On-line filtration system for determining total chromium and chromium in the soluble fraction of industrial effluents by flow injection flame atomic absorption spectrometry

Abstract

Two manifolds were assessed for the purpose of determining both the total chromium content and that present as a soluble form in industrial effluents by flow injection flame atomic absorption spectrometry (FI-FAAS). To determine the chromium content in the soluble fraction the samples were used without additional treatment, a 0.45 microm filter being included in the FI system. To determine the total chromium content, the samples were acidified with nitric acid 20% (v/v) and heated for 30 s in a microwave oven (temperatures of about 70 degrees C were reached). The problem posed by the very different concentration range in which total and soluble chromium are present was overcome by using programmed flow rate methodology and by only partially emptying the sample loop. A personal computer controlled both the rotation speed of a peristaltic pump and the volume of sample injected into the system, thus obtaining the dispersion degree required. Using the manifold proposed, the chromium content in the soluble fraction can be determined in the 0.5-20 microg mL(-1) range using a 10 microg mL(-1) single standard for calibration. To determine the total chromium content, a calibration line in the 20-200 microg mL(-1) range was obtained using a single 50 microg mL(-1) chromium standard solution. The reliability of the semi-automatic devices was verified by comparing the results obtained with those found by treating the samples and using both FAAS in a conventional way and a spectrophotometric method using diphenylcarbazide at the 95% confidence level (ANOVA test). The proposed procedures showed a RSD lower than +/-3%.

Retention Profile of Mercury (II) Ions from Aqueous Solution onto Some Selected Local Solid Sorbents

“…Natural substances such as clay minerals, local soil and active carbon, artificial such as organic compound and synthetic polymers have been reported as excellent sorbents for trace metals ions [1][2][3][4][5] . The sorption behavior of heavy metals and their differential determination employing C18-bonded silica as the column material and silica gel surface immobilized with zirconium (IV) and zirconium (VI) phosphate have been studied [2][3][4][5] .…”

“…The sorption behavior of heavy metals and their differential determination employing C18-bonded silica as the column material and silica gel surface immobilized with zirconium (IV) and zirconium (VI) phosphate have been studied [2][3][4][5] . The Determination of mercury (II) at trace levels in welding fumes employing a strong anion-exchange containing hydrophilic polyether resin substituted with quaternary amine groups has been reported [6] .…”

Atomic spectrometry update. Advances in atomic emission, absorption and fluorescence spectrometry and related techniques

“…Zhao et al 7 constructed a simple flow-injection clean-up system for microwave plasma-torch atomic emission spectrometry in which analytes that exist as anionic (Cr, Mo, and P) or neutral compounds (Ag and Zr in halide acid media) were determined after removal of interfering matrix cations on a strongly acidic cation-exchange resin. In addition to the various calibration and dilution manifolds mentioned earlier, Lopez-Garcia et al 8 devised an on-line filtration system for determining total Cr and Cr in the soluble fraction of industrial effluents by FI-FAAS. The manifold contained a 0.45 mm filter and computer controlled pumps.…”