M.E. Díaz García

On-line aluminium pre-concentration and its application to the determination of the metal in dialysis concentrates by atomic spectrometric methods

Cation and anion exchangers (Dowex 50W-X2 and Amberlite IRA-400), Chelex 100 and a synthetic chelating resin (Kelex 100 adsorbed on Amberlite XAD-7) were packed in a minicolumn inserted in a flow injection pre-concentration manifold with the aim of determining aluminium in the µg l–1 range in dialysis concentrates by atomic absorption and/or inductively coupled plasma atomic emission spectrometry. The optimisation of the operating conditions for the pre-concentration of aluminium has been studied for each of the investigated resins. The selection of appropriate solid phases and their successful application to the determination of aluminium in dialysis concentrates, samples with a high salt content, are discussed.

Room-temperature liquid phosphorimetry of the aluminium-ferron chelate in micellar media : Determination of aluminium☆

Abstract Aluminium reacts with 7-iodo-8-quinolinol-5-sulphonic acid (Ferron) in cetyltrimethylammonium bromide (CTAB) micelles to form a highly phosphorescent complex at room temperature. Suitable experimental conditions and the phosphorescent characteristics of the complex are described. Comparison with the results obtained for the phosphorescent niobium-Ferron complex in CTAB micelles helps to elucidate the mechanism of this type of phosphorescence. For aluminium the detection limit is 5.4 ng ml−1; the relative standard deviation is 4.5% for 20 μg Al. The method is applied to aluminium determination in waters and dialysis fluids.

Flow injection ion-exchange pre-concentration for the determination of aluminium by atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

A flow injection ion-exchange pre-concentration procedure, using a micro-column loaded with Amberlite IRA-400, is outlined for the simple and quantitative determination of trace amounts of aluminium in the ng I–1 range by atomic absorption and/or inductively coupled plasma atomic emission spectrometry. The optimisation of the operating conditions and figures of merit are given and a possible retention mechanism for aluminium in the anion exchanger is discussed. Serum aluminium is so tightly bound by proteins that it is not retained by the resin in the flow procedure. The method can be used, however, for the rapid determination of free aluminium in waters and haemodialysis fluids.

The surfactant-sensitized analytical reaction of niobium with 8-hydroxyquinoline-5-sulphonic acid

Cationic surfactants, such as cetylpyridinium bromide (CPB), sensitize the colour reaction of Nb(V) with 8-hydroxyquinoline-5-sulphonic acid (H(2)L). The formation of a ternary complex of stoichiometry 1:3:3 (Nb-L-CPB) is responsible for the observed enhancement in absorptivity and the quenching in the fluorescence of the Nb-L chelate, when a surfactant is present. The ternary complex exhibits maximum absorption at 383 nm ( = 1.46 +/- 0.01 x 10(4) l.mole(-1).cm(-1)) at pH 5.7, and Beers law is obeyed up to 6-mug ml Nb concentration. Conditional formation constants of the niobium chelate in the presence and absence of CPB have been determined. On the basis of a detailed spectrophotometric and fluorimetric study the nature of the chromophoric reagent-surfactant interaction and the peculiar features of the sensitization by CPB are discussed.

The complexation of Cr(III) and Cr(VI) with flavones in micellar media and its use for the spectrophotometric determination of chromium

The complexation of chromium by different flavonoid dyes in micellar media has been studied, in particular the reaction between chromium and quercetin. Micellar effects, the reaction pathway proposed and the application of the method to the determination of Cr(VI) and Cr(VI) + Cr(III) mixtures are discussed.

Room-Temperature Phosphorescent Complexes with Macromolecular Assemblies and Their (Bio)chemical Applications

A number of metal complexes, including hydroxyquinolines, phthalocyanines, porphyrins, chlorophyls, and others, phosphoresce at room temperature in the presence of macromolecular assemblies such as micelles, vesicles, proteins, and nucleic acids. The aim of this review is to illustrate the applicability of these systems to a variety of analytical problems through the discussion of representative examples. Finally, recent developments and likely prospects in the field of room temperature phosphorescent complexes, such as probes of vascular disorders, are also considered.

Phosphorescence detection in flowing systems : selective determination of aluminium by flow-injection liquid room-temperature phosphorimetry

Abstract The concept of the micelle stabilized liquid room-temperature phosphorescence (MS-LRTP) was applied to the determination of a metal (aluminium) in a flowing system. A three-line flow-injection manifold was developed and various parameters were optimized. A linear calibration graph was obtained for 0–4 μg ml−1 aluminium. The limit of detection was 50 ng ml−1 and the relative standard deviations for 0.1 and 1.0 μg ml−1 aluminium were 2.7 and 1.3% respectively. The proposed procedure is fairly selective. More than 20 common ions studied did not interfere with the determination of aluminium or could be masked by appropriate reagents. The flow-injection method proposed was applied without any preliminary separation to the determination of aluminium in simulated synthetic samples in water and in clinical samples of particular importance in the control of aluminium toxicity in renal failure patients.

Fluorescence and liquid room-temperature phosphorescence of the aluminium-ferron chelate in vesicles

Abstract In order to evaluate the analytical potential of vesicles for enhancing the room-temperature luminescence of metal chelates, the photoluminescence emission of the aluminium-ferron complex in vesicular solutions was examined. The presence of vesicles of didodecyldimethylammonium bromide produced a six-fold enhancement in the fluorescence intensity of the metal chelate. Vesicles also proved to be efficient stabilizers to obtain analytically useful liquid room-temperature phosphorescence for aluminium. Optimum experimental conditions and luminescence characteristics of the aluminium complex in the presence of vesicles are described and compared with those obtained for the same chelate in micellar media. As a result, a vesicle-enhanced fluorimetric procedure is proposed which has been successfully applied to the determination of low levels of aluminium in milk powders.

Exploitation of synthetic surfactant vesicles for enhanced fluorescence of metal chelates

Abstract The use of synthetic surfactant vesicles as a means for enhancing the photoluminescence of metal chelates is illustrated and a sensitive fluorimetric determination of aluminium with quinolin-8-ol-5-sulphonic acid in vesicles of didodecyldimethylammonium bromide is given. The influence of different variables on the organized aluminium-quinolin-8-ol-5-sulphonic acid reaction is investigated and possible mechanisms of the observed enhancing effects are discussed. The limit of detection is 1 μg l −1 of aluminium. The optimized fluorimetric method has been successfully applied to the determination of aluminium in tap waters and dialysis fluids.

Micelle-stabilized liquid room-temperature phosphorimetry for metals: The micellar reaction of gallium with 7-iodo-hydroxyquinoline-5-sulfonic acid and its application to the metal determination

The Ga(III)-7-iodo-8-hydroxyquinoline-5-sulfonic acid complex in the presence of suitable micelles and with sodium sulfite as oxygen scavenger exhibited strong phosphorescence at room temperature in aqueous solutions. This micellar reaction provides the basis for a convenient phosphorimetric determination of traces of gallium. Different types of micelles showed their maximum enhancing effects at different pH ranges, affording greater convenience for various analytical purposes. A phosphorimetric procedure with surfactant cetyltrimethylammonium bromide as enhancing agent is proposed. The detection limit for gallium was 5 ng/ml and the calibration graph was rectilinear in the range of 5 to 600 ng/ml. The relative standard deviation was 4% at 50 ng/ml level. The applicability of this room-temperature phosphorimetric procedure to multi-component analyses for the group III elements, Al(III), Ga(III), and In(III), was demonstrated. Kalman filtering was used to deconvolute the phosphorescence spectra of mixtures of aluminium and gallium allowing the simultaneous determination of both metals with satisfactory results.