Development of an analytical method for beryllium in airborne dust by micellar electrokinetic chromatography

The separation of diacetylacetonato-beryllium [Be(acac)2] from acetylacetone was achieved with micellar electrokinetic chromatography (MEKC) followed by subsequent beryllium analysis carried out using capillary electrophoresis. Analysis using a separation and absorption detector, with a 50 microns capillary cell, could detect approximately 1000 ppb of beryllium in the final sample. Be(acac)2 is a promising reagent for absorption spectrophotometry, because its molar absorption coefficient, (32,000 l mol-1 cm-1) is very large. As the complex and acetylacetone have a similar absorption wavelength, the excess free ligand must removed from the sample to be measured. Acetylacetone is a weak acid with keto-enol tautomerism in aqueous solution. Acetylacetone and neutral Be(acac)2 should be separated with capillary zone electrophoresis (CZE) using a neutral or basic buffer solution as the mobile phase. Although the pH and temperature of the mobile phase were optimized, separation with CZE was interfered with by a portion of acetylacetone. This interfering portion seems to be a neutral keto-form with the same migration time as Be(acac)2. As a neutral species separation method, MEKC with sodium dodecyl sulfate was tried and the separation was completed. The optimum pH value and buffer temperature are pH 7.8 and 15 degrees C, respectively.