The use of samples from students quotidian can get their attention for teaching contents to be presented. We have already presented a series of simple experiments demonstrating the use of flame atomic emission spectrometry in the determination of cations in samples present in our day life. Here sodium is determined in cachaça (sugar cane spirit), a very popular Brazilian drink, to demonstrate de effect of matrix composition and its physico-chemical properties in the volume of sample nebulized in a flame photometer and consequently in analytical signals by using different ethanol:water solvent mixtures for calibration.

Graphite powder was mixed to polyurethane, silicon rubber and Araldite® (epoxy) in order to prepare composite materials to be used in the preparation of electrodes. Results showed that voltammetric response could be obtained when at least 50% of graphite (w.w-1) is present in the material. SEM and thermogravimetry were also used in the characterization of the composites.

The construction and analytical evaluation of a coated graphite Al(III) ion-selective electrode, based on the ionic pair formed between the Al(F)n3-n anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated on a poly(vinylchloride) (PVC) matrix membrane are described. A thin membrane film of this ionic pair and dibutylphthalate (DBPh) in PVC was deposited directly on a cylindric graphite rod (2 cm length x 0.5 cm diameter) attached to the end of a glass tube using epoxy resin. The membrane solution was prepared by dissolving 40% (m/m) of PVC in 10 mL of tetrahydrofuran following addition of 45% (m/m) of DBPh and 15% (m/m) of the ionic pair. The effect of membrane composition, fluoride concentration, and several concomitants as potential interferences on the electrode response were investigated. The aluminium(III) ion-selective electrode showed a linear response ranging from 1.4 x 10-4 to 1.0 x 10-2 mol L-1, a detection limit of 4.0 x 10-5 mol L-1, aslope of -54.3±0.2mV dec-1 and a lifetime of more than 1 year (over 3000 determinations for each membrane). The slope indicates that the ion-selective electrode responds preferentially to the Al(F)4- species. Application of this electrode for the aluminium(III) determination in stomach anti-acid samples is reported.