Developments in UV/VIS spectrophotometry during the past decade are critically reviewed. Advances in instrumentation: sample handling, optical systems, detectors, and signal processing are discussed. The application of spectrophotometric detection in hydrodynamic systems is surveyed. Newer types of color systems employing macrocyclic compounds, porphyrines, surfactants, and basic dyes are evaluated. Separate sections are devoted to advances in spectrophotometric determination both of individual elements and organic compounds. Future trends in spectrophotometric analysis are discussed.

Recent Advances in Ultraviolet-Visible Spectrophotometry

Iminodiacetic acid has been covalently bonded to a bare silica monolith to produce the first reported high-performance monolithic chelating ion exchange column. Using the new column, separation and determination of traces of alkaline earth metal ions (low ppm) in high ionic strength samples (up to 2 M NaCl and KCl brines), could be achieved in under 40 s. At an eluent flow rate of 4 mL min(-1) retention time precision was < 1.2% (n = 9) for Mg(II) and Ca(II), with detector linearity (n = 5) over the range 2-10 mg L(-1) of between R2 = 0.985 and R2 = 0.995. In 1 M KCl and NaCl brine samples, detection limits of 0.2 mg L(-1) were possible.

Iminodiacetic acid functionalised monolithic silica chelating ion exchanger for rapid determination of alkaline earth metal ions in high ionic strength samples.

An on-line preconcentration matrix elimination procedure was developed for the analysis of concentrated brines by inductively coupled plasma mass spectrometry. Elements of interest (alkaline earths and first row transition metals) were concentrated quantitatively and isolated from the sodium chloride matrix using a chelating ion-exchange column. Two columns were evaluated, an in-house dynamically coated chelating exchange resin and a commercially available chelating resin. The method was applied to the determination of the metals in concentrated brines and the analysis of the Open Ocean Sea-water Reference Material NASS-3 (National Research Council of Canada). Linear calibrations were obtained in the concentration range of interest (<200 µg l–1) and excellent agreement with the certified reference values was obtained.

Determination of trace metals in concentrated brines using inductively coupled plasma mass spectrometry on-line preconcentration and matrix elimination with flow injection

Monolithic supports are increasingly used in the field of chromatography. They are appropriate for different applications (e.g., separation of biomolecules, organic acids and inorganic anions). However, only a few research groups are investigating the potential of using monolithic phases for rapid separation of metal cations and elemental speciation analysis. Monolithic supports based on porous monolithic silica have been successfully applied in separation of alkaline-earth and transition-metal cations in environmental waters and high ionic-strength samples. The present review covers applications of monolithic supports for chromatographic separation of metal cations and the potential for using monolithic chromatography in elemental speciation analysis. We critically evaluate the performances and the advantages of monolithic supports and compare them to conventional particle-packed chromatographic supports.

Gogineni Venkata Rattaiah

Papers

Preconcentration and determination of calcium and magnesium in brine with flow-injection systems