Determination of arsenic(V) in freshwaters by flow injection with luminol chemiluminescence detection

Abstract

A simple and rapid flow injection (FI) method is reported for the determination of arsenic(V) based on luminol chemiluminescence (CL) detection. The molybdoarsenic heteropoly acid formed by arsenic and ammonium molybdate in the presence of ammonium vanadate in acidic conditions generated chemiluminescence emission via the oxidation of luminol. The limit of detection was 0.15 μg L⁻¹, with a sample throughput 120 h⁻¹. A linear calibration graph was obtained over the range 0.15 to 7.5 μg L⁻¹ (r ² = 0.9989; n = 9) with relative standard deviation (n = 4) in the range 0.8 to 2.5%. Interfering cations were removed by passing the sample through an in-line iminodiacetate chelating column and phosphate (at 0.6 mg L⁻¹) was removed off-line by magnesium-induced coprecipitation (MAGIC) method. The method was applied to freshwater samples and the results obtained were in reasonable agreement with the results obtained using HGAAS as the reference method.

Keywords:

• flow injection analysis
• chemiluminescence
• arsenate
• heteropoly acid
• freshwaters

Acknowledgements

The authors are grateful to the Higher Education Commission, Pakistan, for financial support in the form of an Indigenous Scholarship (PIN–042-210012-PS2–323) and Department of Chemistry, University of Balochistan for providing facilities.