title: First-derivative solid-phase spectrophotometric determination of molybdenum at the ng ml(-1) level.
abstract: Derivative spectrophotometry was applied to solid-phase spectrophotometry in order to enhance its sensitivity and remove the large background noise caused by the absorption of the resin layer itself, and avoid the necessity of preparing a blank. The determination of micro-amounts of molybdenum (at the ng ml(-1) level) with pyrocatechol violet to form a 11 blue complex in acid medium, which is fixed on a dextran-type anion-exchange resin (Sephadex QAE-A-25), is described as an example of the application of this technique. The absorbance of the resin, packed in a 1 mm spectrophotometric cell, was measured directly. The characteristic peak amplitude of the signal at 716 nm in the first-derivative spectra is useful for quantitative determination of molybdenum (2-8 ng ml(-1); RSD = 4, 30%) in natural and industrial water samples, plant tissues and soil extracts.
authors.affiliation: Department of Analytical Chemistry, Faculty of Experimental Sciences, University of Jaén, E-23071 Jaén, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Molína-Diaz
authors.forename: M I
authors.initials: MI
authors.lastname: Pascual-Reguera
authors.forename: E
authors.initials: E
authors.lastname: Liñán-Veganzones
authors.forename: M L
authors.initials: ML
authors.lastname: Fernández de Córdova
authors.forename: L F
authors.initials: LF
authors.lastname: Capitán-Vallvey