You are here:
EFFECTS OF PH AND COMPETING ANIONS ON THE SPECIATION OF ARSENIC IN FIXED IONIC STRENGTH SOLUTIONS BY SOLID PHASE EXTRACTION CARTRIDGES
Citation:
IMPELLITTERI, C. A. EFFECTS OF PH AND COMPETING ANIONS ON THE SPECIATION OF ARSENIC IN FIXED IONIC STRENGTH SOLUTIONS BY SOLID PHASE EXTRACTION CARTRIDGES. M. Henze (ed.), WATER RESEARCH. Elsevier BV, AMSTERDAM, Netherlands, 38(5):1207-1214, (2004).
Description:
Anion-exchange resins (AERs) separate As(V) and As(lIl) in solution by retaining As(V) and allowing As(lIl) to pass through. AERs offer several advantages including portability, ease of use, and affordability (relative to other As speciation methods). The use of AERs for the instantaneous speciation of As negates the need for sample preservation for As species analysis. The aims of this study were to: 1) Select an AER containing solid phase extraction cartridge (SPEC) based on effectiveness and ease of use. 2) Examine the effects of pH and competing anions on the efficacy of the SPEC in a 0.01 mol L-1 NaNO3 background electrolyte (BG). 3) Identify optimal conditions (e.g. flow rates) for As speciation. 4) Calculate method detection limits and recoveries of As species from spiked samples. A SPEC containing a silica-based AER was selected. The SPEC performed well for As(V) retention through a range of environmentally relevant pH values (4-8). The mass loading capacity for As(V) was reduced in the BG (0.006 mg) compared with As(V) in deionized H2O (0.75 mg). Some retention (10%-20%) of As(lIl) occurred on pre-wetted cartridges. Approximately 95 % of spiked As(lIl) passed through dry cartridges. The recommended flow rate (0.5 mL min-1) was increased to 5 mL min-1 without significant effect on As(V) retention. The presence of anions decreased the retention of As(V) with sulfate and phosphate having the greatest impact. Method detection limits were 0.004 mg L-1 for both inorganic species. Spike recoveries in aqueous soil extracts averaged 94% for As(lIl) and 107% for As(V).