammetric measurements. The presence of lead ions induced a cathodic peak starting at −550 ± 10 mV vs. Ag/AgCl, and an anodic peak starting at −360 ± 10 mV vs. Ag/AgCl. Electroaccumulation of lead ions onto the PEDOT:PSS modified electrode was performed at −650 mV vs. Ag/AgCl for 30 s in a pH 2.2 hydrochloric acid solution. Chronoamperometry measurements were carried out at −350 mV vs. Ag/AgCl allowing the oxidation of accumulated lead. Using this method, lead ions were detected for concentrations ranging between 2.0 nmol L⁻¹ and 0.1 μmol L⁻¹ (R² = 0.999). The detection limit was calculated to be 0.19 nmol L⁻¹ and the quantification limit of 0.63 nmol L⁻¹. The method was shown to be highly precise and sensitive, negligible interference was detected from other metal ions. The proposed method was successfully applied for the detection of lead ions in vegetables.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Surface modification of activated polymeric matrices by dendritic attachments

Aware of the growing interest in materials that exhibit specific physiochemical properties and potential applications, we focused our work on modifying commercial agarose with polyfunctional dendrons capable of molecular recognition through hydrogen bonding. 2,6‐Di(acylamino)pyridine moieties within the internal superstructure of dendritic macromolecules have been reported to be capable of forming H‐bonded complexes with imide groups, such as barbituric acid and its derivatives. We report the synthesis of new dendrons possessing multiple 2,6‐di(acylamino)pyridinyl sites, each capable of molecular recognition, and the development of new polymeric supports of an activated agarose matrix by surface modification. From comparative studies of the beads modified by different dendrons, we found improved results in those dendritic supports possessing 2,6‐di(acylamino)pyridinyl moieties, except when their juxtaposition between the groups promoted inner H bonds. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2779–2786, 2000     

Determination of loads applied perpendicularly to the outer boundary of a ring using coefficients of influence

A procedure is explained to determined the amount of several pairs of diametrical loads applied to the outside boundary of a ring when stresses at selected points of the inside or outside boundaries are known. Coefficients of influence are used, following an approach similar to the one presented in a previous paper. Examples of application are given and the possible increase in precision is shown when the number of points of measurements is larger than the number of loads to be determined.